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use futures::future;
use futures::future::IntoFuture;

use hyper::client::connect::HttpConnector;
use hyper::rt::Future;
use hyper::service::{NewService, Service};
use hyper::{Body, Client, Request, Response};

use std::collections::HashMap;
use std::error::Error;
use std::sync::{Arc, Mutex};

use rand::prelude::*;
use rand::rngs::SmallRng;
use rand::FromEntropy;

use crate::proxy::middleware::MiddlewareResult::*;
use crate::Middlewares;

type BoxFut = Box<Future<Item = hyper::Response<Body>, Error = hyper::Error> + Send>;
pub type State = Arc<Mutex<HashMap<(String, u64), String>>>;

pub struct ProxyService {
    client: Client<HttpConnector, Body>,
    middlewares: Middlewares,
    state: State,
    rng: SmallRng,
}

impl Service for ProxyService {
    type Error = hyper::Error;
    type Future = BoxFut;
    type ReqBody = Body;
    type ResBody = Body;

    fn call(&mut self, req: Request<Self::ReqBody>) -> Self::Future {
        self.clear_state();
        let (parts, body) = req.into_parts();
        let mut req = Request::from_parts(parts, body);

        // Create references for future callbacks
        // references are moved in each chained future (map,then..)
        let mws_failure = Arc::clone(&self.middlewares);
        let mws_success = Arc::clone(&self.middlewares);
        let mws_after = Arc::clone(&self.middlewares);
        let state_failure = Arc::clone(&self.state);
        let state_success = Arc::clone(&self.state);
        let state_after = Arc::clone(&self.state);

        let req_id = self.rng.next_u64();

        let mut before_res: Option<Response<Body>> = None;
        for mw in self.middlewares.lock().unwrap().iter_mut() {
            // Run all middlewares->before_request
            if let Some(res) = match mw.before_request(&mut req, req_id, &self.state) {
                Err(err) => Some(Response::from(err)),
                Ok(RespondWith(response)) => Some(response),
                Ok(Next) => None,
            } {
                // Stop when an early response is wanted
                before_res = Some(res);
                break;
            }
        }

        if let Some(res) = before_res {
            return Box::new(future::ok(self.early_response(req_id, res, &self.state)));
        }

        let res = self
            .client
            .request(req)
            .map_err(move |err| {
                for mw in mws_failure.lock().unwrap().iter_mut() {
                    // TODO: think about graceful handling
                    if let Err(err) = mw.request_failure(&err, req_id, &state_failure) {
                        error!("Request_failure errored: {:?}", &err);
                    }
                }
                err
            })
            .map(move |mut res| {
                for mw in mws_success.lock().unwrap().iter_mut() {
                    match mw.request_success(&mut res, req_id, &state_success) {
                        Err(err) => res = Response::from(err),
                        Ok(RespondWith(response)) => res = response,
                        Ok(Next) => (),
                    }
                }
                res
            })
            .then(move |res| match res {
                // Allows middlewares to catch errors after requests
                Err(err) => {
                    let mut res = Err(err);
                    for mw in mws_after.lock().unwrap().iter_mut() {
                        match mw.after_request(None, req_id, &state_after) {
                            Err(err) => res = Ok(Response::from(err)),
                            Ok(RespondWith(response)) => res = Ok(response),
                            Ok(Next) => (),
                        }
                    }
                    res
                }
                // Allows middlewares to change the response after requests
                Ok(mut res) => {
                    for mw in mws_after.lock().unwrap().iter_mut() {
                        match mw.after_request(Some(&mut res), req_id, &state_after) {
                            Err(err) => res = Response::from(err),
                            Ok(RespondWith(response)) => res = response,
                            Ok(Next) => (),
                        }
                    }
                    Ok(res)
                }
            });

        Box::new(res)
    }
}

impl ProxyService {
    fn early_response(
        &self,
        req_id: u64,
        mut res: Response<Body>,
        state: &State,
    ) -> Response<Body> {
        for mw in self.middlewares.lock().unwrap().iter_mut() {
            match mw.after_request(Some(&mut res), req_id, state) {
                Err(err) => res = Response::from(err),
                Ok(RespondWith(response)) => res = response,
                Ok(Next) => (),
            }
        }
        debug!("Early response is {:?}", &res);
        res
    }

    // Needed to avoid a single connection creating too much data in state
    // Since we need to identify each request in state (HashMap tuple identifier), it grows
    // for each request from the same connection
    fn clear_state(&self) {
        if let Ok(mut state) = self.state.lock() {
            state.clear();
        } else {
            error!("[FATAL] Cannot lock state in clean_stale_state");
        }
    }

    pub fn new(middlewares: Middlewares) -> Self {
        ProxyService {
            state: Arc::new(Mutex::new(HashMap::new())),
            client: Client::new(),
            rng: SmallRng::from_entropy(),
            middlewares,
        }
    }
}

impl IntoFuture for ProxyService {
    type Future = future::FutureResult<Self::Item, Self::Error>;
    type Item = Self;
    type Error = hyper::Error;

    fn into_future(self) -> Self::Future {
        future::ok(self)
    }
}

pub struct ProxyServiceBuilder {
    middlewares: Middlewares,
}

impl ProxyServiceBuilder {
    pub fn new(middlewares: Middlewares) -> Self {
        ProxyServiceBuilder { middlewares }
    }
}

impl NewService for ProxyServiceBuilder {
    type Error = hyper::Error;
    type ReqBody = Body;
    type ResBody = Body;
    type Service = ProxyService;
    type InitError = Box<Error + Send + Sync>;
    type Future = Box<Future<Item = Self::Service, Error = Self::InitError> + Send>;

    fn new_service(&self) -> Self::Future {
        let mws = Arc::clone(&self.middlewares);
        Box::new(future::ok(ProxyService::new(mws)))
    }
}