use std::{
	fs::File,
	sync::{
		Arc,
		Condvar,
		Mutex,
		mpsc,
	},
	thread::{
		self,
	},
	time::{Instant},
};

use anyhow::{
	anyhow,
	bail,
	Result,
};

use cpal::traits::{
	DeviceTrait,
	HostTrait,
	StreamTrait,
};

use fltk::{
	app,
	button::Button,
	enums::CallbackTrigger,
	frame::Frame,
	group::Flex,
	prelude::*,
	window::Window,
};

mod decoder;
mod net_reader;

const BUFFER_SIZE: usize = 5_000;

fn main () -> Result <()> {
	let args: Vec <_> = std::env::args ().collect ();
	
	match args.get (1).map (|s| &s[..]) {
		None => bail! ("First argument must be a subcommand like `play`"),
		Some ("debug-net") => cmd_debug_net (&args [1..]),
		Some ("gui") => cmd_gui (&args [1..]),
		Some ("play") => cmd_play (&args [1..]),
		Some (_) => bail! ("Unrecognized subcommand"),
	}
}

fn cmd_debug_net (args: &[String]) -> Result <()> {
	tracing_subscriber::fmt::init ();
	
	let mut urls: Vec <_> = args.iter ().skip (1).map (|s| s.to_string ()).collect ();
	urls.reverse ();
	
	let (fltk_tx, fltk_rx) = app::channel::<Message> ();
	let app = app::App::default ();
	let window_title = "Music Player".to_string ();
	let mut wind = Window::new (100, 100, 300, 300, None)
	.with_label (&window_title);
	wind.make_resizable (true);
	wind.end ();
	wind.show ();
	
	let mut shared_state = SharedState::default ();
	let silence = vec! [0; 12_000 * 4 * 2];
	shared_state.pcm_buffers.produce_bytes (silence);
	let shared_state = Arc::new ((Mutex::new (shared_state), Condvar::new ()));
	
	let thread_decoder = DecoderThread::new (
		Arc::clone (&shared_state),
		Some (fltk_tx.clone ()),
	);
	let mut audio_output = AudioOutput::new (
		Arc::clone (&shared_state),
		thread_decoder.tx.clone (),
	)?;
	
	if let Some (url) = urls.pop () {
		thread_decoder.tx.send (MessageToDecoder::SetUrl (url))?;
	}
	else {
		bail! ("No URLs to play");
	}
	
	while app.wait () {
		tracing::trace! ("Main thread is waiting on messages...");
		let msg = match fltk_rx.recv () {
			None => continue,
			Some (x) => x,
		};
		
		match msg {
			Message::DecoderStatus (x) => {
				if ! x {
					tracing::debug! ("decoder ended");
					if let Some (url) = urls.pop () {
						thread_decoder.tx.send (MessageToDecoder::SetUrl (url))?;
					}
					else {
						break;
					}
				}
			},
			_ => {},
		}
	}
	
	audio_output.pause ()?;
	thread_decoder.tx.send (MessageToDecoder::Quit)?;
	thread_decoder.join ()?;
	
	Ok (())
}

#[derive (Default)]
pub struct SharedState {
	pub pcm_buffers: decoder::PcmBuffers,
}

struct Gui {
	intend_to_play: bool,
	can_decode: bool,
	audio_is_streaming: bool,
	trying_to_stream: bool,
	
	but_pause: Button,
	but_play: Button,
}

fn set_active <W: WidgetExt> (w: &mut W, b: bool) {
	if b {
		w.activate ();
	}
	else {
		w.deactivate ();
	}
}

impl Gui {
	pub fn sync (&mut self) {
		set_active (
			&mut self.but_pause, 
			self.intend_to_play,
		);
		set_active (
			&mut self.but_play, 
			! self.intend_to_play &&
			self.can_decode
		);
	}
}

#[derive (Clone, Copy, Debug)]
enum Message {
	DecoderStatus (bool),
	RawPlay,
	RawPause,
	RawSet,
	RawSkip,
}

fn cmd_gui (args: &[String]) -> Result <()> {
	use std::io::BufRead;
	
	tracing_subscriber::fmt::init ();
	
	let playlist = {
		let mut files = Vec::with_capacity (2000);
		let file = File::open ("/home/user/music/playlist.m3u")?;
		let reader = std::io::BufReader::new (file);
		
		for line in reader.lines () {
			files.push (line?);
		}
		
		files
	};
	
	let filenames: Vec <_> = args.iter ()
	.skip (1)
	.map (|s| s.to_string ())
	.collect ();
	
	let (fltk_tx, fltk_rx) = app::channel::<Message> ();
	
	let app = app::App::default ();
	let window_title = "Music Player".to_string ();
	let mut wind = Window::new (100, 100, 600, 600, None)
	.with_label (&window_title);
	wind.make_resizable (true);
	
	let mut col = Flex::default ().column ().size_of_parent ();
	
