package main

import (
	"fmt"
	"log"
	"runtime"
	"unsafe"

	vk "github.com/christerso/vulkan-go/vk"
	"github.com/ebitengine/purego"
	sdl "github.com/jupiterrider/purego-sdl3/sdl"
)

const (
	APP_NAME         = "MXL Player"
	APP_VER          = "0.0.1"
	WIN_WIDTH  int32 = 1280
	WIN_HEIGHT int32 = 720
)

const (
	initVideo       uint32 = 0x00000020
	windowVulkan    uint64 = 0x0000000010000000
	windowResizable uint64 = 0x0000000000000020

	eventQuit    uint32 = 0x100
	eventKeyDown uint32 = 0x300
	keyEscape    uint32 = 0x1B
)

var (
	sdlInit                        func(flags uint32) bool
	sdlQuit                        func()
	sdlGetError                    func() uintptr
	sdlCreateWindow                func(title *byte, w, h int32, flags uint64) uintptr
	sdlDestroyWindow               func(window uintptr)
	sdlVulkanGetInstanceExtensions func(count *uint32) uintptr
	sdlVulkanCreateSurface         func(window, instance, allocator uintptr, surface *uint64) bool
	sdlPollEvent                   func(event unsafe.Pointer) bool
	sdlGetWindowSizeInPixels       func(window uintptr, w, h *int32) bool
)

func sdlError() string { return cstr(sdlGetError()) }

var loaded = false

func loadSDLMissing() error {
	if loaded {
		return nil
	}
	h, err := purego.Dlopen("libSDL3.so.0", purego.RTLD_NOW|purego.RTLD_GLOBAL)
	if err != nil {
		return fmt.Errorf("win: load SDL3: %w", err)
	}
	purego.RegisterLibFunc(&sdlInit, h, "SDL_Init")
	purego.RegisterLibFunc(&sdlQuit, h, "SDL_Quit")
	purego.RegisterLibFunc(&sdlGetError, h, "SDL_GetError")
	purego.RegisterLibFunc(&sdlCreateWindow, h, "SDL_CreateWindow")
	purego.RegisterLibFunc(&sdlDestroyWindow, h, "SDL_DestroyWindow")
	purego.RegisterLibFunc(&sdlVulkanGetInstanceExtensions, h, "SDL_Vulkan_GetInstanceExtensions")
	purego.RegisterLibFunc(&sdlVulkanCreateSurface, h, "SDL_Vulkan_CreateSurface")
	purego.RegisterLibFunc(&sdlPollEvent, h, "SDL_PollEvent")
	purego.RegisterLibFunc(&sdlGetWindowSizeInPixels, h, "SDL_GetWindowSizeInPixels")
	loaded = true
	return nil
}

// cstr reads a NUL-terminated C string at p.
func cstr(p uintptr) string {
	if p == 0 {
		return ""
	}
	var n int
	for *(*byte)(unsafe.Pointer(p + uintptr(n))) != 0 {
		n++
	}
	return string(unsafe.Slice((*byte)(unsafe.Pointer(p)), n))
}

// cbytes returns a NUL-terminated copy of s as *byte, kept alive by the caller.
func cbytes(s string) *byte {
	b := make([]byte, len(s)+1)
	copy(b, s)
	runtime.KeepAlive(b)
	return &b[0]
}

func main() {
	runtime.LockOSThread()
	// SDL init
	// if !sdl.Init(sdl.InitVideo) {
	// 	log.Fatal(sdl.GetError())
	// }
	// defer sdl.Quit()

	// window := sdl.CreateWindow(
	// 	fmt.Sprintf("%s ver. %s", APP_NAME, APP_VER),
	// 	1280,
	// 	720,
	// 	sdl.WindowVulkan|sdl.WindowResizable,
	// )
	// if window == nil {
	// 	log.Fatal(sdl.GetError())
	// }
	// defer sdl.DestroyWindow(window)
	if err := loadSDLMissing(); err != nil {
		panic(err)
	}
	if !sdlInit(initVideo) {
		log.Fatalf("SDL_Init: %s", sdlError())
		return
	}

	windowHandler := sdlCreateWindow(cbytes(APP_NAME), WIN_WIDTH, WIN_HEIGHT, windowVulkan|windowResizable)
	if windowHandler == 0 {
		sdlQuit()
		log.Fatalf("SDL_CreateWindow: %s", sdlError())
		return
	}

