//! Handling of multiple [`Host`]s on one instance of Kvarn.
//!
//! A single [`Host`] contains the certificate, caches, and preferences
//! which are needed to run a domain.
//!
//! This also implements the logic needed for [`rustls`] to resolve which [`Host`]
//! to use for a connection. This is done by having an optional default and
//! other defined by their SNI (or `host` header in HTTP/1). If no host is matched,
//! the request is dropped, like when a [unsecure connection is sent to a secure port](Host).

use crate::prelude::{internals::*, *};
#[cfg(feature = "https")]
use rustls::{
    server::{ClientHello, ResolvesServerCert},
    sign, ServerConfig,
};

/// A set of settings for a [virtual host](https://en.wikipedia.org/wiki/Virtual_hosting),
/// allowing multiple DNS entries (domain names) to share a single IP address.
///
/// This is an integral part of Kvarn; the ability to host multiple
/// webpages on a single instance without crosstalk and with high performance
/// makes it a viable option.
///
/// Let's talk about the relations of [`Host::unsecure`] and [`PortDescriptor::unsecure`].
/// A host can be secure and contain a certificate (if the `https` feature is enabled).
/// A [`PortDescriptor`] can accept HTTPS or HTTP requests. [`PortDescriptor::new`] will
/// set up the descriptor to accept only HTTP requests if none of the hosts contains a certificate.
/// It accepts only HTTPS messages if any of the hosts have a certificate. Then, connections to
/// all the other hosts with no certificate are rejected.
///
/// For example, in [the reference implementation](https://github.com/Icelk/kvarn-reference),
/// I use [`PortDescriptor::unsecure`] to bind port 80 and
/// [`PortDescriptor::new`] to bind port 443. Then, all hosts are reachable on port 80,
/// but only the ones with a certificate on port 443.
///
/// # Examples
///
/// See [`RunConfig::execute()`].
#[must_use]
pub struct Host {
    /// The name of the host, will be used in matching the requests [SNI hostname](rustls::server::ClientHello::server_name())
    /// and `host` header to get the requested host to handle the request.
    pub name: CompactString,
    /// The alternative names this host is recognized by.
    /// This should probably be empty unless your certificate also covers these names.
    pub alternative_names: Vec<CompactString>,
    /// The certificate of this host, if any.
    #[cfg(feature = "https")]
    pub certificate: std::sync::RwLock<Option<Arc<sign::CertifiedKey>>>,
    /// Base path of all data for this host.
    ///
    /// If you enabled the `fs` feature (enabled by default),
    /// the public files are in the directory `<path>/public`
    /// (`public` by default; see [`Options::public_data_dir`]).
    ///
    /// Also, all extensions should use this to access data on disk.
    pub path: CompactString,
    /// The extensions of this host.
    pub extensions: Extensions,
    /// The file cache of this host.
    ///
    /// The caches are separated to limit the performance fluctuations of
    /// multiple hosts on the same instance.
    ///
    /// Can be used to clear the cache and to pass to the read functions in [`read`].
    pub file_cache: Option<FileCache>,
    /// The response cache of this host.
    /// See [`comprash`] and [`Host::file_cache`] for more info.
    pub response_cache: Option<ResponseCache>,
    /// The [`LimitManager`] checking for spam attacks
    /// for this host.
    ///
    /// Having this host-specific enables different virtual
    /// hosts to have varying degrees of strictness.
    pub limiter: LimitManager,
    /// Settings for handling caching of responses with the `vary` header.
    pub vary: Vary,

    /// Other settings.
    pub options: Options,
    /// Preferences and options for compression.
    pub compression_options: comprash::CompressionOptions,
    // also add to debug implementation when inserting new field
}
impl Host {
    /// Creates a new [`Host`].
    /// Will read PEM encoded certificates in the specified locations
    /// and return an non-secure host if parsing fails.
    ///
    /// To achieve greater security, use [`Host::with_http_to_https_redirect`] and call [`Host::with_hsts`].
    ///
    /// See [`Host::unsecure`] for a non-failing function,
    /// available regardless of features.
    ///
    /// # Errors
    ///
    /// Will return any error from [`get_certified_key()`] with a [`Host`] containing no certificates.
    #[cfg(feature = "https")]
    pub fn try_read_fs(
        host_name: impl AsRef<str>,
        cert_path: impl AsRef<str>,
        private_key_path: impl AsRef<str>,
        path: impl AsRef<str>,
        extensions: Extensions,
        options: Options,
    ) -> Result<Self, (CertificateError, Self)> {
        let cert = get_certified_key(cert_path, private_key_path);
        match cert {
            Ok((cert, pk)) => Ok(Self::new(host_name, cert, pk, path, extensions, options)),
            Err(err) => Err((err, Self::unsecure(host_name, path, extensions, options))),
        }
    }
    /// Same as [`Self::try_read_fs`], but extracts the host name from the certificate.
    /// This also doesn't fall back to [`Self::unsecure`], as we don't know the name if the
    /// certificate couldn't be parsed.
    ///
    /// # Panics
    ///
    /// Panics if the parsed certificate `.is_empty()` or if the first certificate in the parsed chain is invalid.
    ///
    /// # Errors
    ///
    /// Will return any error from [`get_certified_key()`].
    #[cfg(all(feature = "https", feature = "auto-hostname"))]
    pub fn read_fs_name_from_cert(
        cert_path: impl AsRef<str>,
        private_key_path: impl AsRef<str>,
        path: impl AsRef<str>,
        extensions: Extensions,
        options: Options,
    ) -> Result<Self, CertificateError> {
        let cert = get_certified_key(cert_path, private_key_path);
        match cert {
            Ok((cert, pk)) => Ok(Self::new_name_from_cert(
                cert, pk, path, extensions, options,
            )),
            Err(err) => Err(err),
        }
    }