	{
		let mut row = Flex::default ().row ();
		
		let mut label = Frame::default ().with_label ("Audio output");
		let mut but_audio_play = Button::default ().with_label ("Play");
		let mut but_audio_pause = Button::default ().with_label ("Pause");
		
		row.set_size (&mut label, 100);
		row.set_size (&mut but_audio_play, 100);
		row.set_size (&mut but_audio_pause, 100);
		
		but_audio_play.set_trigger (CallbackTrigger::Release);
		but_audio_pause.set_trigger (CallbackTrigger::Release);
		
		but_audio_play.emit (fltk_tx, Message::RawPlay);
		but_audio_pause.emit (fltk_tx, Message::RawPause);
		
		row.end ();
		
		col.add (&row);
		col.set_size (&mut row, 30);
	}
	
	{
		let mut row = Flex::default ().row ();
		
		let mut label = Frame::default ().with_label ("Decoder");
		let mut but_set = Button::default ().with_label ("Set");
		let mut but_skip = Button::default ().with_label ("Skip");
		
		row.set_size (&mut label, 100);
		row.set_size (&mut but_set, 100);
		row.set_size (&mut but_skip, 100);
		
		but_set.set_trigger (CallbackTrigger::Release);
		but_skip.set_trigger (CallbackTrigger::Release);
		
		but_set.emit (fltk_tx, Message::RawSet);
		but_skip.emit (fltk_tx, Message::RawSkip);
		
		row.end ();
		
		col.add (&row);
		col.set_size (&mut row, 30);
	}
	
	col.end ();
	
	wind.end ();
	wind.show ();
	
	let mut shared_state = SharedState::default ();
	let silence = vec! [0; 12_000 * 4 * 2];
	shared_state.pcm_buffers.produce_bytes (silence);
	let shared_state = Arc::new ((Mutex::new (shared_state), Condvar::new ()));
	
	let thread_decoder = DecoderThread::new (
		Arc::clone (&shared_state),
		Some (fltk_tx.clone ()),
	);
	let mut audio_output = AudioOutput::new (
		Arc::clone (&shared_state),
		thread_decoder.tx.clone (),
	)?;
	
	// Doesn't work.
	// audio_output.pause ()?;
	
	/*
	for filename in filenames {
		//gui.can_decode = true;
		thread_decoder.tx.send (MessageToDecoder::QueueFile (filename))?;
	}
	*/
	
	// let mut play_queue = vec! [];
	
	let mut current_file = None;
	
	while app.wait () {
		let msg = match fltk_rx.recv () {
			None => continue,
			Some (x) => x,
		};
		
		match msg {
			Message::DecoderStatus (x) => {
				if ! x {
					tracing::info! ("Decoder ran dry");
					current_file = None;
				}
			},
			Message::RawPlay => {
				audio_output.play ()?;
			},
			Message::RawPause => {
				audio_output.pause ()?;
			},
			Message::RawSet => {
				use rand::Rng;
				let idx = rand::thread_rng ().gen_range (0..playlist.len ());
				let filename = &playlist [idx];
				tracing::info! ("Set decoder to {}", filename);
				thread_decoder.tx.send (MessageToDecoder::SetFile (format! ("/home/user/music/{}", filename)))?;
				current_file = Some (filename);
			},
			Message::RawSkip => {
				thread_decoder.tx.send (MessageToDecoder::Clear)?;
			},
		}
	}
	
	tracing::info! ("Received FLTK quit signal");
	
	audio_output.pause ()?;
	
	tracing::debug! ("Joining decoder thread...");
	thread_decoder.tx.send (MessageToDecoder::Quit)?;
	thread_decoder.join ()?;
	
	tracing::debug! ("Joining PCM thread...");
	drop (audio_output);
	
	tracing::info! ("Exiting cleanly.");
	
	Ok (())
}
	
fn cmd_play (args: &[String]) -> Result <()> {
	unimplemented! ();
	/*
	tracing_subscriber::fmt::init ();
	
	let filenames: Vec <_> = args.iter ()
	.skip (1)
	.map (|s| s.to_string ())
	.collect ();
	
