From b6e3b23fa94aeaa9c4a8ccfb9a0c365ff6d33ba8 Mon Sep 17 00:00:00 2001
From: Armon Dadgar <armon.dadgar@gmail.com>
Date: Fri, 15 Nov 2013 13:34:15 -0800
Subject: [PATCH] LogStore must also expose FirstIndex(), add to LevelDB

---
 leveldb_store.go      | 19 +++++++++++++++++++
 leveldb_store_test.go | 36 +++++++++++++++++++++++++++++++++++-
 log.go                |  3 +++
 3 files changed, 57 insertions(+), 1 deletion(-)

diff --git a/leveldb_store.go b/leveldb_store.go
index d4e1cd018..4f2100342 100644
--- a/leveldb_store.go
+++ b/leveldb_store.go
@@ -66,6 +66,25 @@ func NewLevelDBLogStore(base string) (*LevelDBLogStore, error) {
 	return ldb, nil
 }
 
+func (l *LevelDBLogStore) FirstIndex() (uint64, error) {
+	// Get an iterator
+	it := l.db.NewIterator(nil)
+	defer it.Release()
+
+	// Seek to the first value
+	it.First()
+
+	// Check if there is a key
+	key := it.Key()
+	if key == nil {
+		// Nothing written yet
+		return 0, it.Error()
+	}
+
+	// Convert the key to the index
+	return bytesToUint64(key), it.Error()
+}
+
 func (l *LevelDBLogStore) LastIndex() (uint64, error) {
 	// Get an iterator
 	it := l.db.NewIterator(nil)
diff --git a/leveldb_store_test.go b/leveldb_store_test.go
index 8a504218e..c710c2ee7 100644
--- a/leveldb_store_test.go
+++ b/leveldb_store_test.go
@@ -134,8 +134,17 @@ func TestLevelDB_Logs(t *testing.T) {
 	}
 	defer l.Close()
 
+	// Should be no first index
+	idx, err := l.FirstIndex()
+	if err != nil {
+		t.Fatalf("err: %v ", err)
+	}
+	if idx != 0 {
+		t.Fatalf("bad idx: %d", idx)
+	}
+
 	// Should be no last index
-	idx, err := l.LastIndex()
+	idx, err = l.LastIndex()
 	if err != nil {
 		t.Fatalf("err: %v ", err)
 	}
@@ -151,6 +160,15 @@ func TestLevelDB_Logs(t *testing.T) {
 
 	// Write out a log
 	log := Log{
+		Index: 1,
+		Term:  1,
+		Type:  LogCommand,
+		Data:  []byte("first"),
+	}
+	if err := l.StoreLog(&log); err != nil {
+		t.Fatalf("err: %v", err)
+	}
+	log = Log{
 		Index: 10,
 		Term:  3,
 		Type:  LogCommand,
@@ -165,6 +183,15 @@ func TestLevelDB_Logs(t *testing.T) {
 		t.Fatalf("err: %v ", err)
 	}
 
+	// Check the lowest index
+	idx, err = l.FirstIndex()
+	if err != nil {
+		t.Fatalf("err: %v ", err)
+	}
+	if idx != 1 {
+		t.Fatalf("bad idx: %d", idx)
+	}
+
 	// Check the highest index
 	idx, err = l.LastIndex()
 	if err != nil {
@@ -180,6 +207,13 @@ func TestLevelDB_Logs(t *testing.T) {
 	}
 
 	// Index should be zero again
+	idx, err = l.FirstIndex()
+	if err != nil {
+		t.Fatalf("err: %v ", err)
+	}
+	if idx != 0 {
+		t.Fatalf("bad idx: %d", idx)
+	}
 	idx, err = l.LastIndex()
 	if err != nil {
 		t.Fatalf("err: %v ", err)
diff --git a/log.go b/log.go
index 11c9b210c..780b5457a 100644
--- a/log.go
+++ b/log.go
@@ -36,6 +36,9 @@ type Log struct {
 // LogStore is used to provide an interface for storing
 // and retrieving logs in a durable fashion
 type LogStore interface {
+	// Returns the first index written. 0 for no entries.
+	FirstIndex() (uint64, error)
+
 	// Returns the last index written. 0 for no entries.
 	LastIndex() (uint64, error)