    /// Creates a new [`Host`] from the [`rustls`]
    /// `cert` and `pk`. When they are in files, consider [`Self::new`]
    /// which reads from files.
    ///
    /// See the considerations of [`Self::new`] for security.
    ///
    /// # Examples
    ///
    /// ```ignore
    /// # use kvarn::prelude::*;
    /// let certificate =
    ///     rcgen::generate_simple_self_signed(vec!["localhost".to_string()]).unwrap();
    /// let cert = vec![rustls::Certificate(certificate.serialize_der().unwrap())];
    /// let pk = rustls::PrivateKey(certificate.serialize_private_key_der());
    /// let pk = Arc::new(rustls::sign::any_supported_type(&pk).unwrap());
    ///
    /// Host::new(
    ///     "localhost",
    ///     cert,
    ///     pk,
    ///     "tests",
    ///     Extensions::default(),
    ///     host::Options::default(),
    /// );
    /// ```
    #[cfg(feature = "https")]
    pub fn new(
        name: impl AsRef<str>,
        cert: Vec<rustls::Certificate>,
        pk: Arc<dyn sign::SigningKey>,
        path: impl AsRef<str>,
        extensions: Extensions,
        options: Options,
    ) -> Self {
        let cert = sign::CertifiedKey::new(cert, pk);

        Self {
            name: name.as_ref().to_compact_string(),
            alternative_names: Vec::new(),
            certificate: std::sync::RwLock::new(Some(Arc::new(cert))),
            path: path.as_ref().to_compact_string(),
            extensions,
            file_cache: Some(MokaCache::default()),
            response_cache: Some(MokaCache::default()),
            options,
            limiter: LimitManager::default(),
            vary: Vary::default(),

            compression_options: comprash::CompressionOptions::default(),
        }
    }
    /// Same as [`Self::new`], but extracts the host name from the certificate.
    ///
    /// # Panics
    ///
    /// Panics if `cert.is_empty()` or if the first certificate in `cert` is invalid.
    #[cfg(all(feature = "https", feature = "auto-hostname"))]
    pub fn new_name_from_cert(
        cert: Vec<rustls::Certificate>,
        pk: Arc<dyn sign::SigningKey>,
        path: impl AsRef<str>,
        extensions: Extensions,
        options: Options,
    ) -> Self {
        use x509_parser::prelude::FromDer;
        let tbs = x509_parser::certificate::X509Certificate::from_der(&cert[0].0)
            .expect("certificate invalid, failed to get host name")
            .1
            .tbs_certificate;
        let mut names = tbs.subject().iter_common_name();
        let name = names
            .next()
            .expect("no common names were found")
            .as_str()
            .expect("the common name contains invalid bytes")
            .to_owned();
        let mut alt_names = Vec::new();
        for name in names.filter_map(|name| name.as_str().ok()) {
            alt_names.push(name.to_compact_string());
        }
        let alt_name = tbs
            .subject_alternative_name()
            .expect("alternative name extension of certificate invalid");
        if let Some(alt_name) = alt_name {
            for name in alt_name
                .value
                .general_names
                .iter()
                .filter_map(|name| match name {
                    x509_parser::prelude::GeneralName::DNSName(name) => Some(name),
                    _ => None,
                })
            {
                alt_names.push((*name).to_compact_string());
            }
        }
        let mut me = Self::new(name, cert, pk, path, extensions, options);
        me.alternative_names = alt_names;
        me
    }
    /// Creates a new [`Host`] without a certificate.
    ///
    /// This host will only support non-encrypted HTTP/1 connections.
    /// Consider enabling the `https` feature and use a self-signed certificate or one from [Let's Encrypt](https://letsencrypt.org/).
    pub fn unsecure(
        host_name: impl AsRef<str>,
        path: impl AsRef<str>,
        extensions: Extensions,
        options: Options,
    ) -> Self {
        Self {
            name: host_name.as_ref().to_compact_string(),
            alternative_names: Vec::new(),
            #[cfg(feature = "https")]
            certificate: std::sync::RwLock::new(None),
            path: path.as_ref().to_compact_string(),
            extensions,
            file_cache: Some(MokaCache::default()),
            response_cache: Some(MokaCache::default()),
            options,
            limiter: LimitManager::default(),
            vary: Vary::default(),
            compression_options: comprash::CompressionOptions::default(),
        }
    }

