package vk

import (
	"fmt"
	"unsafe"
	"github.com/christerso/vulkan-go/pkg/vulkan"
)


// Instance represents a Vulkan instance with high-level management
type Instance struct {
	handle vulkan.Instance
	debug  *DebugMessenger
	layers []string
}

// InstanceConfig holds configuration for creating a Vulkan instance
type InstanceConfig struct {
	ApplicationName    string
	ApplicationVersion Version
	EngineName         string
	EngineVersion      Version
	APIVersion         Version
	EnabledLayers      []string
	EnabledExtensions  []string
	EnableValidation   bool
}

// Version represents a Vulkan API version
type Version struct {
	Major uint32
	Minor uint32
	Patch uint32
}

// Pack converts a Version to Vulkan's packed format
func (v Version) Pack() uint32 {
	return (v.Major << 22) | (v.Minor << 12) | v.Patch
}

// NewVersion creates a Version from packed Vulkan format
func NewVersion(packed uint32) Version {
	return Version{
		Major: (packed >> 22) & 0x3FF,
		Minor: (packed >> 12) & 0x3FF,
		Patch: packed & 0xFFF,
	}
}

// String returns a string representation of the version
func (v Version) String() string {
	return fmt.Sprintf("%d.%d.%d", v.Major, v.Minor, v.Patch)
}

// DefaultInstanceConfig returns a default instance configuration
func DefaultInstanceConfig() InstanceConfig {
	return InstanceConfig{
		ApplicationName:    "Vulkan Go Application",
		ApplicationVersion: Version{Major: 1, Minor: 0, Patch: 0},
		EngineName:         "Vulkan Go Engine",
		EngineVersion:      Version{Major: 1, Minor: 0, Patch: 0},
		APIVersion:         Version{Major: 1, Minor: 4, Patch: 0}, // Latest Vulkan 1.4
		EnabledLayers:      []string{},
		EnabledExtensions:  []string{},
		EnableValidation:   false,
	}
}

// CreateInstance creates a new Vulkan instance with the given configuration
func CreateInstance(config InstanceConfig) (*Instance, error) {
	// Initialize Vulkan loader
	if err := vulkan.Init(); err != nil {
		return nil, fmt.Errorf("failed to initialize Vulkan: %w", err)
	}

	// Check layer support
	if config.EnableValidation {
		config.EnabledLayers = append(config.EnabledLayers, "VK_LAYER_KHRONOS_validation")
	}

	availableLayers, err := enumerateInstanceLayers()
	if err != nil {
		return nil, fmt.Errorf("failed to enumerate layers: %w", err)
	}

	for _, layer := range config.EnabledLayers {
		if !isLayerSupported(layer, availableLayers) {
			return nil, fmt.Errorf("required layer %s is not available", layer)
		}
	}

	// Check extension support
	availableExtensions, err := enumerateInstanceExtensions("")
	if err != nil {
		return nil, fmt.Errorf("failed to enumerate extensions: %w", err)
	}

	if config.EnableValidation {
		debugExtension := "VK_EXT_debug_utils"
		if !isExtensionSupported(debugExtension, availableExtensions) {
			return nil, fmt.Errorf("validation enabled but %s not available", debugExtension)
		}
		config.EnabledExtensions = append(config.EnabledExtensions, debugExtension)
	}

	for _, ext := range config.EnabledExtensions {
		if !isExtensionSupported(ext, availableExtensions) {
			return nil, fmt.Errorf("required extension %s is not available", ext)
		}
	}

	// Create instance
	instance := &Instance{
		layers: config.EnabledLayers,
	}

	// Actual Vulkan instance creation
	handle, result := createVulkanInstance(config)
	if result != vulkan.SUCCESS {
		return nil, fmt.Errorf("vkCreateInstance failed: %v", result)
	}
	
	instance.handle = handle

	// Setup debug messenger if validation is enabled
	if config.EnableValidation {
		debug, err := createDebugMessenger(instance.handle)
		if err != nil {
			instance.Destroy()
			return nil, fmt.Errorf("failed to setup debug messenger: %w", err)
		}
		instance.debug = debug
	}

	return instance, nil
}

// Destroy cleans up the Vulkan instance
func (i *Instance) Destroy() {
	if i.debug != nil {
		i.debug.Destroy()
		i.debug = nil
	}

	if i.handle != nil {
		vulkan.DestroyInstance(i.handle, nil)
		i.handle = nil
	}
}

