better separation of concerns

main.go

@@ -21,9 +21,27 @@ func main() {
 		} else {
 			dir = os.Args[2]
 		}
-		if err := commands.Bind(dir); err != nil {
+		paths, err := commands.GetHorcruxPathsInDir(dir)
+		if err != nil {
 			log.Fatal(err)
 		}
+		overwrite := false
+		for {
+			if err := commands.Bind(paths, "", overwrite); err != nil {
+				if err != os.ErrExist {
+					log.Fatal(err)
+				}
+				overwriteResponse := commands.Prompt("A file already exists at destination. Overwrite? (Y/N):")
+				if overwriteResponse == "Y" || overwriteResponse == "y" || overwriteResponse == "yes" {
+					overwrite = true
+				} else {
+					log.Fatal("You have chosen not to overwrite the file. Cancelling.")
+				}
+			} else {
+				break
+			}
+		}
+
 		return
 	}
 

pkg/commands/bind.go

@@ -1,71 +1,125 @@
 package commands
 
 import (
-	"bufio"
-	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"sort"
+	"strings"
 
 	"github.com/jesseduffield/horcrux/pkg/multiplexing"
 	"github.com/jesseduffield/horcrux/pkg/shamir"
 )
 
-func Bind(dir string) error {
+func GetHorcruxPathsInDir(dir string) ([]string, error) {
 	files, err := ioutil.ReadDir(dir)
 	if err != nil {
-		return err
+		return nil, err
 	}
 
-	filenames := []string{}
+	paths := []string{}
 	for _, file := range files {
 		if filepath.Ext(file.Name()) == ".horcrux" {
-			filenames = append(filenames, file.Name())
+			paths = append(paths, file.Name())
 		}
 	}
 
-	headers := []horcruxHeader{}
-	horcruxFiles := []*os.File{}
+	return paths, nil
+}
 
-	for _, filename := range filenames {
-		file, err := os.Open(filename)
-		defer file.Close()
+type byIndex []Horcrux
+
+func (h byIndex) Len() int {
+	return len(h)
+}
+
+func (h byIndex) Swap(i, j int) {
+	h[i], h[j] = h[j], h[i]
+}
+
+func (h byIndex) Less(i, j int) bool {
+	return h[i].GetHeader().Index < h[j].GetHeader().Index
+}
+
+func GetHorcruxes(paths []string) ([]Horcrux, error) {
+	horcruxes := []Horcrux{}
+
+	for _, path := range paths {
+		currentHorcrux, err := NewHorcrux(path)
 		if err != nil {
-			return err
+			return nil, err
 		}
-
-		currentHeader, err := getHeaderFromHorcruxFile(file)
-		if err != nil {
-			return err
-		}
-
-		for _, header := range headers {
-			if header.Index == currentHeader.Index {
+		for _, horcrux := range horcruxes {
+			if horcrux.GetHeader().Index == currentHorcrux.GetHeader().Index && horcrux.GetHeader().OriginalFilename == currentHorcrux.GetHeader().OriginalFilename {
 				// we've already obtained this horcrux so we'll skip this instance
 				continue
 			}
 		}
 
-		if len(headers) > 0 && (currentHeader.OriginalFilename != headers[0].OriginalFilename || currentHeader.Timestamp != headers[0].Timestamp) {
+		horcruxes = append(horcruxes, *currentHorcrux)
+	}
+
+	sort.Sort(byIndex(horcruxes))
+
+	return horcruxes, nil
+}
+
+func ValidateHorcruxes(horcruxes []Horcrux) error {
+	if len(horcruxes) == 0 {
+		return errors.New("No horcruxes supplied")
+	}
+
+	if len(horcruxes) < horcruxes[0].GetHeader().Threshold {
+		return fmt.Errorf(
+			"You do not have all the required horcruxes. There are %d required to resurrect the original file. You only have %d",
+			horcruxes[0].GetHeader().Threshold,
+			len(horcruxes),
+		)
+	}
+
+	for _, horcrux := range horcruxes {
+		if !strings.HasSuffix(horcrux.GetPath(), ".horcrux") {
+			return fmt.Errorf("%s is not a horcrux file (requires .horcrux extension)", horcrux.GetPath())
+		}
+		if horcrux.GetHeader().OriginalFilename != horcruxes[0].GetHeader().OriginalFilename || horcrux.GetHeader().Timestamp != horcruxes[0].GetHeader().Timestamp {
 			return errors.New("All horcruxes in the given directory must have the same original filename and timestamp.")
 		}
-
-		headers = append(headers, *currentHeader)
-		horcruxFiles = append(horcruxFiles, file)
 	}
 
