List snapshots, accept snapshot id prefix

Example:

    $ ./khepri snapshots
    ID        Date                 Source      Directory
    --------------------------------------------------------------------------------
    fa31d65b  2014-11-24 19:45:11  kasimir     /home/user/testdata
    20bdc140  2014-11-24 20:00:47  kasimir     /home/user/testdata
    326cb59d  2014-11-24 20:01:40  kasimir     /home/user/testdata
    20ff988b  2014-11-24 20:35:35  kasimir     /home/user

backend/generic.go

@@ -4,12 +4,19 @@ import (
 	"bytes"
 	"compress/zlib"
 	"crypto/sha256"
+	"encoding/hex"
+	"errors"
 	"io/ioutil"
 	"sync"
 )
 
 var idPool = sync.Pool{New: func() interface{} { return ID(make([]byte, IDSize)) }}
 
+var (
+	ErrNoIDPrefixFound   = errors.New("no ID found")
+	ErrMultipleIDMatches = errors.New("multiple IDs with prefix found")
+)
+
 // Each lists all entries of type t in the backend and calls function f() with
 // the id and data.
 func Each(be Server, t Type, f func(id ID, data []byte, err error)) error {
@@ -85,3 +92,54 @@ func Hash(data []byte) ID {
 	copy(id, h[:])
 	return id
 }
+
+// Find loads the list of all blobs of type t and searches for IDs which start
+// with prefix. If none is found, nil and ErrNoIDPrefixFound is returned. If
+// more than one is found, nil and ErrMultipleIDMatches is returned.
+func Find(be Server, t Type, prefix string) (ID, error) {
+	p, err := hex.DecodeString(prefix)
+	if err != nil {
+		return nil, err
+	}
+
+	list, err := be.List(t)
+	if err != nil {
+		return nil, err
+	}
+
+	match := ID(nil)
+
+	// TODO: optimize by sorting list etc.
+	for _, id := range list {
+		if bytes.Equal(p, id[:len(p)]) {
+			if match == nil {
+				match = id
+			} else {
+				return nil, ErrMultipleIDMatches
+			}
+		}
+	}
+
+	if match != nil {
+		return match, nil
+	}
+
+	return nil, ErrNoIDPrefixFound
+}
+
+// FindSnapshot takes a string and tries to find a snapshot whose ID matches
+// the string as closely as possible.
+func FindSnapshot(be Server, s string) (ID, error) {
+	// parse ID directly
+	if id, err := ParseID(s); err == nil {
+		return id, nil
+	}
+
+	// find snapshot id with prefix
+	id, err := Find(be, Snapshot, s)
+	if err != nil {
+		return nil, err
+	}
+
+	return id, nil
+}

cmd/khepri/cmd_cat.go

@@ -19,7 +19,17 @@ func commandCat(be backend.Server, key *khepri.Key, args []string) error {
 
 	id, err := backend.ParseID(args[1])
 	if err != nil {
-		return err
+		id = nil
+
+		if tpe != "snapshot" {
+			return err
+		}
+
+		// find snapshot id with prefix
+		id, err = backend.Find(be, backend.Snapshot, args[1])
+		if err != nil {
+			return err
+		}
 	}
 
 	ch, err := khepri.NewContentHandler(be, key)
@@ -105,7 +115,8 @@ func commandCat(be backend.Server, key *khepri.Key, args []string) error {
 		return nil
 	case "snapshot":
 		var sn khepri.Snapshot
-		err := ch.LoadJSONRaw(backend.Snapshot, id, &sn)
+
+		err = ch.LoadJSONRaw(backend.Snapshot, id, &sn)
 		if err != nil {
 			return err
 		}

cmd/khepri/cmd_ls.go

@@ -53,7 +53,7 @@ func commandLs(be backend.Server, key *khepri.Key, args []string) error {
 		return errors.New("usage: ls SNAPSHOT_ID [dir]")
 	}
 
-	id, err := backend.ParseID(args[0])
+	id, err := backend.FindSnapshot(be, args[0])
 	if err != nil {
 		return err
 	}

cmd/khepri/cmd_restore.go

@@ -14,7 +14,7 @@ func commandRestore(be backend.Server, key *khepri.Key, args []string) error {
 		return errors.New("usage: restore ID dir")
 	}
 
