extern crate chrono;
extern crate imap;
extern crate mailparse;
extern crate native_tls;
extern crate rayon;
extern crate toml;
extern crate xdg;

use native_tls::{TlsConnector, TlsStream};
use rayon::prelude::*;

use std::fs::File;
use std::io::prelude::*;
use std::net::TcpStream;
use std::process::Command;
use std::sync::mpsc;
use std::thread;
use std::time::Duration;
use std::io::Write;

#[derive(Clone)]
struct Account {
    name: String,
    server: (String, u16),
    username: String,
    password: String,
}

impl Account {
    pub fn connect(&self) -> Result<Connection<TlsStream<TcpStream>>, imap::error::Error> {
        let tls = TlsConnector::builder().build()?;
        imap::connect((&*self.server.0, self.server.1), &self.server.0, &tls).and_then(|c| {
            let mut c = try!(
                c.login(self.username.trim(), self.password.trim())
                    .map_err(|(e, _)| e)
            );
            let cap = try!(c.capabilities());
            if !cap.iter().any(|&c| c == "IDLE") {
                return Err(imap::error::Error::Bad(cap.iter().cloned().collect()));
            }
            try!(c.select("INBOX"));
            Ok(Connection {
                account: self.clone(),
                socket: c,
            })
        })
    }
}

struct Connection<T: Read + Write> {
    account: Account,
    socket: imap::Session<T>,
}

impl<T: Read + Write + imap::extensions::idle::SetReadTimeout> Connection<T> {
    pub fn handle(mut self, account: usize, mut tx: mpsc::Sender<(usize, usize)>) {
        loop {
            if let Err(e) = self.check(account, &mut tx) {
                // the connection has failed for some reason
                // try to log out (we probably can't)
                eprintln!("connection to {} failed: {:?}", self.account.name, e);
                break;
            }
        }

        // try to reconnect
        let mut wait = 1;
        for _ in 0..5 {
            eprintln!(
                "connection to {} lost; trying to reconnect...",
                self.account.name
            );
            match self.account.connect() {
                Ok(c) => {
                    println!("{} connection reestablished", self.account.name);
                    return c.handle(account, tx);
                }
                Err(e) => {
                    eprintln!("failed to connect to {}: {:?}", self.account.name, e);
                    thread::sleep(Duration::from_secs(wait));
                }
            }

            wait *= 2;
            println!("waittime: {}", wait);
        }
    }

    fn check(
        &mut self,
        account: usize,
        tx: &mut mpsc::Sender<(usize, usize)>,
    ) -> Result<(), imap::error::Error> {
        // Keep track of all the e-mails we have already notified about
        let mut last_notified = 0;

        loop {
            // check current state of inbox
            let mut uids = self.socket.uid_search("UNSEEN 1:*")?;
            let num_unseen = uids.len();
            if uids.iter().all(|&uid| uid <= last_notified) {
                // there are no messages we haven't already notified about
                uids.clear();
            }
            last_notified = std::cmp::max(last_notified, uids.iter().cloned().max().unwrap_or(0));

            tx.send((account, num_unseen)).unwrap();

            // IDLE until we see changes
            self.socket.idle()?.wait_keepalive()?;
        }
    }
}

fn main() {
    // Load the user's config
    let xdg = match xdg::BaseDirectories::new() {
        Ok(xdg) => xdg,
        Err(e) => {
            println!("Could not find configuration file buzz.toml: {}", e);
            return;
        }
    };
    let config = match xdg.find_config_file("buzz/buzz.toml") {
        Some(config) => config,
        None => {
            println!("Could not find configuration file buzz.toml");
            return;
        }
    };
    let config = {
        let mut f = match File::open(config) {
            Ok(f) => f,
            Err(e) => {
                println!("Could not open configuration file buzz.toml: {}", e);
                return;
            }
        };
        let mut s = String::new();
        if let Err(e) = f.read_to_string(&mut s) {
            println!("Could not read configuration file buzz.toml: {}", e);
            return;
        }
        match s.parse::<toml::Value>() {
            Ok(t) => t,
            Err(e) => {
                println!("Could not parse configuration file buzz.toml: {}", e);
                return;
            }
        }
    };

    // Figure out what accounts we have to deal with
    let accounts: Vec<_> = match config.as_table() {
        Some(t) => {
            t.iter()
                .filter_map(|(name, v)| match v.as_table() {
                    None => {
                        println!("Configuration for account {} is broken: not a table", name);
                        None
                    }
                    Some(t) => {
                        let pwcmd = match t.get("pwcmd").and_then(|p| p.as_str()) {
                            None => return None,
                            Some(pwcmd) => pwcmd,
                        };

                        let password = match Command::new("sh").arg("-c").arg(pwcmd).output() {
                            Ok(output) => String::from_utf8_lossy(&output.stdout).into_owned(),
                            Err(e) => {
                                println!("Failed to launch password command for {}: {}", name, e);
                                return None;
                            }
                        };

                        Some(Account {
                            name: name.as_str().to_owned(),
                            server: (
                                t["server"].as_str().unwrap().to_owned(),
                                t["port"].as_integer().unwrap() as u16,
                            ),
                            username: t["username"].as_str().unwrap().to_owned(),
                            password: password,
                        })
                    }
                })
                .collect()
        }
        None => {
            println!("Could not parse configuration file buzz.toml: not a table");
            return;
        }
    };

    if accounts.is_empty() {
        println!("No accounts in config; exiting...");
        return;
    }

    // TODO: w.set_tooltip(&"Whatever".to_string());
    // TODO: app.wait_for_message();

    let accounts: Vec<_> = accounts
        .par_iter()
        .filter_map(|account| {
            let mut wait = 1;
            for _ in 0..5 {
                match account.connect() {
                    Ok(c) => return Some(c),
                    Err(imap::error::Error::Io(e)) => {
                        println!(
                            "Failed to connect account {}: {}; retrying in {}s",
                            account.name,
                            e,
                            wait
                        );
                        thread::sleep(Duration::from_secs(wait));
                    }
                    Err(e) => {
                        println!("{} host produced bad IMAP tunnel: {:?}", account.name, e);
                        break;
                    }
                }

                wait *= 2;
            }

            None
        })
        .collect();

    if accounts.is_empty() {
        println!("No accounts in config worked; exiting...");
        return;
    }

    // We have now connected

    let (tx, rx) = mpsc::channel();
    let mut unseen: Vec<_> = accounts.iter().map(|_| 0).collect();
    for (i, conn) in accounts.into_iter().enumerate() {
        let tx = tx.clone();
        thread::spawn(move || { conn.handle(i, tx); });
    }

    for (i, num_unseen) in rx {
        unseen[i] = num_unseen;
        let output_path = ::std::env::args().nth(1).unwrap();
        let commands = ::std::env::args().nth(2).unwrap();
        let the_output = Command::new("sh").arg("-c").arg(&commands).output()
            .ok().expect("Failed to execute.");
        let mut file = std::fs::File::create(&output_path).expect("create failed");
        file.write_all(num_unseen.to_string().as_bytes()).expect(
            "write failed",
        );
    }
}