// 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.

//go:build (go1.16 && !ios) || (!go1.16 && !darwin) || (!go1.16 && !arm64)
// +build go1.16,!ios !go1.16,!darwin !go1.16,!arm64

package version

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

	"rsc.io/goversion/version"
)

// CmdName returns either the base name of the current binary
// using os.Executable. If os.Executable fails (it shouldn't), then
// "cmd" is returned.
func CmdName() string {
	e, err := os.Executable()
	if err != nil {
		return "cmd"
	}

	// fallbackName, the lowercase basename of the executable, is what we return if
	// we can't find the Go module metadata embedded in the file.
	fallbackName := filepath.Base(strings.TrimSuffix(strings.ToLower(e), ".exe"))

	var ret string
	v, err := version.ReadExe(e)
	if err != nil {
		return fallbackName
	}
	// v is like:
	// "path\ttailscale.com/cmd/tailscale\nmod\ttailscale.com\t(devel)\t\ndep\tgithub.com/apenwarr/fixconsole\tv0.0.0-20191012055117-5a9f6489cc29\th1:muXWUcay7DDy1/hEQWrYlBy+g0EuwT70sBHg65SeUc4=\ndep\tgithub....
	for _, line := range strings.Split(v.ModuleInfo, "\n") {
		if strings.HasPrefix(line, "path\t") {
			goPkg := strings.TrimPrefix(line, "path\t") // like "tailscale.com/cmd/tailscale"
			ret = path.Base(goPkg)                      // goPkg is always forward slashes; use path, not filepath
			break
		}
	}
	if ret == "" {
		return fallbackName
	}
	return ret
}