-	if len(headers) == 0 {
-		return errors.New("No horcruxes in directory")
-	} else if len(headers) < headers[0].Threshold {
-		return errors.New(fmt.Sprintf("You do not have all the required horcruxes. There are %d required to resurrect the original file. You only have %d", headers[0].Threshold, len(headers)))
+	return nil
+}
+
+func Bind(paths []string, dstPath string, overwrite bool) error {
+	horcruxes, err := GetHorcruxes(paths)
+	if err != nil {
+		return err
 	}
 
-	keyFragments := make([][]byte, len(headers))
+	if err := ValidateHorcruxes(horcruxes); err != nil {
+		return err
+	}
+
+	firstHorcrux := horcruxes[0]
+
+	// if dstPath is empty we use the original filename
+	if dstPath == "" {
+		cwd, err := os.Getwd()
+		if err != nil {
+			return err
+		}
+		dstPath = filepath.Join(cwd, firstHorcrux.GetHeader().OriginalFilename)
+	}
+
+	if fileExists(dstPath) && !overwrite {
+		return os.ErrExist
+	}
+
+	keyFragments := make([][]byte, len(horcruxes))
 	for i := range keyFragments {
-		keyFragments[i] = headers[i].KeyFragment
+		keyFragments[i] = horcruxes[i].GetHeader().KeyFragment
 	}
 
 	key, err := shamir.Combine(keyFragments)
@@ -74,28 +128,22 @@ func Bind(dir string) error {
 	}
 
 	var fileReader io.Reader
-	if headers[0].Total == headers[0].Threshold {
-		// sort by index
-		orderedHorcruxFiles := make([]*os.File, len(horcruxFiles))
-		for i, h := range horcruxFiles {
-			orderedHorcruxFiles[headers[i].Index-1] = h
+	if firstHorcrux.GetHeader().Total == firstHorcrux.GetHeader().Threshold {
+		horcruxFiles := make([]*os.File, len(horcruxes))
+		for i, horcrux := range horcruxes {
+			horcruxFiles[i] = horcrux.GetFile()
 		}
 
-		fileReader = &multiplexing.Multiplexer{Readers: orderedHorcruxFiles}
+		fileReader = &multiplexing.Multiplexer{Readers: horcruxFiles}
 	} else {
-		fileReader = horcruxFiles[0] // arbitrarily read from the first horcrux: they all contain the same contents
+		fileReader = firstHorcrux.GetFile() // arbitrarily read from the first horcrux: they all contain the same contents
 	}
 
 	reader := cryptoReader(fileReader, key)
 
-	newFilename := headers[0].OriginalFilename
-	if fileExists(newFilename) {
-		newFilename = prompt("A file already exists named '%s'. Enter new file name: ", newFilename)
-	}
+	_ = os.Truncate(dstPath, 0)
 
-	_ = os.Truncate(newFilename, 0)
-
-	newFile, err := os.OpenFile(newFilename, os.O_WRONLY|os.O_CREATE, 0644)
+	newFile, err := os.OpenFile(dstPath, os.O_WRONLY|os.O_CREATE, 0644)
 	if err != nil {
 		return err
 	}
@@ -108,34 +156,3 @@ func Bind(dir string) error {
 
 	return err
 }
-
-// this function gets the header from the horcrux file and ensures that we leave
-// the file with its read pointer at the start of the encrypted content
-// so that we can later directly read from that point
-// yes this is a side effect, no I'm not proud of it.
-func getHeaderFromHorcruxFile(file *os.File) (*horcruxHeader, error) {
-	currentHeader := &horcruxHeader{}
-	scanner := bufio.NewScanner(file)
-	bytesBeforeBody := 0
-	for scanner.Scan() {
-		line := scanner.Text()
-		bytesBeforeBody += len(scanner.Bytes()) + 1
-		if line == "-- HEADER --" {
-			scanner.Scan()
-			bytesBeforeBody += len(scanner.Bytes()) + 1
-			headerLine := scanner.Bytes()
-			json.Unmarshal(headerLine, currentHeader)
-			scanner.Scan() // one more to get past the body line
-			bytesBeforeBody += len(scanner.Bytes()) + 1
-			break
-		}
-	}
-	if _, err := file.Seek(int64(bytesBeforeBody), io.SeekStart); err != nil {
-		return nil, err
-	}
-
-	if currentHeader == nil {
-		return nil, errors.New("could not find header in horcrux file")
-	}
-	return currentHeader, nil
-}

