/*
 * meli - plugins
 *
 * Copyright 2019  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 super::*;
use fnv::FnvHashMap;
use melib::async_workers::{Async, AsyncBuilder, AsyncStatus, WorkContext};
use melib::backends::FolderHash;
use melib::backends::{
    Backend, BackendOp, Backends, Folder, MailBackend, RefreshEvent, RefreshEventConsumer,
};
use melib::conf::AccountSettings;
use melib::email::{Envelope, EnvelopeHash, Flag};
use melib::error::{MeliError, Result};
use std::collections::BTreeMap;
use std::sync::{Arc, Mutex, RwLock};

// TODO replace with melib::Envelope after simplifying melib::Envelope's
// fields/interface/deserializing
#[derive(Debug, Clone, Serialize, Deserialize)]
struct SimpleEnvelope {
    hash: EnvelopeHash,
    subject: String,
    from: String,
    to: String,
    date: String,
    message_id: String,
    references: String,
}

#[derive(Debug)]
pub struct PluginBackend {
    plugin: Plugin,
    child: std::process::Child,
    channel: Arc<Mutex<RpcChannel>>,
    tag_index: Option<Arc<RwLock<BTreeMap<u64, String>>>>,
    is_online: Arc<Mutex<(std::time::Instant, Result<()>)>>,
}

impl Drop for PluginBackend {
    fn drop(&mut self) {
        if let Err(err) = debug!(self.child.kill()) {
            eprintln!(
                "Error: could not kill process {} spawned by plugin {} ({})",
                self.child.id(),
                &self.plugin.name,
                err
            );
        }
    }
}

impl MailBackend for PluginBackend {
    fn is_online(&self) -> Result<()> {
        if let Ok(mut is_online) = self.is_online.try_lock() {
            let now = std::time::Instant::now();
            if now.duration_since(is_online.0) >= std::time::Duration::new(2, 0) {
                if let Ok(mut channel) = self.channel.try_lock() {
                    channel.write_ref(&rmpv::ValueRef::Ext(BACKEND_FN, b"is_online"))?;
                    debug!(channel.expect_ack())?;
                    let ret: PluginResult<()> = debug!(channel.from_read())?;
                    is_online.0 = now;
                    is_online.1 = ret.into();
                }
            }
            is_online.1.clone()
        } else {
            Err(MeliError::new("busy"))
        }
    }

    fn connect(&mut self) {}

    fn get(&mut self, folder: &Folder) -> Async<Result<Vec<Envelope>>> {
        let mut w = AsyncBuilder::new();
        let _folder_hash = folder.hash();
        let channel = self.channel.clone();
        let handle = {
            let tx = w.tx();
            let closure = move |_work_context| {
                let mut channel = channel.lock().unwrap();
                channel
                    .write_ref(&rmpv::ValueRef::Ext(BACKEND_FN, b"get"))
                    .unwrap();
                channel.expect_ack().unwrap();
                loop {
                    let read_val: Result<PluginResult<Option<Vec<SimpleEnvelope>>>> =
                        channel.from_read();
                    match read_val.map(Into::into).and_then(std::convert::identity) {
                        Ok(Some(a)) => {
                            tx.send(AsyncStatus::Payload(Ok(a
                                .into_iter()
                                .filter_map(
                                    |SimpleEnvelope {
                                         hash,
                                         date,
                                         from,
                                         to,
                                         subject,
                                         message_id,
                                         references,
                                     }| {
                                        let mut env = melib::Envelope::new(hash);
                                        env.set_date(date.as_bytes());
                                        if let Ok(d) = melib::email::parser::date(date.as_bytes()) {
                                            env.set_datetime(d);
                                        }
                                        env.set_message_id(message_id.as_bytes());
                                        let parse_result =
                                            melib::email::parser::rfc2822address_list(
                                                from.as_bytes(),
                                            );
                                        if parse_result.is_done() {
                                            let value = parse_result.to_full_result().unwrap();
                                            env.set_from(value);
                                        }
                                        let parse_result =
                                            melib::email::parser::rfc2822address_list(
                                                to.as_bytes(),
                                            );
                                        if parse_result.is_done() {
                                            let value = parse_result.to_full_result().unwrap();
                                            env.set_to(value);
                                        }
                                        let parse_result =
                                            melib::email::parser::phrase(subject.as_bytes());
                                        if parse_result.is_done() {
                                            let value = parse_result.to_full_result().unwrap();
                                            env.set_subject(value);
                                        }
                                        if !references.is_empty() {
                                            let parse_result = melib::email::parser::references(
                                                references.as_bytes(),
                                            );
                                            if parse_result.is_done() {
                                                for v in parse_result.to_full_result().unwrap() {
                                                    env.push_references(v);
                                                }
                                            }
                                            env.set_references(references.as_bytes());
                                        }

