feature(store): add LastBlockTime set/get functions (#24)

Refactor redis querying code to make it common among block funcs.
Tests for LastBlockTime and Block-related funcs are passing.

store/blocks.go

@@ -12,6 +12,7 @@ var ErrBlockNotFound = fmt.Errorf("block not found")
 
 const (
 	blockFmt       = "block/%d"
+	blockTimeFmt   = "blockTime/%d"
 	defaultTimeout = 100 * 10 * time.Second // we keep the last 100 blocks, assuming block time of 10 seconds
 )
 
@@ -27,8 +28,12 @@ func blockKey(height int64) string {
 	return fmt.Sprintf(blockFmt, height)
 }
 
-func (b *Blocks) Block(height int64) ([]byte, error) {
-	res, err := b.storeInstance.Client.Get(context.Background(), blockKey(height)).Result()
+func blockTimeKey(height int64) string {
+	return fmt.Sprintf(blockTimeFmt, height)
+}
+
+func (b *Blocks) queryRedis(key string) ([]byte, error) {
+	res, err := b.storeInstance.Client.Get(context.Background(), key).Result()
 	if err != nil {
 		if err == redis.Nil {
 			return nil, ErrBlockNotFound
@@ -40,6 +45,29 @@ func (b *Blocks) Block(height int64) ([]byte, error) {
 	return []byte(res), nil
 }
 
+func (b *Blocks) Block(height int64) ([]byte, error) {
+	return b.queryRedis(blockKey(height))
+}
+
+func (b *Blocks) SetLastBlockTime(t time.Time, height int64) error {
+	// TODO: figure out how to get block time from block
+	mt, err := t.MarshalText()
+	if err != nil {
+		return err
+	}
+	return b.storeInstance.Client.Set(context.Background(), blockTimeKey(height), mt, defaultTimeout).Err()
+}
+
+func (b *Blocks) LastBlockTime(height int64) (time.Time, error) {
+	res, err := b.queryRedis(blockTimeKey(height))
+	if err != nil {
+		return time.Time{}, err
+	}
+
+	tt := time.Time{}
+	return tt, tt.UnmarshalText(res)
+}
+
 func (b *Blocks) Add(data []byte, height int64) error {
 	return b.storeInstance.Client.Set(context.Background(), blockKey(height), string(data), defaultTimeout).Err()
 }

store/store_test.go

@@ -3,6 +3,7 @@ package store
 import (
 	"os"
 	"testing"
+	"time"
 
 	"github.com/alicebob/miniredis/v2"
 	sdk "github.com/cosmos/cosmos-sdk/types"
@@ -263,3 +264,17 @@ func TestBlocks(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, data, res)
 }
+
+func TestBlockTime(t *testing.T) {
+	defer ResetTestStore(mr, store)
+	blocks := NewBlocks(store)
+	_, err := blocks.LastBlockTime(123)
+	require.Error(t, err)
+	require.ErrorIs(t, err, ErrBlockNotFound)
+
+	tn := time.Now()
+	require.NoError(t, blocks.SetLastBlockTime(tn, 123))
+	res, err := blocks.LastBlockTime(123)
+	require.NoError(t, err)
+	require.True(t, tn.Equal(res))
+}