pub const colors = @import("./colors.zig");

const hid = @import("hid");

const ona = @import("ona");

const ext = @cImport({
	@cInclude("SDL2/SDL.h");
});

const rendering = @import("./rendering.zig");

const std = @import("std");

pub const Assets = struct {
	window: *ext.SDL_Window,
	texture_formats: ona.stack.Sequential(TextureFormat),
	frame_rendered: std.Thread.ResetEvent = .{},
	pending_work: WorkQueue = .{},
	has_worker_thread: ?std.Thread = null,

	pub const LoadError = std.mem.Allocator.Error;

	pub const LoadFileError = LoadError || ona.files.ReadAllError || error {
		FormatUnsupported,
	};

	pub const TextureFormat = struct {
		extension: []const u8,
		load_file: *const fn (*std.heap.ArenaAllocator, ona.files.Storage, []const u8) LoadFileError!Texture.Desc,
	};

	pub const WorkQueue = ona.asyncio.BlockingQueue(1024, union (enum) {
		load_effect: LoadEffectWork,
		load_texture: LoadTextureWork,
		render_frame: RenderFrameWork,
		shutdown,
		unload_effect: UnloadEffectWork,
		unload_texture: UnloadTextureWork,

		const LoadEffectWork = struct {
			desc: Effect.Desc,
			loaded: *ona.asyncio.Future(std.mem.Allocator.Error!Effect),
		};

		const LoadTextureWork = struct {
			desc: Texture.Desc,
			loaded: *ona.asyncio.Future(std.mem.Allocator.Error!Texture),
		};

		const RenderFrameWork = struct {
			clear_color: Color,
			width: u16,
			height: u16,
			finished: *std.Thread.ResetEvent,
			has_command_params: ?*ona.Params(Commands).Node,
		};

		const UnloadEffectWork = struct {
			handle: Effect,
		};

		const UnloadTextureWork = struct {
			handle: Texture,
		};
	});

	fn deinit(self: *Assets) void {
		self.pending_work.enqueue(.shutdown);

		if (self.has_worker_thread) |worker_thread| {
			worker_thread.join();
		}

		self.texture_formats.deinit();

		self.* = undefined;
	}

	fn init() !Assets {
		const window = create: {
			const position = ext.SDL_WINDOWPOS_CENTERED;
			const flags = ext.SDL_WINDOW_OPENGL;
			const width = 640;
			const height = 480;

			break: create ext.SDL_CreateWindow("Ona", position, position, width, height, flags) orelse {
				return error.Unsupported;
			};
		};

		errdefer {
			ext.SDL_DestroyWindow(window);
		}

		return .{
			.texture_formats = .{.allocator = ona.heap.allocator},
			.window = window,
		};
	}

	pub fn load_effect_file(self: *Assets, storage: ona.files.Storage, path: []const u8) LoadFileError!Effect {
		if (!std.mem.endsWith(u8, path, ".spv")) {
			return error.FormatUnsupported;
		}

		const fragment_file_stat = try storage.stat(path);
		const fragment_spirv_ops = try ona.heap.allocator.alloc(u32, fragment_file_stat.size / @alignOf(u32));

		defer {
			ona.heap.allocator.free(fragment_spirv_ops);
		}

		const bytes_read = try storage.read_all(path, std.mem.sliceAsBytes(fragment_spirv_ops), .{});

		std.debug.assert(bytes_read.len == fragment_file_stat.size);

		var loaded = ona.asyncio.Future(std.mem.Allocator.Error!Effect){};

		self.pending_work.enqueue(.{
			.load_effect = .{
				.desc = .{
					.fragment_spirv_ops = fragment_spirv_ops,
				},