pkg/commands/horcrux.go

@@ -0,0 +1,90 @@
+package commands
+
+import (
+	"bufio"
+	"encoding/json"
+	"errors"
+	"io"
+	"os"
+)
+
+type HorcruxHeader struct {
+	OriginalFilename string `json:"originalFilename"`
+	Timestamp        int64  `json:"timestamp"`
+	Index            int    `json:"index"`
+	Total            int    `json:"total"`
+	Threshold        int    `json:"threshold"`
+	KeyFragment      []byte `json:"keyFragment"`
+}
+
+type Horcrux struct {
+	path   string
+	header HorcruxHeader
+	file   *os.File
+}
+
+// returns a horcrux with its header parsed, and it's file's read pointer
+// right after the header.
+func NewHorcrux(path string) (*Horcrux, error) {
+	file, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+
+	header, err := GetHeaderFromHorcruxFile(file)
+	if err != nil {
+		return nil, err
+	}
+
+	return &Horcrux{
+		path:   path,
+		file:   file,
+		header: *header,
+	}, nil
+}
+
+// this function gets the header from the horcrux file and ensures that we leave
+// the file with its read pointer at the start of the encrypted content
+// so that we can later directly read from that point
+// yes this is a side effect, no I'm not proud of it.
+func GetHeaderFromHorcruxFile(file *os.File) (*HorcruxHeader, error) {
+	currentHeader := &HorcruxHeader{}
+	scanner := bufio.NewScanner(file)
+	bytesBeforeBody := 0
+	for scanner.Scan() {
+		line := scanner.Text()
+		bytesBeforeBody += len(scanner.Bytes()) + 1
+		if line == "-- HEADER --" {
+			scanner.Scan()
+			bytesBeforeBody += len(scanner.Bytes()) + 1
+			headerLine := scanner.Bytes()
+			if err := json.Unmarshal(headerLine, currentHeader); err != nil {
+				return nil, err
+			}
+
+			scanner.Scan() // one more to get past the body line
+			bytesBeforeBody += len(scanner.Bytes()) + 1
+			break
+		}
+	}
+	if _, err := file.Seek(int64(bytesBeforeBody), io.SeekStart); err != nil {
+		return nil, err
+	}
+
+	if currentHeader == nil {
+		return nil, errors.New("could not find header in horcrux file")
+	}
+	return currentHeader, nil
+}
+
+func (h *Horcrux) GetHeader() HorcruxHeader {
+	return h.header
+}
+
+func (h *Horcrux) GetPath() string {
+	return h.path
+}
+
+func (h *Horcrux) GetFile() *os.File {
+	return h.file
+}

pkg/commands/horcrux_header.go

@@ -1,10 +0,0 @@
-package commands
-
-type horcruxHeader struct {
-	OriginalFilename string `json:"originalFilename"`
-	Timestamp        int64  `json:"timestamp"`
-	Index            int    `json:"index"`
-	Total            int    `json:"total"`
-	Threshold        int    `json:"threshold"`
-	KeyFragment      []byte `json:"keyFragment"`
-}

pkg/commands/split.go

@@ -64,7 +64,7 @@ func Split(path string, destination string, total int, threshold int) error {
 	for i := range horcruxFiles {
 		index := i + 1
 
-		headerBytes, err := json.Marshal(&horcruxHeader{
+		headerBytes, err := json.Marshal(&HorcruxHeader{
 			OriginalFilename: originalFilename,
 			Timestamp:        timestamp,
 			Index:            index,
@@ -90,7 +90,9 @@ func Split(path string, destination string, total int, threshold int) error {
 		}
 		defer horcruxFile.Close()
 
-		horcruxFile.WriteString(header(index, total, headerBytes))
+		if _, err := horcruxFile.WriteString(header(index, total, headerBytes)); err != nil {
+			return err
+		}
 
 		horcruxFiles[i] = horcruxFile
 	}
@@ -133,7 +135,7 @@ func obtainTotalAndThreshold() (int, int, error) {
 	threshold := *thresholdPtr
 
 	if total == 0 {
-		totalStr := prompt("How many horcruxes do you want to split this file into? (2-99): ")
+		totalStr := Prompt("How many horcruxes do you want to split this file into? (2-99): ")
 		var err error
 		total, err = strconv.Atoi(totalStr)
 		if err != nil {
@@ -142,7 +144,7 @@ func obtainTotalAndThreshold() (int, int, error) {
 	}
 
 	if threshold == 0 {
-		thresholdStr := prompt("How many horcruxes should be required to reconstitute the original file? If you require all horcruxes, the resulting files will take up less space, but it will feel less magical (2-99): ")
+		thresholdStr := Prompt("How many horcruxes should be required to reconstitute the original file? If you require all horcruxes, the resulting files will take up less space, but it will feel less magical (2-99): ")
 		var err error
 		threshold, err = strconv.Atoi(thresholdStr)
 		if err != nil {

pkg/commands/utils.go

@@ -30,7 +30,7 @@ func fileExists(filename string) bool {
 	return !info.IsDir()
 }
 
-func prompt(message string, args ...interface{}) string {
+func Prompt(message string, args ...interface{}) string {
 	reader := bufio.NewReader(os.Stdin)
 	fmt.Printf(message, args...)
 	input, _ := reader.ReadString('\n')