//! Server module intended to construct a multi-thread HTTP or HTTP/2 web server.
//!

#[allow(unused_imports)]
use hyper::server::conn::AddrIncoming;
#[allow(unused_imports)]
use hyper::server::Server as HyperServer;
use listenfd::ListenFd;
use std::net::{IpAddr, SocketAddr, TcpListener};
use std::sync::Arc;
use tokio::sync::oneshot::Receiver;

use crate::handler::{RequestHandler, RequestHandlerOpts};
#[cfg(any(unix, windows))]
use crate::signals;
#[cfg(feature = "tls")]
use crate::tls::{TlsAcceptor, TlsConfigBuilder};
use crate::{cors, helpers, logger, Settings};
use crate::{service::RouterService, Context, Result};

/// Define a multi-thread HTTP or HTTP/2 web server.
pub struct Server {
    opts: Settings,
    worker_threads: usize,
    max_blocking_threads: usize,
}

impl Server {
    /// Create new multi-thread server instance.
    pub fn new() -> Result<Server> {
        // Get server config
        let opts = Settings::get()?;

        // Configure number of worker threads
        let cpus = num_cpus::get();
        let worker_threads = match opts.general.threads_multiplier {
            0 | 1 => cpus,
            n => cpus * n,
        };
        let max_blocking_threads = opts.general.max_blocking_threads;

        Ok(Server {
            opts,
            worker_threads,
            max_blocking_threads,
        })
    }

    /// Run the multi-thread `Server` as standalone.
    /// It is a top-level function of [run_server_on_rt](#method.run_server_on_rt).
    pub fn run_standalone(self) -> Result {
        // Logging system initialization
        logger::init(&self.opts.general.log_level)?;

        self.run_server_on_rt(None, || {})
    }

    /// Run the multi-thread `Server` which will be used by a Windows service.
    /// It is a top-level function of [run_server_on_rt](#method.run_server_on_rt).
    #[cfg(windows)]
    pub fn run_as_service<F>(self, cancel: Option<Receiver<()>>, cancel_fn: F) -> Result
    where
        F: FnOnce(),
    {
        self.run_server_on_rt(cancel, cancel_fn)
    }

    /// Build and run the multi-thread `Server` on the Tokio runtime.
    pub fn run_server_on_rt<F>(self, cancel_recv: Option<Receiver<()>>, cancel_fn: F) -> Result
    where
        F: FnOnce(),
    {
        tracing::debug!(%self.worker_threads, "initializing tokio runtime with multi thread scheduler");

        tokio::runtime::Builder::new_multi_thread()
            .worker_threads(self.worker_threads)
            .max_blocking_threads(self.max_blocking_threads)
            .thread_name("static-web-server")
            .enable_all()
            .build()?
            .block_on(async {
                tracing::trace!("starting web server");
                if let Err(err) = self.start_server(cancel_recv, cancel_fn).await {
                    tracing::error!("server failed to start up: {:?}", err);
                    std::process::exit(1)
                }
            });

        tracing::trace!("runtime initialized");

        Ok(())
    }

    /// Run the inner Hyper `HyperServer` (HTTP1/HTTP2) forever on the current thread
    // using the given configuration.
    async fn start_server<F>(self, _cancel_recv: Option<Receiver<()>>, _cancel_fn: F) -> Result
    where
        F: FnOnce(),
    {
        // Config "general" options
        let general = self.opts.general;

        // Config-file "advanced" options
        let advanced_opts = self.opts.advanced;

        // Config file option
        if let Some(config_file) = general.config_file {
            let config_file = helpers::adjust_canonicalization(&config_file);
            tracing::info!("config file: {}", config_file);
        }

        // Determine TCP listener either file descriptor or TCP socket
        let (tcp_listener, addr_str);
        match general.fd {
            Some(fd) => {
                addr_str = format!("@FD({fd})");
                tcp_listener = ListenFd::from_env()
                    .take_tcp_listener(fd)?
                    .with_context(|| "failed to convert inherited 'fd' into a 'tcp' listener")?;
                tracing::info!(
                    "converted inherited file descriptor {} to a 'tcp' listener",
                    fd
                );
            }
            None => {
                let ip = general
                    .host
                    .parse::<IpAddr>()
                    .with_context(|| format!("failed to parse {} address", general.host))?;
                let addr = SocketAddr::from((ip, general.port));
                tcp_listener = TcpListener::bind(addr)
                    .with_context(|| format!("failed to bind to {addr} address"))?;
                addr_str = addr.to_string();
                tracing::info!("server bound to tcp socket {}", addr_str);
            }
        }

        // Check for a valid root directory
        let root_dir = helpers::get_valid_dirpath(&general.root)
            .with_context(|| "root directory was not found or inaccessible")?;

        // Custom error pages content
        let page404 = helpers::read_bytes_default(&general.page404);
        let page50x = helpers::read_bytes_default(&general.page50x);

        // Fallback page content
        let page_fallback = helpers::read_bytes_default(&general.page_fallback.unwrap_or_default());

        // Number of worker threads option
        let threads = self.worker_threads;
        tracing::info!("runtime worker threads: {}", threads);

        // Maximum number of blocking threads
        tracing::info!(
            "runtime max blocking threads: {}",
            general.max_blocking_threads
        );

        // Security Headers option
        let security_headers = general.security_headers;
        tracing::info!("security headers: enabled={}", security_headers);

        // Auto compression based on the `Accept-Encoding` header
        let compression = general.compression;
        tracing::info!("auto compression: enabled={}", compression);

