const std = @import("std");
const SDL = @import("sdl2");
const emu = @import("core/emu.zig");

const Apu = @import("core/apu.zig").Apu;
const Arm7tdmi = @import("core/cpu.zig").Arm7tdmi;
const Scheduler = @import("core/scheduler.zig").Scheduler;
const FpsTracker = @import("util.zig").FpsTracker;

const span = @import("util.zig").span;

const pitch = @import("core/ppu.zig").framebuf_pitch;
const scale = @import("core/emu.zig").win_scale;

const default_title: []const u8 = "ZBA";

pub const Gui = struct {
    const Self = @This();
    const log = std.log.scoped(.Gui);

    window: *SDL.SDL_Window,
    title: []const u8,
    renderer: *SDL.SDL_Renderer,
    texture: *SDL.SDL_Texture,
    audio: Audio,

    pub fn init(title: *const [12]u8, apu: *Apu, width: i32, height: i32) Self {
        const ret = SDL.SDL_Init(SDL.SDL_INIT_VIDEO | SDL.SDL_INIT_EVENTS | SDL.SDL_INIT_AUDIO | SDL.SDL_INIT_GAMECONTROLLER);
        if (ret < 0) panic();

        const window = SDL.SDL_CreateWindow(
            default_title.ptr,
            SDL.SDL_WINDOWPOS_CENTERED,
            SDL.SDL_WINDOWPOS_CENTERED,
            @as(c_int, width * scale),
            @as(c_int, height * scale),
            SDL.SDL_WINDOW_SHOWN,
        ) orelse panic();

        const renderer = SDL.SDL_CreateRenderer(window, -1, SDL.SDL_RENDERER_ACCELERATED | SDL.SDL_RENDERER_PRESENTVSYNC) orelse panic();

        const texture = SDL.SDL_CreateTexture(
            renderer,
            SDL.SDL_PIXELFORMAT_RGBA8888,
            SDL.SDL_TEXTUREACCESS_STREAMING,
            @as(c_int, width),
            @as(c_int, height),
        ) orelse panic();

        return Self{
            .window = window,
            .title = span(title),
            .renderer = renderer,
            .texture = texture,
            .audio = Audio.init(apu),
        };
    }

    pub fn run(self: *Self, cpu: *Arm7tdmi, scheduler: *Scheduler) !void {
        var quit = std.atomic.Atomic(bool).init(false);
        var frame_rate = FpsTracker.init();

        const thread = try std.Thread.spawn(.{}, emu.run, .{ &quit, &frame_rate, scheduler, cpu });
        defer thread.join();

        var title_buf: [0x100]u8 = [_]u8{0} ** 0x100;

        emu_loop: while (true) {
            var event: SDL.SDL_Event = undefined;
            while (SDL.SDL_PollEvent(&event) != 0) {
                switch (event.type) {
                    SDL.SDL_QUIT => break :emu_loop,
                    SDL.SDL_KEYDOWN => {
                        const io = &cpu.bus.io;
                        const key_code = event.key.keysym.sym;

                        switch (key_code) {
                            SDL.SDLK_UP => io.keyinput.up.unset(),
                            SDL.SDLK_DOWN => io.keyinput.down.unset(),
                            SDL.SDLK_LEFT => io.keyinput.left.unset(),
                            SDL.SDLK_RIGHT => io.keyinput.right.unset(),
                            SDL.SDLK_x => io.keyinput.a.unset(),
                            SDL.SDLK_z => io.keyinput.b.unset(),
                            SDL.SDLK_a => io.keyinput.shoulder_l.unset(),
                            SDL.SDLK_s => io.keyinput.shoulder_r.unset(),
                            SDL.SDLK_RETURN => io.keyinput.start.unset(),
                            SDL.SDLK_RSHIFT => io.keyinput.select.unset(),
                            else => {},
                        }
                    },
                    SDL.SDL_KEYUP => {
                        const io = &cpu.bus.io;
                        const key_code = event.key.keysym.sym;

