Fix Tiingo crypto volume unmarshal error (#354)

This PR fixes the unmarshal error for crypto assets by changing volume
types to float64. Fixes #352

Author: cinar

GEMINI.md

@@ -15,6 +15,7 @@ Indicator is a Golang library for technical analysis, providing a wide range of
 
 ## Development Standards
 
+- **Finding Tasks:** Use the `gh issue list` command to identify open issues. Issues labeled `good first issue` are typically self-contained indicator or strategy implementations.
 - **No External Dependencies:** This project aims to have no external dependencies. Do not add any new dependencies.
 - **Composition & Reusability:** Build and utilize reusable blocks, particularly those in the `helper/` package. Avoid re-implementing existing logic within a single indicator. For example, if an indicator uses a moving average, it should employ the existing implementation rather than duplicating the logic internally.
 - **Copyright Header:** Every file must start with the copyright notice:

asset/GEMINI.md

@@ -27,6 +27,10 @@ type Repository interface {
 - `SqlRepository`: Database-backed persistence for large datasets.
 - `TiingoRepository`: Remote API connector for fetching real-time data.
 
+## Model Consistency
+
+All price and volume fields in repository models (e.g., `TiingoEndOfDay`) must use `float64`. This ensures compatibility with crypto assets that provide fractional volumes, which would otherwise cause JSON unmarshaling errors if `int64` is used.
+
 ## Testing Pattern
 
 Test files use `asset_test` package and verify repository implementations against mock and real-world data sources.

asset/tiingo_repository.go

@@ -55,7 +55,7 @@ type TiingoEndOfDay struct {
 	Close float64 `json:"close"`
 
 	// Volume is the total volume.
-	Volume int64 `json:"volume"`
+	Volume float64 `json:"volume"`
 
 	// AdjOpen is the adjusted opening price.
 	AdjOpen float64 `json:"adjOpen"`
@@ -70,7 +70,7 @@ type TiingoEndOfDay struct {
 	AdjClose float64 `json:"adjClose"`
 
 	// AdjVolume is the adjusted total volume.
-	AdjVolume int64 `json:"adjVolume"`
+	AdjVolume float64 `json:"adjVolume"`
 
 	// Dividend is the dividend paid out.
 	Dividend float64 `json:"divCash"`
@@ -87,7 +87,7 @@ func (e *TiingoEndOfDay) ToSnapshot() *Snapshot {
 		High:   e.AdjHigh,
 		Low:    e.AdjLow,
 		Close:  e.AdjClose,
-		Volume: float64(e.AdjVolume),
+		Volume: e.AdjVolume,
 	}
 }
 

asset/tiingo_repository_test.go

@@ -182,3 +182,47 @@ func TestTiingoRepositoryAppend(t *testing.T) {
 		t.Fatal(err)
 	}
 }
+
+func TestTiingoRepositoryGetFractionalVolume(t *testing.T) {
+	// JSON with fractional volume, which should fail to unmarshal into int64
+	jsonResponse := `[
+		{
+			"date": "2024-03-01T00:00:00.000Z",
+			"open": 61000.5,
+			"high": 62000.5,
+			"low": 60000.5,
+			"close": 61500.5,
+			"volume": 20297.44489644,
+			"adjOpen": 61000.5,
+			"adjHigh": 62000.5,
+			"adjLow": 60000.5,
+			"adjClose": 61500.5,
+			"adjVolume": 20297.44489644,
+			"divCash": 0.0,
+			"splitFactor": 1.0
+		}
+	]`
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		_, _ = fmt.Fprint(w, jsonResponse)
+	}))
+	defer server.Close()
+
+	repository := asset.NewTiingoRepository("1234")
+	repository.BaseURL = server.URL
+
+	snapshots, err := repository.Get("btcusd")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	snapshot, ok := <-snapshots
+	if !ok {
+		t.Fatal("expected snapshot, but channel closed (probably due to unmarshal error)")
+	}
+
+	expectedVolume := 20297.44489644
+	if snapshot.Volume != expectedVolume {
+		t.Fatalf("actual volume %v expected %v", snapshot.Volume, expectedVolume)
+	}
+}