    /// Same as [`Host::try_read_fs`] with [`Host::with_http_to_https_redirect`].
    /// This does however consider the error from [`Host::try_read_fs`] to be ok.
    /// We log it as an [`log::Level::Error`]
    /// and continue without encryption.
    ///
    /// Consider running [`Host::try_read_fs`] with [`Host::with_http_to_https_redirect`]
    /// and [`Host::with_hsts`] to harden the system.
    #[cfg(feature = "https")]
    pub fn http_redirect_or_unsecure(
        host_name: impl AsRef<str>,
        cert_path: impl AsRef<str>,
        private_key_path: impl AsRef<str>,
        path: impl AsRef<str>,
        extensions: Extensions,
        options: Options,
    ) -> Self {
        match Host::try_read_fs(
            host_name,
            cert_path,
            private_key_path,
            path,
            extensions,
            options,
        ) {
            Ok(mut host) => {
                host.with_http_to_https_redirect();
                host
            }
            Err((err, host_without_cert)) => {
                error!(
                    "Failed to get certificate! Not running host on HTTPS. {:?}",
                    err
                );
                host_without_cert
            }
        }
    }

    /// Adds extensions to redirect unsecure HTTP requests to the secure HTTPS URI.
    ///
    /// See [`Extensions::with_http_to_https_redirect`].
    #[cfg(feature = "https")]
    pub fn with_http_to_https_redirect(&mut self) -> &mut Self {
        self.extensions.with_http_to_https_redirect();
        self
    }

    /// Enables [HSTS](https://en.wikipedia.org/wiki/HSTS) on this [`Host`].
    ///
    /// The [`Package`] extension has a priority of `8`.
    ///
    /// You should be careful using this feature.
    /// If you do not plan to have a certificate for your domain
    /// for at least the following two years, take a look in the source code,
    /// copy paste it and lower the `max-age`.
    ///
    /// Also see [hstspreload.org](https://hstspreload.org/)
    #[cfg(feature = "https")]
    pub fn with_hsts(&mut self) -> &mut Self {
        struct Ext;
        impl extensions::PackageCall for Ext {
            fn call<'a>(
                &'a self,
                response: &'a mut Response<()>,
                request: &'a FatRequest,
                _: &'a Host,
                _: SocketAddr,
            ) -> RetFut<'a, ()> {
                if request.uri().scheme_str() == Some("https") {
                    response
                        .headers_mut()
                        .entry("strict-transport-security")
                        .or_insert(HeaderValue::from_static(
                            "max-age=63072000; includeSubDomains; preload",
                        ));
                }

                ready(())
            }
        }

        self.extensions
            .add_package(Box::new(Ext), extensions::Id::new(8, "Adding HSTS header"));
        self
    }

    /// Add an alternative name to this host.
    ///
    /// See [the fiels](Self::alternative_names) for more details.
    pub fn add_alternative_name(&mut self, name: impl AsRef<str>) -> &mut Self {
        self.alternative_names
            .push(name.as_ref().to_compact_string());
        self
    }

    /// Disables client cache on this host.
    ///
    /// This makes all [`comprash::ClientCachePreference`]s `no-store`.
    /// Use Kvarn extensions' `force_cache` to force certain files to cache.
    pub fn disable_client_cache(&mut self) -> &mut Self {
        self.options.disable_client_cache();
        self
    }

    /// Disables the file system cache for this host.
    /// This can cause degraded performance under heavy load,
    /// but reduces the memoy used.
    pub fn disable_fs_cache(&mut self) -> &mut Self {
        self.file_cache = None;
        self
    }
    /// Disables the response cache for this host.
    /// This can cause degraded performance under heavy load,
    /// but reduces the memoy used.
    pub fn disable_response_cache(&mut self) -> &mut Self {
        self.response_cache = None;
        self
    }
    /// Disables all server caches.
    /// This can cause degraded performance under heavy load,
    /// but reduces the memoy used.
    ///
    /// Right now calls [`Self::disable_fs_cache`] and [`Self::disable_response_cache`].
    pub fn disable_server_cache(&mut self) -> &mut Self {
        self.disable_fs_cache().disable_response_cache()
    }

    /// Whether or not this this host is secured with a certificate.
    ///
    /// See [`Host::certificate`].
    #[cfg(feature = "https")]
    #[inline]
    pub fn is_secure(&self) -> bool {
        self.certificate.read().unwrap().is_some()
    }
    /// Whether or not this this host is secured with a certificate.
    ///
    /// See [`Host::certificate`].
    #[cfg(not(feature = "https"))]
    #[inline]
    pub(crate) fn is_secure(&self) -> bool {
        false
    }