	// let (decoder_tx, decoder_rx) = mpsc::sync_channel (1);
	let (main_tx, main_rx) = mpsc::sync_channel (1);
	
	let shared_state = Arc::new ((Mutex::new (SharedState::default ()), Condvar::new ()));
	let pcm_quit = Arc::new ((Mutex::new (false), Condvar::new ()));
	
	let thread_decoder = DecoderThread::new (
		Arc::clone (&shared_state),
		main_tx.clone (),
	);
	let audio_output = AudioOutput::new (
		Arc::clone (&pcm_quit), 
		Arc::clone (&shared_state),
		thread_decoder.tx.clone (),
	)?;
	
	for filename in filenames {
		thread_decoder.tx.send (MessageToDecoder::QueueFile (filename))?;
	}
	
	while let Ok (msg) = main_rx.recv () { match msg {
		MessageToMain::DecoderEmpty => break,
	}}
	
	tracing::debug! ("Asking decoder to quit...");
	thread_decoder.tx.send (MessageToDecoder::Quit)?;
	tracing::debug! ("Joining decoder thread...");
	thread_decoder.join ()?;
	
	tracing::debug! ("Joining PCM thread...");
	drop (audio_output);
	
	tracing::info! ("Exiting cleanly.");
	Ok (())
	*/
}

struct DecoderThread {
	join_handle: thread::JoinHandle <Result <()>>,
	pub tx: mpsc::SyncSender <MessageToDecoder>,
}

enum MessageToDecoder {
	NeedPcm,
	SetFile (String),
	SetUrl (String),
	Clear,
	Quit,
}

enum Decoder {
	File (decoder::Decoder <decoder::FfmpegDemuxer>),
	Http (decoder::Decoder <decoder::HttpOggDemuxer>),
}

impl DecoderThread {
	pub fn new (
		shared_state: Arc <(Mutex <SharedState>, Condvar)>,
		main_tx: Option <fltk::app::Sender <Message>>,
	) -> Self
	{
		let (tx, rx) = mpsc::sync_channel (4);
		
		let self_tx = tx.clone ();
		
		let join_handle = thread::spawn (move|| {
			let mut decoder: Option <Decoder> = None;
			
			'thread: while let Ok (msg) = rx.recv () { match msg {
				MessageToDecoder::Clear => {
					decoder = None;
					let new_buffers = decoder::PcmBuffers::default ();
					self_tx.send (MessageToDecoder::NeedPcm)?;
					
					let mut shared_state = shared_state.0.lock ().unwrap ();
					shared_state.pcm_buffers = new_buffers;
				},
				MessageToDecoder::NeedPcm => {
					// tracing::trace! ("DecoderThread recv'd NeedPcm");
					let mut bytes_produced = 0;
					let mut status = false;
					
					'pipeline: while bytes_produced < BUFFER_SIZE * 4 * 2 {
						// tracing::trace! ("Pumping multi-file decode pipeline");
						let frame = match &mut decoder {
							None => None,
							Some (Decoder::File (x)) => x.next ()?,
							Some (Decoder::Http (x)) => x.next ()?,
						};
						
						if let Some (frame) = frame {
							// tracing::trace! ("Decoded bytes");
							status = true;
							let mut shared_state = shared_state.0.lock ().unwrap ();
							bytes_produced += frame.data ().len ();
							shared_state.pcm_buffers.produce_bytes (frame.data ().into ());
							continue 'pipeline;
						}
						else if decoder.is_some () {
							decoder = None;
							tracing::trace! ("Decoder ended, telling main thread");
							main_tx.as_ref ().map (|x| x.send (Message::DecoderStatus (false)));
						}
						
						{
							// tracing::trace! ("Decoder thread is producing silence");
							let frame = vec! [0; 2_000 * 4 * 2];
							{
								let mut shared_state = shared_state.0.lock ().unwrap ();
								
								bytes_produced += frame.len ();
								shared_state.pcm_buffers.produce_bytes (frame);
								// tracing::trace! ("PCM buffer: {}", shared_state.pcm_buffers.samples_available ());
							}
							status = false;
							continue 'pipeline;
						}
					}
				},
				MessageToDecoder::SetFile (x) => {
					let (demuxer, codec) = decoder::FfmpegDemuxer::new (&x)?;
					decoder = Some (Decoder::File (decoder::Decoder::new (demuxer, codec)?));
					
					let new_buffers = decoder::PcmBuffers::default ();
					self_tx.send (MessageToDecoder::NeedPcm)?;
					let mut shared_state = shared_state.0.lock ().unwrap ();
					shared_state.pcm_buffers = new_buffers;
				},
				MessageToDecoder::SetUrl (x) => {
					let (demuxer, codec) = decoder::HttpOggDemuxer::new (x)?;
					decoder = Some (Decoder::Http (decoder::Decoder::new (demuxer, codec)?));
					
					let new_buffers = decoder::PcmBuffers::default ();
					self_tx.send (MessageToDecoder::NeedPcm)?;
					let mut shared_state = shared_state.0.lock ().unwrap ();
					shared_state.pcm_buffers = new_buffers;
				},
				MessageToDecoder::Quit => {
					tracing::debug! ("DecoderThread recv'd Quit");
					break 'thread;
				},
			}}
			
			tracing::info! ("Decoder thread quit gracefully");
			
