message/

message.rs

use crate::address::HeaderAddressList;
#[cfg(feature = "impl")]
use crate::dkim::Signer;
#[cfg(feature = "impl")]
use crate::dkim::SIGN_POOL;
pub use crate::queue_name::QueueNameComponents;
use crate::scheduling::Scheduling;
use anyhow::Context;
use bstr::{BString, ByteSlice, ByteVec};
use chrono::{DateTime, Utc};
#[cfg(feature = "impl")]
use config::{any_err, from_lua_value, serialize_options, SerdeWrappedValue};
use futures::{FutureExt, TryFutureExt};
use intrusive_collections::{intrusive_adapter, LinkedList, LinkedListAtomicLink};
use kumo_chrono_helper::*;
#[cfg(feature = "impl")]
use kumo_dkim::arc::ARC;
use kumo_log_types::rfc3464::Report;
use kumo_log_types::rfc5965::ARFReport;
use kumo_prometheus::declare_metric;
#[cfg(feature = "impl")]
use mailparsing::{AuthenticationResult, AuthenticationResults, EncodeHeaderValue};
use mailparsing::{
    CheckFixSettings, DecodedBody, Header, HeaderParseResult, MessageConformance, MimePart,
};
#[cfg(feature = "impl")]
use mlua::{IntoLua, LuaSerdeExt, UserData, UserDataMethods};
#[cfg(feature = "impl")]
use mod_dns_resolver::get_resolver_instance;
use parking_lot::Mutex;
use rfc5321::parser::EnvelopeAddress;
use serde::{Deserialize, Serialize};
use serde_with::formats::PreferOne;
use serde_with::{serde_as, OneOrMany};
use spool::{get_data_spool, get_meta_spool, Spool, SpoolId};
use std::collections::{BTreeMap, HashSet};
use std::hash::Hash;
use std::sync::{Arc, LazyLock, Weak};
use std::time::{Duration, Instant};
use timeq::TimerEntryWithDelay;

bitflags::bitflags! {
    #[derive(Clone, Copy, Debug, PartialEq, Eq)]
    struct MessageFlags: u8 {
        /// true if Metadata needs to be saved
        const META_DIRTY = 1;
        /// true if Data needs to be saved
        const DATA_DIRTY = 2;
        /// true if scheduling restrictions are present in the metadata
        const SCHEDULED = 4;
        /// true if high durability writes should always be used
        const FORCE_SYNC = 8;
    }
}

declare_metric! {
/// Total number of Message objects.
///
/// This encompasses all Message objects in various states, whether
/// they are in a queue, moving between queues, being built as part
/// of an injection, pending logging, message metadata and/or data
/// may be either resident or offloaded to spool.
static MESSAGE_COUNT: IntGauge("message_count");
}

declare_metric! {
/// Total number of Message objects with metadata loaded.
///
/// Tracks how many messages have their `meta` data resident
/// in memory.  This may be because they have not yet saved
/// it, or because the message is being processed and the
/// metadata is required for that processing.
static META_COUNT: IntGauge("message_meta_resident_count");
}

declare_metric! {
/// Total number of Message objects with body data loaded.
///
/// Tracks how many messages have their `data` resident
/// in memory.  This may be because they have not yet saved
/// it, or because the message is being processed and the
/// data is either required to be in memory in order to
/// deliver the message, or because logging or other
/// post-injection policy is configured to operate on
/// the message.
static DATA_COUNT: IntGauge("message_data_resident_count");
}

static NO_DATA: LazyLock<Arc<Box<[u8]>>> = LazyLock::new(|| Arc::new(vec![].into_boxed_slice()));

declare_metric! {
/// How many seconds it takes to save a message to spool.
///
/// This metric encompasses the elapsed time to saved
/// either or both the `meta` and `data` portions of a
/// message to spool.
///
/// High values indicate IO pressure which may be
/// alleviated by tuning other constraints and/or
/// [RocksDB Parameters](../../kumo/define_spool/rocks_params.md)
static SAVE_HIST: Histogram("message_save_latency");
}

declare_metric! {
/// How many seconds it takes to load message data from spool.
///
/// High values indicate IO pressure which may be caused
/// by policy that operates on the message body post-reception.
/// We recommend *avoiding* logging header values as that is
/// the most common cause of this metric spiking and has
/// the biggest impact in resolving it.
///
/// IO pressure may also be alleviated by tuning other constraints and/or
/// [RocksDB Parameters](../../kumo/define_spool/rocks_params.md)
static LOAD_DATA_HIST: Histogram("message_data_load_latency");
}

declare_metric! {
/// How long it takes to load message metadata from spool
///
/// High values indicate IO pressure which may be
/// alleviated by tuning other constraints and/or
/// [RocksDB Parameters](../../kumo/define_spool/rocks_params.md)
static LOAD_META_HIST: Histogram("message_meta_load_latency");
}

#[derive(Debug)]
struct MessageInner {
    metadata: Option<Box<MetaData>>,
    data: Arc<Box<[u8]>>,
    flags: MessageFlags,
    num_attempts: u16,
    due: Option<DateTime<Utc>>,
}

#[derive(Debug)]
pub(crate) struct MessageWithId {
    id: SpoolId,
    inner: Mutex<MessageInner>,
    link: LinkedListAtomicLink,
}

intrusive_adapter!(
    pub(crate) MessageWithIdAdapter = Arc<MessageWithId>: MessageWithId { link: LinkedListAtomicLink }
);

/// A list of messages with an O(1) list overhead; no additional
/// memory per-message is required to track this list.
/// However, a given Message can only belong to one instance
/// of such a list at a time.
pub struct MessageList {
    list: LinkedList<MessageWithIdAdapter>,
    len: usize,
}

impl Default for MessageList {
    fn default() -> Self {
        Self::new()
    }
}

impl MessageList {
    /// Create a new MessageList
    pub fn new() -> Self {
        Self {
            list: LinkedList::new(MessageWithIdAdapter::default()),
            len: 0,
        }
    }

    /// Returns the number of elements contained in the list
    pub fn len(&self) -> usize {
        self.len
    }

    pub fn is_empty(&self) -> bool {
        self.len == 0
    }

    /// Take all of the elements from this list and return them
    /// in a new separate instance of MessageList.
    pub fn take(&mut self) -> Self {
        let new_list = Self {
            list: self.list.take(),
            len: self.len,
        };
        self.len = 0;
        new_list
    }

    /// Push a message to the back of the list
    pub fn push_back(&mut self, message: Message) {
        self.list.push_back(message.msg_and_id);
        self.len += 1;
    }

    /// Pop a message from the front of the list
    pub fn pop_front(&mut self) -> Option<Message> {
        self.list.pop_front().map(|msg_and_id| {
            self.len -= 1;
            Message { msg_and_id }
        })
    }

    /// Pop a message from the back of the list
    pub fn pop_back(&mut self) -> Option<Message> {
        self.list.pop_back().map(|msg_and_id| {
            self.len -= 1;
            Message { msg_and_id }
        })
    }

    /// Pop all of the messages from this list into a vector
    /// of messages.
    /// Memory usage is O(number-of-messages).
    pub fn drain(&mut self) -> Vec<Message> {
        let mut messages = Vec::with_capacity(self.len);
        while let Some(msg) = self.pop_front() {
            messages.push(msg);
        }
        messages
    }

    pub fn extend_from_iter<I>(&mut self, iter: I)
    where
        I: Iterator<Item = Message>,
    {
        for msg in iter {
            self.push_back(msg)
        }
    }
}

impl IntoIterator for MessageList {
    type Item = Message;
    type IntoIter = MessageListIter;
    fn into_iter(self) -> MessageListIter {
        MessageListIter { list: self.list }
    }
}

pub struct MessageListIter {
    list: LinkedList<MessageWithIdAdapter>,
}

impl Iterator for MessageListIter {
    type Item = Message;
    fn next(&mut self) -> Option<Message> {
        self.list
            .pop_front()
            .map(|msg_and_id| Message { msg_and_id })
    }
}

#[derive(Clone, Debug)]
#[cfg_attr(feature = "impl", derive(mlua::FromLua))]
pub struct Message {
    pub(crate) msg_and_id: Arc<MessageWithId>,
}

impl PartialEq for Message {
    fn eq(&self, other: &Self) -> bool {
        self.id() == other.id()
    }
}
impl Eq for Message {}

impl Hash for Message {
    fn hash<H>(&self, hasher: &mut H)
    where
        H: std::hash::Hasher,
    {
        self.id().hash(hasher)
    }
}

#[derive(Clone, Debug)]
pub struct WeakMessage {
    weak: Weak<MessageWithId>,
}

impl WeakMessage {
    pub fn upgrade(&self) -> Option<Message> {
        Some(Message {
            msg_and_id: self.weak.upgrade()?,
        })
    }
}

#[serde_as]
#[derive(Debug, Serialize, Deserialize, Clone)]
pub(crate) struct MetaData {
    pub sender: EnvelopeAddress,
    #[serde_as(as = "OneOrMany<_, PreferOne>")]
    pub recipient: Vec<EnvelopeAddress>,
    pub meta: serde_json::Value,
    #[serde(default)]
    pub schedule: Option<Scheduling>,
}

impl Drop for MessageInner {
    fn drop(&mut self) {
        if self.metadata.is_some() {
            META_COUNT.dec();
        }
        if !self.data.is_empty() {
            DATA_COUNT.dec();
        }
        MESSAGE_COUNT.dec();
    }
}

impl Message {
    /// Create a new message with the supplied data.
    /// The message meta and data are marked as dirty
    pub fn new_dirty(
        id: SpoolId,
        sender: EnvelopeAddress,
        recipient: Vec<EnvelopeAddress>,
        meta: serde_json::Value,
        data: Arc<Box<[u8]>>,
    ) -> anyhow::Result<Self> {
        anyhow::ensure!(meta.is_object(), "metadata must be a json object");
        MESSAGE_COUNT.inc();
        DATA_COUNT.inc();
        META_COUNT.inc();
        Ok(Self {
            msg_and_id: Arc::new(MessageWithId {
                id,
                inner: Mutex::new(MessageInner {
                    metadata: Some(Box::new(MetaData {
                        sender,
                        recipient,
                        meta,
                        schedule: None,
                    })),
                    data,
                    flags: MessageFlags::META_DIRTY | MessageFlags::DATA_DIRTY,
                    num_attempts: 0,
                    due: None,
                }),
                link: LinkedListAtomicLink::default(),
            }),
        })
    }

    pub fn weak(&self) -> WeakMessage {
        WeakMessage {
            weak: Arc::downgrade(&self.msg_and_id),
        }
    }