    /// Set the brotli compression level. 1-10, lower values are faster, but compress less.
    ///
    /// See [some benchmarks](https://quixdb.github.io/squash-benchmark/#results) for more context.
    #[cfg(feature = "br")]
    pub fn set_brotli_level(&mut self, level: u32) -> &mut Self {
        self.compression_options.brotli_level = level;
        self
    }
    /// Set the gzip compression level. 1-10, lower values are faster, but compress less.
    ///
    /// See [some benchmarks](https://quixdb.github.io/squash-benchmark/#results) for more context.
    #[cfg(feature = "gzip")]
    pub fn set_gzip_level(&mut self, level: u32) -> &mut Self {
        self.compression_options.gzip_level = level;
        self
    }

    /// Can be done while the server is running, since this only takes a reference to self
    ///
    /// Sets the certificate if it was [`None`] before. It's however unclear what consequences that
    /// will have while it's running (if you only had unsecure hosts when starting Kvarn, it you
    /// might not have bound `443`?).
    #[cfg(feature = "https")]
    pub fn live_set_certificate(&self, key: sign::CertifiedKey) {
        let mut guard = self.certificate.write().unwrap();
        *guard = Some(Arc::new(key));
    }
}
impl Debug for Host {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        let mut s = f.debug_struct(utils::ident_str!(Host));
        utils::fmt_fields!(
            s,
            (self.name),
            (self.alternative_names),
            #[cfg(feature = "https")]
            (self.certificate, &"[internal certificate]".as_clean()),
            (self.path),
            (self.extensions, &"[internal extension data]".as_clean()),
            (self.file_cache, &"[internal cache]".as_clean()),
            (self.response_cache, &"[internal cache]".as_clean()),
            (self.limiter),
            (self.vary),
            (self.options),
            (self.compression_options),
        );

        s.finish()
    }
}
impl Host {
    /// Clones this [`Host`] without carrying with any extensions or caches.
    /// You'll have to add all extensions (and related settings, such as CSP, CORS, HSTS)
    /// manually.
    ///
    /// Use sparingly.
    pub fn clone_without_extensions(&self) -> Self {
        Self {
            name: self.name.clone(),
            alternative_names: self.alternative_names.clone(),
            #[cfg(feature = "https")]
            certificate: std::sync::RwLock::new(self.certificate.read().unwrap().clone()),
            path: self.path.clone(),
            extensions: Extensions::empty(),
            file_cache: Some(MokaCache::default()),
            response_cache: Some(MokaCache::default()),
            limiter: self.limiter.clone(),
            vary: Vary::default(),
            options: self.options.clone(),
            compression_options: self.compression_options.clone(),
        }
    }
}
/// Options for [`Host`].
/// Values wrapped in [`Option`]s usually use hardcoded defaults when the value is [`None`].
///
/// This can easily be cloned to be shared across multiple hosts.
#[derive(Debug, Clone)]
#[must_use]
pub struct Options {
    // # Miscellaneous
    /// Will be the default for folders; `/js/` will resolve to `/js/<folder_default>`.
    /// E.g. `/posts/` -> `/posts/index.html`
    ///
    /// If no value is passed, `index.html` is assumed.
    pub folder_default: Option<CompactString>,
    /// Will be the default for unspecified file extensions; `/foobar.` will resolve to `/foobar.<extension_default>`.
    /// E.g. `/index.` -> `/index.html`
    ///
    /// If no value is passed, `html` is assumed.
    pub extension_default: Option<CompactString>,
    /// Default data directory for public files.
    /// Default is `public`.
    pub public_data_dir: Option<CompactString>,
    /// Default directory for overriding HTTP error responses.
    /// Default is `errors`.
    pub errors_dir: Option<CompactString>,

    // # Cache
    /// Returns `cache-control` header to be `no-store` by default, if enabled.
    ///
    /// Useful if you have a developing site and don't want traditionally static content to be in the client cache.
    pub disable_client_cache: bool,
    /// Disables further caching by sending a [`StatusCode::NOT_MODIFIED`] when the
    /// `if-modified-since` header is sent and the resource is fresh.
    pub disable_if_modified_since: bool,
    /// Filter to not cache certain [`StatusCode`]s.
    ///
    /// See [`CacheAction`] and [`default_status_code_cache_filter`] for more info.
    pub status_code_cache_filter: fn(StatusCode) -> CacheAction,

