package hardware

import (
	"context"
	"fmt"
	"syscall"
	"time"
	"unsafe"

	"github.com/lxn/win"
	"github.com/wailsapp/wails/v2/pkg/runtime"
	"golang.org/x/sys/windows"
)

// PeripheralEvent is trigger by the finders when the scan is complete
type PeripheralEvent string

const (
	// PeripheralArrival is triggerd when a peripheral has been connected to the system
	PeripheralArrival PeripheralEvent = "PERIPHERAL_ARRIVAL"
	// PeripheralRemoval is triggered when a peripheral has been disconnected from the system
	PeripheralRemoval PeripheralEvent = "PERIPHERAL_REMOVAL"
	debounceDuration                  = 500 * time.Millisecond
)

var (
	debounceTimer *time.Timer
)

// HardwareManager is the class who manages the hardware
type HardwareManager struct {
	finders            []PeripheralFinder // The list of peripherals finders
	peripherals        []Peripheral       // The current list of peripherals
	deviceChangedEvent chan struct{}      // The event when the devices list changed
	ctx                context.Context
}

// NewHardwareManager creates a new HardwareManager
func NewHardwareManager() *HardwareManager {
	return &HardwareManager{
		finders:            make([]PeripheralFinder, 0),
		peripherals:        make([]Peripheral, 0),
		deviceChangedEvent: make(chan struct{}),
	}
}

// Start starts to finding new device events
func (h *HardwareManager) Start(ctx context.Context) error {
	cb := windows.NewCallback(h.wndProc)

	inst := win.GetModuleHandle(nil)
	cn, err := syscall.UTF16PtrFromString("DMXConnect device watcher")
	if err != nil {
		return fmt.Errorf("failed to convert window class name to UTF16: %w", err)
	}
	wc := win.WNDCLASSEX{
		HInstance:     inst,
		LpfnWndProc:   cb,
		LpszClassName: cn,
	}
	wc.CbSize = uint32(unsafe.Sizeof(wc))
	if win.RegisterClassEx(&wc) == 0 {
		return fmt.Errorf("failed to register window class: %w", syscall.GetLastError())
	}
	wName, err := syscall.UTF16PtrFromString("usbevent.exe")
	if err != nil {
		return fmt.Errorf("failed to convert window name to UTF16: %w", err)
	}
	wdw := win.CreateWindowEx(
		0,
		wc.LpszClassName,
		wName,
		win.WS_MINIMIZE|win.WS_OVERLAPPEDWINDOW,
		win.CW_USEDEFAULT,
		win.CW_USEDEFAULT,
		100,
		100,
		0,
		0,
		wc.HInstance,
		nil)
	if wdw == 0 {
		return fmt.Errorf("failed to create window: %w", syscall.GetLastError())
	}

	_ = win.ShowWindow(wdw, win.SW_HIDE)
	win.UpdateWindow(wdw)

	// To continuously get the devices events from Windows
	go func() {
		for {
			select {
			case <-ctx.Done():
				return
			default:
				var msg win.MSG
				got := win.GetMessage(&msg, win.HWND(windows.HWND(wdw)), 0, 0)
				if got == 0 {
					win.TranslateMessage(&msg)
					win.DispatchMessage(&msg)
				}
			}
		}
	}()

	// To handle the peripheral changed
	go func() {
		for {
			select {
			case <-ctx.Done():
				return
			case <-h.deviceChangedEvent:
				fmt.Println("This is the list of devices")
				h.Scan(ctx)
			}
		}
	}()
	return nil
}

// RegisterFinder registers a new peripherals finder
func (h *HardwareManager) RegisterFinder(finder PeripheralFinder) {
	h.finders = append(h.finders, finder)
	fmt.Printf("Success registered the %s finder\n", finder.GetName())
}

// Scan scans all the peripherals for the registered finders
func (h *HardwareManager) Scan(ctx context.Context) error {
	if len(h.finders) == 0 {
		return fmt.Errorf("No peripherals finder registered")
	}
	for _, finder := range h.finders {
		finder := finder
		go func() {
			err := finder.Scan(ctx)
			if err != nil {
				fmt.Printf("Unable to scan peripherals with the %s finder: %s\n", finder.GetName(), err)
				return
			}
		}()
	}
	return nil
}

func (h *HardwareManager) wndProc(hwnd windows.HWND, msg uint32, wParam, lParam uintptr) uintptr {
	switch msg {
	case win.WM_DEVICECHANGE:
		// Trigger the devices scan when the last DEVICE_CHANGE event is received
		if debounceTimer != nil {
			debounceTimer.Stop()
		}
		debounceTimer = time.AfterFunc(debounceDuration, func() {
			fmt.Printf("Devices list has changed, refresh the devices list\n")
			h.deviceChangedEvent <- struct{}{}
		})
	}
	return win.DefWindowProc(win.HWND(hwnd), msg, wParam, lParam)
}

// peripheralsList emits a peripheral event
func emitPeripheralsEvents(ctx context.Context, peripheralsList map[string]Peripheral, peripheralEvent PeripheralEvent) {
	for _, peripheral := range peripheralsList {
		runtime.EventsEmit(ctx, string(peripheralEvent), peripheral.GetInfo())
	}
}

// comparePeripherals compares the peripherals to determine which has been inserted or removed
func comparePeripherals(oldPeripherals map[string]Peripheral, newPeripherals map[string]Peripheral) (map[string]Peripheral, map[string]Peripheral) {
	// Duplicate the lists
	oldList := make(map[string]Peripheral)
	newList := make(map[string]Peripheral)

	for key, value := range oldPeripherals {
		oldList[key] = value
	}
	for key, value := range newPeripherals {
		newList[key] = value
	}
	// Remove in these lists all the commons peripherals
	for key := range newList {
		if _, exists := oldList[key]; exists {
			delete(oldList, key)
			delete(newList, key)
		}
	}
	// Now the old list contains the removed peripherals, and the new list contains the added peripherals
	fmt.Printf("%s\n", oldList)
	fmt.Printf("%s\n", newList)
	return oldList, newList
}