use crate::{
    Input,
    config::{CAMERA_MOVEMENT_SPEED, CHUNK_SIZE},
    sim::{chunk::Chunk, world::World},
};

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

impl Camera {
    pub fn handle_camera_input(&mut self, input: &Input, delta_time: f32) {
        // wasd movement
        let x: f32 = if input.is_left_pressed {
            -1.0
        } else if input.is_right_pressed {
            1.0
        } else {
            0.0
        };
        let y: f32 = if input.is_down_pressed {
            1.0
        } else if input.is_up_pressed {
            -1.0
        } 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_world(&self, screen_x: f64, screen_y: f64) -> (f64, f64) {
        let camera_width = self.zoom * f64::from(1600);
        let camera_height = self.zoom * f64::from(1200);
        let camera_start_x = self.x - camera_width / 2.0;
        let camera_start_y = self.y - camera_height / 2.0;
        (
            (screen_x / 1600 as f64 * camera_width) + camera_start_x,
            (screen_y / 1200 as f64 * camera_height) + camera_start_y,
        )
    }

    pub fn write_frame_view(&self, frame: &mut [u8], world: &World) {
        puffin::profile_function!();

        // for i in 0..frame.len() / 4 {
        //     let idx = i * 4;
        //     frame[idx] = (i / 1000) as u8;
        //     frame[idx + 1] = 0x00;
        //     frame[idx + 2] = 0x00;
        //     frame[idx + 3] = 0xFF;
        // }
        // return;

        const BG: [u8; 4] = [0x00, 0x00, 0x00, 0xFF];
        for px in frame.chunks_exact_mut(4) {
            px.copy_from_slice(&BG);
        }

        // world-space rect covered by the screen
        let (xl, yl) = self.screen_position_to_world(0.0, 0.0);
        let (xu, yu) = self.screen_position_to_world(1600 as f64, 1200 as f64);

        let c = CHUNK_SIZE;
        let cx0 = (xl.floor() as i32).div_euclid(c);
        let cx1 = (xu.ceil() as i32).div_euclid(c);
        let cy0 = (yl.floor() as i32).div_euclid(c);
        let cy1 = (yu.ceil() as i32).div_euclid(c);

        let scale = 1.0 / self.zoom; // pixels per cell

        for cy in cy0..=cy1 {
            for cx in cx0..=cx1 {
                let Some(&idx) = world.chunk_position_to_chunk_idx.get(&(cx, cy)) else {
                    continue;
                };
                self.write_chunk(frame, &world.chunks[idx], cx, cy, xl, yl, scale);
            }
        }
    }

    fn write_chunk(
        &self,
        frame: &mut [u8],
        chunk: &Chunk,
        cx: i32,
        cy: i32,
        xl: f64,
        yl: f64,
        scale: f64,
    ) {
        let c = CHUNK_SIZE;
        let w = 1600 as i32;
        let h = 1200 as i32;

        for ly in 0..c {
            let wy = (cy * c + ly) as f64;
            let sy0 = (((wy - yl) * scale).floor() as i32).max(0);
            let sy1 = (((wy + 1.0 - yl) * scale).floor() as i32).min(h);
            if sy0 >= sy1 {
                continue;
            }

            for lx in 0..c {
                let wx = (cx * c + lx) as f64;
                let sx0 = (((wx - xl) * scale).floor() as i32).max(0);
                let sx1 = (((wx + 1.0 - xl) * scale).floor() as i32).min(w);
                if sx0 >= sx1 {
                    continue;
                }

                let color = chunk
                    .get_cell_at_local_position(lx as u8, ly as u8)
                    .material
                    .def()
                    .color;
                let rgba = [color.0, color.1, color.2, color.3];

                for sy in sy0..sy1 {
                    let start = (sy * w + sx0) as usize * 4;
                    let end = (sy * w + sx1) as usize * 4;
                    for px in frame[start..end].chunks_exact_mut(4) {
                        px.copy_from_slice(&rgba);
                    }
                }
            }
        }
    }
}