    // # Extensions
    /// Disables file system access for public files.
    ///
    /// This still enables custom error messages and reading of files through extensions.
    pub disable_fs: bool,
}
impl Options {
    /// Creates a new [`Options`] with default settings.
    ///
    /// All [`Option`]s are [`None`] and all booleans are `false`.
    /// [`Self::status_code_cache_filter`] uses [`default_status_code_cache_filter`].
    pub fn new() -> Self {
        Self {
            folder_default: None,
            extension_default: None,
            public_data_dir: None,
            errors_dir: None,

            disable_client_cache: false,
            disable_if_modified_since: false,
            status_code_cache_filter: default_status_code_cache_filter,

            disable_fs: false,
        }
    }
    /// Disables client cache on this host.
    ///
    /// This makes all [`comprash::ClientCachePreference`]s `no-store`.
    /// Use Kvarn extensions' `force_cache` to force certain files to cache.
    pub fn disable_client_cache(&mut self) -> &mut Self {
        self.disable_client_cache = true;
        self
    }
    /// Disables accessing the file system for public files.
    ///
    /// See [`Self::disable_fs`] for more info.
    pub fn disable_fs(&mut self) -> &mut Self {
        self.disable_fs = true;
        self
    }
    /// Sets the directory (relative to the [`Host::path`]) to fetch data for the web in.
    /// Defaults to `public`.
    pub fn set_public_data_dir(&mut self, path: impl AsRef<str>) -> &mut Self {
        self.public_data_dir = Some(path.as_ref().to_compact_string());
        self
    }
    /// Sets the directory (relative to the [`Host::path`]) to get HTTP error overrides from.
    /// Defaults to `errors`.
    pub fn set_errors_dir(&mut self, path: impl AsRef<str>) -> &mut Self {
        self.errors_dir = Some(path.as_ref().to_compact_string());
        self
    }

    /// Gets the [`Self::folder_default`], as used by Kvarn.
    /// Uses the default specified there.
    #[must_use]
    pub fn get_folder_default(&self) -> &str {
        self.folder_default.as_deref().unwrap_or("index.html")
    }
    /// Gets the [`Self::extension_default`], as used by Kvarn.
    /// Uses the default specified there.
    #[must_use]
    pub fn get_extension_default(&self) -> &str {
        self.extension_default.as_deref().unwrap_or("html")
    }
    /// Gets the [`Self::public_data_dir`], as used by Kvarn.
    /// Uses the default specified there.
    #[must_use]
    pub fn get_public_data_dir(&self) -> &str {
        self.public_data_dir.as_deref().unwrap_or("public")
    }
    /// Gets the [`Self::errors_dir`], as used by Kvarn.
    /// Uses the default specified there.
    #[must_use]
    pub fn get_errors_dir(&self) -> &str {
        self.public_data_dir.as_deref().unwrap_or("errors")
    }
}
impl Default for Options {
    fn default() -> Self {
        Self::new()
    }
}

/// A builder of [`Collection`]. See [`Collection::builder()`].
#[derive(Debug)]
#[must_use]
pub struct CollectionBuilder(Collection);
impl CollectionBuilder {
    /// Adds `host` to the builder.
    /// This will match the `host` header and SNI hostname for [`Host.name`].
    ///
    /// If it is the first call to this function, [`Self::set_pre_host_limiter`] is called
    /// with [`Host::limiter`].
    #[inline]
    pub fn insert(mut self, host: Host) -> Self {
        self.check_secure(&host);
        if self.0.first.is_none() {
            self.0.first = Some(host.name.clone());
            self.0.pre_host_limiter = host.limiter.clone();
        }
        // it's important to insert the alt-names first, as they might contain the main name.
        // If that happens, the inserted reference is overridden below.
        for alt_name in &host.alternative_names {
            self.0
                .by_name
                .insert(alt_name.clone(), HostValue::Ref(host.name.clone()));
        }
        self.0
            .by_name
            .insert(host.name.clone(), HostValue::Host(host));
        self
    }
    /// Adds a default `host` which is the fallback for all requests with a requested host
    /// which does not match any host added using [`Self::insert`].
    ///
    /// > This is not needed when debugging, as the first [`Host`] to be inserted is used
    /// > for requests to `localhost`.
    ///
    /// **NOTE:** This should be used with care as all secure connections to this server
    /// with a SNI hostname that is not registered in this [`Collection`], the client will get
    /// a security warning, as the certificate of the default host is used.
    /// This is fine with HTTP, as that only delivers the website.
    ///
    /// # Panics
    ///
    /// Panics if this function is called twice on the same struct.
    /// You should only set the default once.
    #[inline]
    pub fn default(mut self, host: Host) -> Self {
        assert!(
            self.0.default.is_none(),
            "Can not set default host multiple times."
        );
        info!("Set default host {:?}", host.name);
        self.0.default = Some(host.name.clone());
        self.insert(host)
    }
    fn check_secure(&mut self, host: &Host) {
        if host.is_secure() {
            self.0.has_secure = true;
        }
    }
    /// Sets the limiter used before any data is read. Only when the [`LimitManager`] returns
    /// [`LimitAction::Drop`] will this do anything here.
    #[inline]
    pub fn set_pre_host_limiter(mut self, limiter: LimitManager) -> Self {
        self.0.pre_host_limiter = limiter;
        self
    }
    /// Puts the inner [`Collection`] in a [`Arc`] and returns it.
    ///
    /// This works great with the overall flow of Kvarn. See [`RunConfig::execute()`] for an example.
    #[inline]
    #[must_use]
    pub fn build(self) -> Arc<Collection> {
        trace!("Build host collection: {:#?}", self.0);
        Arc::new(self.into_inner())
    }
    /// Converts `self` to a [`Collection`].
    #[inline]
    pub fn into_inner(self) -> Collection {
        self.0
    }
}