    /// Helper for creating a message based on spool enumeration.
    /// Given a spool id and the serialized metadata blob, returns
    /// a message holding the deserialized version of that metadata.
    pub fn new_from_spool(id: SpoolId, metadata: Vec<u8>) -> anyhow::Result<Self> {
        let metadata: MetaData = serde_json::from_slice(&metadata)?;
        MESSAGE_COUNT.inc();
        META_COUNT.inc();

        let flags = if metadata.schedule.is_some() {
            MessageFlags::SCHEDULED
        } else {
            MessageFlags::empty()
        };

        Ok(Self {
            msg_and_id: Arc::new(MessageWithId {
                id,
                inner: Mutex::new(MessageInner {
                    metadata: Some(Box::new(metadata)),
                    data: NO_DATA.clone(),
                    flags,
                    num_attempts: 0,
                    due: None,
                }),
                link: LinkedListAtomicLink::default(),
            }),
        })
    }

    pub(crate) fn new_from_parts(id: SpoolId, metadata: MetaData, data: Arc<Box<[u8]>>) -> Self {
        MESSAGE_COUNT.inc();
        META_COUNT.inc();

        let flags = if metadata.schedule.is_some() {
            MessageFlags::SCHEDULED
        } else {
            MessageFlags::empty()
        };

        Self {
            msg_and_id: Arc::new(MessageWithId {
                id,
                inner: Mutex::new(MessageInner {
                    metadata: Some(Box::new(metadata)),
                    data,
                    flags: flags | MessageFlags::META_DIRTY | MessageFlags::DATA_DIRTY,
                    num_attempts: 0,
                    due: None,
                }),
                link: LinkedListAtomicLink::default(),
            }),
        }
    }

    pub async fn new_with_id(id: SpoolId) -> anyhow::Result<Self> {
        let meta_spool = get_meta_spool();
        let data = meta_spool.load(id).await?;
        Self::new_from_spool(id, data)
    }

    pub fn get_num_attempts(&self) -> u16 {
        let inner = self.msg_and_id.inner.lock();
        inner.num_attempts
    }

    pub fn set_num_attempts(&self, num_attempts: u16) {
        let mut inner = self.msg_and_id.inner.lock();
        inner.num_attempts = num_attempts;
    }

    pub fn increment_num_attempts(&self) {
        let mut inner = self.msg_and_id.inner.lock();
        inner.num_attempts += 1;
    }

    pub async fn set_scheduling(
        &self,
        scheduling: Option<Scheduling>,
    ) -> anyhow::Result<Option<Scheduling>> {
        self.load_meta_if_needed().await?;
        let mut inner = self.msg_and_id.inner.lock();
        match &mut inner.metadata {
            None => anyhow::bail!("set_scheduling: metadata must be loaded first"),
            Some(meta) => {
                meta.schedule = scheduling;
                inner
                    .flags
                    .set(MessageFlags::SCHEDULED, scheduling.is_some());
                if let Some(sched) = scheduling {
                    let due = inner.due.unwrap_or_else(Utc::now);
                    inner.due = Some(sched.adjust_for_schedule(due));
                }
                Ok(scheduling)
            }
        }
    }

    pub async fn get_scheduling(&self) -> anyhow::Result<Option<Scheduling>> {
        self.load_meta_if_needed().await?;
        let inner = self.msg_and_id.inner.lock();
        Ok(inner.metadata.as_ref().and_then(|meta| meta.schedule))
    }

    pub fn get_due(&self) -> Option<DateTime<Utc>> {
        let inner = self.msg_and_id.inner.lock();
        inner.due
    }

    pub async fn delay_with_jitter(&self, limit: i64) -> anyhow::Result<Option<DateTime<Utc>>> {
        let scale = rand::random::<f32>();
        let value = (scale * limit as f32) as i64;
        self.delay_by(seconds(value)?).await
    }

    pub async fn delay_by(
        &self,
        duration: chrono::Duration,
    ) -> anyhow::Result<Option<DateTime<Utc>>> {
        let due = Utc::now() + duration;
        self.set_due(Some(due)).await
    }

    /// Delay by requested duration, and add up to 1 minute of jitter
    pub async fn delay_by_and_jitter(
        &self,
        duration: chrono::Duration,
    ) -> anyhow::Result<Option<DateTime<Utc>>> {
        let scale = rand::random::<f32>();
        let value = (scale * 60.) as i64;
        let due = Utc::now() + duration + seconds(value)?;
        self.set_due(Some(due)).await
    }

    pub async fn set_due(
        &self,
        due: Option<DateTime<Utc>>,
    ) -> anyhow::Result<Option<DateTime<Utc>>> {
        let due = {
            let mut inner = self.msg_and_id.inner.lock();

            if !inner.flags.contains(MessageFlags::SCHEDULED) {
                // This is the simple, fast-path, common case
                inner.due = due;
                return Ok(inner.due);
            }

            let due = due.unwrap_or_else(Utc::now);

            if let Some(meta) = &inner.metadata {
                inner.due = match &meta.schedule {
                    Some(sched) => Some(sched.adjust_for_schedule(due)),
                    None => Some(due),
                };
                return Ok(inner.due);
            }

            // We'll need to load the metadata to correctly
            // update the schedule for this message
            due
        };

        self.load_meta().await?;

        {
            let mut inner = self.msg_and_id.inner.lock();
            match &inner.metadata {
                Some(meta) => {
                    inner.due = match &meta.schedule {
                        Some(sched) => Some(sched.adjust_for_schedule(due)),
                        None => Some(due),
                    };
                    Ok(inner.due)
                }
                None => anyhow::bail!("loaded metadata, but metadata is not set!?"),
            }
        }
    }

    fn get_data_if_dirty(&self) -> Option<Arc<Box<[u8]>>> {
        let inner = self.msg_and_id.inner.lock();
        if inner.flags.contains(MessageFlags::DATA_DIRTY) {
            Some(Arc::clone(&inner.data))
        } else {
            None
        }
    }

    fn get_meta_if_dirty(&self) -> Option<MetaData> {
        let inner = self.msg_and_id.inner.lock();
        if inner.flags.contains(MessageFlags::META_DIRTY) {
            inner.metadata.as_ref().map(|md| (**md).clone())
        } else {
            None
        }
    }

    pub(crate) async fn clone_meta_data(&self) -> anyhow::Result<MetaData> {
        self.load_meta_if_needed().await?;
        let inner = self.msg_and_id.inner.lock();
        inner
            .metadata
            .as_ref()
            .ok_or_else(|| anyhow::anyhow!("metadata not loaded even though we just loaded it"))
            .map(|md| (**md).clone())
    }

    pub fn set_force_sync(&self, force: bool) {
        let mut inner = self.msg_and_id.inner.lock();
        inner.flags.set(MessageFlags::FORCE_SYNC, force);
    }

    pub fn needs_save(&self) -> bool {
        let inner = self.msg_and_id.inner.lock();
        inner.flags.contains(MessageFlags::META_DIRTY)
            || inner.flags.contains(MessageFlags::DATA_DIRTY)
    }

    pub async fn save(&self, deadline: Option<Instant>) -> anyhow::Result<()> {
        let _timer = SAVE_HIST.start_timer();
        self.save_to(&**get_meta_spool(), &**get_data_spool(), deadline)
            .await
    }

    pub async fn save_to(
        &self,
        meta_spool: &(dyn Spool + Send + Sync),
        data_spool: &(dyn Spool + Send + Sync),
        deadline: Option<Instant>,
    ) -> anyhow::Result<()> {
        let force_sync = self
            .msg_and_id
            .inner
            .lock()
            .flags
            .contains(MessageFlags::FORCE_SYNC);

        let data_fut: futures::future::BoxFuture<'_, anyhow::Result<bool>> =
            if let Some(data) = self.get_data_if_dirty() {
                anyhow::ensure!(!data.is_empty(), "message data must not be empty");
                data_spool
                    .store(self.msg_and_id.id, data, force_sync, deadline)
                    .map_ok(|_| true)
                    .boxed()
            } else {
                futures::future::ready(Ok(false)).boxed()
            };
        let meta_fut: futures::future::BoxFuture<'_, anyhow::Result<bool>> =
            if let Some(meta) = self.get_meta_if_dirty() {
                let meta = Arc::new(serde_json::to_vec(&meta)?.into_boxed_slice());
                meta_spool
                    .store(self.msg_and_id.id, meta, force_sync, deadline)
                    .map_ok(|_| true)
                    .boxed()
            } else {
                futures::future::ready(Ok(false)).boxed()
            };

        // NOTE: if we have a deadline, it is tempting to want to use
        // timeout_at here to enforce it, but the underlying spool
        // futures are not guaranteed to be fully cancel safe, which
        // is why we pass the deadline down to the save method to allow
        // them to handle timeouts internally.
        let (data_res, meta_res) = tokio::join!(data_fut, meta_fut);

        // Clear the dirty flag for each spool that successfully
        // stored (Ok(true)).  Even when the other spool failed, we
        // must still record the partial success: the caller may
        // unwind by removing from both spools, and the remove on a
        // spool that did not receive the data is harmless.
        if matches!(data_res, Ok(true)) {
            self.msg_and_id
                .inner
                .lock()
                .flags
                .remove(MessageFlags::DATA_DIRTY);
        }
        if matches!(meta_res, Ok(true)) {
            self.msg_and_id
                .inner
                .lock()
                .flags
                .remove(MessageFlags::META_DIRTY);
        }

        // Propagate spool errors so callers (notably the SMTP
        // ingress path and load-shedding-aware code) can react
        // rather than silently accepting a message whose persistent
        // storage failed.
        //
        // For the both-failed case we preserve the typed
        // SpoolUnhealthyError on the returned error chain when
        // either side has one, so callers that match on
        // root_cause (e.g. the SMTP server's user-facing 421
        // shaping) still see the actionable reason.  The
        // non-preferred error is folded into the context message so
        // it is still visible to anything that formats the error
        // with `:#`.
        match (data_res, meta_res) {
            (Ok(_), Ok(_)) => Ok(()),
            (Err(data_err), Ok(_)) => Err(data_err.context("data spool store")),
            (Ok(_), Err(meta_err)) => Err(meta_err.context("meta spool store")),
            (Err(data_err), Err(meta_err)) => {
                let data_unhealthy = data_err.root_cause().is::<::spool::SpoolUnhealthyError>();
                let meta_unhealthy = meta_err.root_cause().is::<::spool::SpoolUnhealthyError>();
                match (data_unhealthy, meta_unhealthy) {
                    (true, _) => Err(data_err.context(format!(
                        "data spool store; meta spool store also failed: {meta_err:#}"
                    ))),
                    (false, true) => Err(meta_err.context(format!(
                        "meta spool store; data spool store also failed: {data_err:#}"
                    ))),
                    (false, false) => Err(anyhow::anyhow!(
                        "data spool store: {data_err:#}; meta spool store: {meta_err:#}"
                    )),
                }
            }
        }
    }

    pub fn id(&self) -> &SpoolId {
        &self.msg_and_id.id
    }

    /// Save the data+meta if needed, then release both
    pub async fn save_and_shrink(&self) -> anyhow::Result<bool> {
        self.save(None).await?;
        self.shrink()
    }