				.loaded = &loaded,
			},
		});

		return loaded.get().*;
	}

	pub fn load_texture(self: *Assets, desc: Texture.Desc) std.mem.Allocator.Error!Texture {
		var loaded = ona.asyncio.Future(std.mem.Allocator.Error!Texture){};

		self.pending_work.enqueue(.{
			.load_texture = .{
				.desc = desc,
				.loaded = &loaded,
			},
		});

		return loaded.get().*;
	}

	pub fn load_texture_file(self: *Assets, storage: ona.files.Storage, path: []const u8) LoadFileError!Texture {
		var arena = std.heap.ArenaAllocator.init(ona.heap.allocator);

		defer {
			arena.deinit();
		}

		for (self.texture_formats.values) |format| {
			if (!std.mem.endsWith(u8, path, format.extension)) {
				continue;
			}

			return self.load_texture(try format.load_file(&arena, storage, path));
		}

		return error.FormatUnsupported;
	}

	pub const thread_restriction = .main;
};

pub const Color = @Vector(4, f32);

pub const Commands = struct {
	pending: *List,

	const Command = union (enum) {
		draw_texture: DrawTextureCommand,
		set_effect: SetEffectCommand,
		set_target: SetTargetCommand,
	};

	pub const DrawTextureCommand = struct {
		texture: Texture,
		transform: Transform2D,
	};

	pub const SetEffectCommand = struct {
		effect: Effect,
		properties: []const u8,
	};

	pub const SetTargetCommand = struct {
		texture: Texture,
		clear_color: ?Color,
		clear_depth: ?f32,
		clear_stencil: ?u8,
	};

	pub const List = struct {
		arena: std.heap.ArenaAllocator,
		stack: ona.stack.Sequential(Command),

		fn clear(self: *List) void {
			self.stack.clear();

			if (!self.arena.reset(.retain_capacity)) {
				std.log.warn("failed to reset the buffer of a gfx queue with retained capacity", .{});
			}
		}

		fn deinit(self: *List) void {
			self.arena.deinit();
			self.stack.deinit();

			self.* = undefined;
		}

		fn init(allocator: std.mem.Allocator) List {
			return .{
				.arena = std.heap.ArenaAllocator.init(allocator),
				.stack = .{.allocator = allocator},
			};
		}
	};

	pub const Param = struct {
		swap_lists: [2]List,
		swap_state: u1 = 0,

		fn deinit(self: *Param) void {
			for (&self.swap_lists) |*list| {
				list.deinit();
			}

			self.* = undefined;
		}

		fn pending_list(self: *Param) *List {
			return &self.swap_lists[self.swap_state];
		}

		fn rotate(self: *Param) void {
			const swapped_state = self.swap_state ^ 1;

			self.swap_lists[swapped_state].clear();

			self.swap_state = swapped_state;
		}

		pub fn submitted_commands(self: Param) []const Command {
			return self.swap_lists[self.swap_state ^ 1].stack.values;
		}
	};

	pub fn bind(_: ona.World.BindContext) std.mem.Allocator.Error!Param {
		return .{
			.swap_lists = .{
				List.init(ona.heap.allocator),
				List.init(ona.heap.allocator),
			},
		};
	}

	pub fn init(param: *Param) Commands {
		return .{
			.pending = param.pending_list(),
		};
	}

	pub fn draw_texture(self: Commands, command: DrawTextureCommand) std.mem.Allocator.Error!void {
		try self.pending.stack.push_grow(.{.draw_texture = command});
	}

	pub fn set_effect(self: Commands, command: SetEffectCommand) std.mem.Allocator.Error!void {
		try self.pending.stack.push_grow(.{
			.set_effect = .{
				.properties = try self.pending.arena.allocator().dupe(u8, command.properties),
				.effect = command.effect,
			},
		});
	}

	pub fn unbind(param: *Param, _: ona.World.UnbindContext) void {
		param.deinit();
	}

	pub fn set_target(self: Commands, command: SetTargetCommand) std.mem.Allocator.Error!void {
		try self.pending.stack.push_grow(.{.set_target = command});
	}
};

pub const Display = struct {
	width: u16 = 1280,
	height: u16 = 720,
	clear_color: Color = colors.black,
};

pub const Effect = enum (u32) {
	default,
	_,

	pub const Desc = struct {
		fragment_spirv_ops: []const u32,
	};
};

pub const Rect = struct {
	left: f32,
	top: f32,
	right: f32,
	bottom: f32,
};