#[derive(Debug)]
#[allow(clippy::large_enum_variant)] // we want direct access to the host.
enum HostValue {
    Host(Host),
    Ref(CompactString),
}
impl HostValue {
    fn as_host(&self) -> Option<&Host> {
        match self {
            Self::Host(h) => Some(h),
            Self::Ref(_) => None,
        }
    }
}

/// A collection of [`Host`]s, with an optional default and
/// arbitrarily many others, indexed by [`Host.name`].
///
/// Tries to route to the host with it's name.
/// If no host with a matching name is found, it'll fall back to [`default`](Self::get_default), if
/// that's [`Some`].
///
/// > When called from `localhost`, the first host added is always used.
///
/// If the feature `https` is enabled, [`rustls::server::ResolvesServerCert`] is implemented
/// using the pattern described above.
#[derive(Debug)]
#[must_use]
pub struct Collection {
    default: Option<CompactString>,
    by_name: HashMap<CompactString, HostValue>,
    first: Option<CompactString>,
    has_secure: bool,
    pre_host_limiter: LimitManager,
}
impl Collection {
    /// Creates a new [`CollectionBuilder`] with `default_host` as the default.
    #[inline]
    pub fn builder() -> CollectionBuilder {
        CollectionBuilder(Self {
            default: None,
            by_name: HashMap::new(),
            first: None,
            has_secure: false,
            pre_host_limiter: LimitManager::default(),
        })
    }
    /// Creates a `Host` without certification, using the directories `./public` and `./templates`.
    /// The host is the default. See [`host`] for more info.
    #[inline]
    pub fn simple_non_secure(default_host_name: impl AsRef<str>, extensions: Extensions) -> Self {
        Self::builder()
            .default(Host::unsecure(
                default_host_name,
                ".",
                extensions,
                Options::default(),
            ))
            .into_inner()
    }

    /// Returns a reference to the default [`Host`].
    ///
    /// Use [`Self::get_from_request`] to get the appropriate host.
    #[inline]
    #[must_use]
    pub fn get_default(&self) -> Option<&Host> {
        trace!("Getting default {:?}", self.default);
        self.default
            .as_ref()
            .and_then(|default| self.get_host(default))
    }
    /// Get a [`Host`] by name.
    #[inline]
    #[must_use]
    pub fn get_host(&self, name: &str) -> Option<&Host> {
        match self.by_name.get(name) {
            Some(v) => match v {
                HostValue::Host(h) => Some(h),
                HostValue::Ref(r) => Some(
                    self.by_name
                        .get(r)
                        .and_then(HostValue::as_host)
                        .expect("internal error when resolving host: Ref pointed to Ref"),
                ),
            },
            None => None,
        }
    }
    /// Get a [`Host`] by name, and returns the [`default`](Self::get_default) if none were found.
    #[inline]
    #[must_use]
    pub fn get_or_default(&self, name: &str) -> Option<&Host> {
        self.get_host(name)
            .or_else(|| name.strip_suffix('.').and_then(|name| self.get_host(name)))
            .or_else(|| self.get_default())
            .or_else(|| {
                let base_host = name.split(':').next();
                if base_host == Some("localhost")
                    || base_host == Some("127.0.0.1")
                    || base_host == Some("::1")
                    || base_host == Some("[::1]")
                {
                    self.first.as_ref().and_then(|host| self.get_host(host))
                } else {
                    None
                }
            })
    }
    /// Get a [`Host`] by name, if any, and returns it or the [`default`](Self::get_default)
    /// if `name` is [`None`] or [`Self::get_or_default`] returns [`None`].
    #[inline]
    #[must_use]
    pub fn get_option_or_default(&self, name: Option<&str>) -> Option<&Host> {
        match name {
            Some(host) => self.get_or_default(host),
            None => self.get_default(),
        }
    }
    /// Get the host depending on [`header::HOST`] and the `sni_hostname`.
    #[inline]
    pub fn get_from_request<'a>(
        &'a self,
        request: &Request<Body>,
        sni_hostname: Option<&str>,
    ) -> Option<&'a Host> {
        fn get_header(headers: &HeaderMap) -> Option<&str> {
            headers
                .get(header::HOST)
                .map(HeaderValue::to_str)
                .and_then(Result::ok)
        }

        let host = sni_hostname.or_else(|| get_header(request.headers()));

        self.get_option_or_default(host)
    }

    /// Returns if any [`Host`]s are [`Host::is_secure`].
    #[inline]
    #[must_use]
    pub fn has_secure(&self) -> bool {
        self.has_secure
    }

