use async_channel::{self, Receiver, Sender};
use async_std::prelude::*;
use async_std::task::{self, JoinHandle};
use rosc::OscMessage;
use std::collections::VecDeque;
use thiserror::Error;

use async_osc::prelude::*;

#[derive(Error, Debug)]
pub enum SwitcherError {
    #[error("Channel for switcher events full")]
    CannotSendEvent(#[from] async_channel::SendError<SwitcherEvent>),
    #[error("Channel for OSC messages full")]
    CannotSendMessage(#[from] async_channel::SendError<OscMessage>),
    #[error("Decode OSC packet failed")]
    Osc(rosc::OscError),

    #[error("IO error")]
    Io(#[from] std::io::Error),
}

impl From<rosc::OscError> for SwitcherError {
    fn from(error: rosc::OscError) -> Self {
        Self::Osc(error)
    }
}

pub type Result<T> = std::result::Result<T, SwitcherError>;

pub type ChannelId = usize;

#[derive(Debug)]
pub enum SwitcherEvent {
    Enable(ChannelId),
    Disable(ChannelId),
}

#[derive(Default)]
pub struct SwitcherState {
    // osc_tx: Sender<OscMessage>,
    channels: Vec<ChannelState>,
    active_channel: usize,
    messages: Messages,
}

#[derive(Default)]
pub struct ChannelState {
    id: ChannelId,
    pub name: String,
    pub locked: bool,
    pub enabled: bool,
}

impl ChannelState {
    pub fn new(id: ChannelId) -> Self {
        Self {
            id,
            ..Default::default()
        }
    }
}

pub struct SwitcherHandle {
    events_tx: Sender<SwitcherEvent>,
    osc_rx: Option<Receiver<OscMessage>>,
    task: JoinHandle<Result<()>>,
}

impl SwitcherHandle {
    pub fn run() -> Self {
        let (osc_tx, osc_rx) = async_channel::unbounded();
        let (events_tx, events_rx) = async_channel::unbounded();
        let state = SwitcherState::new();
        let task = task::spawn(run_loop(state, events_rx, osc_tx));
        SwitcherHandle {
            events_tx,
            osc_rx: Some(osc_rx),
            task,
        }
    }
    pub async fn join(self) -> Result<()> {
        self.task.await
    }

    pub async fn send(&self, event: SwitcherEvent) -> Result<()> {
        log::debug!("switcher got event: {:?}", event);
        self.events_tx.send(event).await?;
        Ok(())
    }

    pub fn sender(&self) -> Sender<SwitcherEvent> {
        self.events_tx.clone()
    }

    pub fn take_receiver(&mut self) -> Option<Receiver<OscMessage>> {
        self.osc_rx.take()
    }
}

pub async fn run_loop(
    mut state: SwitcherState,
    mut events_rx: Receiver<SwitcherEvent>,
    osc_tx: Sender<OscMessage>,
) -> Result<()> {
    state.init();
    loop {
        while let Some(message) = state.pop_message() {
            osc_tx.send(message).await?;
        }
        if let Some(event) = events_rx.next().await {
            state.on_event(event);
        }
    }
}

impl SwitcherState {
    pub fn new() -> Self {
        Default::default()
    }

    pub fn init(&mut self) {
        let num_channels = 4;
        for i in 0..num_channels {
            let channel = ChannelState::new(i);
            self.channels.push(channel);
        }
        self.messages.push("/*", ("xmit", 1));
        self.messages.push("/mixer/out/0/bus/0/on", (1.0,));
        self.messages.push("/mixer/bus/0/ch/0/on", (1.0,));
        self.update_state();
    }

    pub fn on_event(&mut self, event: SwitcherEvent) {
        match event {
            SwitcherEvent::Enable(channel) => self.enable_channel(channel),
            SwitcherEvent::Disable(channel) => self.disable_channel(channel),
        }
        self.update_state();
    }
    pub fn enable_channel(&mut self, channel_id: ChannelId) {
        if let Some(channel) = self.channels.iter_mut().find(|c| c.id == channel_id) {
            if !channel.locked {
                channel.enabled = true;
            }
        }
    }

    pub fn disable_channel(&mut self, channel_id: ChannelId) {
        if let Some(channel) = self.channels.iter_mut().find(|c| c.id == channel_id) {
            if !channel.locked {
                channel.enabled = false;
            }
        }
    }

    fn update_state(&mut self) {
        let next_active_channel = self
            .channels
            .iter()
            .rev()
            .find(|c| c.enabled)
            .or(self.channels.get(0))
            .unwrap()
            .id;
        if next_active_channel != self.active_channel {
            self.active_channel = next_active_channel;
            self.on_channel_change();
        }
    }

    fn on_channel_change(&mut self) {
        for channel in self.channels.iter() {
            if channel.id == self.active_channel {
                self.messages
                    .push(format!("/mixer/bus/0/ch/{}/on", channel.id), (1.0,));
            } else {
                self.messages
                    .push(format!("/mixer/bus/0/ch/{}/on", channel.id), (0.0,));
            }
        }
    }

    fn pop_message(&mut self) -> Option<OscMessage> {
        self.messages.pop()
    }
}

pub struct Messages {
    inner: VecDeque<OscMessage>,
}

impl Default for Messages {
    fn default() -> Self {
        Self::new()
    }
}

impl Messages {
    pub fn new() -> Self {
        Self {
            inner: VecDeque::new(),
        }
    }

    fn push<T>(&mut self, addr: impl ToString, args: T)
    where
        T: IntoOscArgs,
    {
        self.inner.push_back(OscMessage::new(addr, args));
    }

    fn pop(&mut self) -> Option<OscMessage> {
        self.inner.pop_front()
    }
}