pub const Texture = enum (u32) {
	default,
	backbuffer,
	_,

	pub const Desc = struct {
		format: Format,
		access: Access,

		pub const Access = union (enum) {
			static: StaticAccess,
			render: RenderAccess,
		};

		pub const StaticAccess = struct {
			width: u16,
			data: []const u8,
		};

		pub const RenderAccess = struct {
			width: u16,
			height: u16,
		};
	};

	pub const Format = enum {
		rgba8,
		bgra8,

		pub fn byte_size(self: Format) usize {
			return switch (self) {
				.rgba8, .bgra8 => 4,
			};
		}
	};
};

pub const Transform2D = extern struct {
	xbasis: Vector = .{1, 0},
	ybasis: Vector = .{0, 1},
	origin: Vector = @splat(0),

	pub const Simplified = struct {
		translation: Vector = @splat(0),
		rotation: f32 = 0,
		scale: Vector = @splat(1),
		skew: f32 = 0,
	};

	pub const Vector = @Vector(2, f32);

	pub fn from_simplified(simplified: Simplified) Transform2D {
		const rotation_skew = simplified.rotation + simplified.skew;

		return .{
			.xbasis = simplified.scale * Vector{std.math.cos(simplified.rotation), std.math.sin(simplified.rotation)},
			.ybasis = simplified.scale * Vector{-std.math.sin(rotation_skew), std.math.cos(rotation_skew)},
			.origin = simplified.translation,
		};
	}

	pub fn translated(self: Transform2D, translation: Vector) Transform2D {
		var transform = self;

		transform.origin += translation;

		return transform;
	}
};

fn load_bmp_texture(arena: *std.heap.ArenaAllocator, storage: ona.files.Storage, path: []const u8) !Texture.Desc {
	const header = try storage.read_little(path, 0, extern struct {
		type: [2]u8 align (1),
		file_size: u32 align (1),
		reserved: [2]u16 align (1),
		image_offset: u32 align (1),
		header_size: u32 align (1),
		pixel_width: i32 align (1),
		pixel_height: i32 align (1),
		color_planes: u16 align (1),
		bits_per_pixel: u16 align (1),
		compression_method: u32 align (1),
		image_size: u32 align(1),
		pixels_per_meter_x: i32 align (1),
		pixels_per_meter_y: i32 align (1),
		palette_colors_used: u32 align (1),
		important_colors_used: u32 align (1),
	}) orelse {
		return error.FormatUnsupported;
	};

	if (!std.mem.eql(u8, &header.type, "BM")) {
		return error.FormatUnsupported;
	}

	const pixel_width = std.math.cast(u16, header.pixel_width) orelse {
		return error.FormatUnsupported;
	};

	const pixels = try arena.allocator().alloc(u8, header.image_size);
	const bytes_per_pixel = header.bits_per_pixel / @bitSizeOf(u8);
	const alignment = 4;
	const byte_stride = pixel_width * bytes_per_pixel;
	const padded_byte_stride = alignment * @divTrunc((byte_stride + alignment - 1), alignment);
	const byte_padding = ona.scalars.sub(padded_byte_stride, byte_stride) orelse 0;
	var buffer_offset: usize = 0;
	var file_offset = @as(usize, header.image_offset);

	switch (header.bits_per_pixel) {
		32 => {
			while (buffer_offset < pixels.len) {
				const line = pixels[buffer_offset .. buffer_offset + byte_stride];

				if (try storage.read(path, line, file_offset) != byte_stride) {
					return error.FormatUnsupported;
				}

				for (0 .. pixel_width) |i| {
					const line_offset = i * 4;
					const pixel = line[line_offset .. line_offset + 4];

					std.mem.swap(u8, &pixel[0], &pixel[2]);
				}

				file_offset += line.len + byte_padding;
				buffer_offset += padded_byte_stride;
			}
		},

		else => return error.FormatUnsupported,
	}

	return .{
		.format = .rgba8,

		.access = .{
			.static = .{
				.width = pixel_width,
				.data = pixels,
			},
		},
	};
}

pub fn poll(app: ona.Write(ona.App), events: ona.Send(hid.Event)) !void {
	var event = @as(ext.SDL_Event, undefined);

