package main

import (
	"bufio"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"os"
	"path/filepath"
	"runtime"
	"sort"
	"sync"
	"time"

	"code.cloudfoundry.org/bytefmt"

	flag "github.com/spf13/pflag"
)

// Fdhashes struct for holding all informations about one folder.
type Fdhashes struct {
	Path   string
	Hashes map[string]string
	Times  map[string]time.Time
	Dirty  bool
}

var hashes map[string]Fdhashes

var mu sync.RWMutex
var driveLetter string

var rewrite bool
var prune bool
var outputJson bool
var report string

func init() {
	flag.BoolVarP(&rewrite, "rewrite", "r", false, "rewrite all fhhashes files.")
	flag.StringVarP(&report, "equals", "e", "", "compare all file hashes and writing a equlatity report.")
	flag.BoolVarP(&prune, "prune", "p", false, "checking all fdhashes files.")
	flag.BoolVarP(&outputJson, "json", "j", false, "output as json.")
}

func main() {
	log.Println("starting GoHash")
	hashes = make(map[string]Fdhashes)
	flag.Parse()
	myFile := flag.Arg(0)
	file, err := os.Stat(myFile)
	if os.IsNotExist(err) {
		log.Fatalln("File does not exists:", myFile)
	}
	if file.IsDir() {
		log.Println("start with folder:", myFile)
		driveLetter = ""
		if runtime.GOOS == "windows" {
			driveLetter = filepath.VolumeName(myFile) + "/"
		}

		if report != "" {
			compareFolder(myFile)
		} else {
			processFolder(myFile)
			saveAllHashFiles()
		}
	} else {
		log.Printf("file %s has hash %s\n", myFile, getSha256Hash(myFile))
	}

	log.Println("done")
}

func getSha256Hash(fileStr string) string {
	f, err := os.Open(fileStr)
	if err != nil {
		log.Fatal(err)
	}
	defer f.Close()

	h := sha256.New()
	if _, err := io.Copy(h, f); err != nil {
		log.Fatal(err)
	}
	return hex.EncodeToString(h.Sum(nil))
}

var lock1 = sync.RWMutex{}
var lock2 = sync.RWMutex{}

func calculateHash(fileStr string) {
	var hashFile Fdhashes
	doHash := true
	dir, fileName := filepath.Split(fileStr)
	if fileName == ".fdhashes3" {
		return
	}
	// checking if hash is present
	mu.Lock()
	hashFile, ok := hashes[dir]
	if !ok {
		_, err := os.Stat(dir + ".fdhashes3")
		if os.IsNotExist(err) {
			hashFile = Fdhashes{Path: dir, Hashes: make(map[string]string), Times: make(map[string]time.Time), Dirty: true}
		} else {
			hashFile = loadHashfile(dir + ".fdhashes3")
		}
		hashes[dir] = hashFile
	}
	lock1.RLock()
	_, ok = hashFile.Hashes[fileName]
	lock1.RUnlock()
	mu.Unlock()
	doHash = !ok
	// checking if dattime is identically
	file, _ := os.Stat(fileStr)
	time := file.ModTime()
	lock2.RLock()
	savedTime, ok := hashFile.Times[fileName]
	lock2.RUnlock()
	if !time.Equal(savedTime) || !ok {
		doHash = true
	}
	if doHash {
		log.Printf("starting %s\n", fileStr)
		hash := getSha256Hash(fileStr)
		log.Printf("ready %s\n", fileStr)
		mu.Lock()
		lock1.Lock()
		hashFile.Hashes[fileName] = hash
		lock1.Unlock()

		lock2.Lock()
		hashFile.Times[fileName] = time
		lock2.Unlock()
		dirtyHashfile(&hashFile)
		hashes[dir] = hashFile
		mu.Unlock()
		log.Printf("file \"%s\" has hash \"%s\"\n", fileStr, hash)
	}
}

var count int
var addWork int
var startTime time.Time

func processFolder(folder string) {
	startTime = time.Now()
	count = 0
	addWork = 0
	err := filepath.Walk(folder, func(path string, info os.FileInfo, err error) error {
		count++
		if (count % 100) == 0 {
			fmt.Print(".")
		}
		if (count % 10000) == 0 {
			fmt.Println()
		}
		filename := info.Name()
		if filename[0:1] != "." {
			if info.IsDir() {
				fmt.Println(path)
				if prune {
					pruneHash(path)
				}
			}
			if !info.IsDir() {
				addWork++
				calculateHash(path)
				if time.Since(startTime).Seconds() > 10.0 {
					startTime = time.Now()
					saveAllHashFiles()
					addWork = 0
				}
			}
		}
		return nil
	})
	if err != nil {
		panic(err)
	}
}

/* delete unused hash values from the hash file */
func pruneHash(dir string) {
	_, err := os.Stat(dir + "/.fdhashes3")
	if !os.IsNotExist(err) {
		hashFile := loadHashfile(dir + "/.fdhashes3")
		for filename := range hashFile.Hashes {
			_, err := os.Stat(dir + "/" + filename)
			if os.IsNotExist(err) {
				delete(hashFile.Hashes, filename)
				delete(hashFile.Times, filename)
				hashFile.Dirty = true
			}
		}

		for filename := range hashFile.Times {
			_, err := os.Stat(dir + "/" + filename)
			if os.IsNotExist(err) {
				delete(hashFile.Hashes, filename)
				delete(hashFile.Times, filename)
				hashFile.Dirty = true
			}
		}
		saveHashfile(&hashFile)
	}
}

func dirtyHashfile(hashFile *Fdhashes) {
	hashFile.Dirty = true
}

func saveAllHashFiles() {
	hashList := make([]Fdhashes, 0)

	for _, hashFile := range hashes {
		if hashFile.Dirty {
			saveHashfile(&hashFile)
			hashList = append(hashList, hashFile)
		}
	}

	hashes = make(map[string]Fdhashes)
	for _, hashFile := range hashList {
		hashes[hashFile.Path] = hashFile
	}

