use rand::Rng;
use std::collections::HashMap;
use std::fs::File;
use std::io::{BufWriter, Write};

const WIDTH: i32 = 640;
const HEIGHT: i32 = 640;
const N_OF_POINTS: usize = 10;

fn dist(x1: i32, y1: i32, x2: i32, y2: i32) -> f64 {
    let result: f64 = ((x1 - x2).pow(2) as f64 + (y1 - y2).pow(2) as f64); // sqrt is not necessary
    result // fun fact, the last statement of a function just returns
}

#[derive(Debug)]
struct Point {
    x: i32,
    y: i32,
    r: i32,
    g: i32,
    b: i32,
}

pub fn main(filename: &str) {
    let mut rng = rand::rng();
    let f = File::create(filename).unwrap();
    // a BufWriter keeps the file contents in memory, this is much faster than
    // syscalls from writing directly to a file.
    // The best part? BufWriter will write to the file for you when it calls
    // Drop
    let mut file = BufWriter::new(f);
    let header = format!("P3\n{}\n{}\n255\n", WIDTH, HEIGHT);
    file.write_all(header.as_bytes()).unwrap();

    // HashMap was unnessecary, Vec is fine
    // creating with capacity can decrease memory allocation
    let mut points: Vec<Point> = Vec::with_capacity(N_OF_POINTS);

    // Create random points
    for _ in 0..N_OF_POINTS {
        let x = rng.random_range(0..WIDTH);
        let y = rng.random_range(0..HEIGHT);
        let r = rng.random_range(0..=255);
        let g = rng.random_range(0..=255);
        let b = rng.random_range(0..=255);

        let point = Point { x, y, r, g, b };

        points.push(point);
    }

    for y in 0..HEIGHT {
        for x in 0..WIDTH {
            let mut chosen_color = String::new();
            let mut closest_distance: f64 = f64::MAX;

            for point in points.iter() {
                let d = dist(x, y, point.x, point.y);
                if d < closest_distance {
                    closest_distance = d;
                    // .to_string was unnessecary
                    chosen_color = format!("{} {} {}\n", point.r, point.g, point.b);
                }
            }
            file.write_all(chosen_color.as_bytes()).unwrap();
        }
    }
}