package main

import (
	"flag"
	"fmt"
	"io"
	"log"
	"os"
	"regexp"
	"strconv"

	"sourcegraph.com/sourcegraph/go-diff/diff"
)

func main() {
	var diffPath, includes, excludes, label string
	var dryrun bool

	log.SetFlags(0)

	flag.BoolVar(&dryrun, "d", false, "Dry run mode")
	flag.StringVar(&diffPath, "f", "-", "filename of diff (default: stdin)")
	flag.StringVar(&includes, "m", "", "Select files matching this")
	flag.StringVar(&excludes, "x", "", "Excludes files matching this")
	flag.Parse()

	var diffFile *os.File
	if diffPath == "-" {
		diffFile = os.Stdin
	} else {
		var err error
		diffFile, err = os.Open(diffPath)
		if err != nil {
			log.Fatal(err)
		}
	}
	defer diffFile.Close()

	r := diff.NewMultiFileDiffReader(diffFile)
	for i := 0; ; i++ {
		var selected, match bool
		var err error

		fdiff, err := r.ReadFile()
		if fdiff != nil {
			label = fmt.Sprintf("orig(%s) new(%s)", fdiff.OrigName, fdiff.NewName)
		}
		if err == io.EOF {
			break
		}
		if err != nil {
			log.Fatalf("err read %s: %s", label, err)
			continue
		}

		if includes != "" {
			if match, err = regexp.MatchString(includes, fdiff.OrigName); err != nil {
				fmt.Printf("%s\n", err)
			}

			if match, err = regexp.MatchString(includes, fdiff.NewName); err != nil {
				fmt.Printf("%s\n", err)
			}
			if match {
				selected = true
			}
		} else {
			selected = true
		}
		if excludes != "" {
			if match, err = regexp.MatchString(excludes, fdiff.OrigName); err != nil {
				fmt.Printf("%s\n", err)
			}

			if match, err = regexp.MatchString(excludes, fdiff.NewName); err != nil {
				fmt.Printf("%s\n", err)
			}
			if match {
				selected = false
			}
		}
		if dryrun {
			fmt.Printf("File %s : %s is selected: %s\n", fdiff.OrigName, fdiff.NewName, strconv.FormatBool(selected))
			continue
		}
		if !selected {
			continue
		}

		out, err := diff.PrintFileDiff(fdiff)
		if err != nil {
			log.Fatalf("err print %s: %s", label, err)
			continue
		}
		if _, err := os.Stdout.Write(out); err != nil {
			log.Fatal(err)
		}
	}
}