use anyhow::{Context, Result};
use enkou_shaders::Coefficients2;
use enkou_shaders::camera::Camera;
use enkou_shaders::chaos_game::ChaosGame;
use enkou_shaders::transform::Transform;
use glam::{Affine2, Vec2, uvec2, UVec2};
use image::{GrayImage, Luma};
use rand::SeedableRng;
use rand_xoshiro::Xoshiro256StarStar;
use std::mem;
use std::process::Command;
use tempfile::{NamedTempFile};

const ITERATIONS: u32 = 50_000;
const ITERATIONS_DISCARD: u32 = 20;
const IMAGE_DIMENSION: UVec2 = uvec2(600, 600);

pub fn main() -> Result<()> {
    let seed: u64 = 4; // chosen by fair dice roll
    let mut rng = Xoshiro256StarStar::seed_from_u64(seed);

    let transforms = [
        // F_0: (x / 2, y / 2)
        Transform::new(Affine2::from_coefficients(0.5, 0.0, 0.0, 0.0, 0.5, 0.0)),
        // F_1: ((x + 1) / 2, y / 2)
        Transform::new(Affine2::from_coefficients(0.5, 0.0, 0.5, 0.0, 0.5, 0.0)),
        // F_2: (x / 2, (y + 1) / 2)
        Transform::new(Affine2::from_coefficients(0.5, 0.0, 0.0, 0.0, 0.5, 0.5)),
    ];

    let weights = [1.0 / 3.0, 1.0 / 3.0, 1.0 / 3.0];

    let mut image = GrayImage::new(IMAGE_DIMENSION.x, IMAGE_DIMENSION.y);

    // The gasket is defined on the range [0, 1] for both X and Y
    let camera = Camera::new(
        IMAGE_DIMENSION,
        Vec2::ONE * 0.5,
        0.0,
        Vec2::ZERO,
        IMAGE_DIMENSION.as_vec2(),
    );

    let mut chaos_game = ChaosGame::new(&mut rng, &transforms, &weights);
    for i in 0..ITERATIONS {
        let next_point = chaos_game.next().unwrap();

        if i < ITERATIONS_DISCARD {
            continue;
        }

        if let Some(next_point) = camera.transform_point_to_image(next_point) {
            image.put_pixel(next_point.x, next_point.y, Luma([255u8]))
        }
    }

    let temp = NamedTempFile::with_suffix(".png").context("Unable to create file for image")?;
    image.save(temp.path()).context("Unable to save image")?;

    let open_program = cfg_select! {
        unix => "xdg-open",
        _ => panic!("Unknown system"),
    };

    Command::new(open_program)
        .arg(temp.path())
        .spawn()?
        .wait()?;

    // In case the image viewer forks and gives control back prior to reading the file,
    // drop it and don't run the constructor
    mem::forget(temp);

    Ok(())
}