    /// Save the data+meta if needed, then release just the data
    pub async fn save_and_shrink_data(&self) -> anyhow::Result<bool> {
        self.save(None).await?;
        self.shrink_data()
    }

    pub fn shrink_data(&self) -> anyhow::Result<bool> {
        let mut inner = self.msg_and_id.inner.lock();
        let mut did_shrink = false;
        if inner.flags.contains(MessageFlags::DATA_DIRTY) {
            anyhow::bail!("Cannot shrink message: DATA_DIRTY");
        }
        if !inner.data.is_empty() {
            DATA_COUNT.dec();
            did_shrink = true;
        }
        if !inner.data.is_empty() {
            inner.data = NO_DATA.clone();
            did_shrink = true;
        }
        Ok(did_shrink)
    }

    pub fn shrink(&self) -> anyhow::Result<bool> {
        let mut inner = self.msg_and_id.inner.lock();
        let mut did_shrink = false;
        if inner.flags.contains(MessageFlags::DATA_DIRTY) {
            anyhow::bail!("Cannot shrink message: DATA_DIRTY");
        }
        if inner.flags.contains(MessageFlags::META_DIRTY) {
            anyhow::bail!("Cannot shrink message: META_DIRTY");
        }
        if inner.metadata.take().is_some() {
            META_COUNT.dec();
            did_shrink = true;
        }
        if !inner.data.is_empty() {
            DATA_COUNT.dec();
            did_shrink = true;
        }
        if !inner.data.is_empty() {
            inner.data = NO_DATA.clone();
            did_shrink = true;
        }
        Ok(did_shrink)
    }

    pub async fn sender(&self) -> anyhow::Result<EnvelopeAddress> {
        self.load_meta_if_needed().await?;
        let inner = self.msg_and_id.inner.lock();
        match &inner.metadata {
            Some(meta) => Ok(meta.sender.clone()),
            None => anyhow::bail!("Message::sender metadata is not loaded"),
        }
    }

    pub async fn set_sender(&self, sender: EnvelopeAddress) -> anyhow::Result<()> {
        self.load_meta_if_needed().await?;
        let mut inner = self.msg_and_id.inner.lock();
        match &mut inner.metadata {
            Some(meta) => {
                meta.sender = sender;
                inner.flags.set(MessageFlags::DATA_DIRTY, true);
                Ok(())
            }
            None => anyhow::bail!("Message::set_sender: metadata is not loaded"),
        }
    }

    #[deprecated = "use recipient_list or first_recipient instead"]
    pub async fn recipient(&self) -> anyhow::Result<EnvelopeAddress> {
        self.first_recipient().await
    }

    pub async fn first_recipient(&self) -> anyhow::Result<EnvelopeAddress> {
        self.load_meta_if_needed().await?;
        let inner = self.msg_and_id.inner.lock();
        match &inner.metadata {
            Some(meta) => match meta.recipient.first() {
                Some(recip) => Ok(recip.clone()),
                None => anyhow::bail!("recipient list is empty!?"),
            },
            None => anyhow::bail!("Message::first_recipient: metadata is not loaded"),
        }
    }

    pub async fn recipient_list(&self) -> anyhow::Result<Vec<EnvelopeAddress>> {
        self.load_meta_if_needed().await?;
        let inner = self.msg_and_id.inner.lock();
        match &inner.metadata {
            Some(meta) => Ok(meta.recipient.clone()),
            None => anyhow::bail!("Message::recipient_list: metadata is not loaded"),
        }
    }

    pub async fn recipient_list_string(&self) -> anyhow::Result<Vec<String>> {
        self.load_meta_if_needed().await?;
        let inner = self.msg_and_id.inner.lock();
        match &inner.metadata {
            Some(meta) => Ok(meta.recipient.iter().map(|a| a.to_string()).collect()),
            None => anyhow::bail!("Message::recipient_list_string: metadata is not loaded"),
        }
    }

    #[deprecated = "use set_recipient_list instead"]
    pub async fn set_recipient(&self, recipient: EnvelopeAddress) -> anyhow::Result<()> {
        self.set_recipient_list(vec![recipient]).await
    }

    pub async fn set_recipient_list(&self, recipient: Vec<EnvelopeAddress>) -> anyhow::Result<()> {
        self.load_meta_if_needed().await?;

        let mut inner = self.msg_and_id.inner.lock();
        match &mut inner.metadata {
            Some(meta) => {
                meta.recipient = recipient;
                inner.flags.set(MessageFlags::DATA_DIRTY, true);
                Ok(())
            }
            None => anyhow::bail!("Message::set_recipient_list: metadata is not loaded"),
        }
    }

    pub fn is_meta_loaded(&self) -> bool {
        self.msg_and_id.inner.lock().metadata.is_some()
    }

    pub fn is_data_loaded(&self) -> bool {
        !self.msg_and_id.inner.lock().data.is_empty()
    }

    pub async fn load_meta_if_needed(&self) -> anyhow::Result<()> {
        if self.is_meta_loaded() {
            return Ok(());
        }
        self.load_meta().await
    }

    pub async fn data(&self) -> anyhow::Result<Arc<Box<[u8]>>> {
        self.load_data_if_needed().await
    }

    async fn load_data_if_needed(&self) -> anyhow::Result<Arc<Box<[u8]>>> {
        if self.is_data_loaded() {
            return Ok(self.get_data_maybe_not_loaded());
        }
        self.load_data().await
    }

    pub async fn load_meta(&self) -> anyhow::Result<()> {
        let _timer = LOAD_META_HIST.start_timer();
        self.load_meta_from(&**get_meta_spool()).await
    }

    async fn load_meta_from(&self, meta_spool: &(dyn Spool + Send + Sync)) -> anyhow::Result<()> {
        let id = self.id();
        let data = meta_spool.load(*id).await?;
        let mut inner = self.msg_and_id.inner.lock();
        let was_not_loaded = inner.metadata.is_none();
        let metadata: MetaData = serde_json::from_slice(&data)?;
        inner.metadata.replace(Box::new(metadata));
        if was_not_loaded {
            META_COUNT.inc();
        }
        Ok(())
    }

    pub async fn load_data(&self) -> anyhow::Result<Arc<Box<[u8]>>> {
        let _timer = LOAD_DATA_HIST.start_timer();
        self.load_data_from(&**get_data_spool()).await
    }

    async fn load_data_from(
        &self,
        data_spool: &(dyn Spool + Send + Sync),
    ) -> anyhow::Result<Arc<Box<[u8]>>> {
        let data = data_spool.load(*self.id()).await?;
        let mut inner = self.msg_and_id.inner.lock();
        let was_empty = inner.data.is_empty();
        inner.data = Arc::new(data.into_boxed_slice());
        if was_empty {
            DATA_COUNT.inc();
        }
        Ok(inner.data.clone())
    }

    pub fn assign_data(&self, data: Vec<u8>) {
        let mut inner = self.msg_and_id.inner.lock();
        let was_empty = inner.data.is_empty();
        inner.data = Arc::new(data.into_boxed_slice());
        inner.flags.set(MessageFlags::DATA_DIRTY, true);
        if was_empty {
            DATA_COUNT.inc();
        }
    }

    pub fn get_data_maybe_not_loaded(&self) -> Arc<Box<[u8]>> {
        let inner = self.msg_and_id.inner.lock();
        inner.data.clone()
    }

    pub async fn set_meta<S: AsRef<str>, V: Into<serde_json::Value>>(
        &self,
        key: S,
        value: V,
    ) -> anyhow::Result<()> {
        self.load_meta_if_needed().await?;
        let mut inner = self.msg_and_id.inner.lock();
        match &mut inner.metadata {
            None => anyhow::bail!("set_meta: metadata must be loaded first"),
            Some(meta) => {
                let key = key.as_ref();
                let value = value.into();

                match &mut meta.meta {
                    serde_json::Value::Object(map) => {
                        map.insert(key.to_string(), value);
                    }
                    _ => anyhow::bail!("metadata is somehow not a json object"),
                }

                inner.flags.set(MessageFlags::META_DIRTY, true);
                Ok(())
            }
        }
    }

    pub async fn unset_meta<S: AsRef<str>>(&self, key: S) -> anyhow::Result<()> {
        self.load_meta_if_needed().await?;
        let mut inner = self.msg_and_id.inner.lock();
        match &mut inner.metadata {
            None => anyhow::bail!("set_meta: metadata must be loaded first"),
            Some(meta) => {
                let key = key.as_ref();

                match &mut meta.meta {
                    serde_json::Value::Object(map) => {
                        map.remove(key);
                    }
                    _ => anyhow::bail!("metadata is somehow not a json object"),
                }

                inner.flags.set(MessageFlags::META_DIRTY, true);
                Ok(())
            }
        }
    }

    /// Retrieve `key` as a String.
    pub async fn get_meta_string<S: serde_json::value::Index + std::fmt::Display + Copy>(
        &self,
        key: S,
    ) -> anyhow::Result<Option<String>> {
        match self.get_meta(key).await {
            Ok(serde_json::Value::String(value)) => Ok(Some(value.to_string())),
            Ok(serde_json::Value::Null) => Ok(None),
            hmm => {
                anyhow::bail!("expected '{key}' to be a string value, got {hmm:?}");
            }
        }
    }

    pub async fn get_meta_obj(&self) -> anyhow::Result<serde_json::Value> {
        self.load_meta_if_needed().await?;
        let inner = self.msg_and_id.inner.lock();
        match &inner.metadata {
            None => anyhow::bail!("get_meta_obj: metadata must be loaded first"),
            Some(meta) => Ok(meta.meta.clone()),
        }
    }

    pub async fn get_meta<S: serde_json::value::Index>(
        &self,
        key: S,
    ) -> anyhow::Result<serde_json::Value> {
        self.load_meta_if_needed().await?;
        let inner = self.msg_and_id.inner.lock();
        match &inner.metadata {
            None => anyhow::bail!("get_meta: metadata must be loaded first"),
            Some(meta) => match meta.meta.get(key) {
                Some(value) => Ok(value.clone()),
                None => Ok(serde_json::Value::Null),
            },
        }
    }

    pub fn age(&self, now: DateTime<Utc>) -> chrono::Duration {
        self.msg_and_id.id.age(now)
    }

    pub async fn get_queue_name(&self) -> anyhow::Result<String> {
        Ok(match self.get_meta_string("queue").await? {
            Some(name) => name,
            None => {
                let name = QueueNameComponents::format(
                    self.get_meta_string("campaign").await?,
                    self.get_meta_string("tenant").await?,
                    self.first_recipient()
                        .await?
                        .domain()
                        .to_string()
                        .to_lowercase(),
                    self.get_meta_string("routing_domain").await?,
                );
                name.to_string()
            }
        })
    }