    /// Makes a [`rustls::ServerConfig`] from [`Self`].
    ///
    /// This takes [`Self`] in an [`Arc`] and clones it.
    ///
    /// You should not have to call this, since [`PortDescriptor::new`] and [`PortDescriptor::https`] calls it internally.
    /// Though, you could use the [`host`] system by itself, without the rest of Kvarn.
    #[cfg(feature = "https")]
    #[inline]
    #[must_use]
    pub fn make_config(self: &Arc<Self>) -> ServerConfig {
        let mut config = ServerConfig::builder()
            .with_safe_defaults()
            .with_no_client_auth()
            .with_cert_resolver(self.clone());
        config.alpn_protocols = alpn();
        config
    }

    /// Gets the `pre_host_limiter` to manage limits before any of the request is read, or even a
    /// TLS session is initiated.
    pub(crate) fn limiter(&self) -> &LimitManager {
        &self.pre_host_limiter
    }

    /// Clears all response caches.
    #[inline]
    #[allow(clippy::unused_async)] // API compat and future proofing
    pub async fn clear_response_caches(&self, host_filter: Option<&str>) {
        for host in self.by_name.values().filter_map(HostValue::as_host) {
            if host_filter.map_or(false, |h| h != host.name) {
                continue;
            }
            if let Some(cache) = &host.response_cache {
                cache.cache.invalidate_all();
            }
        }
    }
    /// Clears a single `uri` in `host`.
    /// If `host` is `""` or `"default"`, the [default](Self::get_default) host is used.
    ///
    /// # Returns
    ///
    /// (if host was found, cleared page)
    ///
    /// This will probably become a error enum in the future.
    ///
    /// It will never return (false, true).
    pub fn clear_page(&self, host: &str, uri: &Uri) -> (bool, bool) {
        let key = UriKey::path_and_query(uri);

        let mut found = false;
        let mut cleared = false;
        if host.is_empty() || host == "default" {
            if let Some(cache) = self
                .get_default()
                .as_ref()
                .and_then(|h| h.response_cache.as_ref())
            {
                found = true;

                cleared ^= cache.cache.contains_key(&key);
                cache.cache.invalidate(&key);
                if let UriKey::PathQuery(path_query) = key {
                    let key = UriKey::Path(path_query.into_path());
                    cleared |= cache.cache.contains_key(&key);
                    cache.cache.invalidate(&key);
                }
            }
        } else if let Some(host) = self.get_host(host) {
            found = true;
            if let Some(cache) = &host.response_cache {
                cleared ^= cache.cache.contains_key(&key);
                cache.cache.invalidate(&key);
                if let UriKey::PathQuery(path_query) = key {
                    let key = UriKey::Path(path_query.into_path());
                    cleared |= cache.cache.contains_key(&key);
                    cache.cache.invalidate(&key);
                }
            }
        }
        (found, cleared)
    }
    /// Clears all file caches.
    #[inline]
    #[allow(clippy::unused_async)] // API compat and future proofing
    pub async fn clear_file_caches(&self, host_filter: Option<&str>) {
        for host in self.by_name.values().filter_map(HostValue::as_host) {
            if host_filter.map_or(false, |h| h != host.name) {
                continue;
            }
            if let Some(cache) = &host.file_cache {
                cache.cache.invalidate_all();
            }
        }
    }
    /// Clears a single `path` in `host`.
    /// If `host` is `""` or `"default"`, the [default](Self::get_default) host is used.
    ///
    /// # Returns
    ///
    /// (if host was found, cleared page)
    ///
    /// This will probably become a error enum in the future.
    ///
    /// It will never return (false, true).
    ///
    /// This iterates over all caches and [locks](RwLock::write) them, which takes a lot of time.
    /// Though, it's not blocking.
    pub fn clear_file(&self, host: &str, path: impl AsRef<str>) -> (bool, bool) {
        let path = path.as_ref();
        let mut found = false;
        let mut cleared = false;
        if host.is_empty() || host == "default" {
            if let Some(cache) = self
                .get_default()
                .as_ref()
                .and_then(|h| h.file_cache.as_ref())
            {
                found = true;
                cleared |= cache.cache.contains_key(path);
                cache.cache.invalidate(path);
            }
        } else if let Some(host) = self.get_host(host) {
            found = true;
            if let Some(cache) = &host.file_cache {
                cleared |= cache.cache.contains_key(path);
                cache.cache.invalidate(path);
            }
        }
        (found, cleared)
    }
}
unsafe impl Send for Collection {}
unsafe impl Sync for Collection {}
#[cfg(feature = "https")]
impl ResolvesServerCert for Collection {
    #[inline]
    fn resolve(&self, client_hello: ClientHello<'_>) -> Option<Arc<sign::CertifiedKey>> {
        // Mostly returns true, since we have a default
        // Will however return false if certificate is not present
        // in found host or default host.
        self.get_option_or_default(client_hello.server_name())
            .and_then(|host| host.certificate.read().unwrap().as_ref().map(Arc::clone))
    }
}

