// cargo-deps: hsl, image, csv = "1.0.0-beta.4", serde, serde_derive

// ~~~ PUBLIC DOMAIN ~~~
// I, the copyright holder of this work, hereby release it
// into the public domain. This applies worldwide.
// In case this is not legally possible, I grant any entity
// the right to use this work for any purpose, without any
// conditions, unless such conditions are required by law.

extern crate csv;
extern crate hsl;
extern crate image;
extern crate serde;
#[macro_use]
extern crate serde_derive;

use std::collections::{BTreeSet, HashMap};
use std::io;

#[derive(Debug, Deserialize)]
#[serde(rename_all = "camelCase")]
struct Tile {
    tile_x: usize,
    tile_y: usize,
    create_time: u64,
    modify_count: u64,
    modify_time: u64,
    access_count: u64,
    access_time: u64,
}

// Torus size (in tiles).
const TORUS_SZ: u32 = 512;

// Tile width/height (in pixels).
const TILE_W: u32 = 8;
const TILE_H: u32 = 5;

fn main() {
    // Read the `torus.csv` into a 2D array of `(access, modify)`.
    // Also track the values we see in `BTreeSet` (for ordering).
    let mut tiles = [[(0, 0); TORUS_SZ as usize]; TORUS_SZ as usize];
    let mut ord_a = BTreeSet::new();
    let mut ord_m = BTreeSet::new();
    for result in csv::Reader::from_reader(io::stdin()).deserialize() {
        let Tile {
            create_time,
            modify_time,
            access_count: mut a,
            modify_count: mut m,
            tile_x: x,
            tile_y: y,
            ..
        } = result.unwrap();

        // Handle old migrated values.
        if modify_time == create_time && m > 0 {
            a += 1;
            m = 0;
        }

        ord_a.insert(a);
        ord_m.insert(m);

        tiles[y][x] = (a, m);
    }

    // Normalize all values by mapping them to equally spaced values in [0, 1].
    let normal_map = |ord: BTreeSet<u64>| -> HashMap<u64, f64> {
        ord.iter().enumerate().map(|(i, &x)| {
            (x, i as f64 / (ord.len() - 1) as f64)
        }).collect()
    };
    let normal_a = normal_map(ord_a);
    let normal_m = normal_map(ord_m);

    // Compose the heatmap image in-memory from the 2D array.
    let mut heatmap = image::ImageBuffer::new(TORUS_SZ * TILE_W, TORUS_SZ * TILE_H);
    let red = hsl::HSL::from_rgb(&[255, 0, 0]).h;
    // let green = hsl::HSL::from_rgb(&[0, 255, 0]).h;
    // let blue = hsl::HSL::from_rgb(&[0, 0, 255]).h;
    let yellow = hsl::HSL::from_rgb(&[255, 255, 0]).h;
    for y in 0..TORUS_SZ {
        for x in 0..TORUS_SZ {
            // Get and normalize the values.
            let (a, m) = tiles[y as usize][x as usize];
            let a = normal_a[&a].powf(1.0 / 2.0);
            let m = normal_m[&m].powf(1.0 / 3.0);

            // access => luminosity
            let l = ((a + m) * 0.5).min(0.7);
            // modify => saturation + hue (grey -> red -> yellow)
            let interp = |a, b, x| a * (1.0 - x) + b * x;
            let h = interp(red, yellow, m.powf(4.0));
            let s = m;

            let (r, g, b) = hsl::HSL { h, s, l }.to_rgb();
            let rgb = image::Rgb([r, g, b]);

            let coord = |x, dx, px| ((x * 2 + TORUS_SZ + 1) * px / 2 + dx) % (TORUS_SZ * px);
            for dy in 0..TILE_H {
                let y = coord(y, dy, TILE_H);
                for dx in 0..TILE_W {
                    let x = coord(x, dx, TILE_W);
                    heatmap.put_pixel(x, y, rgb);
                }
            }
        }
    }

    // Save the heatmap image.
    heatmap.save("heatmap.png").unwrap();
}