    #[cfg(feature = "impl")]
    pub async fn arc_verify(
        &self,
        opt_resolver_name: Option<String>,
    ) -> anyhow::Result<AuthenticationResult> {
        let resolver = get_resolver_instance(&opt_resolver_name)?;
        let data = self.data().await?;
        let bytes = mailparsing::SharedString::try_from(data.as_ref().as_ref())?;

        let parsed = mailparsing::Header::parse_headers(bytes.clone())?;
        let message = kumo_dkim::ParsedEmail::HeaderOnlyParse { bytes, parsed };

        let arc = ARC::verify(&message, &**resolver).await;
        Ok(arc.authentication_result())
    }

    #[cfg(feature = "impl")]
    pub async fn arc_seal(
        &self,
        signer: Signer,
        auth_results: AuthenticationResults,
        opt_resolver_name: Option<String>,
    ) -> anyhow::Result<()> {
        let resolver = get_resolver_instance(&opt_resolver_name)?;
        let data = self.data().await?;
        let bytes = mailparsing::SharedString::try_from(data.as_ref().as_ref())?;
        let parsed = mailparsing::Header::parse_headers(bytes.clone())?;
        let message = kumo_dkim::ParsedEmail::HeaderOnlyParse { bytes, parsed };
        let arc = ARC::verify(&message, &**resolver).await;

        let headers = arc.seal(&message, auth_results, signer.signer())?;
        if !headers.is_empty() {
            let mut new_data = Vec::<u8>::with_capacity(data.len() + 1024);

            for hdr in headers {
                hdr.write_header(&mut new_data).ok();
            }
            new_data.extend_from_slice(&data);
            self.assign_data(new_data);
        }

        Ok(())
    }

    #[cfg(feature = "impl")]
    pub async fn dkim_verify(
        &self,
        opt_resolver_name: Option<String>,
    ) -> anyhow::Result<Vec<AuthenticationResult>> {
        let resolver = get_resolver_instance(&opt_resolver_name)?;
        let data = self.data().await?;
        let bytes = mailparsing::SharedString::try_from(data.as_ref().as_ref())?;

        let parsed = mailparsing::Header::parse_headers(bytes.clone())?;
        if parsed
            .overall_conformance
            .contains(MessageConformance::NON_CANONICAL_LINE_ENDINGS)
        {
            return Ok(vec![AuthenticationResult {
                method: "dkim".into(),
                method_version: None,
                result: "permerror".into(),
                reason: Some("message has non-canonical line endings".into()),
                props: Default::default(),
            }]);
        }
        let message = kumo_dkim::ParsedEmail::HeaderOnlyParse { bytes, parsed };

        let results = kumo_dkim::verify_email_with_resolver(&message, &**resolver).await?;
        Ok(results)
    }

    /// Parses the content into an owned MimePart.
    /// Changes to that MimePart are NOT reflected in the underlying
    /// message; you must re-assign the message data if you wish to modify
    /// the message content.
    pub async fn parse(&self) -> anyhow::Result<MimePart<'static>> {
        let data = self.data().await?;
        let owned_data = String::from_utf8_lossy(data.as_ref().as_ref()).to_string();
        Ok(MimePart::parse(owned_data)?)
    }

    pub async fn parse_rfc3464(&self) -> anyhow::Result<Option<Report>> {
        let data = self.data().await?;
        Report::parse(&data)
    }

    pub async fn parse_rfc5965(&self) -> anyhow::Result<Option<ARFReport>> {
        let data = self.data().await?;
        ARFReport::parse(&data)
    }

    pub async fn prepend_header(&self, name: Option<&str>, value: &[u8]) -> anyhow::Result<()> {
        let data = self.data().await?;
        let mut new_data = Vec::with_capacity(size_header(name, value) + 2 + data.len());
        emit_header(&mut new_data, name, value);
        new_data.extend_from_slice(&data);
        self.assign_data(new_data);
        Ok(())
    }

    pub async fn append_header(&self, name: Option<&str>, value: &[u8]) -> anyhow::Result<()> {
        let data = self.data().await?;
        let mut new_data = Vec::with_capacity(size_header(name, value.as_bytes()) + 2 + data.len());
        for (idx, window) in data.windows(4).enumerate() {
            if window == b"\r\n\r\n" {
                let headers = &data[0..idx + 2];
                let body = &data[idx + 2..];

                new_data.extend_from_slice(headers);
                emit_header(&mut new_data, name, value);
                new_data.extend_from_slice(body);
                self.assign_data(new_data);
                return Ok(());
            }
        }

        anyhow::bail!("append_header could not find the end of the header block");
    }

    pub async fn get_address_header(
        &self,
        header_name: &str,
    ) -> anyhow::Result<Option<HeaderAddressList>> {
        let data = self.data().await?;
        let HeaderParseResult { headers, .. } =
            mailparsing::Header::parse_headers(data.as_ref().as_ref())?;

        match headers.get_first(header_name) {
            Some(hdr) => {
                let list = hdr.as_address_list()?;
                let result: HeaderAddressList = list.into();
                Ok(Some(result))
            }
            None => Ok(None),
        }
    }

    pub async fn get_first_named_header_value(
        &self,
        name: &str,
    ) -> anyhow::Result<Option<BString>> {
        let data = self.data().await?;
        let HeaderParseResult { headers, .. } = Header::parse_headers(data.as_ref().as_ref())?;

        match headers.get_first(name) {
            Some(hdr) => Ok(Some(
                hdr.as_unstructured()
                    .unwrap_or_else(|_| hdr.get_raw_value().into()),
            )),
            None => Ok(None),
        }
    }

    pub async fn get_all_named_header_values(&self, name: &str) -> anyhow::Result<Vec<BString>> {
        let data = self.data().await?;
        let HeaderParseResult { headers, .. } = Header::parse_headers(data.as_ref().as_ref())?;

        let mut values = vec![];
        for hdr in headers.iter_named(name) {
            values.push(
                hdr.as_unstructured()
                    .unwrap_or_else(|_| hdr.get_raw_value().into()),
            );
        }
        Ok(values)
    }

    pub async fn get_all_headers(&self) -> anyhow::Result<Vec<(BString, BString)>> {
        let data = self.data().await?;
        let HeaderParseResult { headers, .. } = Header::parse_headers(data.as_ref().as_ref())?;

        let mut values = vec![];
        for hdr in headers.iter() {
            values.push((
                hdr.get_name().into(),
                hdr.as_unstructured()
                    .unwrap_or_else(|_| hdr.get_raw_value().into()),
            ));
        }
        Ok(values)
    }

    pub async fn retain_headers<F: FnMut(usize, &Header) -> bool>(
        &self,
        mut func: F,
    ) -> anyhow::Result<()> {
        let data = self.data().await?;
        let mut new_data = Vec::with_capacity(data.len());
        let HeaderParseResult {
            headers,
            body_offset,
            ..
        } = Header::parse_headers(data.as_ref().as_ref())?;
        for (idx, hdr) in headers.iter().enumerate() {
            let retain = (func)(idx, hdr);
            if !retain {
                continue;
            }
            hdr.write_header(&mut new_data)?;
        }
        new_data.extend_from_slice(b"\r\n");
        new_data.extend_from_slice(&data[body_offset..]);
        self.assign_data(new_data);
        Ok(())
    }

    pub async fn remove_first_named_header(&self, name: &str) -> anyhow::Result<()> {
        let mut removed = false;
        self.retain_headers(|_, hdr| {
            if hdr.get_name().eq_ignore_ascii_case(name.as_bytes()) && !removed {
                removed = true;
                false
            } else {
                true
            }
        })
        .await
    }

    pub async fn import_x_headers(&self, names: Vec<String>) -> anyhow::Result<()> {
        let specs = if names.is_empty() {
            vec![ImportHeaderSpec {
                name: "X-*".to_string(),
                ..ImportHeaderSpec::default()
            }]
        } else {
            names
                .into_iter()
                .map(|name| ImportHeaderSpec {
                    name,
                    ..ImportHeaderSpec::default()
                })
                .collect()
        };
        self.import_headers(specs).await
    }

    pub async fn import_headers(&self, specs: Vec<ImportHeaderSpec>) -> anyhow::Result<()> {
        let compiled: Vec<CompiledImportHeaderSpec> = specs
            .into_iter()
            .map(CompiledImportHeaderSpec::compile)
            .collect::<anyhow::Result<_>>()?;

        let data = self.data().await?;
        let HeaderParseResult { headers, .. } = Header::parse_headers(data.as_ref().as_ref())?;

        let mut accumulators: Vec<PerSpecAccumulator> = compiled
            .iter()
            .map(|s| PerSpecAccumulator::new(s.match_mode))
            .collect();
        let mut indices_to_remove: HashSet<usize> = HashSet::new();

        for (idx, hdr) in headers.iter().enumerate() {
            let hdr_name = hdr.get_name();
            for (spec_idx, spec) in compiled.iter().enumerate() {
                if spec.matches(hdr_name) {
                    let key = spec.target_key(&hdr.get_name_lossy());
                    let value = hdr.as_unstructured()?.to_str_lossy().to_string();
                    accumulators[spec_idx].record(key, value);
                    if spec.remove {
                        indices_to_remove.insert(idx);
                    }
                    break;
                }
            }
        }

        for acc in accumulators {
            acc.write_to(self).await?;
        }

        if !indices_to_remove.is_empty() {
            self.retain_headers(|idx, _| !indices_to_remove.contains(&idx))
                .await?;
        }

        Ok(())
    }

    pub async fn remove_x_headers(&self, names: Vec<String>) -> anyhow::Result<()> {
        self.retain_headers(|_, hdr| {
            if names.is_empty() {
                !is_x_header(hdr.get_name())
            } else {
                !names
                    .iter()
                    .any(|n| hdr.get_name().eq_ignore_ascii_case(n.as_bytes()))
            }
        })
        .await
    }

    pub async fn remove_all_named_headers(&self, name: &str) -> anyhow::Result<()> {
        self.retain_headers(|_, hdr| !hdr.get_name().eq_ignore_ascii_case(name.as_bytes()))
            .await
    }

    #[cfg(feature = "impl")]
    pub async fn dkim_sign(&self, signer: Signer) -> anyhow::Result<()> {
        let data = self.data().await?;
        let header = if let Some(runtime) = SIGN_POOL.get() {
            runtime.spawn_blocking(move || signer.sign(&data)).await??
        } else {
            signer.sign(&data)?
        };
        self.prepend_header(None, header.as_bytes()).await?;
        Ok(())
    }

    pub async fn import_scheduling_header(
        &self,
        header_name: &str,
        remove: bool,
    ) -> anyhow::Result<Option<Scheduling>> {
        if let Some(value) = self.get_first_named_header_value(header_name).await? {
            let sched: Scheduling = serde_json::from_slice(&value).with_context(|| {
                format!("{value} from header {header_name} is not a valid Scheduling header")
            })?;
            let result = self.set_scheduling(Some(sched)).await?;

            if remove {
                self.remove_all_named_headers(header_name).await?;
            }

