use std::{
    fmt,
    net::SocketAddr,
    sync::Arc,
    task::{Context, Poll},
    time::Instant,
};

use axum::extract::{ConnectInfo, MatchedPath};
use futures::Future;
use http::{Method, Request, Response};
use http_body::Body;
use log::log;
#[cfg(feature = "prometheus")]
use prometheus::{register_histogram_vec, HistogramVec};
use tower_layer::Layer;
use tower_service::Service;

#[derive(Clone)]
pub struct LoggerConfig {
    pub log_level_filter: Arc<dyn Fn(&str) -> log::Level + Send + Sync>,
    pub honor_xff: bool,
    #[cfg(feature = "prometheus")]
    pub metric_name: String,
}

#[derive(Clone)]
pub struct LoggerLayer {
    config: LoggerConfig,
    #[cfg(feature = "prometheus")]
    metric: Arc<HistogramVec>,
}

impl LoggerLayer {
    pub fn new(config: LoggerConfig) -> Self {
        Self {
            #[cfg(feature = "prometheus")]
            metric: Arc::new(
                register_histogram_vec!(
                    &config.metric_name,
                    "status, elapsed time, and count of responses",
                    &["route", "status"]
                )
                .unwrap(),
            ),
            config,
        }
    }
}

impl<S> Layer<S> for LoggerLayer {
    type Service = Logger<S>;

    fn layer(&self, service: S) -> Self::Service {
        Logger::new(
            self.config.clone(),
            #[cfg(feature = "prometheus")]
            self.metric.clone(),
            service,
        )
    }
}

#[derive(Clone)]
pub struct Logger<S> {
    config: LoggerConfig,
    #[cfg(feature = "prometheus")]
    metric: Arc<HistogramVec>,
    inner: S,
}

impl<S> Logger<S> {
    pub fn new(
        config: LoggerConfig,
        #[cfg(feature = "prometheus")] metric: Arc<HistogramVec>,
        inner: S,
    ) -> Self {
        Self {
            #[cfg(feature = "prometheus")]
            metric,
            config,
            inner,
        }
    }
}

#[pin_project::pin_project]
pub struct LoggerFuture<S, ReqBody, ResBody>
where
    S: Service<Request<ReqBody>, Response = Response<ResBody>>,
    S::Error: fmt::Display + 'static,
{
    remote_addr: String,
    path: String,
    matched_path: String,
    level: log::Level,
    method: Method,
    start: Instant,
    #[cfg(feature = "prometheus")]
    metric: Arc<HistogramVec>,
    #[pin]
    inner: S::Future,
}

impl<S, ReqBody, ResBody> Future for LoggerFuture<S, ReqBody, ResBody>
where
    S: Service<Request<ReqBody>, Response = Response<ResBody>>,
    S::Error: fmt::Display + 'static,
{
    type Output = <S::Future as Future>::Output;

    fn poll(self: std::pin::Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        let this = self.project();
        match this.inner.poll(cx) {
            Poll::Pending => Poll::Pending,
            Poll::Ready(Ok(response)) => {
                //TODO: include a filtered query parameter list
                let elapsed = this.start.elapsed().as_secs_f64() * 1000.0;
                #[cfg(feature = "prometheus")]
                this.metric
                    .with_label_values(&[&*this.matched_path, response.status().as_str()])
                    .observe(elapsed);
                log!(
                    *this.level,
                    "[{}] {} {} -> {} [{:.02} ms]",
                    this.remote_addr,
                    this.method,
                    this.path,
                    response.status(),
                    elapsed
                );
                Poll::Ready(Ok(response))
            }
            Poll::Ready(Err(e)) => {
                let elapsed = this.start.elapsed().as_secs_f64() * 1000.0;
                #[cfg(feature = "prometheus")]
                this.metric
                    .with_label_values(&[&*this.matched_path, "INTERNAL"])
                    .observe(elapsed);

                log!(
                    *this.level,
                    "[{}] {} {} -> FAIL {} [{:.02} ms]",
                    this.remote_addr,
                    this.method,
                    this.path,
                    e,
                    elapsed
                );
                Poll::Ready(Err(e))
            }
        }
    }
}

impl<S, ReqBody, ResBody> Service<Request<ReqBody>> for Logger<S>
where
    S: Service<Request<ReqBody>, Response = Response<ResBody>>,
    ReqBody: Body,
    ResBody: Body,
    ResBody::Error: fmt::Display + 'static,
    S::Error: fmt::Display + 'static,
{
    type Response = Response<ResBody>;
    type Error = S::Error;
    type Future = LoggerFuture<S, ReqBody, ResBody>;

    fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
        self.inner.poll_ready(cx)
    }

    fn call(&mut self, req: Request<ReqBody>) -> Self::Future {
        let start = Instant::now();

        let path = req.uri().path().to_string();
        let mut remote_addr = req
            .extensions()
            .get::<ConnectInfo<SocketAddr>>()
            .expect("missing ConnectInfo")
            .0
            .to_string();
        if self.config.honor_xff {
            if let Some(forwarded) = req
                .headers()
                .get("x-forwarded-for")
                .and_then(|x| x.to_str().ok())
                .map(|x| x.split_once(',').map(|x| x.0).unwrap_or(x).trim())
            {
                remote_addr = forwarded.to_string();
            }
        }
        let matched_path = req
            .extensions()
            .get::<MatchedPath>()
            .map(|x| x.as_str().to_string())
            .unwrap_or_default();

        let method = req.method().clone();
        let future = self.inner.call(req);

        let level = (self.config.log_level_filter)(&matched_path);

        LoggerFuture {
            start,
            level,
            method,
            remote_addr,
            path,
            matched_path,
            inner: future,
            #[cfg(feature = "prometheus")]
            metric: self.metric.clone(),
        }
    }
}