			Ok::<_, anyhow::Error> (())
		});
		
		Self {
			join_handle,
			tx,
		}
	}
	
	pub fn join (self) -> Result <()> {
		self.join_handle.join ().unwrap ()
	}
}

struct AudioOutput {
	_host: cpal::Host,
	_device: cpal::Device,
	stream: cpal::Stream,
}

impl AudioOutput {
	pub fn new (
		shared_state: Arc <(Mutex <SharedState>, Condvar)>,
		decoder_tx: mpsc::SyncSender <MessageToDecoder>,
	) -> Result <Self> 
	{
		let host = cpal::default_host ();
		let device = host.default_output_device ().ok_or_else (|| anyhow! ("can't open cpal device"))?;
		
		let mut supported_configs_range = device.supported_output_configs ()?
		.filter (|c| c.channels () == 2 && c.sample_format () == cpal::SampleFormat::F32);
		
		let config = supported_configs_range.next ()
		.ok_or_else (|| anyhow! ("can't get stereo f32 audio output"))?
		.with_sample_rate (cpal::SampleRate (decoder::SAMPLE_RATE))
		.config ();
		
		let stream = device.build_output_stream (
			&config,
			move |data: &mut [f32], _: &cpal::OutputCallbackInfo| {
				let (lock, _) = &*shared_state;
				
				let time_start = Instant::now ();
				let need_pcm;
				let status;
				{
					let mut decoder_state = match lock.lock () {
						Ok (x) => x,
						Err (_) => return,
					};
					let time_stop = Instant::now ();
					let dur = time_stop - time_start;
					if dur.as_micros () > 100 {
						tracing::warn! ("PCM thread waited {} us for a lock", dur.as_micros ());
					}
					
					let pcm_buffers = &mut decoder_state.pcm_buffers;
					
					if ! pcm_buffers.consume_exact (data) {
						tracing::warn! ("PCM buffer underflow");
						status = false;
						
						for x in data {
							*x = 0.0;
						}
					}
					else {
						status = true;
					}
					
					need_pcm = pcm_buffers.samples_available () < BUFFER_SIZE;
				}
				
				if need_pcm {
					decoder_tx.try_send (MessageToDecoder::NeedPcm).ok ();
					// tracing::trace! ("AudioOutput sent NeedPcm");
				}
			},
			move |err| {
				tracing::error! ("{:?}", err);
			},
		)?;
		
		Ok (Self {
			_host: host,
			_device: device,
			stream,
		})
	}
	
	pub fn play (&mut self) -> Result <()> {
		Ok (self.stream.play ()?)
	}
	
	pub fn pause (&mut self) -> Result <()> {
		Ok (self.stream.pause ()?)
	}
}

#[cfg (test)]
mod test {
	use super::*;
	
	#[test]
	fn decode () -> Result <()> {
		ffmpeg_next::init ()?;
		
		let mut input_ctx = ffmpeg_next::format::input (&"test.opus")?;
		let stream = input_ctx
		.streams ()
		.best (ffmpeg_next::media::Type::Audio)
		.ok_or_else (|| anyhow! ("can't find good audio stream"))?;
		let best_stream_idx = stream.index ();
		
		let mut decoder = stream.codec ().decoder ().audio ()?;
		
		let mut packet_count = 0;
		let mut frame_count = 0;
		let mut frame = ffmpeg_next::util::frame::Audio::empty ();
		
		let mut packets = input_ctx.packets ();
		
		loop {
			let mut did_anything = false;
			
			while decoder.receive_frame (&mut frame).is_ok () {
				frame_count += 1;
				did_anything = true;
			}
			
			match packets.next () {
				None => {},
				Some ((stream, packet)) => {
					did_anything = true;
					if stream.index () == best_stream_idx {
						packet_count += 1;
						decoder.send_packet (&packet)?;
					}
				},
			}
			
			if ! did_anything {
				break;
			}
		}
		
		Ok (())
	}
}