            Ok(result)
        } else {
            Ok(None)
        }
    }

    pub async fn append_text_plain(&self, content: &str) -> anyhow::Result<bool> {
        let data = self.data().await?;
        let mut msg = MimePart::parse(data.as_ref().as_ref())?;
        let parts = msg.simplified_structure_pointers()?;
        if let Some(p) = parts.text_part.and_then(|p| msg.resolve_ptr_mut(p)) {
            match p.body()? {
                DecodedBody::Text(text) => {
                    let mut text = text.as_bytes().to_vec();
                    text.push_str("\r\n");
                    text.push_str(content);
                    p.replace_text_body("text/plain", &*text)?;

                    let new_data = msg.to_message_bytes();
                    self.assign_data(new_data);
                    Ok(true)
                }
                DecodedBody::Binary(_) => {
                    anyhow::bail!("expected text/plain part to be text, but it is binary");
                }
            }
        } else {
            Ok(false)
        }
    }

    pub async fn append_text_html(&self, content: &str) -> anyhow::Result<bool> {
        let data = self.data().await?;
        let mut msg = MimePart::parse(data.as_ref().as_ref())?;
        let parts = msg.simplified_structure_pointers()?;
        if let Some(p) = parts.html_part.and_then(|p| msg.resolve_ptr_mut(p)) {
            match p.body()? {
                DecodedBody::Text(text) => {
                    let mut text = text.as_bytes().to_vec();

                    match text.rfind("</body>").or_else(|| text.rfind("</BODY>")) {
                        Some(idx) => {
                            text.insert_str(idx, content);
                            text.insert_str(idx, "\r\n");
                        }
                        None => {
                            // Just append
                            text.push_str("\r\n");
                            text.push_str(content);
                        }
                    }

                    p.replace_text_body("text/html", &*text)?;

                    let new_data = msg.to_message_bytes();
                    self.assign_data(new_data);
                    Ok(true)
                }
                DecodedBody::Binary(_) => {
                    anyhow::bail!("expected text/html part to be text, but it is binary");
                }
            }
        } else {
            Ok(false)
        }
    }

    pub async fn check_fix_conformance(
        &self,
        check: MessageConformance,
        fix: MessageConformance,
        settings: Option<&CheckFixSettings>,
    ) -> anyhow::Result<()> {
        let data = self.data().await?;
        let data_bytes = data.as_ref().as_ref();
        let msg = MimePart::parse(data_bytes)?;

        let mut settings = settings.map(Clone::clone).unwrap_or_default();

        if fix.contains(MessageConformance::MISSING_MESSAGE_ID_HEADER)
            && settings.message_id.is_none()
            && matches!(msg.headers().message_id(), Err(_) | Ok(None))
        {
            let sender = self.sender().await?;
            let domain = sender.domain();
            let id = *self.id();
            settings.message_id.replace(format!("{id}@{domain}"));
        }

        if settings.detect_encoding {
            settings.data_bytes.replace(data.clone());
        }

        let opt_msg = msg.check_fix_conformance(check, fix, settings)?;

        if let Some(msg) = opt_msg {
            let new_data = msg.to_message_bytes();
            self.assign_data(new_data);
        }

        Ok(())
    }
}

fn imported_header_name(name: &str) -> String {
    name.chars()
        .map(|c| match c.to_ascii_lowercase() {
            '-' => '_',
            c => c,
        })
        .collect()
}

fn is_x_header(name: &[u8]) -> bool {
    name.starts_with_str("X-") || name.starts_with_str("x-")
}

#[derive(Default, Debug, Clone, Copy, Deserialize, Serialize, PartialEq, Eq)]
#[serde(rename_all = "snake_case")]
pub enum MatchMode {
    First,
    #[default]
    Last,
    All,
}

#[derive(Default, Debug, Clone, Copy, Deserialize, Serialize, PartialEq, Eq)]
#[serde(rename_all = "snake_case")]
pub enum NameTransform {
    #[default]
    SnakeCase,
    KebabCase,
    CamelCase,
    PascalCase,
}

#[derive(Debug, Clone, Deserialize)]
#[serde(deny_unknown_fields)]
pub struct ImportHeaderSpec {
    pub name: String,
    #[serde(default, rename = "match")]
    pub match_mode: MatchMode,
    #[serde(default)]
    pub transform: NameTransform,
    #[serde(default)]
    pub target: Option<String>,
    #[serde(default)]
    pub remove: bool,
}

impl Default for ImportHeaderSpec {
    fn default() -> Self {
        Self {
            name: String::new(),
            match_mode: MatchMode::default(),
            transform: NameTransform::default(),
            target: None,
            remove: false,
        }
    }
}

#[derive(Debug, Clone)]
enum HeaderPattern {
    /// Case-insensitive exact match.
    Exact(String),
    /// Matches any header whose name (case-insensitively) starts with the
    /// given prefix. Built from a pattern like `X-*`.
    Prefix(String),
}

#[derive(Debug, Clone)]
struct CompiledImportHeaderSpec {
    pattern: HeaderPattern,
    match_mode: MatchMode,
    transform: NameTransform,
    target: Option<String>,
    remove: bool,
}

impl CompiledImportHeaderSpec {
    fn compile(spec: ImportHeaderSpec) -> anyhow::Result<Self> {
        let pattern = compile_header_pattern(&spec.name)?;
        if spec.target.is_some() && matches!(pattern, HeaderPattern::Prefix(_)) {
            anyhow::bail!(
                "import_headers: `target` cannot be used with wildcard pattern {:?}",
                spec.name
            );
        }
        Ok(Self {
            pattern,
            match_mode: spec.match_mode,
            transform: spec.transform,
            target: spec.target,
            remove: spec.remove,
        })
    }

    fn matches(&self, hdr_name: &[u8]) -> bool {
        match &self.pattern {
            HeaderPattern::Exact(s) => hdr_name.eq_ignore_ascii_case(s.as_bytes()),
            HeaderPattern::Prefix(p) => {
                hdr_name.len() >= p.len() && hdr_name[..p.len()].eq_ignore_ascii_case(p.as_bytes())
            }
        }
    }

    fn target_key(&self, matched_name: &str) -> String {
        if let Some(target) = &self.target {
            return target.clone();
        }
        apply_name_transform(matched_name, self.transform)
    }
}

fn compile_header_pattern(pat: &str) -> anyhow::Result<HeaderPattern> {
    if pat.is_empty() {
        anyhow::bail!("import_headers: header name pattern must not be empty");
    }
    let star_count = pat.chars().filter(|c| *c == '*').count();
    if star_count == 0 {
        return Ok(HeaderPattern::Exact(pat.to_string()));
    }
    let Some(prefix) = pat.strip_suffix('*') else {
        anyhow::bail!(
            "import_headers: only a single trailing `*` is supported in pattern {:?}",
            pat
        );
    };
    if star_count > 1 {
        anyhow::bail!(
            "import_headers: only a single trailing `*` is supported in pattern {:?}",
            pat
        );
    }
    if prefix.is_empty() {
        anyhow::bail!("import_headers: bare `*` patterns are not supported");
    }
    Ok(HeaderPattern::Prefix(prefix.to_string()))
}

fn apply_name_transform(name: &str, transform: NameTransform) -> String {
    match transform {
        NameTransform::SnakeCase => imported_header_name(name),
        NameTransform::KebabCase => name
            .split('-')
            .map(|p| p.to_ascii_lowercase())
            .collect::<Vec<_>>()
            .join("-"),
        NameTransform::CamelCase => name
            .split('-')
            .enumerate()
            .map(|(i, p)| {
                if i == 0 {
                    p.to_ascii_lowercase()
                } else {
                    titlecase_ascii(p)
                }
            })
            .collect::<Vec<_>>()
            .join(""),
        NameTransform::PascalCase => name
            .split('-')
            .map(titlecase_ascii)
            .collect::<Vec<_>>()
            .join(""),
    }
}

fn titlecase_ascii(s: &str) -> String {
    let mut chars = s.chars();
    match chars.next() {
        None => String::new(),
        Some(first) => {
            let mut out = String::with_capacity(s.len());
            out.push(first.to_ascii_uppercase());
            for c in chars {
                out.push(c.to_ascii_lowercase());
            }
            out
        }
    }
}

enum AccValue {
    Str(String),
    Arr(Vec<String>),
}

struct PerSpecAccumulator {
    mode: MatchMode,
    by_key: BTreeMap<String, AccValue>,
}

impl PerSpecAccumulator {
    fn new(mode: MatchMode) -> Self {
        Self {
            mode,
            by_key: BTreeMap::new(),
        }
    }

    fn record(&mut self, key: String, value: String) {
        match self.mode {
            MatchMode::First => {
                self.by_key.entry(key).or_insert(AccValue::Str(value));
            }
            MatchMode::Last => {
                self.by_key.insert(key, AccValue::Str(value));
            }
            MatchMode::All => {
                let entry = self
                    .by_key
                    .entry(key)
                    .or_insert_with(|| AccValue::Arr(Vec::new()));
                if let AccValue::Arr(v) = entry {
                    v.push(value);
                }
            }
        }
    }

    async fn write_to(self, msg: &Message) -> anyhow::Result<()> {
        for (key, value) in self.by_key {
            match value {
                AccValue::Str(s) => msg.set_meta(key, s).await?,
                AccValue::Arr(arr) => {
                    let json = serde_json::Value::Array(
                        arr.into_iter().map(serde_json::Value::String).collect(),
                    );
                    msg.set_meta(key, json).await?;
                }
            }
        }
        Ok(())
    }
}

fn size_header(name: Option<&str>, value: &[u8]) -> usize {
    name.map(|name| name.len() + 2).unwrap_or(0) + value.len()
}

fn emit_header(dest: &mut Vec<u8>, name: Option<&str>, value: &[u8]) {
    if let Some(name) = name {
        dest.extend_from_slice(name.as_bytes());
        dest.extend_from_slice(b": ");
    }
    dest.extend_from_slice(value);
    if !value.ends_with_str("\r\n") {
        dest.extend_from_slice(b"\r\n");
    }
}

