//go:build windows

// Package desktop holds the small Windows shell integrations that do not
// belong to any one feature: opening a URL in the default browser, and the
// HKCU Run key that starts ipswap with Windows.
package desktop

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

	"golang.org/x/sys/windows/registry"

	"gitea.apointless.space/bsncubed/ipswap/internal/config"
)

var (
	shell32       = syscall.NewLazyDLL("shell32.dll")
	shellExecuteW = shell32.NewProc("ShellExecuteW")
)

const runKeyPath = `Software\Microsoft\Windows\CurrentVersion\Run`

// OpenURL opens a URL in the default browser.
//
// ShellExecuteW rather than `cmd /c start`: no console window to suppress and
// no quoting rules to get wrong around a URL that already contains "?" and "&".
func OpenURL(url string) error {
	verb, err := syscall.UTF16PtrFromString("open")
	if err != nil {
		return err
	}
	target, err := syscall.UTF16PtrFromString(url)
	if err != nil {
		return err
	}
	ret, _, callErr := shellExecuteW.Call(
		0,
		uintptr(unsafe.Pointer(verb)),
		uintptr(unsafe.Pointer(target)),
		0, 0, 1, // no args, no cwd, SW_SHOWNORMAL
	)
	if ret <= 32 {
		return fmt.Errorf("could not open %s (ShellExecuteW returned %d: %v)", url, ret, callErr)
	}
	return nil
}

// SetRunAtLogin adds or removes ipswap from the current user's Run key.
//
// HKCU rather than HKLM deliberately: HKLM needs elevation, and ipswap is
// designed to run unelevated. It also keeps the setting per-user on a shared
// support laptop.
func SetRunAtLogin(enabled bool) error {
	key, _, err := registry.CreateKey(registry.CURRENT_USER, runKeyPath, registry.SET_VALUE)
	if err != nil {
		return fmt.Errorf("opening the Run key: %w", err)
	}
	defer key.Close()

	if !enabled {
		err := key.DeleteValue(config.AppName)
		if err != nil && err != registry.ErrNotExist {
			return fmt.Errorf("removing the Run key value: %w", err)
		}
		return nil
	}

	exe, err := os.Executable()
	if err != nil {
		return fmt.Errorf("locating the running executable: %w", err)
	}
	exe, err = filepath.Abs(exe)
	if err != nil {
		return err
	}

	// Quoted: the path routinely contains spaces (the install lives under
	// %APPDATA%, and a user profile can have a space in its name) and the Run
	// key value is a command line, not a path.
	//
	// --background is what stops a browser tab appearing at every login. A
	// launch from the shortcut has no such flag and does open the editor.
	if err := key.SetStringValue(config.AppName, `"`+exe+`" --background`); err != nil {
		return fmt.Errorf("writing the Run key value: %w", err)
	}
	return nil
}

// RunAtLogin reports whether the Run key entry is present.
func RunAtLogin() bool {
	key, err := registry.OpenKey(registry.CURRENT_USER, runKeyPath, registry.QUERY_VALUE)
	if err != nil {
		return false
	}
	defer key.Close()

	v, _, err := key.GetStringValue(config.AppName)
	return err == nil && v != ""
}