use crate::{debug::draw_debug, huff::read_huff, split::split, Block, Frame, Pixel, View, P2};
use rayon::join;
use std::io::{BufReader, BufWriter, Read, Result, Write};

pub fn decode(size: P2, debug: bool, input: impl Read, output: impl Write) -> Result<()> {
    let mut input = BufReader::new(input);
    let mut output = BufWriter::new(output);

    let mut frame = Frame::new(size);
    let mut last_frame = Frame::new(size);
    let mut debug_frame = if debug { Some(Frame::new(size)) } else { None };

    let huff = true;
    loop {
        let b = if huff {
            let mut buf = vec![];
            read_huff(&mut input, &mut buf)?;
            let mut buf = std::io::Cursor::new(&mut buf);
            Block::read(&mut buf, View::all(size))?
        } else {
            Block::read(&mut input, View::all(size))?
        };

        decode_block(&last_frame, &mut frame, View::all(size), &b);

        if let Some(debug_frame) = &mut debug_frame {
            debug_frame.pixels.copy_from_slice(&frame.pixels);
            draw_debug(debug_frame, View::all(size), &b);
            Frame::write(&mut output, &debug_frame)?;
        } else {
            Frame::write(&mut output, &frame)?;
        }

        last_frame.pixels.copy_from_slice(&frame.pixels); // TODO use mem::swap
        frame.pixels.iter_mut().for_each(|e| *e = Pixel::BLACK);
    }
}

pub fn decode_block(last_frame: &Frame, frame: &mut Frame, view: View, block: &Block) {
    match block {
        Block::Lit(pxs) => frame.import(view, &pxs),
        Block::Split(a, b) => {
            let [av, bv] = split(view);
            let (frame1, frame2) =
                unsafe { (&mut *(frame as *mut Frame), &mut *(frame as *mut Frame)) };
            join(
                || decode_block(last_frame, frame1, av, &a),
                || decode_block(last_frame, frame2, bv, &b),
            );
        }
        Block::Ref(r) => {
            for y in view.a.y..view.b.y {
                for x in view.a.x..view.b.x {
                    let p = P2 { x, y };
                    frame[p] = last_frame[p + r.pos_off] + r.color_off
                }
            }
        }
    }
}