// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package version

import (
	"os"
	"path/filepath"
	"runtime"
	"strconv"
	"strings"
	"sync"

	"tailscale.com/syncs"
)

// IsMobile reports whether this is a mobile client build.
func IsMobile() bool {
	return runtime.GOOS == "android" || runtime.GOOS == "ios"
}

// OS returns runtime.GOOS, except instead of returning "darwin" it
// returns "iOS" or "macOS".
func OS() string {
	if runtime.GOOS == "ios" {
		return "iOS"
	}
	if runtime.GOOS == "darwin" {
		return "macOS"
	}
	return runtime.GOOS
}

// IsSandboxedMacOS reports whether this process is a sandboxed macOS
// process (either the app or the extension). It is true for the Mac App Store
// and macsys (System Extension) version on macOS, and false for
// tailscaled-on-macOS.
func IsSandboxedMacOS() bool {
	if runtime.GOOS != "darwin" {
		return false
	}
	if IsMacSysExt() {
		return true
	}
	exe, _ := os.Executable()
	return strings.HasSuffix(exe, "/Contents/MacOS/Tailscale") || strings.HasSuffix(exe, "/Contents/MacOS/IPNExtension")
}

var isMacSysExt syncs.AtomicValue[bool]

// IsMacSysExt whether this binary is from the standalone "System
// Extension" (a.k.a. "macsys") version of Tailscale for macOS.
func IsMacSysExt() bool {
	if runtime.GOOS != "darwin" {
		return false
	}
	if b, ok := isMacSysExt.LoadOk(); ok {
		return b
	}
	exe, err := os.Executable()
	if err != nil {
		return false
	}
	v := filepath.Base(exe) == "io.tailscale.ipn.macsys.network-extension"
	isMacSysExt.Store(v)
	return v
}

// IsWindowsGUI reports whether the current process is the Windows GUI.
func IsWindowsGUI() bool {
	if runtime.GOOS != "windows" {
		return false
	}
	exe, _ := os.Executable()
	exe = filepath.Base(exe)
	return strings.EqualFold(exe, "tailscale-ipn.exe") || strings.EqualFold(exe, "tailscale-ipn")
}

var (
	isUnstableOnce  sync.Once
	isUnstableBuild bool
)

// IsUnstableBuild reports whether this is an unstable build.
// That is, whether its minor version number is odd.
func IsUnstableBuild() bool {
	isUnstableOnce.Do(initUnstable)
	return isUnstableBuild
}

func initUnstable() {
	_, rest, ok := strings.Cut(Short, ".")
	if !ok {
		return
	}
	minorStr, _, ok := strings.Cut(rest, ".")
	if !ok {
		return
	}
	minor, err := strconv.Atoi(minorStr)
	if err != nil {
		return
	}
	isUnstableBuild = minor%2 == 1
}