#[cfg(feature = "impl")]
impl UserData for Message {
    fn add_methods<M: UserDataMethods<Self>>(methods: &mut M) {
        methods.add_async_method(
            "set_meta",
            move |_, this, (name, value): (String, mlua::Value)| async move {
                let value = serde_json::value::to_value(value).map_err(any_err)?;
                this.set_meta(name, value).await.map_err(any_err)?;
                Ok(())
            },
        );
        methods.add_async_method("get_meta", move |lua, this, name: String| async move {
            let value = this.get_meta(name).await.map_err(any_err)?;
            Ok(Some(lua.to_value_with(&value, serialize_options())?))
        });
        methods.add_async_method("get_data", |lua, this, _: ()| async move {
            let data = this.data().await.map_err(any_err)?;
            lua.create_string(&*data)
        });
        methods.add_method("set_data", move |_lua, this, data: mlua::String| {
            this.assign_data(data.as_bytes().to_vec());
            Ok(())
        });

        methods.add_async_method("parse_mime", |_lua, this, _: ()| async move {
            let data = this.data().await.map_err(any_err)?;
            let owned_data = BString::new(data.as_ref().to_vec());
            let part = MimePart::parse(owned_data).map_err(any_err)?;
            Ok(mod_mimepart::PartRef::new(part))
        });

        methods.add_async_method("append_text_plain", |_lua, this, data: String| async move {
            this.append_text_plain(&data).await.map_err(any_err)
        });

        methods.add_async_method("append_text_html", |_lua, this, data: String| async move {
            this.append_text_html(&data).await.map_err(any_err)
        });

        methods.add_method("id", move |_, this, _: ()| Ok(this.id().to_string()));
        methods.add_async_method("sender", move |_, this, _: ()| async move {
            this.sender().await.map_err(any_err)
        });

        methods.add_method("num_attempts", move |_, this, _: ()| {
            Ok(this.get_num_attempts())
        });
        methods.add_method("increment_num_attempts", move |_, this, _: ()| {
            Ok(this.increment_num_attempts())
        });

        methods.add_async_method("queue_name", move |_, this, _: ()| async move {
            this.get_queue_name().await.map_err(any_err)
        });

        methods.add_async_method("set_due", move |lua, this, due: mlua::Value| async move {
            let due: Option<DateTime<Utc>> = lua.from_value(due)?;
            let revised_due = this.set_due(due).await.map_err(any_err)?;
            lua.to_value(&revised_due)
        });

        methods.add_async_method(
            "set_sender",
            move |lua, this, value: mlua::Value| async move {
                let sender = match value {
                    mlua::Value::String(s) => {
                        let s = s.to_str()?;
                        EnvelopeAddress::parse(&s).map_err(any_err)?
                    }
                    _ => lua.from_value::<EnvelopeAddress>(value.clone())?,
                };
                this.set_sender(sender).await.map_err(any_err)
            },
        );

        methods.add_async_method("recipient", move |lua, this, _: ()| async move {
            let mut recipients = this.recipient_list().await.map_err(any_err)?;
            match recipients.len() {
                0 => Ok(mlua::Value::Nil),
                1 => {
                    let recip: EnvelopeAddress = recipients.pop().expect("have 1");
                    recip.into_lua(&lua)
                }
                _ => recipients.into_lua(&lua),
            }
        });

        methods.add_async_method("recipient_list", move |lua, this, _: ()| async move {
            let recipients = this.recipient_list().await.map_err(any_err)?;
            recipients.into_lua(&lua)
        });

        methods.add_async_method(
            "set_recipient",
            move |lua, this, value: mlua::Value| async move {
                let recipients = match value {
                    mlua::Value::String(s) => {
                        let s = s.to_str()?;
                        vec![EnvelopeAddress::parse(&s).map_err(any_err)?]
                    }
                    _ => {
                        if let Ok(recips) = lua.from_value::<Vec<EnvelopeAddress>>(value.clone()) {
                            recips
                        } else {
                            vec![lua.from_value::<EnvelopeAddress>(value.clone())?]
                        }
                    }
                };
                this.set_recipient_list(recipients).await.map_err(any_err)
            },
        );

        #[cfg(feature = "impl")]
        methods.add_async_method("dkim_sign", |_, this, signer: Signer| async move {
            this.dkim_sign(signer).await.map_err(any_err)
        });

        methods.add_async_method("shrink", |_, this, _: ()| async move {
            if this.needs_save() {
                this.save(None).await.map_err(any_err)?;
            }
            this.shrink().map_err(any_err)
        });

        methods.add_async_method("shrink_data", |_, this, _: ()| async move {
            if this.needs_save() {
                this.save(None).await.map_err(any_err)?;
            }
            this.shrink_data().map_err(any_err)
        });

        methods.add_async_method(
            "add_authentication_results",
            |lua, this, (serv_id, results): (mlua::String, mlua::Value)| async move {
                let results: Vec<AuthenticationResult> = lua.from_value(results)?;
                let results = AuthenticationResults {
                    serv_id: serv_id.as_bytes().as_ref().into(),
                    version: None,
                    results,
                };

                this.prepend_header(
                    Some("Authentication-Results"),
                    results.encode_value().as_bytes(),
                )
                .await
                .map_err(any_err)?;

                Ok(())
            },
        );

        #[cfg(feature = "impl")]
        methods.add_async_method(
            "arc_verify",
            |lua, this, opt_resolver_name: Option<String>| async move {
                let results = this.arc_verify(opt_resolver_name).await.map_err(any_err)?;
                lua.to_value_with(&results, serialize_options())
            },
        );

        #[cfg(feature = "impl")]
        methods.add_async_method(
            "arc_seal",
            |lua,
             this,
             (signer, serv_id, auth_res, opt_resolver_name): (
                Signer,
                mlua::String,
                mlua::Value,
                Option<String>,
            )| async move {
                let results: Vec<AuthenticationResult> = lua.from_value(auth_res)?;
                this.arc_seal(
                    signer,
                    AuthenticationResults {
                        serv_id: serv_id.as_bytes().as_ref().into(),
                        version: None,
                        results,
                    },
                    opt_resolver_name,
                )
                .await
                .map_err(any_err)
            },
        );

        #[cfg(feature = "impl")]
        methods.add_async_method(
            "dkim_verify",
            |lua, this, opt_resolver_name: Option<String>| async move {
                let results = this.dkim_verify(opt_resolver_name).await.map_err(any_err)?;
                lua.to_value_with(&results, serialize_options())
            },
        );

        methods.add_async_method(
            "prepend_header",
            |_, this, (name, value, encode): (String, String, Option<bool>)| async move {
                let encode = encode.unwrap_or(false);
                if encode {
                    let header = Header::new_unstructured(name.clone(), value);
                    this.prepend_header(Some(&name), header.get_raw_value())
                        .await
                        .map_err(any_err)?;
                } else {
                    this.prepend_header(Some(&name), value.as_bytes())
                        .await
                        .map_err(any_err)?;
                }
                Ok(())
            },
        );
        methods.add_async_method(
            "append_header",
            |_, this, (name, value, encode): (String, String, Option<bool>)| async move {
                let encode = encode.unwrap_or(false);
                if encode {
                    let header = Header::new_unstructured(name.clone(), value);
                    this.append_header(Some(&name), header.get_raw_value())
                        .await
                        .map_err(any_err)?;
                } else {
                    this.append_header(Some(&name), value.as_bytes())
                        .await
                        .map_err(any_err)?;
                }
                Ok(())
            },
        );
        methods.add_async_method("get_address_header", |_, this, name: String| async move {
            this.get_address_header(&name).await.map_err(any_err)
        });
        methods.add_async_method("from_header", |_, this, ()| async move {
            this.get_address_header("From").await.map_err(any_err)
        });
        methods.add_async_method("to_header", |_, this, ()| async move {
            this.get_address_header("To").await.map_err(any_err)
        });

        methods.add_async_method(
            "get_first_named_header_value",
            |_, this, name: String| async move {
                this.get_first_named_header_value(&name)
                    .await
                    .map_err(any_err)
            },
        );
        methods.add_async_method(
            "get_all_named_header_values",
            |_, this, name: String| async move {
                this.get_all_named_header_values(&name)
                    .await
                    .map_err(any_err)
            },
        );
        methods.add_async_method("get_all_headers", |_, this, _: ()| async move {
            Ok(this
                .get_all_headers()
                .await
                .map_err(any_err)?
                .into_iter()
                .map(|(name, value)| vec![name, value])
                .collect::<Vec<Vec<BString>>>())
        });
        methods.add_async_method(
            "import_x_headers",
            |_, this, names: Option<Vec<String>>| async move {
                this.import_x_headers(names.unwrap_or_default())
                    .await
                    .map_err(any_err)
            },
        );
        methods.add_async_method(
            "import_headers",
            |_, this, specs: SerdeWrappedValue<Vec<ImportHeaderSpec>>| async move {
                this.import_headers(specs.0).await.map_err(any_err)
            },
        );

        methods.add_async_method(
            "remove_x_headers",
            |_, this, names: Option<Vec<String>>| async move {
                this.remove_x_headers(names.unwrap_or_default())
                    .await
                    .map_err(any_err)
            },
        );
        methods.add_async_method(
            "remove_all_named_headers",
            |_, this, name: String| async move {
                this.remove_all_named_headers(&name).await.map_err(any_err)
            },
        );

        methods.add_async_method(
            "import_scheduling_header",
            |lua, this, (header_name, remove): (String, bool)| async move {
                let opt_schedule = this
                    .import_scheduling_header(&header_name, remove)
                    .await
                    .map_err(any_err)?;
                lua.to_value(&opt_schedule)
            },
        );

        methods.add_async_method(
            "set_scheduling",
            move |lua, this, params: mlua::Value| async move {
                let sched: Option<Scheduling> = from_lua_value(&lua, params)?;
                let opt_schedule = this.set_scheduling(sched).await.map_err(any_err)?;
                lua.to_value(&opt_schedule)
            },
        );

        methods.add_async_method("parse_rfc3464", |lua, this, _: ()| async move {
            let report = this.parse_rfc3464().await.map_err(any_err)?;
            match report {
                Some(report) => lua.to_value_with(&report, serialize_options()),
                None => Ok(mlua::Value::Nil),
            }
        });

        methods.add_async_method("parse_rfc5965", |lua, this, _: ()| async move {
            let report = this.parse_rfc5965().await.map_err(any_err)?;
            match report {
                Some(report) => lua.to_value_with(&report, serialize_options()),
                None => Ok(mlua::Value::Nil),
            }
        });

        methods.add_async_method("save", |_, this, ()| async move {
            this.save(None).await.map_err(any_err)
        });

        methods.add_method("set_force_sync", move |_, this, force: bool| {
            this.set_force_sync(force);
            Ok(())
        });

        methods.add_async_method(
            "check_fix_conformance",
            |lua, this, (check, fix, settings): (String, String, Option<mlua::Value>)| async move {
                use std::str::FromStr;
                let check = MessageConformance::from_str(&check).map_err(any_err)?;
                let fix = MessageConformance::from_str(&fix).map_err(any_err)?;

                let settings = match settings {
                    Some(v) => Some(lua.from_value(v).map_err(any_err)?),
                    None => None,
                };

                match this
                    .check_fix_conformance(check, fix, settings.as_ref())
                    .await
                {
                    Ok(_) => Ok(None),
                    Err(err) => Ok(Some(format!("{err:#}"))),
                }
            },
        );
    }
}

impl TimerEntryWithDelay for WeakMessage {
    fn delay(&self) -> Duration {
        match self.upgrade() {
            None => {
                // Dangling/Cancelled. Make it appear due immediately
                Duration::from_millis(0)
            }
            Some(msg) => msg.delay(),
        }
    }
}

impl TimerEntryWithDelay for Message {
    fn delay(&self) -> Duration {
        let inner = self.msg_and_id.inner.lock();
        match inner.due {
            Some(time) => {
                let now = Utc::now();
                let delta = time - now;
                delta.to_std().unwrap_or(Duration::from_millis(0))
            }
            None => Duration::from_millis(0),
        }
    }
}

