use image::{GenericImageView, ImageBuffer, Rgba};

const TILE_PX: u32 = 16;

const ROWS: &[(&str, u8)] = &[
    ("assets/sky.png", 0),           // air (transparent)
    ("assets/grass_floor.png", 1),   // grass
    ("assets/dirt_floor.png", 2),    // dirt
    ("assets/rock_floor.png", 3),    // rock
    ("assets/bedrock_floor.png", 4), // bedrock
    ("assets/sky.png", 5),           // sky (transparent)
    ("assets/dirt_wall.png", 6),     // dirt_wall fixture
    ("assets/rock_wall.png", 7),     // rock_wall fixture
    ("assets/bedrock_wall.png", 8),  // bedrock_wall fixture
    ("assets/log.png", 9),           // log fixture
    ("assets/leaves.png", 10),       // leaves fixture
];

fn main() {
    let rows = ROWS.len() as u32;
    let mut combined: ImageBuffer<Rgba<u8>, Vec<u8>> =
        ImageBuffer::from_pixel(TILE_PX, TILE_PX * rows, Rgba([0, 0, 0, 0]));

    for (i, (path, _id)) in ROWS.iter().enumerate() {
        let y = i as u32 * TILE_PX;
        match image::open(path) {
            Ok(img) => {
                image::imageops::overlay(&mut combined, &img, 0, y as i64);
                println!("cargo:rerun-if-changed={}", path);
            }
            Err(e) => {
                eprintln!(
                    "Warning: could not open {} — leaving row {} blank ({})",
                    path, i, e
                );
                let mut row_pixels = combined.rows_mut();
                if let Some(row) = row_pixels.nth(i) {
                    for px in row {
                        *px = Rgba([255, 0, 255, 255]);
                    }
                }
            }
        }
    }

    combined
        .save("assets/tileset.png")
        .expect("Failed to write assets/tileset.png");
    println!("cargo:rerun-if-changed=build.rs");
}