use image::{ImageBuffer, Rgb};
use rayon::prelude::*;

// Number of frames to generate.
const FRAMES = 200;

// Frame size.
const IMGW: u32 = 1024;
const IMGH: u32 = 1024;

// Fractal settings.
const MAXITER: u32 = IMGW;
const MAXITER_F64: f64 = MAXITER as f64;
const ESCRAD: f64 = 2.4;

// Target coordinates (what to "zoom in on" with each new frame.)
const TARGX = -0.4638686756;
const TARGX = 0.0723647;

fn main() {
    let w = IMGW as f64;
    let h = IMGH as f64;

    // Fractal bounds.
    let mut width: f64 = 2.0; // Initial frame width
    let mut xmin: f64 = -1.0;
    let mut ymin: f64 = -1.0;

    let zoom_factor = 1.2;

    for i in 1..FRAMES {
        let pxs: Vec<u8> = (0..IMGH)
            .into_par_iter()
            .flat_map(|y| {
                let fy = y as f64;
                (0..IMGW)
                    .into_par_iter()
                    .flat_map(move |x| {
                        let cx = map_range(x as f64, 0.0, w, xmin, xmin + width);
                        let cy = map_range(fy, 0.0, h, ymin, ymin + width);
                        let c = num_complex::Complex::new(cx, cy);

                        // Compute color for each pixel.
                        col_map(esc_time(c)).to_vec()
                    })
                    .collect::<Vec<u8>>()
            })
            .collect();

        // Create the image from the pixel buffer.
        let img = ImageBuffer::<Rgb<u8>, _>::from_raw(IMGW, IMGH, pxs).unwrap();

        img.save(format!("imgs/{i}.png")).unwrap();
        println!("#{i} done.");

        // Adjust bounds for the next zoom level
        xmin = TARGX - width / 2.0;
        ymin = TARGY - width / 2.0;
        width /= zoom_factor; // Zoom in by reducing width
    }
}


// Maps a value from one range to another.
fn map_range(val: f64, imin: f64, imax: f64, omin: f64, omax: f64) -> f64 {
    omin + (val - imin) * (omax - omin) / (imax - imin)
}

// Computes the escape time for a given point in the complex plane.
fn esc_time(c: num_complex::Complex<f64>) -> u32 {
    let mut z = c;
    for i in 0..MAXITER {
        if z.norm() > ESCRAD {
            return i;
        }
        z = (-z).ln() / z.ln();
    }
    MAXITER
}

// Maps the iteration count to a color.
fn col_map(iter: u32) -> [u8; 3] {
    if iter == MAXITER {
        [0, 0, 0] // Black for points that never escape.
    } else {
        // TODO: Fancy colors.
        let t = iter as f64 / MAXITER_F64;
        let c = (t * MAXITER_F64) as u8;
        [c, c, c]
    }
}
