use crate::{
    debug::draw_debug, huff::read_huff, impls::join, split::split, Block, Frame, View, P2,
};
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 d = Decoder::new(size);
    let mut f = Frame::new(size);
    loop {
        d.decode_frame(&mut input, &mut f, debug)?;
        Frame::write(&mut output, &f)?;
    }
}

pub struct Decoder {
    last_frame: Frame,
    size: P2,
}

impl Decoder {
    pub fn new(size: P2) -> Self {
        Self {
            size,
            last_frame: Frame::new(size),
        }
    }
    pub fn decode_frame(
        &mut self,
        mut input: impl Read,
        output: &mut Frame,
        debug: bool,
    ) -> Result<()> {
        let huff = true;
        let b = if huff {
            let mut buf = vec![];
            read_huff(&mut input, &mut buf)?;
            eprintln!("{}", buf.len());
            let mut buf = std::io::Cursor::new(&mut buf);
            Block::read(&mut buf, View::all(self.size))?
        } else {
            Block::read(&mut input, View::all(self.size))?
        };

        decode_block(&self.last_frame, output, View::all(self.size), &b);
        self.last_frame.pixels.copy_from_slice(&output.pixels); // TODO use mem::swap
        if debug {
            draw_debug(output, View::all(self.size), &b);
        }
        Ok(())
    }
}

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
                }
            }
        }
    }
}