//! 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;

use std::{cell::RefCell, ops::Div, rc::Rc};

use dungeon::{Direction, Dungeon, Entity, EntityKind, FPos, Floor, MAP_SIZE, Pos, Tile};
use raylib::{
	RaylibThread,
	camera::Camera2D,
	color::Color,
	math::{Rectangle, Vector2},
	prelude::{
		RaylibDraw, RaylibDrawHandle, RaylibHandle, RaylibMode2D, RaylibMode2DExt,
		RaylibTextureModeExt,
	},
	texture::{RaylibTexture2D, RenderTexture2D},
};

use crate::assets::{AtlasTexture, BASE_TILE_SIZE, ImageData, WALL_HEIGHT};

/// The `FrameInfo` struct stores information used during a single frame
#[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 `State` struct stores persistant renderer data used across multiple frames
#[derive(Debug)]
struct State {
	/// Set of sprites to be drawn
	image: ImageData,
	/// Top layer of the tile map (used for back and top sides of walls)
	tiles_tex_fg: RefCell<RenderTexture2D>,
	/// Bottom layer of the tile map (used for most things)
	tiles_tex_bg: RefCell<RenderTexture2D>,
	/// Hash of tiles used to draw the tile textures
	tiles_hash: RefCell<u64>,
}
impl State {
	fn new(
		handle: &mut RaylibHandle,
		thread: &RaylibThread,
		image: ImageData,
	) -> crate::Result<Self> {
		let tex_size = MAP_SIZE as u32 * BASE_TILE_SIZE as u32;
		let tiles_tex_fg = handle.load_render_texture(thread, tex_size, tex_size)?;
		let tiles_tex_bg = handle.load_render_texture(thread, tex_size, tex_size)?;

		Ok(Self {
			image,
			tiles_tex_fg: RefCell::new(tiles_tex_fg),
			tiles_tex_bg: RefCell::new(tiles_tex_bg),
			tiles_hash: RefCell::new(0),
		})
	}
}

/// The `Renderer` struct is the persistant renderer
/// for the duration for the application.
#[derive(Debug)]
pub struct Renderer {
	/// Persistant render state
	state: Rc<State>,
}
impl Renderer {
	pub(crate) fn new(
		handle: &mut RaylibHandle,
		thread: &RaylibThread,
		image: ImageData,
	) -> crate::Result<Self> {
		let state = Rc::new(State::new(handle, thread, image)?);

		Ok(Self { state })
	}

	/// 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);
		let state = Rc::clone(&self.state);
		FrameRenderer {
			handle: handle.begin_drawing(thread),
			thread,
			info,
			state,
		}
	}
}

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

macro_rules! tex_renderer {
	($fr:expr, $tex:expr) => {
		FrameRenderer {
			handle: $fr.handle.begin_texture_mode($fr.thread, $tex),
			thread: &$fr.thread,
			info: $fr.info,
			state: Rc::clone(&$fr.state),
		}
	};
}

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,
	/// Persistant render state
	state: Rc<State>,
}
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(Color::BLACK);
		self.draw_dungeon(dungeon);
		self.draw_ui(dungeon);
	}

	/// Draws the dungeon, (tiles and entities)
	pub fn draw_dungeon(&mut self, dungeon: &Dungeon) {
		self.update_tilemaps(&dungeon.floor);
		let camera = dungeon.camera();
		let mut renderer = self.camera_renderer(camera);
		renderer.draw_tiles_bg();
		renderer.draw_entities(dungeon);
		renderer.draw_tiles_fg();
	}
}
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,
			state: Rc::clone(&self.state),
		}
	}
}
impl<'a, T> FrameRenderer<'a, T>
where
	T: RaylibDraw + RaylibTextureModeExt,
{
	/// Updates all tilemaps
	fn update_tilemaps(&mut self, floor: &Floor) {
		let hash = floor.hash();
		let old_hash = std::mem::replace(&mut *self.state.tiles_hash.borrow_mut(), hash);
		if old_hash == hash {
			// Textures are up to date
			return;
		}

		self.update_fg_tilemap(floor);
		self.update_bg_tilemap(floor);
	}

	/// Draws the foregound tile map
	fn update_fg_tilemap(&mut self, floor: &Floor) {
		let size = BASE_TILE_SIZE as f32;
		let tex = &mut self.state.tiles_tex_fg.borrow_mut();
		let mut renderer = tex_renderer!(self, tex);
		renderer.clear(Color::BLANK);

		for pos in Pos::values() {
			let (fx, fy) = FPos::from(pos).xy();
			let (xs, ys) = (fx * size, fy * size);

			// fg layer only draws a top walls
			if floor.get(pos) != Tile::Wall {
				continue;
			};

