//! Regenerate the PNG and multi-resolution Windows ICO from the editable SVG.
use image::codecs::ico::{IcoEncoder, IcoFrame};
use std::{error::Error, fs::File};

fn main() -> Result<(), Box<dyn Error>> {
    let tree = resvg::usvg::Tree::from_data(
        include_bytes!("../assets/icon.svg"),
        &resvg::usvg::Options::default(),
    )?;
    let mut frames = Vec::new();
    for size in [16, 24, 32, 48, 64, 128, 256, 512] {
        let mut pixmap = resvg::tiny_skia::Pixmap::new(size, size).ok_or("invalid size")?;
        resvg::render(
            &tree,
            resvg::tiny_skia::Transform::from_scale(size as f32 / 512.0, size as f32 / 512.0),
            &mut pixmap.as_mut(),
        );
        // tiny-skia stores premultiplied pixels; PNG and ICO need straight alpha.
        let mut rgba = pixmap.take();
        for pixel in rgba.as_chunks_mut::<4>().0 {
            let alpha = pixel[3] as u32;
            for channel in &mut pixel[..3] {
                *channel = (*channel as u32 * 255 + alpha / 2)
                    .checked_div(alpha)
                    .unwrap_or(0)
                    .min(255) as u8;
            }
        }
        if size == 512 {
            image::save_buffer(
                "assets/icon.png",
                &rgba,
                size,
                size,
                image::ColorType::Rgba8,
            )?;
        } else {
            frames.push(IcoFrame::as_png(
                &rgba,
                size,
                size,
                image::ExtendedColorType::Rgba8,
            )?);
        }
    }
    IcoEncoder::new(File::create("assets/icon.ico")?).encode_images(&frames)?;
    Ok(())
}