//! The `render` module contains the structures for displaying
//! the game, with each frame represented by a `Renderer` and
//! frame specific information in `FrameInfo`.

/// The (prefered) view distance of the game
const VIEW_DISTANCE: i32 = 5;

/// The baseline size of all ingame sprites and tile textures
const BASE_TILE_SIZE: i32 = 16;

use std::ops::Div;

use dungeon::{Dungeon, Entity, FPos, Floor, MAP_SIZE, Pos, Tile};
use raylib::{
	RaylibThread,
	camera::Camera2D,
	color::Color,
	math::Vector2,
	prelude::{
		RaylibDraw, RaylibDrawHandle, RaylibHandle, RaylibMode2D, RaylibMode2DExt,
		RaylibTextureModeExt,
	},
	texture::RenderTexture2D,
};

use crate::assets::ImageData;

/// The `FrameInfo` struct stores persistant information used thought a frame not
/// accessable from `RaylibDraw`
#[derive(Clone, Copy, Debug)]
struct FrameInfo {
	/// The last calculated fps
	fps: u32,
	/// The render width of the framebuffer in pixels
	width: i32,
	/// The render height of the framebuffer in pixels
	height: i32,
	/// The tile size in pixels
	tile_size: i32,
}
impl FrameInfo {
	fn new(handle: &RaylibHandle) -> Self {
		let fps = handle.get_fps();
		let width = handle.get_render_width();
		let height = handle.get_render_height();
		let tile_size = {
			let size = width.min(height);
			let dist = VIEW_DISTANCE * 2 + 1;
			let pixels = size.div(dist).max(BASE_TILE_SIZE);
			1 << (i32::BITS - pixels.leading_zeros())
		};

		Self {
			fps,
			width,
			height,
			tile_size,
		}
	}
}

/// The `Renderer` struct is the persistant renderer
/// for the duration for the application.
#[derive(Debug)]
pub struct Renderer {
	/// Set of sprites to be drawn
	#[expect(dead_code)]
	image: ImageData,
	/// Pre-rendered map texture that updates if the map changes
	/// Stores the hash of the map tiles to check this
	tiles_tex: RenderTexture2D,
	/// Hash of tiles used to draw on `tiles_tex`
	tiles_hash: u64,
}
impl Renderer {
	pub(crate) fn new(
		handle: &mut RaylibHandle,
		thread: &RaylibThread,
		image: ImageData,
	) -> crate::Result<Self> {
		let tiles_tex = {
			let size = MAP_SIZE as u32 * BASE_TILE_SIZE as u32;
			handle.load_render_texture(thread, size, size)?
		};

		Ok(Self {
			image,
			tiles_tex,
			tiles_hash: 0,
		})
	}

	/// Invokes the renderer for the current frame
	pub(crate) fn invoke<'a>(
		&'a mut self,
		handle: &'a mut RaylibHandle,
		thread: &'a RaylibThread,
	) -> FrameRendererImpl<'a> {
		let info = FrameInfo::new(handle);
		FrameRenderer {
			handle: handle.begin_drawing(thread),
			thread,
			info,
			renderer: self,
		}
	}
}

pub type FrameRendererImpl<'a> = FrameRenderer<'a, RaylibDrawHandle<'a>>;

pub struct FrameRenderer<'a, T>
where
	T: RaylibDraw,
{
	/// The current draw handle for raylib
	handle: T,
	/// The raylib thread
	thread: &'a RaylibThread,
	/// Non drawing information for this current frame
	info: FrameInfo,
	/// Mutable reference to the main renderer (stores persistant data)
	renderer: &'a mut Renderer,
}
impl<'a, T> FrameRenderer<'a, T>
where
	T: RaylibDraw + RaylibMode2DExt + RaylibTextureModeExt,
{
	/// Draws an entire frame
	pub fn draw_frame(&mut self, dungeon: &Dungeon) {
		self.clear();
		self.draw_dungeon(dungeon);
		self.draw_ui(dungeon);
	}

