/*
 * meli - mailbox module.
 *
 * Copyright 2017 Manos Pitsidianakis
 *
 * This file is part of meli.
 *
 * meli is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * meli is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with meli. If not, see <http://www.gnu.org/licenses/>.
 */

use mailbox::email::{Envelope, Flag};
use error::{MeliError, Result};
use mailbox::backends::{BackendOp, BackendOpGenerator, MailBackend, RefreshEvent, RefreshEventConsumer};
use mailbox::email::parser;
use conf::Folder;

extern crate notify;

use self::notify::{Watcher, RecursiveMode, watcher, DebouncedEvent};
use std::time::Duration;

use std::sync::mpsc::channel;
//use std::sync::mpsc::sync_channel;
//use std::sync::mpsc::SyncSender;
//use std::time::Duration;
use std::thread;
extern crate crossbeam;
use std::path::PathBuf;
use memmap::{Mmap, Protection};

/// `BackendOp` implementor for Maildir
#[derive(Debug, Default)]
pub struct MaildirOp {
    path: String,
    slice: Option<Mmap>,
}

impl Clone for MaildirOp {
    fn clone(&self) -> Self {
        MaildirOp {
            path: self.path.clone(),
            slice: None,
        }
    }
}

impl MaildirOp {
    pub fn new(path: String) -> Self {
        MaildirOp {
            path: path,
            slice: None,
        }
    }
}

impl BackendOp for MaildirOp {
    fn description(&self) -> String {
        format!("Path of file: {}", self.path)
    }
    fn as_bytes(&mut self) -> Result<&[u8]> {
        if self.slice.is_none() {
            self.slice = Some(
                Mmap::open_path(self.path.to_string(), Protection::Read)?,
            );
        }
        /* Unwrap is safe since we use ? above. */
        Ok(unsafe { self.slice.as_ref().unwrap().as_slice() })
    }
    fn fetch_headers(&mut self) -> Result<&[u8]> {
        let raw = self.as_bytes()?;
        let result = parser::headers_raw(raw).to_full_result()?;
        Ok(result)
    }
    fn fetch_body(&mut self) -> Result<&[u8]> {
        let raw = self.as_bytes()?;
        let result = parser::headers_raw(raw).to_full_result()?;
        Ok(result)
    }
    fn fetch_flags(&self) -> Flag {
        let mut flag = Flag::default();
        let path = PathBuf::from(&self.path);
        let filename = path.file_name().unwrap().to_str().unwrap();
        if !filename.contains(":2,") {
            return flag;
        }

        for f in filename.chars().rev() {
            match f {
                ',' => break,
                'P' => flag |= Flag::PASSED,
                'R' => flag |= Flag::REPLIED,
                'S' => flag |= Flag::SEEN,
                'T' => flag |= Flag::TRASHED,
                'D' => flag |= Flag::DRAFT,
                'F' => flag |= Flag::FLAGGED,
                 _  => panic!(),
            }

        }


        flag
    }
}


/// Maildir backend https://cr.yp.to/proto/maildir.html
#[derive(Debug)]
pub struct MaildirType {
    path: String,
}


impl MailBackend for MaildirType {
    fn get(&self, folder: &Folder) -> Result<Vec<Envelope>> {
        self.get_multicore(4, folder)
    }
    fn watch(&self, sender: RefreshEventConsumer, folders: &[Folder]) -> () {
        let folders = folders.to_vec();

        thread::Builder::new().name("folder watch".to_string()).spawn(move || {
            let (tx, rx) = channel();
            let mut watcher = watcher(tx, Duration::from_secs(1)).unwrap();
            for f in folders {
                if MaildirType::is_valid(&f).is_err() {
                    continue;
                }
                let mut p = PathBuf::from(&f.get_path());
                p.push("cur");
                watcher.watch(&p, RecursiveMode::NonRecursive).unwrap();
                p.pop();
                p.push("new");
                watcher.watch(&p, RecursiveMode::NonRecursive).unwrap();
            }
            loop {
                match rx.recv() {
                    Ok(event) => {
                        match event {
                            DebouncedEvent::Create(pathbuf) => {
                                sender.send(RefreshEvent { folder: format!("{}", pathbuf.parent().unwrap().to_str().unwrap()) });
                            },
                            _ => {},
                        }
                    }
                    Err(e) => eprintln!("watch error: {:?}", e),
                }
            }
        }).unwrap();
    }
}

impl MaildirType {
    pub fn new(path: &str) -> Self {
        MaildirType {
            path: path.to_string(),
        }
    }
    fn is_valid(f: &Folder) -> Result<()> {
        let path = f.get_path();
        let mut p = PathBuf::from(path);
        for d in &["cur", "new", "tmp"] {
            p.push(d);
            if !p.is_dir() {
                return Err(MeliError::new(
                    format!("{} is not a valid maildir folder", path),
                ));
            }
            p.pop();
        }
        Ok(())
    }
    pub fn get_multicore(&self, cores: usize, folder: &Folder) -> Result<Vec<Envelope>> {
        MaildirType::is_valid(folder)?;
        let path = folder.get_path();
        let mut path = PathBuf::from(path);
        path.push("cur");
        let iter = path.read_dir()?;
        let count = path.read_dir()?.count();
        let mut files: Vec<String> = Vec::with_capacity(count);
        let mut r = Vec::with_capacity(count);
        for e in iter {
            let e = e.and_then(|x| {
                let path = x.path();
                Ok(path.to_str().unwrap().to_string())
            })?;
            files.push(e);
        }
        let mut threads = Vec::with_capacity(cores);
        if !files.is_empty() {
            crossbeam::scope(|scope| {
                let chunk_size = if count / cores > 0 {
                    count / cores
                } else {
                    count
                };
                for chunk in files.chunks(chunk_size) {
                    let s = scope.spawn(move || {
                        let mut local_r: Vec<Envelope> = Vec::with_capacity(chunk.len());
                        for e in chunk {
                            let e_copy = e.to_string();
                            if let Some(mut e) = Envelope::from(Box::new(BackendOpGenerator::new(
                                Box::new(move || Box::new(MaildirOp::new(e_copy.clone()))),
                            ))) {
                                e.populate_headers();
                                local_r.push(e);
                            }
                        }
                        local_r
                    });
                    threads.push(s);
                }
            });
        }
        for t in threads {
            let mut result = t.join();
            r.append(&mut result);
        }
        Ok(r)
    }
}