#[cfg(test)]
pub(crate) mod test {
    use super::*;
    use serde_json::json;

    pub fn new_msg_body<S: AsRef<[u8]>>(s: S) -> Message {
        Message::new_dirty(
            SpoolId::new(),
            EnvelopeAddress::parse("sender@example.com").unwrap(),
            vec![EnvelopeAddress::parse("recip@example.com").unwrap()],
            serde_json::json!({}),
            Arc::new(s.as_ref().to_vec().into_boxed_slice()),
        )
        .unwrap()
    }

    fn data_as_string(msg: &Message) -> String {
        String::from_utf8(msg.get_data_maybe_not_loaded().to_vec()).unwrap()
    }

    const X_HDR_CONTENT: &str =
        "X-Hello: there\r\nX-Header: value\r\nSubject: Hello\r\nFrom :Someone\r\n\r\nBody";

    #[tokio::test]
    async fn import_all_x_headers() {
        let msg = new_msg_body(X_HDR_CONTENT);

        msg.import_x_headers(vec![]).await.unwrap();
        k9::assert_equal!(
            msg.get_meta_obj().await.unwrap(),
            json!({
                "x_hello": "there",
                "x_header": "value",
            })
        );
    }

    #[tokio::test]
    async fn meta_and_nil() {
        let msg = new_msg_body(X_HDR_CONTENT);
        // Ensure that json null round-trips
        msg.set_meta("test", serde_json::Value::Null).await.unwrap();
        k9::assert_equal!(msg.get_meta("test").await.unwrap(), serde_json::Value::Null);

        // and that it is exposed to lua as nil
        let lua = mlua::Lua::new();
        lua.globals().set("msg", msg).unwrap();
        lua.load("assert(msg:get_meta('test') == nil)")
            .exec()
            .unwrap();
    }

    #[tokio::test]
    async fn import_some_x_headers() {
        let msg = new_msg_body(X_HDR_CONTENT);

        msg.import_x_headers(vec!["x-hello".to_string()])
            .await
            .unwrap();
        k9::assert_equal!(
            msg.get_meta_obj().await.unwrap(),
            json!({
                "x_hello": "there",
            })
        );
    }

    #[tokio::test]
    async fn import_headers_wildcard_remove() {
        let msg = new_msg_body(X_HDR_CONTENT);

        msg.import_headers(vec![ImportHeaderSpec {
            name: "X-*".to_string(),
            remove: true,
            ..ImportHeaderSpec::default()
        }])
        .await
        .unwrap();
        k9::assert_equal!(
            msg.get_meta_obj().await.unwrap(),
            json!({
                "x_hello": "there",
                "x_header": "value",
            })
        );
        k9::assert_equal!(
            data_as_string(&msg),
            "Subject: Hello\r\nFrom :Someone\r\n\r\nBody"
        );
    }

    #[tokio::test]
    async fn import_headers_match_modes() {
        let body =
            "Received: from a\r\nReceived: from b\r\nReceived: from c\r\nSubject: hi\r\n\r\nBody";
        for (mode, expected) in [
            (MatchMode::First, json!("from a")),
            (MatchMode::Last, json!("from c")),
            (MatchMode::All, json!(["from a", "from b", "from c"])),
        ] {
            let msg = new_msg_body(body);
            msg.import_headers(vec![ImportHeaderSpec {
                name: "Received".to_string(),
                match_mode: mode,
                ..ImportHeaderSpec::default()
            }])
            .await
            .unwrap();
            k9::assert_equal!(
                msg.get_meta_obj().await.unwrap(),
                json!({ "received": expected })
            );
        }
    }

    #[tokio::test]
    async fn import_headers_no_match_skips_meta() {
        let msg = new_msg_body(X_HDR_CONTENT);
        msg.import_headers(vec![ImportHeaderSpec {
            name: "Nonexistent".to_string(),
            match_mode: MatchMode::All,
            ..ImportHeaderSpec::default()
        }])
        .await
        .unwrap();
        k9::assert_equal!(msg.get_meta_obj().await.unwrap(), json!({}));
    }

    #[tokio::test]
    async fn import_headers_specific_before_wildcard() {
        let body = "X-Campaign-Id: 42\r\nX-Mailer: foo\r\n\r\nBody";
        let msg = new_msg_body(body);
        msg.import_headers(vec![
            ImportHeaderSpec {
                name: "X-Campaign-Id".to_string(),
                target: Some("campaign".to_string()),
                ..ImportHeaderSpec::default()
            },
            ImportHeaderSpec {
                name: "X-*".to_string(),
                ..ImportHeaderSpec::default()
            },
        ])
        .await
        .unwrap();
        k9::assert_equal!(
            msg.get_meta_obj().await.unwrap(),
            json!({
                "campaign": "42",
                "x_mailer": "foo",
            })
        );
    }

    #[test]
    fn name_transforms() {
        let n = "X-Campaign-Id";
        k9::assert_equal!(
            apply_name_transform(n, NameTransform::SnakeCase),
            "x_campaign_id"
        );
        k9::assert_equal!(
            apply_name_transform(n, NameTransform::KebabCase),
            "x-campaign-id"
        );
        k9::assert_equal!(
            apply_name_transform(n, NameTransform::CamelCase),
            "xCampaignId"
        );
        k9::assert_equal!(
            apply_name_transform(n, NameTransform::PascalCase),
            "XCampaignId"
        );
    }

    #[test]
    fn pattern_compile_rejects_bad_patterns() {
        compile_header_pattern("").unwrap_err();
        compile_header_pattern("*").unwrap_err();
        compile_header_pattern("*-Id").unwrap_err();
        compile_header_pattern("X-*-Id").unwrap_err();
        compile_header_pattern("X-**").unwrap_err();
        assert!(matches!(
            compile_header_pattern("Subject").unwrap(),
            HeaderPattern::Exact(_)
        ));
        assert!(matches!(
            compile_header_pattern("X-*").unwrap(),
            HeaderPattern::Prefix(_)
        ));
    }

    #[tokio::test]
    async fn import_headers_target_with_wildcard_rejected() {
        let msg = new_msg_body(X_HDR_CONTENT);
        msg.import_headers(vec![ImportHeaderSpec {
            name: "X-*".to_string(),
            target: Some("oops".to_string()),
            ..ImportHeaderSpec::default()
        }])
        .await
        .unwrap_err();
    }

    #[tokio::test]
    async fn remove_all_x_headers() {
        let msg = new_msg_body(X_HDR_CONTENT);

        msg.remove_x_headers(vec![]).await.unwrap();
        k9::assert_equal!(
            data_as_string(&msg),
            "Subject: Hello\r\nFrom :Someone\r\n\r\nBody"
        );
    }

    #[tokio::test]
    async fn prepend_header_2_params() {
        let msg = new_msg_body(X_HDR_CONTENT);

        msg.prepend_header(Some("Date"), b"Today").await.unwrap();
        k9::assert_equal!(
            data_as_string(&msg),
            "Date: Today\r\nX-Hello: there\r\nX-Header: value\r\nSubject: Hello\r\nFrom :Someone\r\n\r\nBody"
        );
    }

    #[tokio::test]
    async fn prepend_header_1_params() {
        let msg = new_msg_body(X_HDR_CONTENT);

        msg.prepend_header(None, b"Date: Today").await.unwrap();
        k9::assert_equal!(
            data_as_string(&msg),
            "Date: Today\r\nX-Hello: there\r\nX-Header: value\r\nSubject: Hello\r\nFrom :Someone\r\n\r\nBody"
        );
    }

    #[tokio::test]
    async fn append_header_2_params() {
        let msg = new_msg_body(X_HDR_CONTENT);

        msg.append_header(Some("Date"), b"Today").await.unwrap();
        k9::assert_equal!(
            data_as_string(&msg),
            "X-Hello: there\r\nX-Header: value\r\nSubject: Hello\r\nFrom :Someone\r\nDate: Today\r\n\r\nBody"
        );
    }

    #[tokio::test]
    async fn append_header_1_params() {
        let msg = new_msg_body(X_HDR_CONTENT);

        msg.append_header(None, b"Date: Today").await.unwrap();
        k9::assert_equal!(
            data_as_string(&msg),
            "X-Hello: there\r\nX-Header: value\r\nSubject: Hello\r\nFrom :Someone\r\nDate: Today\r\n\r\nBody"
        );
    }

    const MULTI_HEADER_CONTENT: &str =
        "X-Hello: there\r\nX-Header: value\r\nSubject: Hello\r\nX-Header: another value\r\nFrom :Someone@somewhere\r\n\r\nBody";

    #[tokio::test]
    async fn get_first_header() {
        let msg = new_msg_body(MULTI_HEADER_CONTENT);
        k9::assert_equal!(
            msg.get_first_named_header_value("X-header")
                .await
                .unwrap()
                .unwrap(),
            "value"
        );
    }

    #[tokio::test]
    async fn get_all_header() {
        let msg = new_msg_body(MULTI_HEADER_CONTENT);
        k9::assert_equal!(
            msg.get_all_named_header_values("X-header").await.unwrap(),
            vec!["value".to_string(), "another value".to_string()]
        );
    }

    #[tokio::test]
    async fn remove_first() {
        let msg = new_msg_body(MULTI_HEADER_CONTENT);
        msg.remove_first_named_header("X-header").await.unwrap();
        k9::assert_equal!(
            data_as_string(&msg),
            "X-Hello: there\r\nSubject: Hello\r\nX-Header: another value\r\nFrom :Someone@somewhere\r\n\r\nBody"
        );
    }

    #[tokio::test]
    async fn remove_all() {
        let msg = new_msg_body(MULTI_HEADER_CONTENT);
        msg.remove_all_named_headers("X-header").await.unwrap();
        k9::assert_equal!(
            data_as_string(&msg),
            "X-Hello: there\r\nSubject: Hello\r\nFrom :Someone@somewhere\r\n\r\nBody"
        );
    }

