feat: support the encodingFormat in embedding models (#1035)

**Description**

This PR is support EncodingFormat in embedding models

**Related Issues/PRs (if applicable)**

Fixes #1034

Signed-off-by: misakazhou <[email protected]>

Author: Hyzhou

internal/apischema/openai/openai.go

@@ -1113,13 +1113,43 @@ type Embedding struct {
 	// Object: The object type, which is always "embedding".
 	Object string `json:"object"`
 
-	// Embedding: The embedding vector, which is a list of floats. The length of vector depends on the model as listed in the embedding guide.
-	Embedding []float64 `json:"embedding"`
+	// Embedding: The embedding vector, which can be a list of floats or a string.
+	// The length of vector depends on the model as listed in the embedding guide.
+	Embedding EmbeddingUnion `json:"embedding"`
 
 	// Index: The index of the embedding in the list of embeddings.
 	Index int `json:"index"`
 }
 
+// EmbeddingUnion is a union type that can handle both []float64 and string formats.
+type EmbeddingUnion struct {
+	Value interface{}
+}
+
+// UnmarshalJSON implements json.Unmarshaler to handle both []float64 and string formats.
+func (e *EmbeddingUnion) UnmarshalJSON(data []byte) error {
+	// Try to unmarshal as []float64 first.
+	var floats []float64
+	if err := json.Unmarshal(data, &floats); err == nil {
+		e.Value = floats
+		return nil
+	}
+
+	// Try to unmarshal as string.
+	var str string
+	if err := json.Unmarshal(data, &str); err == nil {
+		e.Value = str
+		return nil
+	}
+
+	return errors.New("embedding must be either []float64 or string")
+}
+
+// MarshalJSON implements json.Marshaler.
+func (e EmbeddingUnion) MarshalJSON() ([]byte, error) {
+	return json.Marshal(e.Value)
+}
+
 // EmbeddingUsage represents the usage information for an embeddings request.
 // https://platform.openai.com/docs/api-reference/embeddings/object#embeddings/object-usage
 type EmbeddingUsage struct {

internal/apischema/openai/openai_test.go

@@ -969,3 +969,45 @@ func TestChatCompletionResponseChunkChoice(t *testing.T) {
 		require.JSONEq(t, expected, string(jsonData))
 	})
 }
+
+func TestEmbeddingUnionUnmarshal(t *testing.T) {
+	tests := []struct {
+		name    string
+		input   string
+		want    interface{}
+		wantErr bool
+	}{
+		{
+			name:  "unmarshal array of floats",
+			input: `[1.0, 2.0, 3.0]`,
+			want:  []float64{1.0, 2.0, 3.0},
+		},
+		{
+			name:  "unmarshal string",
+			input: `"base64response"`,
+			want:  "base64response",
+		},
+		{
+			name:    "unmarshal int should error",
+			input:   `123`,
+			wantErr: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var eu EmbeddingUnion
+			err := json.Unmarshal([]byte(tt.input), &eu)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("EmbeddingUnion Unmarshal Error. error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if !tt.wantErr {
+				// Use reflect.DeepEqual to compare
+				if !cmp.Equal(eu.Value, tt.want) {
+					t.Errorf("EmbeddingUnion Unmarshal Error. got = %v, want %v", eu.Value, tt.want)
+				}
+			}
+		})
+	}
+}