                        switch (key_code) {
                            SDL.SDLK_UP => io.keyinput.up.set(),
                            SDL.SDLK_DOWN => io.keyinput.down.set(),
                            SDL.SDLK_LEFT => io.keyinput.left.set(),
                            SDL.SDLK_RIGHT => io.keyinput.right.set(),
                            SDL.SDLK_x => io.keyinput.a.set(),
                            SDL.SDLK_z => io.keyinput.b.set(),
                            SDL.SDLK_a => io.keyinput.shoulder_l.set(),
                            SDL.SDLK_s => io.keyinput.shoulder_r.set(),
                            SDL.SDLK_RETURN => io.keyinput.start.set(),
                            SDL.SDLK_RSHIFT => io.keyinput.select.set(),
                            SDL.SDLK_i => log.err("Sample Count: {}", .{@intCast(u32, SDL.SDL_AudioStreamAvailable(cpu.bus.apu.stream)) / (2 * @sizeOf(u16))}),
                            SDL.SDLK_j => log.err("Scheduler Capacity: {} | Scheduler Event Count: {}", .{ scheduler.queue.capacity(), scheduler.queue.count() }),
                            SDL.SDLK_k => {
                                // Dump IWRAM to file
                                log.info("PC: 0x{X:0>8}", .{cpu.r[15]});
                                log.info("LR: 0x{X:0>8}", .{cpu.r[14]});
                                // const iwram_file = try std.fs.cwd().createFile("iwram.bin", .{});
                                // defer iwram_file.close();

                                // try iwram_file.writeAll(cpu.bus.iwram.buf);
                            },
                            else => {},
                        }
                    },
                    else => {},
                }
            }

            // Emulator has an internal Double Buffer
            const framebuf = cpu.bus.ppu.framebuf.get(.Renderer);
            _ = SDL.SDL_UpdateTexture(self.texture, null, framebuf.ptr, pitch);
            _ = SDL.SDL_RenderCopy(self.renderer, self.texture, null, null);
            SDL.SDL_RenderPresent(self.renderer);

            const dyn_title = std.fmt.bufPrint(&title_buf, "ZBA | {s} [Emu: {}fps] ", .{ self.title, frame_rate.value() }) catch unreachable;
            SDL.SDL_SetWindowTitle(self.window, dyn_title.ptr);
        }

        quit.store(true, .SeqCst); // Terminate Emulator Thread
    }

    pub fn deinit(self: *Self) void {
        self.audio.deinit();
        SDL.SDL_DestroyTexture(self.texture);
        SDL.SDL_DestroyRenderer(self.renderer);
        SDL.SDL_DestroyWindow(self.window);
        SDL.SDL_Quit();
        self.* = undefined;
    }
};

const Audio = struct {
    const Self = @This();
    const log = std.log.scoped(.PlatformAudio);
    const sample_rate = @import("core/apu.zig").host_sample_rate;

    device: SDL.SDL_AudioDeviceID,

    fn init(apu: *Apu) Self {
        var have: SDL.SDL_AudioSpec = undefined;
        var want: SDL.SDL_AudioSpec = std.mem.zeroes(SDL.SDL_AudioSpec);
        want.freq = sample_rate;
        want.format = SDL.AUDIO_U16;
        want.channels = 2;
        want.samples = 0x100;
        want.callback = Self.callback;
        want.userdata = apu;

        const device = SDL.SDL_OpenAudioDevice(null, 0, &want, &have, 0);
        if (device == 0) panic();

        SDL.SDL_PauseAudioDevice(device, 0); // Unpause Audio

        return .{ .device = device };
    }

    fn deinit(self: *Self) void {
        SDL.SDL_CloseAudioDevice(self.device);
        self.* = undefined;
    }

    export fn callback(userdata: ?*anyopaque, stream: [*c]u8, len: c_int) void {
        const apu = @ptrCast(*Apu, @alignCast(@alignOf(*Apu), userdata));
        _ = SDL.SDL_AudioStreamGet(apu.stream, stream, len);

        // If we don't write anything, play silence otherwise garbage will be played
        // FIXME: I don't think this hack to remove DC Offset is acceptable :thinking:
        // if (written == 0) std.mem.set(u8, stream[0..@intCast(usize, len)], 0x40);
    }
};

fn panic() noreturn {
    const str = @as(?[*:0]const u8, SDL.SDL_GetError()) orelse "unknown error";
    @panic(std.mem.sliceTo(str, 0));
}