// +build windows

// We both need to
//   * use the registry editor directly to avoid possible PATH  truncation
//     ( https://stackoverflow.com/questions/9546324/adding-directory-to-path-environment-variable-in-windows )
//     ( https://superuser.com/questions/387619/overcoming-the-1024-character-limit-with-setx )
//   * explicitly send WM_SETTINGCHANGE
//     ( https://github.com/golang/go/issues/18680#issuecomment-275582179 )
//   * also install as a service
//     ( https://github.com/golang/sys/blob/master/windows/svc/example/install.go )
package main

import (
	"fmt"
	"os"
	"path/filepath"
	"strings"

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

var sendmsg func()

func usage() {
	fmt.Fprintf(os.Stderr, "Usage: winpath show|append|prepend|remove <path>\n")
}

func main() {
	fmt.Println("PATH:", os.Getenv("PATH"))
	//fpath, err := exec.LookPath("reg")
	//fmt.Println("LookPath(\"reg\"):", fpath, err)

	shell := os.Getenv("SHELL")
	if "" == shell {
		if strings.HasSuffix(os.Getenv("COMSPEC"), "/cmd.exe") {
			shell = "cmd"
		}
	}
	fmt.Println("SHELL?", shell)
	fmt.Println("os.PathListSeparator:", string(os.PathListSeparator))
	// WM_SETTING_CHANGE
	// https://gist.github.com/microo8/c1b9525efab9bb462adf9d123e855c52
	// os.Setenv("PATH")

	// TODO --system to add to the system PATH rather than the user PATH
	if len(os.Args) < 2 {
		usage()
		os.Exit(1)
	}
	action := os.Args[1]

	paths, err := Paths()
	if nil != err {
		fmt.Fprintf(os.Stderr, "%s\n", err)
		os.Exit(2)
	}

	if "show" == action {
		if len(os.Args) > 2 {
			usage()
		}
		fmt.Println()
		for i := range paths {
			fmt.Println("\t" + paths[i])
		}
		fmt.Println()
		return
	}

	if len(os.Args) < 3 {
		usage()
		os.Exit(1)
	}

	pathname := os.Args[2]
	abspath, err := filepath.Abs(pathname)
	if nil != err {
		fmt.Fprintf(os.Stderr, "%s\n", err)
		os.Exit(2)
	}
	if "remove" != action {
		stat, err := os.Stat(pathname)
		if nil != err {
			fmt.Fprintf(os.Stderr, "%s\n", err)
			os.Exit(2)
		}
		if !stat.IsDir() {
			fmt.Fprintf(os.Stderr, "%q is not a directory (folder)\n", pathname)
			os.Exit(2)
		}
	}

	index := -1
	for i := range paths {
		if pathname == paths[i] {
			index = i
			break
		}
		if abspath == paths[i] {
			index = i
			break
		}
	}

	switch action {
	default:
		usage()
		os.Exit(1)
	case "append":
		if index >= 0 {
			fmt.Fprintf(os.Stderr, "%q is already in PATH at position %d. Remove it first to re-order.\n", pathname, index)
			os.Exit(3)
		}
		paths = append(paths, pathname)
		fmt.Println("Run this to cause settings to take affect immediately:")
		fmt.Println("\tPATH %PATH%;" + pathname)
	case "prepend":
		if index >= 0 {
			fmt.Fprintf(os.Stderr, "%q is already in PATH at position %d. Remove it first to re-order.\n", pathname, index)
			os.Exit(3)
		}
		paths = append([]string{pathname}, paths...)
		fmt.Println("Run this to cause settings to take affect immediately:")
		fmt.Println("\tPATH " + pathname + ";%PATH%")
	case "remove":
		if index < 0 {
			fmt.Fprintf(os.Stderr, "%q is NOT in PATH.\n", pathname)
			os.Exit(3)
		}
		oldpaths := paths
		paths = []string{}
		for i := range oldpaths {
			if i != index {
				paths = append(paths, oldpaths[i])
			}
		}
	}

	k, err := registry.OpenKey(registry.CURRENT_USER, `Environment`, registry.SET_VALUE)
	if err != nil {
		fmt.Fprintf(os.Stderr, "%s\n", err)
		os.Exit(4)
	}
	defer k.Close()
	// ";" on Windows
	err = k.SetStringValue(`Path`, strings.Join(paths, string(os.PathListSeparator)))
	if nil != err {
		fmt.Fprintf(os.Stderr, "%s\n", err)
		os.Exit(4)
	}
	err = k.Close()
	if nil != err {
		fmt.Fprintf(os.Stderr, "%s\n", err)
		os.Exit(4)

	}

	err = os.Setenv(`PATH`, strings.Join(paths, string(os.PathListSeparator)))
	if nil != err {
		fmt.Fprintf(os.Stderr, "%s\n", err)
		os.Exit(4)
	}
	if nil != sendmsg {
		fmt.Println("Open a new Terminal for the updated PATH")
		sendmsg()
	} else {
		fmt.Println("You'll need to reboot for setting to take affect")
	}
}

func Paths() ([]string, error) {
	k, err := registry.OpenKey(registry.CURRENT_USER, `Environment`, registry.QUERY_VALUE)
	if err != nil {
		return nil, err
	}
	defer k.Close()

	// This is case insensitive (PATH, Path, path)
	s, _, err := k.GetStringValue("Path")
	if err != nil {
		return nil, err
	}
	// ";" on Windows
	return strings.Split(s, string(os.PathListSeparator)), nil

	/*
		shstr := loader()
		if "" == shstr {
			shstr = "NO_SHELL_DETECTED"
		}
		if "" == s {
			s = "NO_WINREG_PATH"
		}

		return fmt.Sprintf("%s\n%s", s, shstr)
	*/
}