// Dergchat, a free XMPP client.
// Copyright (C) 2023 Werner Kroneman
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// This program 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 Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

use crate::types::{LoginCredentials, Message};
use dioxus::hooks::{UnboundedReceiver, UseRef, UseState};
use futures_util::stream::StreamExt;
use jid::BareJid;
use log::{error, info};
use std::collections::HashMap;
use std::future::Future;

use crate::widgets::login_screen::LoginStatus;
use tokio::select;
use xmpp::parsers::message::MessageType;
use xmpp::{Agent, ClientBuilder, ClientType};

/// An enum of commands that can be sent to the XMPP interface.
///
/// These very loosely correspond to XMPP stanzas, but are more high level.
#[derive(Debug)]
pub enum NetworkCommand {
    /// Start a new login attempt, resulting in either a successful login or an error.
    TryLogin { credentials: LoginCredentials },

    /// Join a room.
    JoinRoom { room: BareJid },

    /// Leave a room.
    LeaveRoom { room: BareJid },

    /// Send a message to a recipient.
    SendMessage { recipient: BareJid, message: String },

    Logout,
}

async fn handle_event(
    event: xmpp::Event,
    agent: &mut xmpp::Agent,
    messages: &mut UseRef<HashMap<BareJid, Vec<Message>>>,
) {
    match event {
        xmpp::Event::JoinRoom(jid, _conference) => {
            println!("Will auto-join room: {}", &jid);
            agent.join_room(jid, None, None, "en/us", "online").await;
        }
        xmpp::Event::RoomJoined(room_jid) => {
            println!("Joined room: {}", &room_jid);
            messages.with_mut(move |m| {
                m.entry(room_jid.clone()).or_insert(vec![]);
            });
        }
        xmpp::Event::RoomLeft(room_jid) => {
            println!("Left room: {}", &room_jid);
            messages.with_mut(move |m| {
                m.remove(&room_jid);
            });
        }
        xmpp::Event::ChatMessage(_id, sender, body) => {
            println!("Message from {}: {}", &sender, &body.0);
            messages.with_mut(move |m| {
                m.entry(sender.clone()).or_insert(vec![]).push(Message {
                    sender: sender.to_string(),
                    body: body.0,
                });
            });
        }
        xmpp::Event::RoomMessage(_id, room_jid, sender_nick, body) => {
            println!(
                "Message in {} from {}: {}",
                &room_jid, &sender_nick, &body.0
            );
            messages.with_mut(move |m| {
                m.entry(room_jid.clone()).or_insert(vec![]).push(Message {
                    sender: sender_nick,
                    body: body.0,
                })
            });
        }
        xmpp::Event::RoomPrivateMessage(_id, room_jid, sender_nick, body) => {
            println!(
                "Private message in {} from {}: {}",
                &room_jid, &sender_nick, &body.0
            );
            messages.with_mut(move |m| {
                m.entry(room_jid.clone()).or_insert(vec![]).push(Message {
                    sender: sender_nick,
                    body: body.0,
                })
            });
        }
        _ => {
            log::debug!("Received unsupported event {:?}", event);
        }
    }
}

pub fn xmpp_mainloop<'a>(
    agent: &'a mut Agent,
    mut room_data: &'a mut UseRef<HashMap<BareJid, Vec<Message>>>,
    commands: &'a mut UnboundedReceiver<NetworkCommand>,
) -> impl Future<Output = ()> + Sized + 'a {
    async move {
        loop {
            select! {
                events = agent.wait_for_events() => {
                    if let Some(events) = events {
                        for event in events {
                            handle_event(event, agent, &mut room_data).await;
                        }
                    } else {
                        info!("Disconnected");
                    }
                },
                command = commands.next() => {
                    if let Some(command) = command {
                        match command {
                            NetworkCommand::JoinRoom { room } => {
                                agent.join_room(room.clone(), None, None, "en-us", "online").await;
                            },
                            NetworkCommand::LeaveRoom { room } => {
                                agent.leave_room(
                                    room,
                                    "dergchat".to_string(),
                                    "en-us",
                                    "User left the room.").await;
                            },
                            NetworkCommand::SendMessage { recipient, message } => {
                                agent.send_message(recipient.into(), MessageType::Groupchat, "en-us", &message).await;
                            },
                            NetworkCommand::TryLogin { credentials: _ } => {
                                panic!("Already logged in.");
                            },
                            NetworkCommand::Logout => {
                                agent.disconnect().await;
                                break;
                            }
                        }
                    } else {
                        info!("Command channel closed");
                        break;
                    }
                },
            }
        }
    }
}

/// Wait for the agent to go online.
///
/// This function mutably borrows an Agent and waits for either an Online or Disconnected event.
///
/// The future resolves to Ok(()) if the agent went online, or Err(String) if the agent disconnected.
async fn await_online(agent: &mut Agent) -> Result<(), String> {
    // Wait for the next batch of events.
    let events = agent
        .wait_for_events()
        .await
        .ok_or("Stream closed unexpectedly".to_string())?;

    // We expect exactly one event; we operate under the assumption that xmpp-rs emits
    // exactly one events when it receives a connect/disconnect stanza from the server,
    // and that that is the first stanza it receives.
    // TODO: This is brittle; need to talk to the xmpp-rs to get stronger guarantees.
    assert_eq!(events.len(), 1);

    // We expect the first event to be either Online or Disconnected.
    match events.into_iter().next().expect("No events") {
        xmpp::Event::Online => {
            info!("Login attempt successful; connected.");
            Ok(())
        }
        xmpp::Event::Disconnected => {
            error!("Login attempt resulted in disconnect.");
            Err("Disconnected".to_string())
        }
        // We don't expect any other events; if we get one, we panic. (The assumption we made must be wrong.)
        // TODO: This is ugly.
        e => {
            panic!("Unexpected event: {:?}", e);
        }
    }
}

pub async fn run_xmpp_toplevel(
    connection_status: UseState<LoginStatus>,
    mut messages: UseRef<HashMap<BareJid, Vec<Message>>>,
    mut commands: UnboundedReceiver<NetworkCommand>,
) {
    // Await a login attempt:
    loop {
        let cmd = commands.next().await;

        if let Some(NetworkCommand::TryLogin { credentials }) = cmd {
            println!("Received credentials: {:?}", credentials);

            connection_status.set(LoginStatus::LoggingIn);

            let mut agent = ClientBuilder::new(credentials.username, &credentials.password.0)
                .set_client(ClientType::Pc, "dergchat")
                .build();

            match await_online(&mut agent).await {
                Ok(_) => {
                    connection_status.set(LoginStatus::LoggedIn);
                    info!("Connected");

                    xmpp_mainloop(&mut agent, &mut messages, &mut commands).await;
                }
                Err(e) => {
                    error!("Failed to connect: {}", e);
                    connection_status.set(LoginStatus::Error("Failed to connect".to_string()));
                }
            }
        } else {
            panic!("Expected TryLogin command");
        }
    }
}