loopdb: add new bucket to save liquidity params

This commit adds a new bucket to save liquidity parameters. We've
skipped the serialization and deserialization implementations here and
leave them to be handled by the liquidity package.

loopdb/interface.go

@@ -33,6 +33,20 @@ type SwapStore interface {
 	UpdateLoopIn(hash lntypes.Hash, time time.Time,
 		state SwapStateData) error
 
+	// PutLiquidityParams writes the serialized `manager.Parameters` bytes
+	// into the bucket.
+	//
+	// NOTE: it's the caller's responsibility to encode the param. Atm,
+	// it's encoding using the proto package's `Marshal` method.
+	PutLiquidityParams(params []byte) error
+
+	// FetchLiquidityParams reads the serialized `manager.Parameters` bytes
+	// from the bucket.
+	//
+	// NOTE: it's the caller's responsibility to decode the param. Atm,
+	// it's decoding using the proto package's `Unmarshal` method.
+	FetchLiquidityParams() ([]byte, error)
+
 	// Close closes the underlying database.
 	Close() error
 }

loopdb/store.go

@@ -94,6 +94,14 @@ var (
 	// value: uint32 confirmation value
 	confirmationsKey = []byte("confirmations")
 
+	// liquidtyBucket is a root bucket used to save liquidity manager
+	// related info.
+	liquidityBucket = []byte("liquidity")
+
+	// liquidtyParamsKey specifies the key used to store the liquidity
+	// parameters.
+	liquidtyParamsKey = []byte("params")
+
 	byteOrder = binary.BigEndian
 
 	keyLength = 33
@@ -190,6 +198,12 @@ func NewBoltSwapStore(dbPath string, chainParams *chaincfg.Params) (
 			return err
 		}
 
+		// Create liquidity manager's bucket.
+		_, err = tx.CreateBucketIfNotExists(liquidityBucket)
+		if err != nil {
+			return err
+		}
+
 		return nil
 	})
 	if err != nil {
@@ -712,3 +726,41 @@ func (s *boltSwapStore) UpdateLoopIn(hash lntypes.Hash, time time.Time,
 func (s *boltSwapStore) Close() error {
 	return s.db.Close()
 }
+
+// PutLiquidityParams writes the serialized `manager.Parameters` bytes into the
+// bucket.
+//
+// NOTE: it's the caller's responsibility to encode the param. Atm, it's
+// encoding using the proto package's `Marshal` method.
+func (s *boltSwapStore) PutLiquidityParams(params []byte) error {
+	return s.db.Update(func(tx *bbolt.Tx) error {
+		// Read the root bucket.
+		rootBucket := tx.Bucket(liquidityBucket)
+		if rootBucket == nil {
+			return errors.New("liquidity bucket does not exist")
+		}
+		return rootBucket.Put(liquidtyParamsKey, params)
+	})
+}
+
+// FetchLiquidityParams reads the serialized `manager.Parameters` bytes from
+// the bucket.
+//
+// NOTE: it's the caller's responsibility to decode the param. Atm, it's
+// decoding using the proto package's `Unmarshal` method.
+func (s *boltSwapStore) FetchLiquidityParams() ([]byte, error) {
+	var params []byte
+
+	err := s.db.View(func(tx *bbolt.Tx) error {
+		// Read the root bucket.
+		rootBucket := tx.Bucket(liquidityBucket)
+		if rootBucket == nil {
+			return errors.New("liquidity bucket does not exist")
+		}
+
+		params = rootBucket.Get(liquidtyParamsKey)
+		return nil
+	})
+
+	return params, err
+}

loopdb/store_test.go

@@ -471,3 +471,31 @@ func TestLegacyOutgoingChannel(t *testing.T) {
 		t.Fatal("invalid outgoing channel")
 	}
 }
+
+// TestLiquidityParams checks that reading and writing to liquidty bucket are
+// as expected.
+func TestLiquidityParams(t *testing.T) {
+	tempDirName, err := ioutil.TempDir("", "clientstore")
+	require.NoError(t, err, "failed to db")
+	defer os.RemoveAll(tempDirName)
+
+	store, err := NewBoltSwapStore(tempDirName, &chaincfg.MainNetParams)
+	require.NoError(t, err, "failed to create store")
+
+	// Test when there's no params saved before, an empty bytes is
+	// returned.
+	params, err := store.FetchLiquidityParams()
+	require.NoError(t, err, "failed to fetch params")
+	require.Empty(t, params, "expect empty bytes")
+
+	params = []byte("test")
+
+	// Test we can save the params.
+	err = store.PutLiquidityParams(params)
+	require.NoError(t, err, "failed to put params")
+
+	// Now fetch the db again should return the above saved bytes.
+	paramsRead, err := store.FetchLiquidityParams()
+	require.NoError(t, err, "failed to fetch params")
+	require.Equal(t, params, paramsRead, "unexpected return value")
+}