// Handle returns the underlying Vulkan instance handle
func (i *Instance) Handle() vulkan.Instance {
	return i.handle
}

// EnumeratePhysicalDevices returns all available physical devices
func (i *Instance) EnumeratePhysicalDevices() ([]*PhysicalDevice, error) {
	var deviceCount uint32
	result := vulkan.EnumeratePhysicalDevices(i.handle, &deviceCount, nil)
	if result != vulkan.SUCCESS {
		return nil, fmt.Errorf("failed to enumerate devices: %v", result)
	}
	
	if deviceCount == 0 {
		return nil, fmt.Errorf("no physical devices found")
	}
	
	vulkanDevices := make([]vulkan.PhysicalDevice, deviceCount)
	result = vulkan.EnumeratePhysicalDevices(i.handle, &deviceCount, &vulkanDevices[0])
	if result != vulkan.SUCCESS {
		return nil, fmt.Errorf("failed to get physical devices: %v", result)
	}
	
	devices := make([]*PhysicalDevice, deviceCount)
	for i, vulkanDevice := range vulkanDevices {
		// Get device properties
		var properties [1024]byte // Large enough for VkPhysicalDeviceProperties
		vulkan.GetPhysicalDeviceProperties(vulkanDevice, unsafe.Pointer(&properties[0]))
		
		// Extract device name (starts at offset 4, max 256 chars)
		deviceName := (*[256]byte)(unsafe.Pointer(&properties[4]))[:256]
		nameLen := 0
		for j, b := range deviceName {
			if b == 0 {
				nameLen = j
				break
			}
		}
		
		// Get queue family properties for this device
		var queueFamilyCount uint32
		vulkan.GetPhysicalDeviceQueueFamilyProperties(vulkanDevice, &queueFamilyCount, nil)
		
		queueFams := make([]QueueFamilyProperties, queueFamilyCount)
		if queueFamilyCount > 0 {
			// Create a simple queue family with graphics support
			queueFams[0] = QueueFamilyProperties{
				QueueFlags: QueueGraphicsBit,
				QueueCount: 1,
			}
		}
		
		devices[i] = &PhysicalDevice{
			handle: vulkanDevice,
			properties: PhysicalDeviceProperties{
				DeviceName: string(deviceName[:nameLen]),
				DeviceType: DeviceTypeDiscreteGPU, // Assume discrete for now
			},
			queueFams: queueFams,
		}
	}
	
	return devices, nil
}

// GetPhysicalDevice returns the best suitable physical device
func (i *Instance) GetPhysicalDevice(requirements PhysicalDeviceRequirements) (*PhysicalDevice, error) {
	devices, err := i.EnumeratePhysicalDevices()
	if err != nil {
		return nil, err
	}

	if len(devices) == 0 {
		return nil, fmt.Errorf("no physical devices found")
	}

	// Score devices based on requirements
	bestDevice := devices[0]
	bestScore := scorePhysicalDevice(bestDevice, requirements)

	for _, device := range devices[1:] {
		score := scorePhysicalDevice(device, requirements)
		if score > bestScore {
			bestDevice = device
			bestScore = score
		}
	}

	if bestScore == 0 {
		return nil, fmt.Errorf("no suitable physical device found")
	}

	return bestDevice, nil
}

// Helper functions (placeholders for actual implementation)

func createVulkanInstance(config InstanceConfig) (vulkan.Instance, vulkan.Result) {
	// Use the same approach as the working test.go
	appName := vulkan.CString(config.ApplicationName)
	engineName := vulkan.CString(config.EngineName)
	defer vulkan.FreeCString(appName)
	defer vulkan.FreeCString(engineName)
	
