// 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.

package main

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

// 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)
}

// 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{
	cmdBuild,
	cmdClean,
	cmdDoc,
	cmdFix,
	cmdFmt,
	cmdGet,
	cmdInstall,
	cmdList,
	cmdRun,
	cmdTest,
	cmdTool,
	cmdVersion,
	cmdVet,

	helpGopath,
	helpImportpath,
	helpRemote,
	helpTestflag,
	helpTestfunc,
}

var exitStatus = 0
var exitMu sync.Mutex

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

func main() {
	flag.Usage = usage
	flag.Parse()
	log.SetFlags(0)

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

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

	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, "Unknown command %#q\n\n", args[0])
	usage()
}

var usageTemplate = `Go is a tool for managing Go source code.

Usage: go command [arguments]

The commands are:
{{range .}}{{if .Run}}
    {{.Name | printf "%-11s"}} {{.Short}}{{end}}{{end}}

Use "go help [command]" for more information about a command.

Additional help topics:
{{range .}}{{if not .Run}}
    {{.Name | printf "%-11s"}} {{.Short}}{{end}}{{end}}

Use "go help [topic]" for more information about that topic.

`

var helpTemplate = `{{if .Run}}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.

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

{{end}}{{if .Run}}Usage:

	go {{.UsageLine}}

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


{{end}}*/
package documentation

// 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 'go help'.
		return
	}
	if len(args) != 1 {
		fmt.Fprintf(os.Stderr, "usage: go help command\n\nToo many arguments given.\n")
		os.Exit(2) // failed at 'go 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 'go help'.\n", arg)
	os.Exit(2) // failed at 'go help cmd'
}

// importPaths returns the import paths to use for the given command line.
func importPaths(args []string) []string {
	if len(args) == 0 {
		return []string{"."}
	}
	var out []string
	for _, a := range args {
		if isLocalPath(a) && strings.Contains(a, "...") {
			out = append(out, allPackagesInFS(a)...)
			continue
		}
		if a == "all" || a == "std" || strings.Contains(a, "...") {
			out = append(out, allPackages(a)...)
			continue
		}
		out = append(out, a)
	}
	return out
}

var atexitFuncs []func()

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

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

func fatalf(format string, args ...interface{}) {
	errorf(format, args...)
	exit()
}

func errorf(format string, args ...interface{}) {
	log.Printf(format, args...)
	setExitStatus(1)
}

var logf = log.Printf

func exitIfErrors() {
	if exitStatus != 0 {
		exit()
	}
}

func run(cmdargs ...interface{}) {
	cmdline := stringList(cmdargs...)
	cmd := exec.Command(cmdline[0], cmdline[1:]...)
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	if err := cmd.Run(); err != nil {
		errorf("%v", err)
	}
}

func runOut(dir string, cmdargs ...interface{}) []byte {
	cmdline := stringList(cmdargs...)
	cmd := exec.Command(cmdline[0], cmdline[1:]...)
	cmd.Dir = dir
	out, err := cmd.CombinedOutput()
	if err != nil {
		os.Stderr.Write(out)
		errorf("%v", err)
		out = nil
	}
	return out
}

// matchPattern(pattern)(name) reports whether
// name matches pattern.  Pattern is a limited glob
// pattern in which '...' means 'any string' and there
// is no other special syntax.
func matchPattern(pattern string) func(name string) bool {
	re := regexp.QuoteMeta(pattern)
	re = strings.Replace(re, `\.\.\.`, `.*`, -1)
	reg := regexp.MustCompile(`^` + re + `$`)
	return func(name string) bool {
		return reg.MatchString(name)
	}
}

// allPackages returns all the packages that can be found
// under the $GOPATH directories and $GOROOT matching pattern.
// The pattern is either "all" (all packages), "std" (standard packages)
// or a path including "...".
func allPackages(pattern string) []string {
	match := func(string) bool { return true }
	if pattern != "all" && pattern != "std" {
		match = matchPattern(pattern)
	}

	have := map[string]bool{
		"builtin": true, // ignore pseudo-package that exists only for documentation
	}
	if !buildContext.CgoEnabled {
		have["runtime/cgo"] = true // ignore during walk
	}
	var pkgs []string