                                        Some(env)
                                    },
                                )
                                .collect::<Vec<Envelope>>())))
                                .unwrap();
                        }
                        Ok(None) => {
                            tx.send(AsyncStatus::Finished).unwrap();
                            return;
                        }
                        Err(err) => {
                            tx.send(AsyncStatus::Payload(Err(err))).unwrap();
                            tx.send(AsyncStatus::Finished).unwrap();
                            return;
                        }
                    };
                }
            };
            Box::new(closure)
        };
        w.build(handle)
    }

    fn refresh(
        &mut self,
        _folder_hash: FolderHash,
        _sender: RefreshEventConsumer,
    ) -> Result<Async<Result<Vec<RefreshEvent>>>> {
        Err(MeliError::new("Unimplemented."))
    }
    fn watch(
        &self,
        _sender: RefreshEventConsumer,
        _work_context: WorkContext,
    ) -> Result<std::thread::ThreadId> {
        Err(MeliError::new("Unimplemented."))
    }

    fn folders(&self) -> Result<FnvHashMap<FolderHash, Folder>> {
        let mut ret: FnvHashMap<FolderHash, Folder> = Default::default();
        ret.insert(0, Folder::default());
        Ok(ret)
    }

    fn operation(&self, hash: EnvelopeHash) -> Box<dyn BackendOp> {
        Box::new(PluginOp {
            hash,
            channel: self.channel.clone(),
            tag_index: self.tag_index.clone(),
            bytes: None,
        })
    }

    fn save(&self, _bytes: &[u8], _folder: &str, _flags: Option<Flag>) -> Result<()> {
        Err(MeliError::new("Unimplemented."))
    }
    fn create_folder(&mut self, _name: String) -> Result<Folder> {
        Err(MeliError::new("Unimplemented."))
    }
    fn tags(&self) -> Option<Arc<RwLock<BTreeMap<u64, String>>>> {
        self.tag_index.clone()
    }
    fn as_any(&self) -> &dyn::std::any::Any {
        self
    }
}

impl PluginBackend {
    pub fn new(
        listener: UnixListener,
        plugin: Plugin,
        _s: &AccountSettings,
        _is_subscribed: Box<dyn Fn(&str) -> bool>,
    ) -> Result<Box<dyn MailBackend>> {
        if plugin.kind != PluginKind::Backend {
            return Err(MeliError::new(format!(
                "Error: Plugin `{}` is not a mail backend plugin, it's `{:?}`",
                &plugin.name, &plugin.kind
            )));
        }
        let parts = split_command!(&plugin.executable);
        let child = std::process::Command::new(&parts[0])
            .args(&parts[1..])
            .stdin(Stdio::piped())
            .stdout(Stdio::piped())
            .spawn()?;
        let (stream, _) = listener.accept()?;
        /* send init message to plugin to register hooks */
        let session = Uuid::new_v4();
        let channel = RpcChannel::new(stream, &session)?;
        let now = std::time::Instant::now() - std::time::Duration::from_secs(5);

        Ok(Box::new(PluginBackend {
            child,
            plugin,
            channel: Arc::new(Mutex::new(channel)),
            tag_index: None,
            is_online: Arc::new(Mutex::new((now, Err(MeliError::new("Unitialized"))))),
        }))
    }

    pub fn register(listener: UnixListener, plugin: Plugin, backends: &mut Backends) {
        backends.register(
            plugin.name.clone(),
            Backend {
                create_fn: Box::new(move || {
                    let plugin = plugin.clone();
                    let listener = listener.try_clone().unwrap();
                    Box::new(move |f, i| {
                        let plugin = plugin.clone();
                        let listener = listener.try_clone().unwrap();
                        PluginBackend::new(listener, plugin, f, i)
                    })
                }),
                validate_conf_fn: Box::new(|_| Ok(())),
            },
        );
    }
}

#[derive(Debug)]
struct PluginOp {
    hash: EnvelopeHash,
    channel: Arc<Mutex<RpcChannel>>,
    tag_index: Option<Arc<RwLock<BTreeMap<u64, String>>>>,
    bytes: Option<String>,
}

impl BackendOp for PluginOp {
    fn description(&self) -> String {
        String::new()
    }

    fn as_bytes(&mut self) -> Result<&[u8]> {
        if let Some(ref bytes) = self.bytes {
            return Ok(bytes.as_bytes());
        }

        if let Ok(mut channel) = self.channel.try_lock() {
            channel.write_ref(&rmpv::ValueRef::Ext(BACKEND_OP_FN, b"as_bytes"))?;
            debug!(channel.expect_ack())?;
            channel.write_ref(&rmpv::ValueRef::Integer(self.hash.into()))?;
            debug!(channel.expect_ack())?;
            let bytes: Result<PluginResult<String>> = channel.from_read();
            self.bytes = Some(bytes.map(Into::into).and_then(std::convert::identity)?);
            Ok(self.bytes.as_ref().map(String::as_bytes).unwrap())
        } else {
            Err(MeliError::new("busy"))
        }
    }

    fn fetch_flags(&self) -> Flag {
        let flag = Flag::default();

        flag
    }

    fn set_flag(&mut self, __envelope: &mut Envelope, _f: Flag, _value: bool) -> Result<()> {
        Err(MeliError::new("Unimplemented."))
    }

    fn set_tag(&mut self, _envelope: &mut Envelope, _tag: String, _value: bool) -> Result<()> {
        Err(MeliError::new("Unimplemented."))
    }
}