			// draw base wall top texture
			renderer.draw_atlas(AtlasTexture::WallBase, xs, ys, size, 0.0);

			// draw top wall borders
			let is_wall =
				|dir| pos.step(dir).map_or(Tile::Wall, |p| floor.get(p)).is_wall();
			if !is_wall(Direction::North) {
				renderer.draw_atlas(AtlasTexture::WallEdgeNorth, xs, ys, size, 0.0);
			}
			if !is_wall(Direction::East) {
				renderer.draw_atlas(AtlasTexture::WallEdgeEast, xs, ys, size, 0.0);
			}
			if !is_wall(Direction::South) {
				renderer.draw_atlas(AtlasTexture::WallEdgeSouth, xs, ys, size, 0.0);
			}
			if !is_wall(Direction::West) {
				renderer.draw_atlas(AtlasTexture::WallEdgeWest, xs, ys, size, 0.0);
			}
		}
	}

	/// Draws the foregound tile map
	fn update_bg_tilemap(&mut self, floor: &Floor) {
		let size = BASE_TILE_SIZE as f32;
		let tex = &mut self.state.tiles_tex_bg.borrow_mut();
		let mut renderer = tex_renderer!(self, tex);
		renderer.clear(Color::BLACK);

		for pos in Pos::values() {
			let (x, y) = pos.xy();
			let tile = floor.get(pos);
			let tex = match tile {
				Tile::Wall => AtlasTexture::Wall,
				Tile::Air if (x + y) % 2 == 0 => AtlasTexture::FloorFull,
				Tile::Air if (x + y) % 2 == 1 => AtlasTexture::FloorEmpty,
				_ => AtlasTexture::Error,
			};
			renderer.draw_atlas(tex, x as f32 * size, y as f32 * size, size, 0.0);
		}
	}
}
impl<'a, T> FrameRenderer<'a, T>
where
	T: RaylibDraw,
{
	/// Clear the screen
	pub fn clear(&mut self, color: Color) {
		self.handle.clear_background(color);
	}

	/// 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
	fn draw_entity(&mut self, entity: &Entity) {
		let size = self.info.tile_size as f32;
		let x = entity.fpos.x();
		let y = entity.fpos.y();
		let tex = match entity.kind {
			EntityKind::Player => AtlasTexture::Player,
			_ => AtlasTexture::Error,
		};
		self.draw_atlas(tex, x * size, y * size, size, 0.0);
	}

	/// Draw dungeon tiles (background layer)
	fn draw_tiles_bg(&mut self) {
		let tex = &*self.state.tiles_tex_bg.borrow();
		let size = self.info.tile_size as f32;
		let offset = 0.0;
		self.handle.draw_tilemap(tex, size, offset);
	}

	/// Draw dungeon tiles (foreground layer)
	fn draw_tiles_fg(&mut self) {
		let tex = &*self.state.tiles_tex_fg.borrow();
		let size = self.info.tile_size as f32;
		let offset = WALL_HEIGHT as f32;
		self.handle.draw_tilemap(tex, size, offset);
	}

	/// Draw an atlas texture index
	fn draw_atlas(&mut self, tex: AtlasTexture, x: f32, y: f32, size: f32, rotation: f32) {
		let source_rec = Rectangle {
			x: (tex.x() * BASE_TILE_SIZE) as f32,
			y: (tex.y() * BASE_TILE_SIZE) as f32,
			width: BASE_TILE_SIZE as f32,
			height: BASE_TILE_SIZE as f32,
		};
		let dest_rec = Rectangle {
			x,
			y,
			width: size,
			height: size,
		};
		let origin = Vector2 {
			x: dest_rec.width / 2.0,
			y: dest_rec.height / 2.0,
		};
		self.handle.draw_texture_pro(
			&self.state.image.atlas,
			source_rec,
			dest_rec,
			origin,
			rotation,
			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);
	}
}

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))
	}
}

trait RaylibDrawExt: RaylibDraw {
	/// Draw dungeon tiles helper function
	fn draw_tilemap(&mut self, tex: &RenderTexture2D, size: f32, offset: f32) {
		let scale = size / BASE_TILE_SIZE as f32;
		let width = tex.width() as f32;
		let height = tex.height() as f32;
		let source_rec = Rectangle {
			x: 0.0,
			y: 0.0,
			width,
			height: -height,
		};
		let dest_rec = Rectangle {
			x: 0.0,
			y: -(offset * scale),
			width: width * scale,
			height: height * scale,
		};
		let origin = Vector2::zero();
		self.draw_texture_pro(tex, source_rec, dest_rec, origin, 0.0, Color::WHITE);
	}
}
impl<T: RaylibDraw> RaylibDrawExt for T {}