	/// Draws the dungeon, (tiles and entities)
	pub fn draw_dungeon(&mut self, dungeon: &Dungeon) {
		self.update_tilemap(&dungeon.floor);
		let camera = dungeon.camera();
		let mut renderer = self.camera_renderer(camera);
		renderer.draw_tiles();
		renderer.draw_entities(dungeon);
	}
}
impl<'a, T> FrameRenderer<'a, T>
where
	T: RaylibDraw + RaylibMode2DExt,
{
	/// Returns a raylib camera for the given position
	#[must_use]
	fn camera_renderer<'b>(
		&'b mut self,
		cpos: FPos,
	) -> FrameRenderer<'b, RaylibMode2D<'b, T>> {
		let width = self.info.width;
		let height = self.info.height;
		let camera = Camera2D {
			target: Vector2::from(cpos.xy())
				.scale_by(self.info.tile_size as f32)
				.max(Vector2::new(width as f32 / 2.0, height as f32 / 2.0))
				.min(Vector2::new(
					(MAP_SIZE as i32 * self.info.tile_size) as f32 - (width as f32 / 2.0),
					(MAP_SIZE as i32 * self.info.tile_size) as f32 - (height as f32 / 2.0),
				)),
			offset: Vector2::new(width as f32 / 2.0, height as f32 / 2.0),
			rotation: 0.0,
			zoom: 1.0,
		};
		let handle = self.handle.begin_mode2D(camera);
		FrameRenderer {
			handle,
			thread: self.thread,
			info: self.info,
			renderer: self.renderer,
		}
	}
}
impl<'a, T> FrameRenderer<'a, T>
where
	T: RaylibDraw + RaylibTextureModeExt,
{
	/// Draw tiles on a provided texture
	fn update_tilemap(&mut self, floor: &Floor) {
		let hash = floor.hash();
		if self.renderer.tiles_hash == hash {
			// Texture is up to date
			return;
		}

		self.renderer.tiles_hash = hash;
		let size = BASE_TILE_SIZE;
		let tex = &mut self.renderer.tiles_tex;
		let mut handle = self.handle.begin_texture_mode(self.thread, tex);
		for pos in Pos::values() {
			let (x, y) = pos.xy();
			let color = tile_color(floor.get(pos));
			handle.draw_rectangle(x as i32 * size, y as i32 * size, size, size, color);
		}
	}
}
impl<'a, T> FrameRenderer<'a, T>
where
	T: RaylibDraw,
{
	/// Clear the screen
	pub fn clear(&mut self) {
		self.handle.clear_background(Color::BLACK);
	}

	/// Draws player HP, inventory, and floor number
	pub fn draw_ui(&mut self, _dungeon: &Dungeon) {
		#[cfg(feature = "debug")]
		// Draw fps (debug only)
		self.draw_fps();
	}

	/// Draws the entities on the map
	fn draw_entities(&mut self, dungeon: &Dungeon) {
		self.draw_entity(&dungeon.player.entity);
	}

	/// Draws an entity
	#[expect(clippy::cast_possible_truncation)]
	fn draw_entity(&mut self, entity: &Entity) {
		let size = self.info.tile_size;
		let x = (entity.fpos.x() * size as f32) as i32;
		let y = (entity.fpos.y() * size as f32) as i32;
		// TODO: per entity color
		self.handle.draw_rectangle(x, y, size, size, Color::GREEN);
	}

	/// Draw dungeon tiles
	fn draw_tiles(&mut self) {
		let tex = &self.renderer.tiles_tex;
		self.handle.draw_texture_ex(
			tex,
			Vector2::zero(),
			0.0,
			(self.info.tile_size / BASE_TILE_SIZE) as f32,
			Color::WHITE,
		);
	}

	/// Draw FPS counter
	fn draw_fps(&mut self) {
		let fps_str = format!("{}", self.info.fps);
		self.handle.draw_text(&fps_str, 10, 10, 30, Color::YELLOW);
	}
}

fn tile_color(tile: Tile) -> Color {
	// TODO: use textures instead of colors :)
	match tile {
		Tile::Wall => Color::BLUE,
		Tile::Air => Color::RED,
		Tile::Stairs => Color::GRAY,
	}
}

trait Vector2Ext {
	fn min(self, other: Self) -> Self;
	fn max(self, other: Self) -> Self;
}
impl Vector2Ext for Vector2 {
	fn min(self, other: Self) -> Self {
		Self::new(self.x.min(other.x), self.y.min(other.y))
	}

	fn max(self, other: Self) -> Self {
		Self::new(self.x.max(other.x), self.y.max(other.y))
	}
}