use std::{

    fs::{File, OpenOptions},

    io::{Error, ErrorKind, Read, Result, Write},

    sync::mpsc,

    thread,

};

use crate::server::{

    database::Database,

    handlers::{IoResult, IoTask},

};

use log::*;

use mio::{Evented, Poll, PollOpt};

use mio_extras::channel;

pub type RequestId = u32;

pub struct IOThread {

    core_tx: mpsc::Sender<(RequestId, IoTask)>,

    core_rx: channel::Receiver<(RequestId, IoResult)>,

}

impl IOThread {

    pub fn new() -> Self {

        let (core_tx, io_rx) = mpsc::channel();

        let (io_tx, core_rx) = channel::channel();

        let mut db = Database::new();

        db.connect("localhost");

        thread::spawn(move || {

            while let Ok((request_id, task)) = io_rx.try_recv() {

                let response = match task {

                    IoTask::GetAccount {

                        nick,

                        protocol,

                        password_hash,

                        client_salt,

                        server_salt,

                    } => {

                        match db.get_account(

                            &nick,

                            protocol,

                            &password_hash,

                            &client_salt,

                            &server_salt,

                        ) {

                            Ok(account) => IoResult::Account(account),

                                IoResult::Account(None)

                            }

                        }

                    }

                    IoTask::SaveRoom {

                        room_id,

                        filename,

                        contents,

                    } => {

                        let result = match save_file(&filename, &contents) {

                            Ok(()) => true,

                            Err(e) => {

                                warn!(

                                    "Error while writing the room config file \"{}\": {}",

                                    filename, e

                                );

                                false

                            }

                        };

                        IoResult::SaveRoom(room_id, result)

                    }

                    IoTask::LoadRoom { room_id, filename } => {

                        let result = match load_file(&filename) {

                            Ok(contents) => Some(contents),

                            Err(e) => {

                                warn!(

                                    "Error while writing the room config file \"{}\": {}",

                                    filename, e

                                );

                                None

                            }

                        };

                        IoResult::LoadRoom(room_id, result)

                    }

                };

                io_tx.send((request_id, response));

            }

        });

        Self { core_rx, core_tx }

    }

    pub fn send(&self, request_id: RequestId, task: IoTask) {

        self.core_tx.send((request_id, task)).unwrap();

    }

    pub fn try_recv(&self) -> Option<(RequestId, IoResult)> {

        match self.core_rx.try_recv() {

            Ok(result) => Some(result),

            Err(mpsc::TryRecvError::Empty) => None,

            Err(mpsc::TryRecvError::Disconnected) => unreachable!(),

        }

    }

    pub fn register_rx(&self, poll: &mio::Poll, token: mio::Token) -> Result<()> {

        self.core_rx

            .register(poll, token, mio::Ready::readable(), PollOpt::edge())

    }

}

fn save_file(filename: &str, contents: &str) -> Result<()> {

    let mut writer = OpenOptions::new().create(true).write(true).open(filename)?;

    writer.write_all(contents.as_bytes())

}

fn load_file(filename: &str) -> Result<String> {

    let mut reader = File::open(filename)?;

    let mut result = String::new();

    reader.read_to_string(&mut result)?;

    Ok(result)

}