	// Commands
	goroot := build.Path[0].Path
	cmd := filepath.Join(goroot, "src/cmd") + string(filepath.Separator)
	filepath.Walk(cmd, func(path string, fi os.FileInfo, err error) error {
		if err != nil || !fi.IsDir() || path == cmd {
			return nil
		}
		name := path[len(cmd):]
		// Commands are all in cmd/, not in subdirectories.
		if strings.Contains(name, string(filepath.Separator)) {
			return filepath.SkipDir
		}

		_, err = build.ScanDir(path)
		if err != nil {
			return nil
		}

		// We use, e.g., cmd/gofmt as the pseudo import path for gofmt.
		name = "cmd/" + name
		if !have[name] {
			have[name] = true
			if match(name) {
				pkgs = append(pkgs, name)
			}
		}
		return nil
	})

	for _, t := range build.Path {
		if pattern == "std" && !t.Goroot {
			continue
		}
		src := t.SrcDir() + string(filepath.Separator)
		filepath.Walk(src, func(path string, fi os.FileInfo, err error) error {
			if err != nil || !fi.IsDir() || path == src {
				return nil
			}

			// Avoid .foo, _foo, and testdata directory trees.
			_, elem := filepath.Split(path)
			if strings.HasPrefix(elem, ".") || strings.HasPrefix(elem, "_") || elem == "testdata" {
				return filepath.SkipDir
			}

			name := filepath.ToSlash(path[len(src):])
			if pattern == "std" && strings.Contains(name, ".") {
				return filepath.SkipDir
			}
			if have[name] {
				return nil
			}
			have[name] = true

			_, err = build.ScanDir(path)
			if err != nil {
				return nil
			}

			if match(name) {
				pkgs = append(pkgs, name)
			}

			// Avoid go/build test data.
			// TODO: Move it into a testdata directory.
			if path == filepath.Join(build.Path[0].SrcDir(), "go/build") {
				return filepath.SkipDir
			}

			return nil
		})
	}

	if len(pkgs) == 0 {
		fmt.Fprintf(os.Stderr, "warning: %q matched no packages\n", pattern)
	}
	return pkgs
}

// allPackagesInFS is like allPackages but is passed a pattern
// beginning ./ or ../, meaning it should scan the tree rooted
// at the given directory.  There are ... in the pattern too.
func allPackagesInFS(pattern string) []string {
	// Find directory to begin the scan.
	// Could be smarter but this one optimization
	// is enough for now, since ... is usually at the
	// end of a path.
	i := strings.Index(pattern, "...")
	dir, _ := path.Split(pattern[:i])

	// pattern begins with ./ or ../.
	// path.Clean will discard the ./ but not the ../.
	// We need to preserve the ./ for pattern matching
	// and in the returned import paths.
	prefix := ""
	if strings.HasPrefix(pattern, "./") {
		prefix = "./"
	}
	match := matchPattern(pattern)

	var pkgs []string
	filepath.Walk(dir, func(path string, fi os.FileInfo, err error) error {
		if err != nil || !fi.IsDir() || path == dir {
			return nil
		}

		// Avoid .foo, _foo, and testdata directory trees.
		_, elem := filepath.Split(path)
		if strings.HasPrefix(elem, ".") || strings.HasPrefix(elem, "_") || elem == "testdata" {
			return filepath.SkipDir
		}

		name := prefix + filepath.ToSlash(path)
		if !match(name) {
			return nil
		}
		if _, err = build.ScanDir(path); err != nil {
			return nil
		}
		pkgs = append(pkgs, name)
		return nil
	})

	if len(pkgs) == 0 {
		fmt.Fprintf(os.Stderr, "warning: %q matched no packages\n", pattern)
	}
	return pkgs
}

// stringList's arguments should be a sequence of string or []string values.
// stringList flattens them into a single []string.
func stringList(args ...interface{}) []string {
	var x []string
	for _, arg := range args {
		switch arg := arg.(type) {
		case []string:
			x = append(x, arg...)
		case string:
			x = append(x, arg)
		default:
			panic("stringList: invalid argument")
		}
	}
	return x
}

// isLocalPath returns true if arg is an import path denoting
// a local file system directory.  That is, it returns true if the
// path begins with ./ or ../ .
func isLocalPath(arg string) bool {
	return arg == "." || arg == ".." || strings.HasPrefix(arg, "./") || strings.HasPrefix(arg, "../")
}