// Copyright (c) 2013 GPMGo Members. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.

// gpm(Go Package Manager) is a Go package manage tool for search, install, update and share packages in Go.

package main

import (
	"bytes"
	"flag"
	"fmt"
	"go/build"
	"io"
	"log"
	"os"
	"path/filepath"
	"runtime"
	"strings"
	"sync"
	"text/template"
	"unicode"
	"unicode/utf8"

	"github.com/BurntSushi/toml"
)

var (
	config tomlConfig
)

type tomlConfig struct {
	Title, Version string
	Lang           string `toml:"user_language"`
}

// A Command is an implementation of a go command
// like go build or go fix.
type Command struct {
	// Run runs the command.
	// The args are the arguments after the command name.
	Run func(cmd *Command, args []string)

	// UsageLine is the one-line usage message.
	// The first word in the line is taken to be the command name.
	UsageLine string

	// Short is the short description shown in the 'go help' output.
	Short string

	// Long is the long message shown in the 'go help <this-command>' output.
	Long string

	// Flag is a set of flags specific to this command.
	Flag flag.FlagSet

	// CustomFlags indicates that the command will do its own
	// flag parsing.
	CustomFlags bool
}

// Name returns the command's name: the first word in the usage line.
func (c *Command) Name() string {
	name := c.UsageLine
	i := strings.Index(name, " ")
	if i >= 0 {
		name = name[:i]
	}
	return name
}

func (c *Command) Usage() {
	fmt.Fprintf(os.Stderr, "usage: %s\n\n", c.UsageLine)
	fmt.Fprintf(os.Stderr, "%s\n", strings.TrimSpace(c.Long))
	os.Exit(2)
}

// Runnable reports whether the command can be run; otherwise
// it is a documentation pseudo-command such as importpath.
func (c *Command) Runnable() bool {
	return c.Run != nil
}

// Commands lists the available commands and help topics.
// The order here is the order in which they are printed by 'go help'.
var commands = []*Command{}

var exitStatus = 0
var exitMu sync.Mutex

func setExitStatus(n int) {
	exitMu.Lock()
	if exitStatus < n {
		exitStatus = n
	}
	exitMu.Unlock()
}

func main() {
	// Load configuration.
	if _, err := toml.DecodeFile("i18n/gpm.toml", &config); err != nil {
		fmt.Println(err)
		return
	}

	// Load usage template by language.
	f, err := os.Open("i18n/usage_" + config.Lang + ".tpl")
	if err != nil {
		fmt.Println(err)
		return
	}
	defer f.Close()
	// Read usage.
	fi, _ := f.Stat()
	usageBytes := make([]byte, fi.Size())
	f.Read(usageBytes)
	usageTemplate = string(usageBytes)

	// Initialization.
	flag.Usage = usage
	flag.Parse()
	log.SetFlags(0)

	args := flag.Args()
	if len(args) < 1 {
		usage()
	}

	if args[0] == "help" {
		help(args[1:])
		return
	}

	// Diagnose common mistake: GOPATH==GOROOT.
	// This setting is equivalent to not setting GOPATH at all,
	// which is not what most people want when they do it.
	if gopath := os.Getenv("GOPATH"); gopath == runtime.GOROOT() {
		fmt.Fprintf(os.Stderr, "warning: GOPATH set to GOROOT (%s) has no effect\n", gopath)
	} else {
		for _, p := range filepath.SplitList(gopath) {
			// Note: using HasPrefix instead of Contains because a ~ can appear
			// in the middle of directory elements, such as /tmp/git-1.8.2~rc3
			// or C:\PROGRA~1. Only ~ as a path prefix has meaning to the shell.
			if strings.HasPrefix(p, "~") {
				fmt.Fprintf(os.Stderr, "go: GOPATH entry cannot start with shell metacharacter '~': %q\n", p)
				os.Exit(2)
			}
			if build.IsLocalImport(p) {
				fmt.Fprintf(os.Stderr, "go: GOPATH entry is relative; must be absolute path: %q.\nRun 'go help gopath' for usage.\n", p)
				os.Exit(2)
			}
		}
	}

	for _, cmd := range commands {
		if cmd.Name() == args[0] && cmd.Run != nil {
			cmd.Flag.Usage = func() { cmd.Usage() }
			if cmd.CustomFlags {
				args = args[1:]
			} else {
				cmd.Flag.Parse(args[1:])
				args = cmd.Flag.Args()
			}
			cmd.Run(cmd, args)
			exit()
			return
		}
	}

	fmt.Fprintf(os.Stderr, "go: unknown subcommand %q\nRun 'go help' for usage.\n", args[0])
	setExitStatus(2)
	exit()
}

var usageTemplate string
var helpTemplate = `{{if .Runnable}}usage: go {{.UsageLine}}

{{end}}{{.Long | trim}}
`

var documentationTemplate = `// Copyright 2011 The Go Authors.  All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// DO NOT EDIT THIS FILE. GENERATED BY mkdoc.sh.
// Edit the documentation in other files and rerun mkdoc.sh to generate this one.

/*
{{range .}}{{if .Short}}{{.Short | capitalize}}

{{end}}{{if .Runnable}}Usage:

	go {{.UsageLine}}

{{end}}{{.Long | trim}}


{{end}}*/
package main

// NOTE: cmdDoc is in fmt.go.
`

// tmpl executes the given template text on data, writing the result to w.
func tmpl(w io.Writer, text string, data interface{}) {
	t := template.New("top")
	t.Funcs(template.FuncMap{"trim": strings.TrimSpace, "capitalize": capitalize})
	template.Must(t.Parse(text))
	if err := t.Execute(w, data); err != nil {
		panic(err)
	}
}

func capitalize(s string) string {
	if s == "" {
		return s
	}
	r, n := utf8.DecodeRuneInString(s)
	return string(unicode.ToTitle(r)) + s[n:]
}

func printUsage(w io.Writer) {
	tmpl(w, usageTemplate, commands)
}

func usage() {
	printUsage(os.Stderr)
	os.Exit(2)
}

// help implements the 'help' command.
func help(args []string) {
	if len(args) == 0 {
		printUsage(os.Stdout)
		// not exit 2: succeeded at 'gpm help'.
		return
	}
	if len(args) != 1 {
		fmt.Fprintf(os.Stderr, "usage: gpm help command\n\nToo many arguments given.\n")
		os.Exit(2) // failed at 'gpm help'
	}

	arg := args[0]

	// 'go help documentation' generates doc.go.
	if arg == "documentation" {
		buf := new(bytes.Buffer)
		printUsage(buf)
		usage := &Command{Long: buf.String()}
		tmpl(os.Stdout, documentationTemplate, append([]*Command{usage}, commands...))
		return
	}

	for _, cmd := range commands {
		if cmd.Name() == arg {
			tmpl(os.Stdout, helpTemplate, cmd)
			// not exit 2: succeeded at 'go help cmd'.
			return
		}
	}

	fmt.Fprintf(os.Stderr, "Unknown help topic %#q.  Run 'gpm help'.\n", arg)
	os.Exit(2) // failed at 'go help cmd'
}

var atexitFuncs []func()

func atexit(f func()) {
	atexitFuncs = append(atexitFuncs, f)
}

func exit() {
	for _, f := range atexitFuncs {
		f()
	}
	os.Exit(exitStatus)
}