use crate::{
    Input,
    config::{CAMERA_MOVEMENT_SPEED, PIXEL_BUFFER_HEIGHT, PIXEL_BUFFER_WIDTH},
    sim::board::Board,
};

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

impl Camera {
    pub fn handle_camera_input(&mut self, input: &Input, delta_time: f32) {
        // wasd movement
        let x = if input.is_left_pressed {
            -CAMERA_MOVEMENT_SPEED
        } else if input.is_right_pressed {
            CAMERA_MOVEMENT_SPEED
        } else {
            0.0
        };
        let y = if input.is_down_pressed {
            CAMERA_MOVEMENT_SPEED
        } else if input.is_up_pressed {
            -CAMERA_MOVEMENT_SPEED
        } else {
            0.0
        };

        if x == 0.0 && y == 0.0 {
            return;
        }

        let magnitude = (x.powi(2) + y.powi(2)).sqrt();
        let adjusted_x = x / magnitude * self.zoom as f32 * CAMERA_MOVEMENT_SPEED * delta_time;
        let adjusted_y = y / magnitude * self.zoom as f32 * CAMERA_MOVEMENT_SPEED * delta_time;

        self.x += adjusted_x as f64;
        self.y += adjusted_y as f64;
    }

    pub fn screen_position_to_board(
        &self,
        board: &Board,
        screen_x: f64,
        screen_y: f64,
    ) -> (f64, f64) {
        let camera_width = self.zoom * f64::from(board.size_x);
        let camera_height = self.zoom * f64::from(board.size_y);
        let camera_start_x = self.x - camera_width / 2.0;
        let camera_start_y = self.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(
        &self,
        frame: &mut [u8],
        board: &Board,
        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) =
                    self.screen_position_to_board(board, 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 = c.material.def();
                    (m.color[0], m.color[1], m.color[2], 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);
            }
        }
    }
}