use embedded_graphics::{geometry::Size, pixelcolor::Rgb565, primitives::Rectangle, prelude::Point};
use embedded_graphics_core::draw_target::DrawTarget;
use crate::display::palette::Rgb;

pub fn render_sprite_onto_ili9341<D>(ili9341: &mut D, sprite: &[u8], palette: &[Rgb; 16])
where
    D: DrawTarget<Color = Rgb565>,
{
    let pixel_count = sprite.len() * 2;
    if pixel_count == 0 {
        return;
    }

    // OPTIMIZATION 1: Pre-compute the 16-color palette to Rgb565 once.
    let mut palette565 = [Rgb565::new(0, 0, 0); 16];
    for (i, Rgb(r, g, b)) in palette.iter().enumerate() {
        palette565[i] = Rgb565::new(*r >> 3, *g >> 2, *b >> 3);
    }

    let mut src_width = 1usize;
    while src_width * src_width < pixel_count {
        src_width += 1;
    }

    let target_width = 240usize;
    let scale = core::cmp::max(1, target_width / src_width);

    for y in 0..src_width {
        for x in 0..src_width {
            let pixel_index = y * src_width + x;
            if pixel_index >= pixel_count {
                break;
            }

            // Bitwise operations are slightly faster than division/modulo
            let byte_index = pixel_index >> 1;
            let pixel_byte = sprite[byte_index];
            let color_index = if pixel_index.is_multiple_of(2) {
                (pixel_byte >> 4) & 0x0F
            } else {
                pixel_byte & 0x0F
            };

            let color = palette565[color_index as usize];

            let start_x = (x * scale) as i32;
            let start_y = (y * scale) as i32;
            let end_x = core::cmp::min(start_x + scale as i32, target_width as i32);
            let end_y = core::cmp::min(start_y + scale as i32, target_width as i32);

            let width = u32::try_from(end_x - start_x).unwrap();
            let height = u32::try_from(end_y - start_y).unwrap();

            let area = Rectangle::new(
                Point::new(start_x.try_into().unwrap(), start_y.try_into().unwrap()),
                Size::new(width, height),
            );

            let _ = ili9341.fill_solid(&area, color);
        }
    }
}