use std::time::Duration;
use std::io;
use std::str;
use std::rc::Rc;
use std::sync::{Arc,Mutex};
use std::error::Error;
use std::cell::{Cell,RefCell};
use std::fs::File;
use std::io::Read;

use serde::{Serialize,Deserialize};

use rand::rngs::{StdRng, OsRng};
use rand::{RngCore, SeedableRng};

use std::str::FromStr;
use hyper;
use hyper::client::Client;

use riker::actors::*;

use super::types::*;
use super::config::Config;

#[derive(Deserialize, Serialize, Debug, Clone)]
pub struct Params {
    pub fridge_setpoint: f32,
    pub fridge_difference: f32,
    pub overshoot_delay: u64,
    pub overshoot_factor: f32,
    pub disabled: bool,
    pub nowort: bool,
    pub fridge_range_lower: f32,
    pub fridge_range_upper: f32,
}

impl Params {
    pub fn defaults() -> Params {
        Params {
            fridge_setpoint: 16.0,
            fridge_difference: 0.2,
            overshoot_delay: 720, // 12 minutes
            overshoot_factor: 1.0,
            disabled: false,
            nowort: false,
            fridge_range_lower: 3.0,
            fridge_range_upper: 3.0,
            }
    }

    fn try_load(filename: &str) -> Result<Params, TemplogError> {
        let mut s = String::new();
        File::open(filename)?.read_to_string(&mut s)?;
        Ok(serde_json::from_str(&s)?)
    }

    pub fn load(config: &Config) -> Params {
        Self::try_load(&config.PARAMS_FILE)
            .unwrap_or_else(|_| Params::defaults())
    }

}

pub struct ParamWaiter {
    limitlog: NotTooOften,
    // last_etag is used for long-polling.
    last_etag: RefCell<String>,
    epoch: String,
    chan: ChannelRef<Params>,

    config: Config,
}

const LOG_MINUTES: u64 = 15;
const MAX_RESPONSE_SIZE: usize = 10000;
const TIMEOUT_MINUTES: u64 = 5;

impl ParamWaiter {

    fn new(config: Config) -> Self {
        let mut b = [0u8; 15]; // 15 bytes -> 20 characters base64
        OsRng.fill_bytes(&mut b);
        let epoch = base64::encode(&b);

        ParamWaiter {
            limitlog: NotTooOften::new(LOG_MINUTES*60),
            last_etag: RefCell::new(String::new()),
            epoch: epoch,
            config: config,
        }
    }


    async fn keep_waiting(&mut self) {
        loop {
            self.wait_updates().await;
        }
    }

    async fn wait_updates(&mut self) {

        let uri = self.config.SETTINGS_URL.parse().expect("Bad SETTINGS_URL in config");
        let mut req = hyper::Request::new(hyper::Method::Get, uri);
        req.headers_mut().insert(hyper::header::ETAG, self.last_etag.borrow());
        let resp = hyper::Client::new(&self.handle).request(req).await?;
        let b = resp.body().concat2().await?;
        let new_params = self.handle_response(b)?;
        self.chan.tell(Publish{msg: new_params, topic: "params".into()}, None);
    }

    fn handle_response(&self, buf : hyper::Chunk, status: hyper::StatusCode) -> Result<Params, TemplogError> {
        #[derive(Deserialize, Debug)]
        struct Response {
            // sent as an opaque etag: header. Has format "epoch-nonce",
            // responses where the epoch do not match ParamWaiter::epoch are dropped
            etag: String,
            params: Params,
        }

        let text = String::from_utf8_lossy(buf.as_ref());
        match status {
            hyper::StatusCode::Ok => {
                // new params
                let r: Response = serde_json::from_str(&text)?;
                let mut le = self.last_etag.borrow_mut();
                *le = r.etag;

                // update params if the epoch is correct
                if let Some(e) = le.split('-').next() {
                    if e == &self.epoch {
                        self.write_params(&r.params);
                        return Ok(r.params);
                    }
                }
                Err(TemplogError::new(&format!("Bad epoch from server '{}' expected '{}'", *le, self.epoch)))
            }
            hyper::StatusCode::NotModified => {
                // XXX this isn't really an error. Should handle_response() return 
                // Result<Option<Params>, TemplogError> instead?

                Err(TemplogError::new("304 unmodified (long polling timeout at the server)"))
            },
            _ => {
                Err(TemplogError::new(&format!("Wrong server response code {}: {}", status.as_u16(), text)))
            },
        }
    }

    fn write_params(&self, params: &Params) {
        let p = atomicwrites::AtomicFile::new(&self.config.PARAMS_FILE, atomicwrites::AllowOverwrite);
        p.write(|f| {
            serde_json::to_writer(f, params)
        });
    }
}

impl Actor for ParamWaiter {

    fn post_start(&mut self, ctx: &Context<Self::Msg>) {
        self.chan = channel("params", &ctx.system).unwrap();
        ctx.run(self.wait_updates());
    }
}

    // pub fn stream(config: Config, handle: Handle) -> Result<(), TemplogError> {
    //     let rcself = Rc::new(ParamWaiter::new(config, handle));

    //     let dur = Duration::from_millis(4000);
    //     for _ in Interval::new(dur, &rcself.handle).unwrap() {
    //         // fetch params
    //         // TODO - skip if inflight.
    //         let r = await!(rcself.make_request()).map_err(|e| TemplogError::new_hyper("response", e))?;
    //         let status = r.status();
    //         let b = await!(r.body().concat2()).map_err(|e| TemplogError::new_hyper("body", e))?;
    //         if let Ok(params) = rcself.handle_response(b, status) {
    //             stream_yield!(params);
    //         }
    //     }
    //     Ok(())
    // }