	while (ext.SDL_PollEvent(&event) != 0) {
		switch (event.type) {
			ext.SDL_QUIT => {
				app.state.quit();
			},

			ext.SDL_KEYUP => {
				try events.push(.{.key_up = @enumFromInt(event.key.keysym.scancode)});
			},

			ext.SDL_KEYDOWN => {
				try events.push(.{.key_down = @enumFromInt(event.key.keysym.scancode)});
			},

			ext.SDL_MOUSEBUTTONUP => {
				try events.push(.{
					.mouse_up = switch (event.button.button) {
						ext.SDL_BUTTON_LEFT => .left,
						ext.SDL_BUTTON_RIGHT => .right,
						ext.SDL_BUTTON_MIDDLE => .middle,
						else => unreachable,
					},
				});
			},

			ext.SDL_MOUSEBUTTONDOWN => {
				try events.push(.{
					.mouse_down = switch (event.button.button) {
						ext.SDL_BUTTON_LEFT => .left,
						ext.SDL_BUTTON_RIGHT => .right,
						ext.SDL_BUTTON_MIDDLE => .middle,
						else => unreachable,
					},
				});
			},

			ext.SDL_MOUSEMOTION => {
				try events.push(.{
					.mouse_motion = .{
						.relative_position = .{@floatFromInt(event.motion.xrel), @floatFromInt(event.motion.yrel)},
						.absolute_position = .{@floatFromInt(event.motion.x), @floatFromInt(event.motion.y)},
					},
				});
			},

			else => {},
		}
	}
}

pub fn setup(world: *ona.World, events: ona.App.Events) (error {Unsupported} || std.Thread.SpawnError || std.mem.Allocator.Error)!void {
	if (ext.SDL_Init(ext.SDL_INIT_VIDEO | ext.SDL_INIT_EVENTS) != 0) {
		return error.Unsupported;
	}

	const assets = create: {
		var assets = try Assets.init();

		errdefer {
			assets.deinit();
		}

		break: create try world.set_get_state(assets);
	};

	assets.frame_rendered.set();

	errdefer {
		assets.deinit();
	}

	assets.has_worker_thread = try std.Thread.spawn(.{}, rendering.process_work, .{
		&assets.pending_work,
		assets.window,
	});

	const builtin_texture_formats = [_]Assets.TextureFormat{
		.{
			.extension = "bmp",
			.load_file = load_bmp_texture,
		},
	};

	for (builtin_texture_formats) |format| {
		try assets.texture_formats.push_grow(format);
	}

	try world.set_state(Display{});
	try world.on_event(events.pre_update, ona.system_fn(poll), .{.label = "poll gfx"});
	try world.on_event(events.exit, ona.system_fn(stop), .{.label = "stop gfx"});
	try world.on_event(events.finish, ona.system_fn(synchronize), .{.label = "synchronize gfx"});
}

pub fn stop(assets: ona.Write(Assets)) void {
	assets.state.deinit();
}

pub fn synchronize(exclusive: ona.Exclusive(&.{Assets, Display})) !void {
	const assets, const display = exclusive.states;

	assets.frame_rendered.wait();
	assets.frame_rendered.reset();

	{
		var has_command_param = exclusive.world.get_params(Commands).has_head;

		while (has_command_param) |command_param| : (has_command_param = command_param.has_next) {
			command_param.param.rotate();
		}
	}

	var display_width, var display_height = [_]c_int{0, 0};

	ext.SDL_GL_GetDrawableSize(assets.window, &display_width, &display_height);

	if (display.width != display_width or display.height != display_height) {
		ext.SDL_SetWindowSize(assets.window, display.width, display.height);
	}

	if (exclusive.world.get_params(Commands).has_head) |command_param| {
		assets.pending_work.enqueue(.{
			.render_frame = .{
				.has_command_params = command_param,
				.width = display.width,
				.height = display.height,
				.clear_color = display.clear_color,
				.finished = &assets.frame_rendered,
			},
		});
	} else {
		assets.frame_rendered.set();
	}
}