package main

import (
	"crypto/sha1"
	"flag"
	"fmt"
	"io"
	"log"
	"os"
	"path/filepath"
	"strings"
)

var root = flag.String("root", "", "root directory to search for dups")

var debug = debugT(false)

type debugT bool

func (d debugT) Print(args ...interface{}) {
	if d {
		log.Print(args...)
	}
}

func (d debugT) Printf(format string, args ...interface{}) {
	if d {
		log.Printf(format, args...)
	}
}

type Checksum struct {
	Checksum, Filename string
}

func main() {
	flag.Parse()

	if *root == "" {
		log.Fatal("Must specify root")
	}

	numWorkers := 10
	fns := make(chan string, numWorkers)
	sums := make(chan Checksum, numWorkers)
	done := make(chan bool)

	for i := 0; i < numWorkers; i++ {
		go checksumer(fns, sums, done)
	}
	go computeDups(sums, done)
	//go printer(sums, done)

	err := filepath.Walk(*root, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}
		if info.IsDir() {
			return nil
		}
		fns <- path
		return nil
	})
	if err != nil {
		log.Fatalf("Failed to walk %s: %v", *root, err)
	}

	close(fns)

	for i := 0; i < numWorkers; i++ {
		<-done
	}

	close(sums)
	<-done
}

func removeDups(dups map[string][]string) {
	log.Print("Removing dups")
	for _, fns := range dups {
		if len(fns) > 1 {
			log.Print("Skipping: ", fns[0])
			log.Print("Deleting")
			for _, fn := range fns[1:] {
				log.Print("\t", fn)
				err := os.Remove(fn)
				if err != nil {
					log.Fatalf("Failed to remove file: %s", err)
				}
			}
		}
	}
}

func computeDups(sums <-chan Checksum, done chan bool) {
	dups := map[string][]string{}
	count := 0
	for sum := range sums {
		dups[sum.Checksum] = append(dups[sum.Checksum], sum.Filename)

		if count > 0 && (count%1000) == 0 {
			log.Printf("Processed %d files", count)
		}
		count++
	}

	count = 0
	for _, fns := range dups {
		if len(fns) > 1 {
			count++
		}
	}

	if count == 0 {
		log.Print("No dups found")
	} else {
		log.Printf("Found %d files with dups, delete them? [y/n]", count)
		var answer string
		fmt.Scan(&answer)
		if strings.HasPrefix(strings.ToLower(answer), "y") {
			removeDups(dups)
		}
	}

	done <- true
}

func printer(sums <-chan Checksum, done chan bool) {
	for sum := range sums {
		fmt.Println(sum.Checksum, sum.Filename)
	}
	done <- true
}

func checksumer(fns <-chan string, sums chan<- Checksum, done chan bool) {
	for fn := range fns {
		f, err := os.Open(fn)
		if err != nil {
			log.Print("Error opening file: ", err)
			continue
		}
		fi, err := f.Stat()
		if err != nil {
			log.Print("Error stating file: ", err)
		} else {
			debug.Printf("Mode %s for %q", fi.Mode(), fn)
			if (fi.Mode() & os.ModeType) != 0 {
				debug.Print("Skipping non-file ", fn)
			}
		}

		h := sha1.New()
		io.Copy(h, f)
		f.Close()
		sums <- Checksum{
			Checksum: fmt.Sprintf("%x", h.Sum(nil)),
			Filename: fn,
		}
	}
	done <- true
}