use std::ops::Sub;
use std::time::{Duration, Instant};

use minifb::{ScaleMode, Window, WindowOptions};

use crsn::asm::data::literal::Value;
use crsn::asm::instr::Cond;
use crsn::module::{EvalRes, OpTrait};
use crsn::runtime::fault::Fault;
use crsn::runtime::run_thread::{state::RunState, ThreadInfo};

use crate::defs::ScreenOp;

#[derive(Debug)]
struct Opts {
    auto_blit: bool,
    frame_rate: Duration,
}

#[derive(Debug)]
struct Backend {
    width: usize,
    height: usize,
    buffer: Vec<u32>,
    window: Option<Window>,
    last_render: Instant,
    opts: Opts,
}

impl Default for Backend {
    fn default() -> Self {
        Self {
            width: 0,
            height: 0,
            buffer: vec![],
            window: None,
            last_render: Instant::now().sub(Duration::from_secs(1)),
            opts: Opts {
                auto_blit: true,
                frame_rate: Duration::from_micros(16600),
            },
        }
    }
}

const OPT_AUTO_BLIT: u64 = 1;
const OPT_FRAME_RATE: u64 = 2;

// Hack for Window
unsafe impl std::marker::Send for Backend {}

impl OpTrait for ScreenOp {
    fn execute(&self, _info: &ThreadInfo, state: &mut RunState) -> Result<EvalRes, Fault> {
        let eres = EvalRes::default();
        match self {
            ScreenOp::ScreenInit { width, height } => {
                let w = state.read(*width)?;
                let h = state.read(*height)?;
                init(state, w, h)?;
            }
            ScreenOp::SetOpt { opt, val } => {
                let opt = state.read(*opt)?;
                let val = state.read(*val)?;
                let backend: &mut Backend = state.ext_mut();

                match opt {
                    OPT_AUTO_BLIT => {
                        backend.opts.auto_blit = val != 0;
                        debug!("Set auto blit to {:?}", backend.opts.auto_blit);
                    }
                    OPT_FRAME_RATE => {
                        backend.opts.frame_rate = Duration::from_micros(1_000_000 as u64 / val);
                        debug!("Set frame rate to {:?}", backend.opts.frame_rate);
                    }
                    other => {
                        warn!("Bad screen opt: {}", other);
                        state.set_flag(Cond::Invalid, true);
                    }
                }
            }
            ScreenOp::Blit { force } => {
                let force = state.read(*force)?;
                let backend: &mut Backend = state.ext_mut();

                if force != 0 {
                    blit(backend)
                } else {
                    blit_maybe(backend)
                }
            }
            ScreenOp::SetPixel { x, y, color } => {
                let x = state.read(*x)?;
                let y = state.read(*y)?;
                let color = state.read(*color)?;

                let backend: &mut Backend = state.ext_mut();

                if x >= backend.width as u64 || y >= backend.height as u64 {
                    state.set_flag(Cond::Overflow, true);
                    return Ok(eres);
                }

                match &mut backend.window {
                    Some(_w) => {
                        let index = y * backend.width as u64 + x;
                        if index as usize > backend.buffer.len() {
                            warn!("Screen set pixel out of bounds");
                            state.set_flag(Cond::Invalid, true);
                        } else {
                            backend.buffer[index as usize] = color as u32;

                            if backend.opts.auto_blit {
                                blit_maybe(backend);
                            }
                        }
                    }
                    None => {
                        state.set_flag(Cond::Invalid, true);
                    }
                }
            }
        }

        Ok(eres)
    }
    //
}

fn init(state: &mut RunState, width: Value, height: Value) -> Result<(), Fault> {
    let window = Window::new(
        "Croissant",
        width as usize,
        height as usize,
        WindowOptions {
            resize: true,
            scale_mode: ScaleMode::UpperLeft,
            ..WindowOptions::default()
        },
    ).expect("Unable to create window"); // TODO fault


    let backend: &mut Backend = state.ext_mut();

    if backend.window.is_some() {
        return Err(Fault::NotAllowed("Screen already initialized".into()));
    }

    backend.width = width as usize;
    backend.height = height as usize;
    backend.buffer = vec![0; (width * height) as usize];

    // window.limit_update_rate(Some(std::time::Duration::from_micros(16600)));
    // window.limit_update_rate(None);

    backend.window = Some(window);

    blit_maybe(backend);

    Ok(())
}

fn blit_maybe(backend: &mut Backend) {
    if backend.last_render.elapsed() >= backend.opts.frame_rate {
        blit(backend);
    }
}

fn blit(backend: &mut Backend) {
    backend.window.as_mut().unwrap()
        .update_with_buffer(&backend.buffer, backend.width, backend.height)
        .expect("Update screen"); // TODO fault

    backend.last_render = Instant::now();
}