/// All the supported ALPN protocols.
///
/// > ***Note:** this is often not needed, as the ALPN protocols
/// are set in [`host::Collection::make_config()`].*
#[must_use]
#[allow(unused_mut)]
pub fn alpn() -> Vec<Vec<u8>> {
    let mut vec = vec![
        #[cfg(feature = "http2")]
        b"h2".to_vec(),
        b"http/1.1".to_vec(),
    ];
    #[cfg(feature = "http3")]
    {
        vec.insert(0, b"h3-29".to_vec());
        vec.insert(0, b"h3-30".to_vec());
        vec.insert(0, b"h3-31".to_vec());
        vec.insert(0, b"h3-31".to_vec());
        vec.insert(0, b"h3-32".to_vec());
        vec.insert(0, b"h3".to_vec());
    }
    vec
}

/// Per host filter output of whether or not to cache a response with some [`StatusCode`].
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[must_use]
pub enum CacheAction {
    /// Cache this status code response.
    Cache,
    /// Don't cache, in hope following responses have status codes which can be cached.
    Drop,
}
impl CacheAction {
    /// Returns [`Self::Cache`] if `cache` is true. Else [`Self::Drop`].
    pub fn from_cache(cache: bool) -> Self {
        if cache {
            Self::Cache
        } else {
            Self::Drop
        }
    }
    /// Returns [`Self::Drop`] if `drop` is true. Else [`Self::Cache`].
    pub fn from_drop(drop: bool) -> Self {
        Self::from_cache(!drop)
    }
    /// Returns true if `self` is [`Self::Cache`].
    #[must_use]
    pub fn into_cache(self) -> bool {
        matches!(self, Self::Cache)
    }
    /// Returns true if `self` is [`Self::Drop`].
    #[must_use]
    pub fn into_drop(self) -> bool {
        matches!(self, Self::Drop)
    }
}

/// This is the default for [`Options::status_code_cache_filter`].
///
/// This caches the request on every [`StatusCode`] except
/// - client errors, however `404 Not Found` and `410 Gone` are still cached
/// - any [informational response](https://developer.mozilla.org/en-US/docs/Web/HTTP/Status#information_responses)
/// - [304 Not Modified](https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/304)
pub fn default_status_code_cache_filter(code: StatusCode) -> CacheAction {
    CacheAction::from_drop(matches!(code.as_u16(), 400..=403 | 405..=409 | 411..=499|100..=199|304))
}

/// An error regarding creation of a [`rustls::sign::CertifiedKey`].
#[cfg(feature = "https")]
#[derive(Debug)]
pub enum CertificateError {
    /// An error occurred while reading from the fs.
    Io(io::Error),
    /// The private key is of improper format.
    ImproperPrivateKeyFormat,
    /// THe certificate (public key) is of improper format.
    ImproperCertificateFormat,
    /// No key was found.
    NoKey,
    /// The private key doesn't match the public key.
    InvalidPrivateKey,
}
#[cfg(feature = "https")]
impl From<io::Error> for CertificateError {
    #[inline]
    fn from(error: io::Error) -> Self {
        Self::Io(error)
    }
}

/// A pair of [`rustls::Certificate`] and [`sign::SigningKey`].
///
/// Returned from [`get_certified_key`].
#[cfg(feature = "https")]
pub type CertKeyPair = (Vec<rustls::Certificate>, Arc<dyn sign::SigningKey>);

/// Extracts a [`sign::CertifiedKey`] from `cert_path` and `private_key_path`.
///
/// # Errors
///
/// Will return any errors while reading the files, or any parsing errors.
#[cfg(feature = "https")]
pub fn get_certified_key(
    cert_path: impl AsRef<str>,
    private_key_path: impl AsRef<str>,
) -> Result<CertKeyPair, CertificateError> {
    let mut chain = io::BufReader::new(std::fs::File::open(cert_path.as_ref())?);
    let mut private_key = io::BufReader::new(std::fs::File::open(private_key_path.as_ref())?);

    let mut private_keys = Vec::with_capacity(4);
    private_keys.extend(match rustls_pemfile::pkcs8_private_keys(&mut private_key) {
        Ok(key) => key,
        Err(_) => return Err(CertificateError::ImproperPrivateKeyFormat),
    });
    if private_keys.is_empty() {
        private_keys.extend(match rustls_pemfile::rsa_private_keys(&mut private_key) {
            Ok(key) => key,
            Err(_) => return Err(CertificateError::ImproperPrivateKeyFormat),
        });
    }
    let key = match private_keys.into_iter().next() {
        Some(key) => rustls::PrivateKey(key),
        None => return Err(CertificateError::NoKey),
    };

    let key = sign::any_supported_type(&key).map_err(|_| CertificateError::InvalidPrivateKey)?;
    let chain = match rustls_pemfile::certs(&mut chain) {
        Ok(cert) => cert,
        Err(_) => return Err(CertificateError::ImproperCertificateFormat),
    };

    let chain = chain.into_iter().map(rustls::Certificate).collect();

    Ok((chain, key))
}