use std::fmt;

use crate::{
	channel::{ChannelKind, Channels},
	parse,
};

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ChanSpec {
	PulseA,
	PulseB,
	Triangle,
	Noise,
}
impl fmt::Display for ChanSpec {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
		match self {
			Self::PulseA => f.write_str("pulsea"),
			Self::PulseB => f.write_str("pulseb"),
			Self::Triangle => f.write_str("triangle"),
			Self::Noise => f.write_str("noise"),
		}
	}
}

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum Instruction {
	Pause(u16),
	PauseLen(u16),
	Jump(u16),
	SetVolume(ChanSpec, u8),
	SetPitch(ChanSpec, u8),
	SetPulseDutyA(u8),
	SetPulseDutyB(u8),
	SetNoiseMode(bool),
}
impl fmt::Display for Instruction {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
		match self {
			Self::Pause(len) => write!(f, "pause {len}"),
			Self::PauseLen(len) => write!(f, "pause_len {len}"),
			Self::Jump(pc) => write!(f, "jump {pc}"),
			Self::SetVolume(chan, v) => write!(f, "{chan} volume {v}"),
			Self::SetPitch(chan, p) => write!(f, "{chan} pitch {p}"),
			Self::SetPulseDutyA(dc) => write!(f, "{} duty_cycle {dc}", ChanSpec::PulseA),
			Self::SetPulseDutyB(dc) => write!(f, "{} duty_cycle {dc}", ChanSpec::PulseB),
			Self::SetNoiseMode(mode) => write!(f, "{} mode {mode}", ChanSpec::Noise),
		}
	}
}
use Instruction as I;

fn map_pitch(pitch: u8) -> f32 {
	const HALF_STEP: f32 = 1.059_463_1;
	HALF_STEP.powf(pitch as f32 - 128.0)
}

const fn map_volume(volume: u8) -> f32 {
	if volume > 100 {
		1.0
	} else {
		(volume as f32) / 100.0
	}
}

#[derive(Debug, Clone)]
pub struct Program {
	ins: Vec<Instruction>,
	pc: usize,
	pause_cnt: usize,
	pause_len: usize,
	looping: bool,
	playing: bool,
}
impl Program {
	pub const fn new(ins: Vec<Instruction>, looping: bool) -> Self {
		Self {
			ins,
			pc: 0,
			pause_cnt: 0,
			pause_len: 4,
			looping,
			playing: false,
		}
	}

	pub fn parse(src: &str, looping: bool) -> parse::Result<Self> {
		let ins = parse::parse(src)?;
		Ok(Self::new(ins, looping))
	}

	pub fn merge(self, other: Self) -> Self {
		let mut res = vec![];

		let mut l = 0;
		let mut r = 0;
		let mut l_pause = 0;
		let mut r_pause = 0;
		let l_ins = self.ins;
		let r_ins = other.ins;

		loop {
			if l >= l_ins.len() && r >= r_ins.len() {
				// were done here
				break;
			}

			while l < l_ins.len() {
				if l_pause > 0 {
					break;
				}
				let ins = l_ins[l];
				l += 1;
				if let I::Pause(cnt) = ins {
					l_pause = cnt;
					break;
				}
				res.push(ins);
			}

			while r < r_ins.len() {
				if r_pause > 0 {
					break;
				}
				let ins = r_ins[r];
				r += 1;
				if let I::Pause(cnt) = ins {
					r_pause = cnt;
					break;
				}
				res.push(ins);
			}

			if l_pause > 0 {
				if r_pause > 0 && l_pause >= r_pause {
					l_pause -= r_pause;
					res.push(I::Pause(r_pause));
					r_pause = 0;
				} else if r_pause == 0 {
					res.push(I::Pause(l_pause));
					l_pause = 0;
				}
			}

			if r_pause > 0 {
				if l_pause > 0 && r_pause >= l_pause {
					r_pause -= l_pause;
					res.push(I::Pause(l_pause));
					l_pause = 0;
				} else if l_pause == 0 {
					res.push(I::Pause(r_pause));
					r_pause = 0;
				}
			}
		}

		Self::new(res, self.looping)
	}

	fn exec_ins(&mut self, channels: &mut Channels, ins: Instruction) {
		use Instruction as I;
		match ins {
			I::Pause(cnt) => {
				self.pause_cnt = self.pause_len * (cnt as usize);
			}
			I::PauseLen(pause_len) => {
				self.pause_len = pause_len as usize;
			}
			I::Jump(pc) => {
				self.pc = pc as usize;
			}
			I::SetVolume(chan_spec, volume) => {
				// set the volume (amplitude) on a given channel
				use ChanSpec as C;
				let v = map_volume(volume);
				match chan_spec {
					C::PulseA => channels.pulse_a.volume = v,
					C::PulseB => channels.pulse_b.volume = v,
					C::Triangle => channels.triangle.volume = v,
					C::Noise => channels.noise.volume = v,
				}
			}
			I::SetPitch(chan_spec, pitch) => {
				// set the pitch (freq) on a given channel
				use ChanSpec as C;
				let p = map_pitch(pitch);
				match chan_spec {
					C::PulseA => channels.pulse_a.pitch = p,
					C::PulseB => channels.pulse_b.pitch = p,
					C::Triangle => channels.triangle.pitch = p,
					C::Noise => channels.noise.pitch = p,
				}
			}
			I::SetPulseDutyA(dc) => {
				if let ChannelKind::Pulse { duty_cycle } = &mut channels.pulse_a.kind {
					*duty_cycle = dc;
				}
			}
			I::SetPulseDutyB(dc) => {
				if let ChannelKind::Pulse { duty_cycle } = &mut channels.pulse_b.kind {
					*duty_cycle = dc;
				}
			}
			I::SetNoiseMode(m) => {
				if let ChannelKind::Noise { mode, .. } = &mut channels.noise.kind {
					*mode = m;
				}
			}
		}
	}

	pub fn exec(&mut self, channels: &mut Channels) {
		if !self.playing {
			return;
		}
		if self.pause_cnt > 0 {
			self.pause_cnt -= 1;
		}
		loop {
			if self.pause_cnt > 0 {
				break;
			}
			if self.is_finished() {
				if self.looping {
					self.pc = 0;
				} else {
					self.playing = false;
					break;
				}
			}
			let ins = self.ins[self.pc];
			self.exec_ins(channels, ins);
			self.pc += 1;
		}
	}

	pub const fn is_finished(&self) -> bool {
		self.pc >= self.ins.len()
	}

	pub const fn is_playing(&self) -> bool {
		self.playing
	}

	pub const fn play(&mut self) {
		self.playing = true;
		self.pc = 0;
	}

	pub const fn set_looping(&mut self, looping: bool) {
		self.looping = looping;
	}
}
impl fmt::Display for Program {
	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
		for (idx, ins) in self.ins.iter().enumerate() {
			if idx != 0 {
				writeln!(f)?;
			}
			write!(f, "{ins}")?;
		}
		Ok(())
	}
}