	// Vulkan init
	if err := vk.Load(); err != nil {
		panic(err)
	}

	// Vulkan instance extensions SDL needs.
	var sdlExtCount uint32
	arr := sdlVulkanGetInstanceExtensions(&sdlExtCount)
	if arr == 0 {
		log.Fatal("sdlVulkanGetInstanceExtensions is 0")
		return
	}
	sdlExtensions := make([]string, sdlExtCount)
	for i := uint32(0); i < sdlExtCount; i++ {
		p := *(*uintptr)(unsafe.Pointer(arr + uintptr(i)*unsafe.Sizeof(uintptr(0))))
		sdlExtensions[i] = cstr(p)
	}
	// Vulkan Instance creation
	var vkLayers []string
	vkExtensions := append(sdlExtensions, vk.ExtDebugUtils)
	vkInstance, err := vk.CreateInstance(vk.InstanceConfig{
		ApplicationName: APP_NAME,
		EngineName:      "no engine",
		Extensions:      vkExtensions,
		Layers:          vkLayers,
	})
	if err != nil {
		log.Fatalf(err.Error())
		panic(err)
	}
	defer vkInstance.Destroy()
	// Vulkan surface
	var vkSurface uint64
	if !sdlVulkanCreateSurface(windowHandler, uintptr(vkInstance), 0, &vkSurface) {
		log.Fatalf("SDL_Vulkan_CreateSurface: %s", sdlError())
		return
	}
	vkSurf := vk.SurfaceKHR(vkSurface)
	defer vkInstance.DestroySurface(vkSurf)

	// Vulkan Physical Device
	devices, err := vkInstance.EnumeratePhysicalDevices()
	if err != nil || len(devices) == 0 {
		panic("No Vulkan devices")
	}
	for _, pd := range devices {
		info := pd.Info()
		fmt.Printf("%s (%s)\n", info.Name, info.Type)
	}
	vkPhysDevice := devices[0]
	// Vulkan Surface & Graphics Queue
	gfx, err := vkPhysDevice.GraphicsFamily()
	if err != nil {
		panic(err.Error())
	}
	if !vkPhysDevice.SurfaceSupport(gfx, vkSurf) {
		log.Fatalf("graphics queue cannot present")
		return
	}
	vkDevice, vkQueue, err := vkPhysDevice.CreateDevice(vk.DeviceConfig{
		GraphicsFamily: gfx,
		Extensions:     []string{"VK_KHR_swapchain"},
	})
	if err != nil {
		panic(err)
	}
	defer vkDevice.Destroy()
	defer vkDevice.WaitIdle()
	// TODO: colorspace & render pass
	var vkFormat vk.Format
	var vkColorSpace uint32
	formats, _ := vkPhysDevice.SurfaceFormats(vkSurf)
	for _, f := range formats {
		if f.Format == vk.FormatB8G8R8A8Srgb && f.ColorSpace == vk.ColorSpaceSRGBNonlinear {
			vkFormat = f.Format
			vkColorSpace = f.ColorSpace
		}
	}
	var vkPresentMode vk.PresentMode
	modes, _ := vkPhysDevice.SurfacePresentModes(vkSurf)
	for _, m := range modes {
		if m == vk.PresentModeMailbox {
			vkPresentMode = m
		}
	}

	vkRenderPass, err := vkDevice.CreateColorDepthRenderPass(vkFormat, vk.FormatD32Sfloat)
	if err != nil {
		panic(err.Error())
	}
	defer vkDevice.DestroyRenderPass(vkRenderPass)

	// Vulkan Command Pool
	vkCommandPool, err := vkDevice.CreateCommandPool(gfx)
	if err != nil {
		panic(err.Error())
	}
	defer vkDevice.DestroyCommandPool(vkCommandPool)
	vkCommands, err := vkDevice.AllocateCommandBuffers(vkCommandPool, 1)
	if err != nil {
		panic(err.Error())
	}

	// Core Loop
	running := true
	for running {
		var event sdl.Event

		for sdl.PollEvent(&event) {
			switch event.Type() {
			case sdl.EventQuit:
				running = false
			}
		}
	}
}