use std::rc::Rc;
use std::iter::FromIterator;
use std::collections::HashMap;

use serde_json;
use rand::{self, Rng};
use futures::Future;
use futures::future::{Either, ok as FutOk, err as FutErr};
use redis_async::resp::RespValue;
use cookie::{CookieJar, Cookie, Key};
use http::header::{self, HeaderValue};
use actix::prelude::*;
use actix_web::{error, Error, Result, HttpRequest, HttpResponse};
use actix_web::middleware::{SessionImpl, SessionBackend, Response as MiddlewareResponse};

use redis::{Command, RedisActor};


/// Session that stores data in redis
pub struct RedisSession {
    changed: bool,
    inner: Rc<Inner>,
    state: HashMap<String, String>,
    value: Option<String>,
}

impl SessionImpl for RedisSession {

    fn get(&self, key: &str) -> Option<&str> {
        if let Some(s) = self.state.get(key) {
            Some(s)
        } else {
            None
        }
    }

    fn set(&mut self, key: &str, value: String) {
        self.changed = true;
        self.state.insert(key.to_owned(), value);
    }

    fn remove(&mut self, key: &str) {
        self.changed = true;
        self.state.remove(key);
    }

    fn clear(&mut self) {
        self.changed = true;
        self.state.clear()
    }

    fn write(&self, resp: HttpResponse) -> Result<MiddlewareResponse> {
        if self.changed {
            Ok(MiddlewareResponse::Future(
                self.inner.update(&self.state, resp, self.value.as_ref())))
        } else {
            Ok(MiddlewareResponse::Done(resp))
        }
    }
}

/// Use redis as session storage.
///
/// You need to pass an address of the redis server and random value to the
/// constructor of `RedisSessionBackend`. This is private key for cookie session,
/// When this value is changed, all session data is lost.
///
/// Note that whatever you write into your session is visible by the user (but not modifiable).
///
/// Constructor panics if key length is less than 32 bytes.
pub struct RedisSessionBackend(Rc<Inner>);

impl RedisSessionBackend {
    /// Create new redis session backend
    ///
    /// * `addr` - address of the redis server
    pub fn new<S: Into<String>>(addr: S, key: &[u8]) -> RedisSessionBackend {
        RedisSessionBackend(
            Rc::new(Inner{key: Key::from_master(key),
                          ttl: "7200".to_owned(),
                          addr: RedisActor::start(addr),
                          name: "actix-session".to_owned()}))
    }

    /// Set time to live in seconds for session value
    pub fn ttl(mut self, ttl: u16) -> Self {
        Rc::get_mut(&mut self.0).unwrap().ttl = format!("{}", ttl);
        self
    }

    pub fn cookie_name(mut self, name: &str) -> Self {
        Rc::get_mut(&mut self.0).unwrap().name = name.to_owned();
        self
    }
}

impl<S> SessionBackend<S> for RedisSessionBackend {

    type Session = RedisSession;
    type ReadFuture = Box<Future<Item=RedisSession, Error=Error>>;

    fn from_request(&self, req: &mut HttpRequest<S>) -> Self::ReadFuture {
        let inner = Rc::clone(&self.0);

        Box::new(self.0.load(req).map(move |state| {
            if let Some((state, value)) = state {
                RedisSession {
                    changed: false,
                    inner: inner,
                    state: state,
                    value: Some(value),
                }
            } else {
                RedisSession {
                    changed: false,
                    inner: inner,
                    state: HashMap::new(),
                    value: None,
                }
            }
        }))
    }
}

struct Inner {
    key: Key,
    ttl: String,
    name: String,
    addr: Address<RedisActor>,
}

impl Inner {
    fn load<S>(&self, req: &mut HttpRequest<S>)
               -> Box<Future<Item=Option<(HashMap<String, String>, String)>, Error=Error>> {
        if let Ok(cookies) = req.cookies() {
            for cookie in cookies {
                if cookie.name() == self.name {
                    let mut jar = CookieJar::new();
                    jar.add_original(cookie.clone());
                    if let Some(cookie) = jar.signed(&self.key).get(&self.name) {
                        let value = cookie.value().to_owned();
                        return Box::new(
                            self.addr.call_fut(Command(resp_array!["GET", cookie.value()]))
                                .map_err(Error::from)
                                .and_then(move |res| {
                                    match res {
                                        Ok(val) => {
                                            match val {
                                                RespValue::Error(err) =>
                                                    return Err(
                                                        error::ErrorInternalServerError(err).into()),
                                                RespValue::SimpleString(s) =>
                                                    if let Ok(val) = serde_json::from_str(&s) {
                                                        return Ok(Some((val, value)))
                                                    },
                                                RespValue::BulkString(s) => {
                                                    if let Ok(val) = serde_json::from_slice(&s) {
                                                        return Ok(Some((val, value)))
                                                    }
                                                },
                                                _ => (),
                                            }
                                            Ok(None)
                                        },
                                        Err(err) => Err(error::ErrorInternalServerError(err).into())
                                    }
                                }))
                    } else {
                        return Box::new(FutOk(None))
                    }
                }
            }
        }
        Box::new(FutOk(None))
    }

    fn update(&self, state: &HashMap<String, String>,
              mut resp: HttpResponse,
              value: Option<&String>) -> Box<Future<Item=HttpResponse, Error=Error>>
    {
        let (value, jar) = if let Some(value) = value {
            (value.clone(), None)
        } else {
            let mut rng = rand::OsRng::new().unwrap();
            let value = String::from_iter(rng.gen_ascii_chars().take(32));

            let mut cookie = Cookie::new(self.name.clone(), value.clone());
            cookie.set_path("/");
            cookie.set_http_only(true);

            // set cookie
            let mut jar = CookieJar::new();
            jar.signed(&self.key).add(cookie);

            (value, Some(jar))
        };

        Box::new(
            match serde_json::to_string(state) {
                Err(e) => Either::A(FutErr(e.into())),
                Ok(body) => {
                    Either::B(
                        self.addr.call_fut(
                            Command(resp_array!["SET", value, body,"EX", &self.ttl]))
                            .map_err(Error::from)
                            .and_then(move |res| {
                                match res {
                                    Ok(_) => {
                                        if let Some(jar) = jar {
                                            for cookie in jar.delta() {
                                                let val = HeaderValue::from_str(
                                                    &cookie.to_string())?;
                                                resp.headers_mut().append(header::SET_COOKIE, val);
                                            }
                                        }
                                        Ok(resp)
                                    },
                                    Err(err) => Err(error::ErrorInternalServerError(err).into())
                                }
                            }))
                }
            })
    }
}