use std::collections::{BTreeMap, HashMap, HashSet};

use image::RgbaImage;
use itertools::Itertools;
use sixel_image::SixelColor;

fn render_sixel(img: &RgbaImage) -> String {
    let colors: HashMap<[u8; 3], u16> = img
        .pixels()
        .map(|p| [p[0], p[1], p[2]].map(compress))
        .collect::<HashSet<[u8; 3]>>() // dedup
        .into_iter()
        .enumerate()
        .map(|(i, c)| (c, wrapping_into(i)))
        .collect();
    let color_registers: BTreeMap<u16, SixelColor> = colors
        .iter()
        .map(|(&c, &i)| (i, SixelColor::Rgb(c[0], c[1], c[2])))
        .collect();

    let pixels: Vec<Vec<sixel_image::Pixel>> = img
        .pixels()
        .map(|p| {
            let c = [p[0], p[1], p[2]].map(compress);
            let ci = colors[&c];
            unimplemented!("can't construct the `Pixel` from external crate")
        })
        .chunks(img.width() as usize)
        .into_iter()
        .map(|c| c.collect())
        .collect();

    sixel_image::SixelSerializer::new(&color_registers, &pixels).serialize()
}

fn wrapping_into(u: usize) -> u16 {
    (u % u16::MAX as usize) as u16
}

/// compress a color value from the range [0, 255] to the range [0, 100]
fn compress(a: u8) -> u8 {
    (a as u16 * 100 / 255) as u8
}

fn main() {
    let img = image::RgbaImage::new(100, 100);
    println!("{}", render_sixel(&img));
}