}

func saveHashfile(hashFile *Fdhashes) {
	if hashFile.Dirty {
		hashFile.Dirty = false
		b, err := json.Marshal(hashFile)
		if err != nil {
			fmt.Println(err)
			return
		}
		err = ioutil.WriteFile(hashFile.Path+"/.fdhashes3", b, 0644)
		if err != nil {
			panic(err)
		}
	}
}

func loadHashfile(fileStr string) Fdhashes {
	dir, _ := filepath.Split(fileStr)
	dir = filepath.ToSlash(filepath.Clean(dir))
	data := Fdhashes{Path: dir, Hashes: make(map[string]string), Times: make(map[string]time.Time), Dirty: false}
	if !rewrite {
		file, err := ioutil.ReadFile(fileStr)
		if err != nil {
			panic(err)
		}
		err = json.Unmarshal([]byte(file), &data)
		if err != nil {
			log.Printf("can't read file %s", fileStr)
		}
	}
	if data.Path != dir {
		data.Path = dir
		data.Dirty = true
	}
	return data
}

func compareFolder(folder string) {
	loadAllHashFiles(folder)

	// putting all hashes into one big map key = hash, value list of files with that hash
	index := make(map[string][]string)
	for _, hashFile := range hashes {
		for filename, hash := range hashFile.Hashes {
			values := index[hash]
			if values == nil {
				values = make([]string, 0)
			}
			values = append(values, fmt.Sprintf("%s/%s", hashFile.Path, filename))
			index[hash] = values
		}
	}

	// sorting list of files for every hash and deleting hashes with only 1 entry
	size := len(index)
	myHashes := make([]string, 0)
	for hash, values := range index {
		count++
		if count%100 == 0 {
			fmt.Printf("%d (%d) sorting\n", count, size)
		}
		if len(values) > 1 {
			sort.Strings(values)
			index[hash] = values
			myHashes = append(myHashes, hash)
			//			for _, filename := range values {
			//				fmt.Printf("  %s\n", filename)
			//			}
		} else {
			delete(index, hash)
		}
	}
	sort.Slice(myHashes, func(i, j int) bool { return index[myHashes[i]][0] < index[myHashes[j]][0] })

	if outputJson {
		size = len(index)
		var filesize int64
		fileCount := 0
		for _, hash := range myHashes {
			values := index[hash]
			count++
			if count%100 == 0 {
				fmt.Printf("%d (%d) checking\n", count, size)
			}
			if len(values) > 1 {
				info, err := os.Stat(values[0])
				if err == nil {
					fmt.Printf("found identically hash: %s size: %d\n", hash, info.Size())
					filesize += int64(len(values)-1) * info.Size()
				}
				fileCount += len(values) - 1
				for _, filename := range values {
					fmt.Printf("  %s\n", filename)
				}
			} else {
				delete(index, hash)
			}
		}

		b, err := json.Marshal(index)
		if err != nil {
			fmt.Println(err)
			return
		}
		err = ioutil.WriteFile(report, b, 0644)
		if err != nil {
			panic(err)
		}
	} else {
		size := len(index)
		f, err := os.Create(report)
		check(err)
		w := bufio.NewWriter(f)
		count := 0
		var filesize int64
		fileCount := 0
		for _, hash := range myHashes {
			values := index[hash]
			count++
			if count%100 == 0 {
				fmt.Printf("%d (%d) checking\n", count, size)
			}
			if len(values) > 1 {
				info, err := os.Stat(values[0])
				if err == nil {
					w.WriteString(fmt.Sprintf("found identically hash: size: %d\n", info.Size()))
					filesize += int64(len(values)-1) * info.Size()
				}
				fileCount += len(values) - 1
				for _, filename := range values {
					w.WriteString(fmt.Sprintf("  %s\n", filename))
				}
				w.Flush()
			}
		}
		w.WriteString(fmt.Sprintf("can save up to %s on %d files\n", bytefmt.ByteSize(uint64(filesize)), fileCount))
		w.Flush()
	}
}

func search(srcHash string, exFilename string, exFilepath string) (value string, found bool) {
	for _, hashFile := range hashes {
		for filename, hash := range hashFile.Hashes {
			if (filename != exFilename) && (hashFile.Path != exFilepath) {
				if hash == srcHash {
					value += fmt.Sprintf("%s/%s;", hashFile.Path, filename)
					found = true
				}
			}
		}
	}
	return
}

func loadAllHashFiles(folder string) {
	count = 0
	addWork = 0
	err := filepath.Walk(folder, func(path string, info os.FileInfo, err error) error {
		if info != nil {
			if info.IsDir() {
				count++
				fmt.Print(".")
				if (count % 100) == 0 {
					fmt.Println()
				}
				hashFile, ok := hashes[path]
				if !ok {
					_, err := os.Stat(path + "/.fdhashes3")
					if os.IsNotExist(err) {
						hashFile = Fdhashes{Path: path, Hashes: make(map[string]string), Times: make(map[string]time.Time), Dirty: true}
					} else {
						hashFile = loadHashfile(path + "/.fdhashes3")
					}
					hashes[path] = hashFile
				}
			}
		}
		return nil
	})
	if err != nil {
		panic(err)
	}
	fmt.Printf("\nfound %d hash files.\n", len(hashes))
}

func check(e error) {
	if e != nil {
		panic(e)
	}
}