    #[tokio::test]
    async fn append_text_plain() {
        let msg = new_msg_body(MULTI_HEADER_CONTENT);
        msg.append_text_plain("I am at the bottom").await.unwrap();
        k9::assert_equal!(
            data_as_string(&msg),
            "X-Hello: there\r\n\
             X-Header: value\r\n\
             Subject: Hello\r\n\
             X-Header: another value\r\n\
             From :Someone@somewhere\r\n\
             Content-Type: text/plain;\r\n\
             \tcharset=\"us-ascii\"\r\n\
             \r\n\
             Body\r\n\
             I am at the bottom\r\n"
        );
    }

    const MIXED_CONTENT: &str = "Content-Type: multipart/mixed;\r\n\
\tboundary=\"my-boundary\"\r\n\
\r\n\
--my-boundary\r\n\
Content-Type: text/plain;\r\n\
\tcharset=\"us-ascii\"\r\n\
\r\n\
plain text\r\n\
--my-boundary\r\n\
Content-Type: text/html;\r\n\
\tcharset=\"us-ascii\"\r\n\
\r\n\
<b>rich</b> text\r\n\
--my-boundary\r\n\
Content-Type: application/octet-stream\r\n\
Content-Transfer-Encoding: base64\r\n\
Content-Disposition: attachment;\r\n\
\tfilename=\"woot.bin\"\r\n\
Content-ID: <woot.id@somewhere>\r\n\
\r\n\
AAECAw==\r\n\
--my-boundary--\r\n\
\r\n";

    const MIXED_CONTENT_ENCLOSING_BODY: &str = "Content-Type: multipart/mixed;\r\n\
\tboundary=\"my-boundary\"\r\n\
\r\n\
--my-boundary\r\n\
Content-Type: text/plain;\r\n\
\tcharset=\"us-ascii\"\r\n\
\r\n\
plain text\r\n\
--my-boundary\r\n\
Content-Type: text/html;\r\n\
\tcharset=\"us-ascii\"\r\n\
\r\n\
<BODY>\r\n\
<b>rich</b> text\r\n\
</BODY>\r\n\
--my-boundary\r\n\
Content-Type: application/octet-stream\r\n\
Content-Transfer-Encoding: base64\r\n\
Content-Disposition: attachment;\r\n\
\tfilename=\"woot.bin\"\r\n\
Content-ID: <woot.id>\r\n\
\r\n\
AAECAw==\r\n\
--my-boundary--\r\n\
\r\n";

    #[tokio::test]
    async fn append_text_html() {
        let msg = new_msg_body(MIXED_CONTENT);
        msg.append_text_html("bottom html").await.unwrap();
        k9::snapshot!(
            data_as_string(&msg),
            r#"
Content-Type: multipart/mixed;\r
\tboundary="my-boundary"\r
\r
--my-boundary\r
Content-Type: text/plain;\r
\tcharset="us-ascii"\r
\r
plain text\r
--my-boundary\r
Content-Type: text/html;\r
\tcharset="us-ascii"\r
\r
<b>rich</b> text\r
\r
bottom html\r
--my-boundary\r
Content-Type: application/octet-stream\r
Content-Transfer-Encoding: base64\r
Content-Disposition: attachment;\r
\tfilename="woot.bin"\r
Content-ID: <woot.id@somewhere>\r
\r
AAECAw==\r
--my-boundary--\r
\r

"#
        );

        let msg = new_msg_body(MIXED_CONTENT_ENCLOSING_BODY);
        msg.append_text_html("bottom html 👻").await.unwrap();
        k9::snapshot!(
            data_as_string(&msg),
            r#"
Content-Type: multipart/mixed;\r
\tboundary="my-boundary"\r
\r
--my-boundary\r
Content-Type: text/plain;\r
\tcharset="us-ascii"\r
\r
plain text\r
--my-boundary\r
Content-Type: text/html;\r
\tcharset="utf-8"\r
Content-Transfer-Encoding: quoted-printable\r
\r
<BODY>\r
<b>rich</b> text\r
\r
bottom html =F0=9F=91=BB</BODY>\r
--my-boundary\r
Content-Type: application/octet-stream\r
Content-Transfer-Encoding: base64\r
Content-Disposition: attachment;\r
\tfilename="woot.bin"\r
Content-ID: <woot.id>\r
\r
AAECAw==\r
--my-boundary--\r
\r

"#
        );
    }

    #[tokio::test]
    async fn append_text_plain_mixed() {
        let msg = new_msg_body(MIXED_CONTENT);
        msg.append_text_plain("bottom text 👾").await.unwrap();
        k9::snapshot!(
            data_as_string(&msg),
            r#"
Content-Type: multipart/mixed;\r
\tboundary="my-boundary"\r
\r
--my-boundary\r
Content-Type: text/plain;\r
\tcharset="utf-8"\r
Content-Transfer-Encoding: quoted-printable\r
\r
plain text\r
\r
bottom text =F0=9F=91=BE\r
--my-boundary\r
Content-Type: text/html;\r
\tcharset="us-ascii"\r
\r
<b>rich</b> text\r
--my-boundary\r
Content-Type: application/octet-stream\r
Content-Transfer-Encoding: base64\r
Content-Disposition: attachment;\r
\tfilename="woot.bin"\r
Content-ID: <woot.id@somewhere>\r
\r
AAECAw==\r
--my-boundary--\r
\r

"#
        );
    }

    #[tokio::test]
    async fn check_conformance_angle_msg_id() {
        const DOUBLE_ANGLE_ONLY: &str = "Subject: hello\r
Message-ID: <<1234@example.com>>\r
\r
Hello";
        let msg = new_msg_body(DOUBLE_ANGLE_ONLY);
        k9::snapshot!(
            msg.check_fix_conformance(
                MessageConformance::MISSING_MESSAGE_ID_HEADER,
                MessageConformance::empty(),
                None,
            )
            .await
            .unwrap_err()
            .to_string(),
            "Message has conformance issues: MISSING_MESSAGE_ID_HEADER"
        );

        msg.check_fix_conformance(
            MessageConformance::MISSING_MESSAGE_ID_HEADER,
            MessageConformance::MISSING_MESSAGE_ID_HEADER,
            None,
        )
        .await
        .unwrap();

        // Can't use a snapshot test here because the fixed header
        // has a unique random component
        /*
                k9::snapshot!(
                    data_as_string(&msg),
                    r#"
        Subject: hello\r
        Message-ID: <4106566d2ce911ef9dcd0242289ea0df@example.com>\r
        \r
        Hello
        "#
                );
        */

        const DOUBLE_ANGLE_AND_LONG_LINE: &str = "Subject: hello\r
Message-ID: <<1234@example.com>>\r
\r
Hello this is a really long line Hello this is a really long line \
Hello this is a really long line Hello this is a really long line \
Hello this is a really long line Hello this is a really long line \
Hello this is a really long line Hello this is a really long line \
Hello this is a really long line Hello this is a really long line \
Hello this is a really long line Hello this is a really long line \
Hello this is a really long line Hello this is a really long line
";
        let msg = new_msg_body(DOUBLE_ANGLE_AND_LONG_LINE);
        msg.check_fix_conformance(
            MessageConformance::MISSING_COLON_VALUE,
            MessageConformance::MISSING_MESSAGE_ID_HEADER | MessageConformance::LINE_TOO_LONG,
            None,
        )
        .await
        .unwrap();

        // Can't use a snapshot test here because the fixed header
        // has a random component
        /*
                k9::snapshot!(
                    data_as_string(&msg),
                    r#"
        Content-Type: text/plain;\r
        \tcharset="us-ascii"\r
        Content-Transfer-Encoding: quoted-printable\r
        Subject: hello\r
        Message-ID: <749fc87e2cea11ef96a50242289ea0df@example.com>\r
        \r
        Hello this is a really long line Hello this is a really long line Hello thi=\r
        s is a really long line Hello this is a really long line Hello this is a re=\r
        ally long line Hello this is a really long line Hello this is a really long=\r
         line Hello this is a really long line Hello this is a really long line Hel=\r
        lo this is a really long line Hello this is a really long line Hello this i=\r
        s a really long line Hello this is a really long line Hello this is a reall=\r
        y long line=0A\r

        "#
                );
        */
    }

    #[tokio::test]
    async fn check_conformance() {
        let msg = new_msg_body(MULTI_HEADER_CONTENT);
        msg.check_fix_conformance(
            MessageConformance::default(),
            MessageConformance::MISSING_MIME_VERSION,
            None,
        )
        .await
        .unwrap();
        k9::snapshot!(
            data_as_string(&msg),
            r#"
X-Hello: there\r
X-Header: value\r
Subject: Hello\r
X-Header: another value\r
From :Someone@somewhere\r
Mime-Version: 1.0\r
\r
Body
"#
        );

        let msg = new_msg_body(MULTI_HEADER_CONTENT);
        msg.check_fix_conformance(
            MessageConformance::default(),
            MessageConformance::MISSING_MIME_VERSION | MessageConformance::NAME_ENDS_WITH_SPACE,
            None,
        )
        .await
        .unwrap();
        k9::snapshot!(
            data_as_string(&msg),
            r#"
Content-Type: text/plain;\r
\tcharset="us-ascii"\r
X-Hello: there\r
X-Header: value\r
Subject: Hello\r
X-Header: another value\r
From: <Someone@somewhere>\r
Mime-Version: 1.0\r
\r
Body\r

"#
        );
    }

    #[tokio::test]
    async fn check_fix_latin_input() {
        const POUNDS: &[u8] = b"Subject: \xa3\r\n\r\nGBP\r\n";
        let msg = new_msg_body(&*POUNDS);
        msg.check_fix_conformance(
            MessageConformance::default(),
            MessageConformance::NEEDS_TRANSFER_ENCODING,
            Some(&CheckFixSettings {
                detect_encoding: true,
                include_encodings: vec!["iso-8859-1".to_string()],
                ..Default::default()
            }),
        )
        .await
        .unwrap();

        let subject = msg
            .get_first_named_header_value("subject")
            .await
            .unwrap()
            .unwrap();
        assert_eq!(subject, "£");
    }

    #[tokio::test]
    async fn set_scheduling() -> anyhow::Result<()> {
        let msg = new_msg_body(MULTI_HEADER_CONTENT);
        assert!(msg.get_due().is_none(), "due is implicitly now");

        let now = Utc::now();
        let one_day = chrono::Duration::try_days(1).expect("1 day to be valid");

        msg.set_scheduling(Some(Scheduling {
            restriction: None,
            first_attempt: Some((now + one_day).into()),
            expires: None,
        }))
        .await?;

        let due = msg.get_due().expect("due to now be set");
        assert!(due - now >= one_day, "due time is at least 1 day away");

        Ok(())
    }

    #[cfg(all(test, target_pointer_width = "64"))]
    #[test]
    fn sizes() {
        assert_eq!(std::mem::size_of::<Message>(), 8);
        assert_eq!(std::mem::size_of::<MessageInner>(), 32);
        assert_eq!(std::mem::size_of::<MessageWithId>(), 72);
    }
}