#![cfg(feature = "client")]
use hickory_proto::rr::rdata::TLSA;
use lruttl::LruCacheWithTtl;
use openssl::ssl::SslOptions;
use parking_lot::Mutex;
use std::sync::{Arc, LazyLock};
use std::time::{Duration, Instant};
use tokio_rustls::rustls::client::danger::ServerCertVerifier;
use tokio_rustls::rustls::crypto::{aws_lc_rs as provider, CryptoProvider};
use tokio_rustls::rustls::{ClientConfig, SupportedCipherSuite};
use tokio_rustls::TlsConnector;

struct RustlsCacheKey {
    insecure: bool,
    rustls_cipher_suites: Vec<SupportedCipherSuite>,
}

// SupportedCipherSuite has a PartialEq impl but not an Eq impl.
// Since we need RustlsCacheKey to be Hash we cannot simply derive
// PartialEq and then add an explicit impl for Eq on RustlsCacheKey
// because we don't know the implementation details of the underlying
// PartialEq impl. So we define our own here where we explicitly compare
// the suite names. This may not be strictly necessary, but it seems
// wise to be robust to possible future weirdness in that type, and
// to be certain that our Hash impl is consistent with the Eq impl.
impl std::cmp::PartialEq for RustlsCacheKey {
    fn eq(&self, other: &RustlsCacheKey) -> bool {
        if self.insecure != other.insecure {
            return false;
        }
        self.rustls_cipher_suites
            .iter()
            .map(|s| s.suite())
            .eq(other.rustls_cipher_suites.iter().map(|s| s.suite()))
    }
}

impl std::cmp::Eq for RustlsCacheKey {}

impl std::hash::Hash for RustlsCacheKey {
    fn hash<H>(&self, hasher: &mut H)
    where
        H: std::hash::Hasher,
    {
        self.insecure.hash(hasher);
        for suite in &self.rustls_cipher_suites {
            suite.suite().as_str().hash(hasher);
        }
    }
}

static RUSTLS_CACHE: LazyLock<Mutex<LruCacheWithTtl<RustlsCacheKey, Arc<ClientConfig>>>> =
    LazyLock::new(|| Mutex::new(LruCacheWithTtl::new(32)));

impl RustlsCacheKey {
    fn get(&self) -> Option<Arc<ClientConfig>> {
        RUSTLS_CACHE.lock().get(self)
    }

    fn set(self, value: Arc<ClientConfig>) {
        RUSTLS_CACHE.lock().insert(
            self,
            value,
            // We allow the state to be cached for up to 15 minutes at
            // a time so that we have an opportunity to reload the
            // system certificates within a reasonable time frame
            // as/when they are updated by the system.
            Instant::now() + Duration::from_secs(15 * 60),
        );
    }
}

#[derive(Debug, Clone, Default)]
pub struct TlsOptions {
    pub insecure: bool,
    pub alt_name: Option<String>,
    pub dane_tlsa: Vec<TLSA>,
    pub prefer_openssl: bool,
    pub openssl_cipher_list: Option<String>,
    pub openssl_cipher_suites: Option<String>,
    pub openssl_options: Option<SslOptions>,
    pub rustls_cipher_suites: Vec<SupportedCipherSuite>,
}

impl TlsOptions {
    /// Produce a TlsConnector for this set of TlsOptions.
    /// We need to employ a cache around the verifier as loading
    /// the system certificate store can be a non-trivial operation
    /// and not be something we want to do repeatedly in a hot code
    /// path.  The cache does unfortunately complicate some of the
    /// internals here.
    pub fn build_tls_connector(&self) -> TlsConnector {
        let key = RustlsCacheKey {
            insecure: self.insecure,
            rustls_cipher_suites: self.rustls_cipher_suites.clone(),
        };

        if let Some(config) = key.get() {
            return TlsConnector::from(config);
        }
        let cipher_suites = if self.rustls_cipher_suites.is_empty() {
            provider::DEFAULT_CIPHER_SUITES
        } else {
            &self.rustls_cipher_suites
        };

        let provider = Arc::new(CryptoProvider {
            cipher_suites: cipher_suites.to_vec(),
            ..provider::default_provider()
        });

        let verifier: Arc<dyn ServerCertVerifier> = if self.insecure {
            Arc::new(danger::NoCertificateVerification::new(provider.clone()))
        } else {
            Arc::new(rustls_platform_verifier::Verifier::new().with_provider(provider.clone()))
        };

        let config = Arc::new(
            ClientConfig::builder_with_provider(provider)
                .with_protocol_versions(tokio_rustls::rustls::DEFAULT_VERSIONS)
                .expect("inconsistent cipher-suite/versions selected")
                .dangerous()
                .with_custom_certificate_verifier(verifier)
                .with_no_client_auth(),
        );
        key.set(config.clone());

        TlsConnector::from(config)
    }
}

mod danger {
    use std::sync::Arc;
    use tokio_rustls::rustls::client::danger::{
        HandshakeSignatureValid, ServerCertVerified, ServerCertVerifier,
    };
    use tokio_rustls::rustls::crypto::{
        verify_tls12_signature, verify_tls13_signature, CryptoProvider,
    };
    use tokio_rustls::rustls::pki_types::{CertificateDer, ServerName, UnixTime};
    use tokio_rustls::rustls::DigitallySignedStruct;

    #[derive(Debug)]
    pub struct NoCertificateVerification(Arc<CryptoProvider>);

    impl NoCertificateVerification {
        pub fn new(provider: Arc<CryptoProvider>) -> Self {
            Self(provider)
        }
    }

    impl ServerCertVerifier for NoCertificateVerification {
        fn verify_server_cert(
            &self,
            _end_entity: &CertificateDer<'_>,
            _intermediates: &[CertificateDer<'_>],
            _server_name: &ServerName<'_>,
            _ocsp: &[u8],
            _now: UnixTime,
        ) -> Result<ServerCertVerified, tokio_rustls::rustls::Error> {
            Ok(ServerCertVerified::assertion())
        }

        fn verify_tls12_signature(
            &self,
            message: &[u8],
            cert: &CertificateDer<'_>,
            dss: &DigitallySignedStruct,
        ) -> Result<HandshakeSignatureValid, tokio_rustls::rustls::Error> {
            verify_tls12_signature(
                message,
                cert,
                dss,
                &self.0.signature_verification_algorithms,
            )
        }

        fn verify_tls13_signature(
            &self,
            message: &[u8],
            cert: &CertificateDer<'_>,
            dss: &DigitallySignedStruct,
        ) -> Result<HandshakeSignatureValid, tokio_rustls::rustls::Error> {
            verify_tls13_signature(
                message,
                cert,
                dss,
                &self.0.signature_verification_algorithms,
            )
        }

        fn supported_verify_schemes(&self) -> Vec<tokio_rustls::rustls::SignatureScheme> {
            self.0.signature_verification_algorithms.supported_schemes()
        }
    }
}