use crate::qr::QrCode;
use image::{ImageBuffer, Luma};

pub fn render_png(qr: &QrCode, module_size: u8) -> Result<Vec<u8>, image::ImageError> {
    let matrix_size = qr.size() as u32;
    let margin = qr.margin as u32;
    let total_size = matrix_size + 2 * margin;
    let img_size = total_size * module_size as u32;

    let mut img = ImageBuffer::new(img_size, img_size);

    for y in 0..total_size {
        for x in 0..total_size {
            let module_x = x.saturating_sub(margin);
            let module_y = y.saturating_sub(margin);

            let is_dark = if module_x < matrix_size && module_y < matrix_size {
                qr.modules()[module_y as usize][module_x as usize]
            } else {
                false // 白边
            };

            let px_val = if is_dark { 0u8 } else { 255u8 };
            for dy in 0..module_size as u32 {
                for dx in 0..module_size as u32 {
                    img.put_pixel(
                        x * module_size as u32 + dx,
                        y * module_size as u32 + dy,
                        Luma([px_val]),
                    );
                }
            }
        }
    }

    let mut buf = Vec::new();
    img.write_to(&mut std::io::Cursor::new(&mut buf), image::ImageFormat::Png)?;
    Ok(buf)
}