        // Check pre-compressed files based on the `Accept-Encoding` header
        let compression_static = general.compression_static;
        tracing::info!("compression static: enabled={}", compression_static);

        // Directory listing option
        let dir_listing = general.directory_listing;
        tracing::info!("directory listing: enabled={}", dir_listing);

        // Directory listing order number
        let dir_listing_order = general.directory_listing_order;
        tracing::info!("directory listing order code: {}", dir_listing_order);

        // Directory listing format
        let dir_listing_format = general.directory_listing_format;
        tracing::info!("directory listing format: {}", dir_listing_format);

        // Cache control headers option
        let cache_control_headers = general.cache_control_headers;
        tracing::info!("cache control headers: enabled={}", cache_control_headers);

        // CORS option
        let cors = cors::new(
            general.cors_allow_origins.trim(),
            general.cors_allow_headers.trim(),
            general.cors_expose_headers.trim(),
        );

        // `Basic` HTTP Authentication Schema option
        let basic_auth = general.basic_auth.trim().to_owned();
        tracing::info!(
            "basic authentication: enabled={}",
            !general.basic_auth.is_empty()
        );

        // Log remote address option
        let log_remote_address = general.log_remote_address;
        tracing::info!("log remote address: enabled={}", log_remote_address);

        // Log redirect trailing slash option
        let redirect_trailing_slash = general.redirect_trailing_slash;
        tracing::info!(
            "redirect trailing slash: enabled={}",
            redirect_trailing_slash
        );

        // Ignore hidden files option
        let ignore_hidden_files = general.ignore_hidden_files;
        tracing::info!("ignore hidden files: enabled={}", ignore_hidden_files);

        // Grace period option
        let grace_period = general.grace_period;
        tracing::info!("grace period before graceful shutdown: {}s", grace_period);

        // Create a service router for Hyper
        let router_service = RouterService::new(RequestHandler {
            opts: Arc::from(RequestHandlerOpts {
                root_dir,
                compression,
                compression_static,
                dir_listing,
                dir_listing_order,
                dir_listing_format,
                cors,
                security_headers,
                cache_control_headers,
                page404,
                page50x,
                page_fallback,
                basic_auth,
                log_remote_address,
                redirect_trailing_slash,
                ignore_hidden_files,
                advanced_opts,
            }),
        });

        // Run the corresponding HTTP Server asynchronously with its given options
        #[cfg(feature = "http2")]
        if general.http2 {
            // HTTP/2 + TLS

            tcp_listener
                .set_nonblocking(true)
                .with_context(|| "failed to set TCP non-blocking mode")?;
            let listener = tokio::net::TcpListener::from_std(tcp_listener)
                .with_context(|| "failed to create tokio::net::TcpListener")?;
            let mut incoming = AddrIncoming::from_listener(listener).with_context(|| {
                "failed to create an AddrIncoming from the current tokio::net::TcpListener"
            })?;
            incoming.set_nodelay(true);

            let http2_tls_cert = match general.http2_tls_cert {
                Some(v) => v,
                _ => bail!("failed to initialize TLS because cert file missing"),
            };
            let http2_tls_key = match general.http2_tls_key {
                Some(v) => v,
                _ => bail!("failed to initialize TLS because key file missing"),
            };

            let tls = TlsConfigBuilder::new()
                .cert_path(&http2_tls_cert)
                .key_path(&http2_tls_key)
                .build()
                .with_context(|| {
                    "failed to initialize TLS probably because invalid cert or key file"
                })?;

            #[cfg(unix)]
            let signals = signals::create_signals()
                .with_context(|| "failed to register termination signals")?;
            #[cfg(unix)]
            let handle = signals.handle();

            let server =
                HyperServer::builder(TlsAcceptor::new(tls, incoming)).serve(router_service);

            #[cfg(unix)]
            let server =
                server.with_graceful_shutdown(signals::wait_for_signals(signals, grace_period));
            #[cfg(windows)]
            let server = server.with_graceful_shutdown(signals::wait_for_ctrl_c(
                _cancel_recv,
                _cancel_fn,
                grace_period,
            ));

            tracing::info!(
                parent: tracing::info_span!("Server::start_server", ?addr_str, ?threads),
                "listening on https://{}",
                addr_str
            );

            tracing::info!("press ctrl+c to shut down the server");

            server.await?;

            #[cfg(unix)]
            handle.close();

            tracing::warn!("termination signal caught, shutting down the server execution");
            return Ok(());
        }

        // HTTP/1

        #[cfg(unix)]
        let signals =
            signals::create_signals().with_context(|| "failed to register termination signals")?;
        #[cfg(unix)]
        let handle = signals.handle();

        tcp_listener
            .set_nonblocking(true)
            .with_context(|| "failed to set TCP non-blocking mode")?;

        let server = HyperServer::from_tcp(tcp_listener)
            .unwrap()
            .tcp_nodelay(true)
            .serve(router_service);

        #[cfg(unix)]
        let server =
            server.with_graceful_shutdown(signals::wait_for_signals(signals, grace_period));
        #[cfg(windows)]
        let server = server.with_graceful_shutdown(signals::wait_for_ctrl_c(
            _cancel_recv,
            _cancel_fn,
            grace_period,
        ));

        tracing::info!(
            parent: tracing::info_span!("Server::start_server", ?addr_str, ?threads),
            "listening on http://{}",
            addr_str
        );

        tracing::info!("press ctrl+c to shut down the server");

        server.await?;

        #[cfg(unix)]
        handle.close();

        tracing::warn!("termination signal caught, shutting down the server execution");
        Ok(())
    }
}