Add method to create repository

Also disables automatic creation on open

cmd/khepri/cmd_init.go

@@ -0,0 +1,20 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/fd0/khepri"
+)
+
+func commandInit(path string) error {
+	repo, err := khepri.CreateRepository(path)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "creating repository at %s failed: %v\n", path, err)
+		os.Exit(1)
+	}
+
+	fmt.Printf("created khepri repository at %s\n", repo.Path())
+
+	return nil
+}

cmd/khepri/main.go

@@ -4,15 +4,13 @@ import (
 	"fmt"
 	"log"
 	"os"
-	"sort"
-	"strings"
 
 	"github.com/fd0/khepri"
 	"github.com/jessevdk/go-flags"
 )
 
 var Opts struct {
-	Repo string `short:"r" long:"repo"    description:"Repository directory to backup to/restor from"`
+	Repo string `short:"r" long:"repo"    description:"Repository directory to backup to/restore from"`
 }
 
 func errx(code int, format string, data ...interface{}) {
@@ -50,17 +48,16 @@ func main() {
 		os.Exit(0)
 	}
 
-	if len(args) == 0 {
-		cmds := []string{}
-		for k := range commands {
-			cmds = append(cmds, k)
-		}
-		sort.Strings(cmds)
-		fmt.Printf("nothing to do, available commands: [%v]\n", strings.Join(cmds, "|"))
-		os.Exit(0)
+	cmd := args[0]
+
+	if cmd == "init" {
+		err = commandInit(Opts.Repo)
+		if err != nil {
+			errx(1, "error executing command %q: %v", cmd, err)
 		}
 
-	cmd := args[0]
+		return
+	}
 
 	f, ok := commands[cmd]
 	if !ok {
@@ -70,7 +67,7 @@ func main() {
 	repo, err := khepri.NewRepository(Opts.Repo)
 
 	if err != nil {
-		errx(1, "unable to create/open repo: %v", err)
+		errx(1, "unable to open repo: %v", err)
 	}
 
 	err = f(repo, args[1:])

repository.go

@@ -1,7 +1,10 @@
 package khepri
 
 import (
+	"crypto/rand"
 	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"hash"
@@ -18,6 +21,7 @@ const (
 	blobPath       = "blobs"
 	refPath        = "refs"
 	tempPath       = "tmp"
+	configFileName = "config.json"
 )
 
 var (
@@ -36,8 +40,25 @@ type HashFunc func() hash.Hash
 type Repository struct {
 	path   string
 	hash   HashFunc
+	config *Config
 }
 
+type Config struct {
+	Salt string
+	N    uint
+	R    uint `json:"r"`
+	P    uint `json:"p"`
+}
+
+// TODO: figure out scrypt values on the fly depending on the current
+// hardware.
+const (
+	scrypt_N        = 65536
+	scrypt_r        = 8
+	scrypt_p        = 1
+	scrypt_saltsize = 64
+)
+
 type Type int
 
 const (
@@ -67,15 +88,16 @@ func (t Type) String() string {
 	panic(fmt.Sprintf("unknown type %d", t))
 }
 
-// NewDirRepository creates a new dir-baked repository at the given path.
+// NewRepository opens a dir-baked repository at the given path.
 func NewRepository(path string) (*Repository, error) {
+	var err error
+
 	d := &Repository{
 		path: path,
 		hash: sha256.New,
 	}
 
-	err := d.create()
-
+	d.config, err = d.read_config()
 	if err != nil {
 		return nil, err
 	}
@@ -83,22 +105,92 @@ func NewRepository(path string) (*Repository, error) {
 	return d, nil
 }
 
-func (r *Repository) create() error {
-	dirs := []string{
-		r.path,
-		path.Join(r.path, blobPath),
-		path.Join(r.path, refPath),
-		path.Join(r.path, tempPath),
+func (r *Repository) read_config() (*Config, error) {
+	// try to open config file
+	f, err := os.Open(path.Join(r.path, configFileName))
+	if err != nil {
+		return nil, err
 	}
 
+	cfg := new(Config)
+	buf, err := ioutil.ReadAll(f)
+	if err != nil {
+		return nil, err
+	}
+
+	err = json.Unmarshal(buf, cfg)
+	if err != nil {
+		return nil, err
+	}
+
+	return cfg, nil
+}
+
+// CreateRepository creates all the necessary files and directories for the
+// Repository.
+func CreateRepository(p string) (*Repository, error) {
+	dirs := []string{
+		p,
+		path.Join(p, blobPath),
+		path.Join(p, refPath),
+		path.Join(p, tempPath),
+	}
+
+	var configfile = path.Join(p, configFileName)
+
+	// test if repository directories or config file already exist
+	if _, err := os.Stat(configfile); err == nil {
+		return nil, fmt.Errorf("config file %s already exists", configfile)
+	}
+
+	for _, d := range dirs[1:] {
+		if _, err := os.Stat(d); err == nil {
+			return nil, fmt.Errorf("dir %s already exists", d)
+		}
+	}
+
+	// create initial json configuration
+	cfg := &Config{
+		N: scrypt_N,
+		R: scrypt_r,
+		P: scrypt_p,
+	}
+
+	// generate salt
+	buf := make([]byte, scrypt_saltsize)
+	n, err := rand.Read(buf)
+	if n != scrypt_saltsize || err != nil {
+		panic("unable to read enough random bytes for salt")
+	}
+	cfg.Salt = hex.EncodeToString(buf)
+
+	// create ps for blobs, refs and temp
 	for _, dir := range dirs {
 		err := os.MkdirAll(dir, dirMode)
 		if err != nil {
-			return err
+			return nil, err
 		}
 	}
 
-	return nil
+	// write config file
+	f, err := os.Create(configfile)
+	defer f.Close()
+	if err != nil {
+		return nil, err
+	}
+
+	s, err := json.Marshal(cfg)
+	if err != nil {
+		return nil, err
+	}
+
+	_, err = f.Write(s)
+	if err != nil {
+		return nil, err
+	}
+
+	// open repository
+	return NewRepository(p)
 }
 
 // SetHash changes the hash function used for deriving IDs. Default is SHA256.

repository_test.go

@@ -30,7 +30,7 @@ func setupRepo() (*khepri.Repository, error) {
 		return nil, err
 	}
 
-	repo, err := khepri.NewRepository(tempdir)
+	repo, err := khepri.CreateRepository(tempdir)
 	if err != nil {
 		return nil, err
 	}

test/test-backup.sh

@@ -1,6 +1,7 @@
 set -e
 
 prepare
+run khepri init
 run khepri backup "${BASE}/fake-data"
 run khepri restore "$(khepri list ref)" "${BASE}/fake-data-restore"
 dirdiff "${BASE}/fake-data" "${BASE}/fake-data-restore"