//go:build windows

package browser

import (
	"context"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"syscall"
	"unsafe"

	"chub/internal/domain"
)

const chromeMessageWindowClass = "Chrome_MessageWindow"

const processQueryLimitedInformation = 0x1000

var (
	user32                    = syscall.NewLazyDLL("user32.dll")
	kernel32                  = syscall.NewLazyDLL("kernel32.dll")
	findWindowExW             = user32.NewProc("FindWindowExW")
	getWindowThreadProcessID  = user32.NewProc("GetWindowThreadProcessId")
	queryFullProcessImageName = kernel32.NewProc("QueryFullProcessImageNameW")
	waitForSingleObject       = kernel32.NewProc("WaitForSingleObject")
)

type windowsProcessInspector struct{}

func NewWindowsProcessInspector() ProcessInspector { return windowsProcessInspector{} }

func (windowsProcessInspector) Inspect(ctx context.Context, pid int) (ProcessIdentity, error) {
	if err := ctx.Err(); err != nil {
		return ProcessIdentity{}, err
	}
	if pid <= 0 {
		return ProcessIdentity{}, fmt.Errorf("%w: invalid PID", ErrIdentityUnavailable)
	}
	handle, err := syscall.OpenProcess(syscall.SYNCHRONIZE|processQueryLimitedInformation, false, uint32(pid))
	if err != nil {
		return ProcessIdentity{}, fmt.Errorf("%w: open process: %v", ErrIdentityUnavailable, err)
	}
	defer syscall.CloseHandle(handle)
	path, err := queryImagePath(handle)
	if err != nil {
		return ProcessIdentity{}, fmt.Errorf("%w: query executable: %v", ErrIdentityUnavailable, err)
	}
	return ProcessIdentity{PID: pid, Executable: path}, nil
}

func (windowsProcessInspector) Alive(ctx context.Context, pid int) (bool, error) {
	if err := ctx.Err(); err != nil {
		return false, err
	}
	if pid <= 0 {
		return false, nil
	}
	handle, err := syscall.OpenProcess(syscall.SYNCHRONIZE, false, uint32(pid))
	if err != nil {
		return false, nil
	}
	defer syscall.CloseHandle(handle)
	const waitTimeout = 258
	result, _, callErr := waitForSingleObject.Call(uintptr(handle), 0)
	if callErr != syscall.Errno(0) {
		return false, callErr
	}
	return result == waitTimeout, nil
}

func queryImagePath(handle syscall.Handle) (string, error) {
	buffer := make([]uint16, syscall.MAX_PATH)
	for {
		size := uint32(len(buffer))
		result, _, callErr := queryFullProcessImageName.Call(uintptr(handle), 0, uintptr(unsafe.Pointer(&buffer[0])), uintptr(unsafe.Pointer(&size)))
		if result != 0 {
			return syscall.UTF16ToString(buffer[:size]), nil
		}
		if callErr != syscall.ERROR_INSUFFICIENT_BUFFER || len(buffer) >= 32768 {
			return "", callErr
		}
		buffer = make([]uint16, len(buffer)*2)
	}
}

type windowsProfileInspector struct{ process ProcessInspector }

func NewWindowsProfileInspector() ExternalProfileInspector {
	return windowsProfileInspector{process: NewWindowsProcessInspector()}
}

func (i windowsProfileInspector) InspectProfile(ctx context.Context, kind domain.BrowserKind, userDataDir string, historicalPID int) (ProfileUse, error) {
	if err := ctx.Err(); err != nil {
		return ProfileUse{}, err
	}
	profile, err := filepath.Abs(filepath.Clean(userDataDir))
	if err != nil {
		return ProfileUse{}, err
	}
	if pid, found, err := findProfileWindow(profile); err != nil {
		return ProfileUse{}, err
	} else if found {
		identity, identityErr := i.process.Inspect(ctx, pid)
		if identityErr == nil && executableMatchesKind(identity.Executable, kind) {
			return ProfileUse{Occupied: true, PID: pid, Source: ProfileSourceMessageWindow}, nil
		}
		return ProfileUse{Occupied: true, PID: pid, Source: ProfileSourceUnknown}, nil
	}

	lockPath := filepath.Join(profile, "lockfile")
	file, err := os.OpenFile(lockPath, os.O_WRONLY, 0)
	if err == nil {
		_ = file.Close()
		if historicalPID > 0 {
			alive, aliveErr := i.process.Alive(ctx, historicalPID)
			if aliveErr == nil && alive {
				return ProfileUse{Source: ProfileSourceStalePID}, nil
			}
		}
		return ProfileUse{Source: ProfileSourceStaleLock}, nil
	}
	if errors.Is(err, os.ErrNotExist) {
		return ProfileUse{}, nil
	}
	if isSharingViolation(err) {
		pid := 0
		if historicalPID > 0 {
			alive, aliveErr := i.process.Alive(ctx, historicalPID)
			if aliveErr == nil && alive {
				pid = historicalPID
			}
		}
		return ProfileUse{Occupied: true, PID: pid, Source: ProfileSourceLock}, nil
	}
	return ProfileUse{}, fmt.Errorf("inspect browser lock: %w", err)
}

func findProfileWindow(profile string) (int, bool, error) {
	className, err := syscall.UTF16PtrFromString(chromeMessageWindowClass)
	if err != nil {
		return 0, false, err
	}
	windowName, err := syscall.UTF16PtrFromString(profile)
	if err != nil {
		return 0, false, err
	}
	const hwndMessage = ^uintptr(2)
	hwnd, _, callErr := findWindowExW.Call(hwndMessage, 0, uintptr(unsafe.Pointer(className)), uintptr(unsafe.Pointer(windowName)))
	if hwnd == 0 {
		if callErr != syscall.Errno(0) {
			return 0, false, callErr
		}
		return 0, false, nil
	}
	var pid uint32
	threadID, _, callErr := getWindowThreadProcessID.Call(hwnd, uintptr(unsafe.Pointer(&pid)))
	if threadID == 0 || pid == 0 {
		if callErr == syscall.Errno(0) {
			callErr = errors.New("profile window has no process")
		}
		return 0, false, callErr
	}
	return int(pid), true, nil
}

func isSharingViolation(err error) bool {
	const (
		sharingViolation syscall.Errno = 32
		lockViolation    syscall.Errno = 33
	)
	var pathErr *os.PathError
	if !errors.As(err, &pathErr) {
		return false
	}
	errno, ok := pathErr.Err.(syscall.Errno)
	return ok && (errno == sharingViolation || errno == lockViolation)
}