main.go

package main

import (
	"bytes"
	"errors"
	"flag"
	"fmt"
	"go/scanner"
	"io"
	"io/ioutil"
	"log"
	"os"
	"os/exec"
	"path/filepath"
	"runtime"
	"strings"
)

type Options struct {
	TabWidth  int
	TabIndent bool
	Comments  bool
}

var (
	// main operation modes
	list   = flag.Bool("l", false, "list files whose formatting differs from gqlfmt's")
	write  = flag.Bool("w", false, "write result to (source) file instead of stdout")
	doDiff = flag.Bool("d", false, "display diffs instead of rewriting files")

	verbose bool // verbose logging

	options = &Options{
		TabWidth:  4,
		TabIndent: true,
		Comments:  true,
	}

	exitCode = 0
)

func report(err error) {
	scanner.PrintError(os.Stderr, err)
	exitCode = 2
}

func usage() {
	fmt.Fprintf(os.Stderr, "usage: gqlfmt [flags] [path ...]\n")
	flag.PrintDefaults()
	os.Exit(2)
}

func isGQLFile(f os.FileInfo) bool {
	name := f.Name()
	return !f.IsDir() && !strings.HasPrefix(name, ".") && strings.HasSuffix(name, ".graphql")
}

// argumentType is which mode gqlfmt was invoked as.
type argumentType int

const (
	// fromStdin means the user is piping their source into gqlfmt.
	fromStdin argumentType = iota

	// singleArg is the common case from editors, when gqlfmt is run on
	// a single file.
	singleArg

	// multipleArg is when the user ran "gqlfmt file1.go file2.go"
	// or ran gqlfmt on a directory tree.
	multipleArg
)

func processFile(filename string, in io.Reader, out io.Writer, argType argumentType) error {
	opt := options
	if argType == fromStdin {
		nopt := *options
		opt = &nopt
	}

	if in == nil {
		f, err := os.Open(filename)
		if err != nil {
			return err
		}
		defer f.Close()
		in = f
	}

	src, err := ioutil.ReadAll(in)
	if err != nil {
		return err
	}

	res, err := process(filename, src, opt)
	if err != nil {
		return err
	}

	if !bytes.Equal(src, res) {
		// formatting has changed
		if *list {
			fmt.Fprintln(out, filename)
		}
		if *write {
			if argType == fromStdin {
				// filename is "<standard input>"
				return errors.New("can't use -w on stdin")
			}
			err = ioutil.WriteFile(filename, res, 0)
			if err != nil {
				return err
			}
		}
		if *doDiff {
			if argType == fromStdin {
				filename = "stdin.go" // because <standard input>.orig looks silly
			}
			data, err := diff(src, res, filename)
			if err != nil {
				return fmt.Errorf("computing diff: %s", err)
			}
			fmt.Printf("diff -u %s %s\n", filepath.ToSlash(filename+".orig"), filepath.ToSlash(filename))
			out.Write(data)
		}
	}

	if !*list && !*write && !*doDiff {
		_, err = out.Write(res)
	}

	return err
}

func visitFile(path string, f os.FileInfo, err error) error {
	if err == nil && isGQLFile(f) {
		err = processFile(path, nil, os.Stdout, multipleArg)
	}
	if err != nil {
		report(err)
	}
	return nil
}

func walkDir(path string) {
	filepath.Walk(path, visitFile)
}

func main() {
	runtime.GOMAXPROCS(runtime.NumCPU())

	// call gofmtMain in a separate function
	// so that it can use defer and have them
	// run before the exit.
	gqlfmtMain()
	os.Exit(exitCode)
}

// parseFlags parses command line flags and returns the paths to process.
// It's a var so that custom implementations can replace it in other files.
var parseFlags = func() []string {
	flag.BoolVar(&verbose, "v", false, "verbose logging")

	flag.Parse()
	return flag.Args()
}

func gqlfmtMain() {
	flag.Usage = usage
	paths := parseFlags()

	if verbose {
		log.SetFlags(log.LstdFlags | log.Lmicroseconds)
	}
	if options.TabWidth < 0 {
		fmt.Fprintf(os.Stderr, "negative tabwidth %d\n", options.TabWidth)
		exitCode = 2
		return
	}

	if len(paths) == 0 {
		if err := processFile("<standard input>", os.Stdin, os.Stdout, fromStdin); err != nil {
			report(err)
		}
		return
	}

	argType := singleArg
	if len(paths) > 1 {
		argType = multipleArg
	}

	for _, path := range paths {
		switch dir, err := os.Stat(path); {
		case err != nil:
			report(err)
		case dir.IsDir():
			walkDir(path)
		default:
			if err := processFile(path, nil, os.Stdout, argType); err != nil {
				report(err)
			}
		}
	}
}

func writeTempFile(dir, prefix string, data []byte) (string, error) {
	file, err := ioutil.TempFile(dir, prefix)
	if err != nil {
		return "", err
	}
	_, err = file.Write(data)
	if err1 := file.Close(); err == nil {
		err = err1
	}
	if err != nil {
		os.Remove(file.Name())
		return "", err
	}
	return file.Name(), nil
}

func diff(b1, b2 []byte, filename string) (data []byte, err error) {
	f1, err := writeTempFile("", "gofmt", b1)
	if err != nil {
		return
	}
	defer os.Remove(f1)

	f2, err := writeTempFile("", "gofmt", b2)
	if err != nil {
		return
	}
	defer os.Remove(f2)

	cmd := "diff"
	if runtime.GOOS == "plan9" {
		cmd = "/bin/ape/diff"
	}

	data, err = exec.Command(cmd, "-u", f1, f2).CombinedOutput()
	if len(data) > 0 {
		// diff exits with a non-zero status when the files don't match.
		// Ignore that failure as long as we get output.
		return replaceTempFilename(data, filename)
	}
	return
}

// replaceTempFilename replaces temporary filenames in diff with actual one.
//
// --- /tmp/gofmt316145376	2017-02-03 19:13:00.280468375 -0500
// +++ /tmp/gofmt617882815	2017-02-03 19:13:00.280468375 -0500
// ...
// ->
// --- path/to/file.go.orig	2017-02-03 19:13:00.280468375 -0500
// +++ path/to/file.go	2017-02-03 19:13:00.280468375 -0500
// ...
func replaceTempFilename(diff []byte, filename string) ([]byte, error) {
	bs := bytes.SplitN(diff, []byte{'\n'}, 3)
	if len(bs) < 3 {
		return nil, fmt.Errorf("got unexpected diff for %s", filename)
	}
	// Preserve timestamps.
	var t0, t1 []byte
	if i := bytes.LastIndexByte(bs[0], '\t'); i != -1 {
		t0 = bs[0][i:]
	}
	if i := bytes.LastIndexByte(bs[1], '\t'); i != -1 {
		t1 = bs[1][i:]
	}
	// Always print filepath with slash separator.
	f := filepath.ToSlash(filename)
	bs[0] = []byte(fmt.Sprintf("--- %s%s", f+".orig", t0))
	bs[1] = []byte(fmt.Sprintf("+++ %s%s", f, t1))
	return bytes.Join(bs, []byte{'\n'}), nil
}