use crate::{
    config::{PIXEL_BUFFER_HEIGHT, PIXEL_BUFFER_WIDTH},
    sim::{board::Board, materials::MATERIALS},
};

pub struct CameraState {
    // centre coords
    pub x: f64,
    pub y: f64,
    // zoom scale factor, 1.0 = board <-> frame
    pub zoom: f64,
}

pub fn screen_position_to_board(
    board: &Board,
    camera: &CameraState,
    screen_x: f64,
    screen_y: f64,
) -> (f64, f64) {
    let camera_width = camera.zoom * f64::from(board.size_x);
    let camera_height = camera.zoom * f64::from(board.size_y);
    let camera_start_x = camera.x - camera_width / 2.0;
    let camera_start_y = camera.y - camera_height / 2.0;
    (
        (screen_x / PIXEL_BUFFER_WIDTH as f64 * camera_width) + camera_start_x,
        (screen_y / PIXEL_BUFFER_HEIGHT as f64 * camera_height) + camera_start_y,
    )
}

pub fn write_frame_view(
    frame: &mut [u8],
    board: &Board,
    camera: &CameraState,
    get_overlay: impl Fn(i32, i32) -> (u8, u8, u8, u8),
) {
    for frame_y in 0..PIXEL_BUFFER_HEIGHT {
        for frame_x in 0..PIXEL_BUFFER_WIDTH {
            let (x_coord, y_coord) =
                screen_position_to_board(board, camera, frame_x as f64, frame_y as f64);

            let cell = board.cell_at_position(x_coord as i32, y_coord as i32);
            let cell_color: Option<(u8, u8, u8, u8)> = cell.map(|c| {
                let m = MATERIALS[c.material as usize];
                (m.r, m.g, m.b, 0xFF)
            });
            let off_grid_color: (u8, u8, u8, u8) = (0x00, 0x00, 0x00, 0xFF);

            let target_color: (u8, u8, u8, u8) = cell_color.unwrap_or(off_grid_color);
            let overlay = get_overlay(x_coord as i32, y_coord as i32);

            let frame_idx = ((frame_y * PIXEL_BUFFER_WIDTH + frame_x) * 4) as usize;
            frame[frame_idx] = target_color.0.saturating_add(overlay.0);
            frame[frame_idx + 1] = target_color.1.saturating_add(overlay.1);
            frame[frame_idx + 2] = target_color.2.saturating_add(overlay.2);
            frame[frame_idx + 3] = target_color.3.saturating_add(overlay.3);
        }
    }
}