	appInfo := vulkan.ApplicationInfo{
		PApplicationName:   appName,
		ApplicationVersion: config.ApplicationVersion.Pack(),
		PEngineName:       engineName,
		EngineVersion:     config.EngineVersion.Pack(),
		ApiVersion:        config.APIVersion.Pack(),
	}
	
	createInfo := vulkan.InstanceCreateInfo{
		PApplicationInfo:        &appInfo,
		EnabledLayerCount:       0, // Simplify - no layers for now
		PpEnabledLayerNames:     nil,
		EnabledExtensionCount:   0, // Simplify - no extensions for now
		PpEnabledExtensionNames: nil,
	}
	
	var instance vulkan.Instance
	result := vulkan.CreateInstance(&createInfo, nil, &instance)
	return instance, result
}

func enumerateInstanceLayers() ([]LayerProperties, error) {
	// TODO: Implement vkEnumerateInstanceLayerProperties
	return []LayerProperties{}, nil
}

func enumerateInstanceExtensions(layerName string) ([]ExtensionProperties, error) {
	// TODO: Implement vkEnumerateInstanceExtensionProperties
	return []ExtensionProperties{}, nil
}

func isLayerSupported(layer string, available []LayerProperties) bool {
	for _, available := range available {
		if available.LayerName == layer {
			return true
		}
	}
	return false
}

func isExtensionSupported(extension string, available []ExtensionProperties) bool {
	for _, available := range available {
		if available.ExtensionName == extension {
			return true
		}
	}
	return false
}

// Properties structures
type LayerProperties struct {
	LayerName             string
	SpecVersion           uint32
	ImplementationVersion uint32
	Description           string
}

type ExtensionProperties struct {
	ExtensionName string
	SpecVersion   uint32
}

// PhysicalDeviceRequirements defines requirements for selecting a physical device
type PhysicalDeviceRequirements struct {
	RequiredExtensions []string
	PreferredDeviceType DeviceType
	RequireGraphicsQueue bool
	RequireComputeQueue  bool
	RequirePresentQueue  bool
	MinMemorySize        uint64
}

// DeviceType represents the type of physical device
type DeviceType uint32

const (
	DeviceTypeOther DeviceType = iota
	DeviceTypeIntegratedGPU
	DeviceTypeDiscreteGPU
	DeviceTypeVirtualGPU
	DeviceTypeCPU
)

func scorePhysicalDevice(device *PhysicalDevice, requirements PhysicalDeviceRequirements) int {
	score := 1000 // Base score for any working device
	
	// Prefer discrete GPUs
	if device.properties.DeviceType == DeviceTypeDiscreteGPU {
		score += 1000
	}
	
	// TODO: Add more sophisticated scoring based on requirements
	// For now, any device that exists gets a positive score
	
	return score
}

// Debug messenger functionality
type DebugMessenger struct {
	handle vulkan.Instance // Placeholder - would be actual debug messenger handle
}

func createDebugMessenger(instance vulkan.Instance) (*DebugMessenger, error) {
	// TODO: Implement debug messenger creation
	return &DebugMessenger{handle: instance}, nil
}

func (d *DebugMessenger) Destroy() {
	// TODO: Implement debug messenger destruction
}

// DebugCallback is called when validation layers report messages
type DebugCallback func(severity DebugSeverity, messageType DebugMessageType, message string)

type DebugSeverity uint32
type DebugMessageType uint32

const (
	DebugSeverityVerbose DebugSeverity = 1
	DebugSeverityInfo    DebugSeverity = 16
	DebugSeverityWarning DebugSeverity = 256
	DebugSeverityError   DebugSeverity = 4096
)

const (
	DebugMessageTypeGeneral     DebugMessageType = 1
	DebugMessageTypeValidation  DebugMessageType = 2
	DebugMessageTypePerformance DebugMessageType = 4
)