-	id, err := backend.ParseID(args[0])
+	id, err := backend.FindSnapshot(be, args[0])
 	if err != nil {
 		errx(1, "invalid id %q: %v", args[0], err)
 	}

cmd/khepri/cmd_snapshots.go

@@ -3,34 +3,79 @@ package main
 import (
 	"errors"
 	"fmt"
+	"os"
+	"sort"
+	"strings"
+	"time"
 
 	"github.com/fd0/khepri"
 	"github.com/fd0/khepri/backend"
 )
 
-const TimeFormat = "02.01.2006 15:04:05 -0700"
+const (
+	minute = 60
+	hour   = 60 * minute
+	day    = 24 * hour
+	week   = 7 * day
+)
+
+const TimeFormat = "2006-01-02 15:04:05"
+
+func reltime(t time.Time) string {
+	sec := uint64(time.Since(t).Seconds())
+
+	switch {
+	case sec > week:
+		return t.Format(TimeFormat)
+	case sec > day:
+		return fmt.Sprintf("%d days ago", sec/day)
+	case sec > hour:
+		return fmt.Sprintf("%d hours ago", sec/hour)
+	case sec > minute:
+		return fmt.Sprintf("%d minutes ago", sec/minute)
+	default:
+		return fmt.Sprintf("%d seconds ago", sec)
+	}
+}
 
 func commandSnapshots(be backend.Server, key *khepri.Key, args []string) error {
 	if len(args) != 0 {
 		return errors.New("usage: snapshots")
 	}
 
-	// ch, err := khepri.NewContentHandler(be, key)
-	// if err != nil {
-	// 	return err
-	// }
+	ch, err := khepri.NewContentHandler(be, key)
+	if err != nil {
+		return err
+	}
+
+	fmt.Printf("%-8s  %-19s  %-10s  %s\n", "ID", "Date", "Source", "Directory")
+	fmt.Printf("%s\n", strings.Repeat("-", 80))
+
+	list := []*khepri.Snapshot{}
 
 	backend.EachID(be, backend.Snapshot, func(id backend.ID) {
-		// sn, err := ch.LoadSnapshot(id)
-		// if err != nil {
-		// 	fmt.Fprintf(os.Stderr, "error loading snapshot %s: %v\n", id, err)
-		// 	return
-		// }
+		sn, err := ch.LoadSnapshot(id)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "error loading snapshot %s: %v\n", id, err)
+			return
+		}
 
-		// fmt.Printf("snapshot %s\n    %s at %s by %s\n",
-		// 	id, sn.Dir, sn.Time, sn.Username)
-		fmt.Println(id)
+		pos := sort.Search(len(list), func(i int) bool {
+			return list[i].Time.After(sn.Time)
+		})
+
+		if pos < len(list) {
+			list = append(list, nil)
+			copy(list[pos+1:], list[pos:])
+			list[pos] = sn
+		} else {
+			list = append(list, sn)
+		}
 	})
 
+	for _, sn := range list {
+		fmt.Printf("%-8s  %-19s  %-10s  %s\n", sn.ID().String()[:8], sn.Time.Format(TimeFormat), sn.Hostname, sn.Dir)
+	}
+
 	return nil
 }

snapshot.go

@@ -51,7 +51,7 @@ func NewSnapshot(dir string) *Snapshot {
 }
 
 func LoadSnapshot(ch *ContentHandler, id backend.ID) (*Snapshot, error) {
-	sn := &Snapshot{}
+	sn := &Snapshot{id: id}
 	err := ch.LoadJSON(backend.Snapshot, id, sn)
 	if err != nil {
 		return nil, err
@@ -60,6 +60,10 @@ func LoadSnapshot(ch *ContentHandler, id backend.ID) (*Snapshot, error) {
 	return sn, nil
 }
 
-func (sn *Snapshot) String() string {
+func (sn Snapshot) String() string {
 	return fmt.Sprintf("<Snapshot %q at %s>", sn.Dir, sn.Time)
 }
+
+func (sn Snapshot) ID() backend.ID {
+	return sn.id
+}