优化 OpenAI API 兼容性实现

根据 PR #1512 代码审查意见，进行以下优化：

**安全性修复 (P0)**
- 修复 JSON 注入安全漏洞：移除不安全的字符串拼接构造 JSON 的方式
- 添加 NewStringContent 和 NewArrayContent 构造函数，直接构造对象而非通过 JSON 序列化

**性能优化**
- String() 方法使用 strings.Builder 替代字符串拼接，提升性能
- 多个 text 部分之间添加空格分隔符，避免语义错误

**测试覆盖**
- 添加完整的单元测试覆盖 MessageContent 类型
- 测试字符串格式解析（包括特殊字符、Unicode、换行符等）
- 测试数组格式解析（单个/多个 text 部分、混合类型）
- 测试无效输入处理
- 测试序列化/反序列化往返

**代码改进**
- 更新 handler/share/chat.go 使用安全的构造函数
- 所有测试通过验证

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-authored-by: MonkeyCode-AI <monkeycode-ai@chaitin.com>

Co-authored-by: MonkeyCode-AI <monkeycode-ai@chaitin.com>

backend/domain/openai.go

@@ -1,10 +1,17 @@
 package domain
 
+import (
+	"encoding/json"
+	"fmt"
+	"strings"
+)
+
 // OpenAI API 请求结构体
 type OpenAICompletionsRequest struct {
 	Model            string                `json:"model" validate:"required"`
 	Messages         []OpenAIMessage       `json:"messages" validate:"required"`
 	Stream           bool                  `json:"stream,omitempty"`
+	StreamOptions    *OpenAIStreamOptions  `json:"stream_options,omitempty"`
 	Temperature      *float64              `json:"temperature,omitempty"`
 	MaxTokens        *int                  `json:"max_tokens,omitempty"`
 	TopP             *float64              `json:"top_p,omitempty"`
@@ -17,9 +24,89 @@ type OpenAICompletionsRequest struct {
 	ResponseFormat   *OpenAIResponseFormat `json:"response_format,omitempty"`
 }
 
+type OpenAIStreamOptions struct {
+	IncludeUsage bool `json:"include_usage,omitempty"`
+}
+
+// MessageContent 支持字符串或内容数组
+type MessageContent struct {
+	isString bool
+	strValue string
+	arrValue []OpenAIContentPart
+}
+
+// OpenAIContentPart 表示内容数组中的单个元素
+type OpenAIContentPart struct {
+	Type string `json:"type"`
+	Text string `json:"text,omitempty"`
+}
+
+// UnmarshalJSON 自定义解析，支持 string 或 array 格式
+func (mc *MessageContent) UnmarshalJSON(data []byte) error {
+	// 尝试解析为字符串
+	var str string
+	if err := json.Unmarshal(data, &str); err == nil {
+		mc.isString = true
+		mc.strValue = str
+		return nil
+	}
+
+	// 尝试解析为数组
+	var arr []OpenAIContentPart
+	if err := json.Unmarshal(data, &arr); err == nil {
+		mc.isString = false
+		mc.arrValue = arr
+		return nil
+	}
+
+	return fmt.Errorf("content must be string or array")
+}
+
+// MarshalJSON 自定义序列化
+func (mc MessageContent) MarshalJSON() ([]byte, error) {
+	if mc.isString {
+		return json.Marshal(mc.strValue)
+	}
+	return json.Marshal(mc.arrValue)
+}
+
+// NewStringContent 创建字符串类型的 MessageContent
+func NewStringContent(s string) *MessageContent {
+	return &MessageContent{
+		isString: true,
+		strValue: s,
+	}
+}
+
+// NewArrayContent 创建数组类型的 MessageContent
+func NewArrayContent(parts []OpenAIContentPart) *MessageContent {
+	return &MessageContent{
+		isString: false,
+		arrValue: parts,
+	}
+}
+
+// String 获取文本内容
+func (mc *MessageContent) String() string {
+	if mc.isString {
+		return mc.strValue
+	}
+	// 从数组中提取文本
+	var builder strings.Builder
+	for i, part := range mc.arrValue {
+		if part.Type == "text" {
+			if i > 0 && part.Text != "" {
+				builder.WriteString(" ")
+			}
+			builder.WriteString(part.Text)
+		}
+	}
+	return builder.String()
+}
+
 type OpenAIMessage struct {
 	Role       string           `json:"role" validate:"required"`
-	Content    string           `json:"content,omitempty"`
+	Content    *MessageContent  `json:"content,omitempty"`
 	Name       string           `json:"name,omitempty"`
 	ToolCalls  []OpenAIToolCall `json:"tool_calls,omitempty"`
 	ToolCallID string           `json:"tool_call_id,omitempty"`
@@ -90,12 +177,13 @@ type OpenAIStreamResponse struct {
 	Created int64                `json:"created"`
 	Model   string               `json:"model"`
 	Choices []OpenAIStreamChoice `json:"choices"`
+	Usage   *OpenAIUsage         `json:"usage,omitempty"`
 }
 
 type OpenAIStreamChoice struct {
-	Index        int           `json:"index"`
-	Delta        OpenAIMessage `json:"delta"`
-	FinishReason *string       `json:"finish_reason,omitempty"`
+	Index        int            `json:"index"`
+	Delta        OpenAIMessage  `json:"delta"`
+	FinishReason *string        `json:"finish_reason,omitempty"`
 }
 
 // OpenAI 错误响应结构体

backend/domain/openai_test.go

@@ -0,0 +1,186 @@
+package domain
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestMessageContent_UnmarshalJSON_String(t *testing.T) {
+	tests := []struct {
+		name     string
+		json     string
+		expected string
+	}{
+		{"simple string", `"hello"`, "hello"},
+		{"with quotes", `"say \"hello\""`, `say "hello"`},
+		{"with newline", `"line1\nline2"`, "line1\nline2"},
+		{"empty string", `""`, ""},
+		{"unicode", `"你好 🌍"`, "你好 🌍"},
+		{"special chars", `"Hello \"World\"\nNew Line\tTab"`, "Hello \"World\"\nNew Line\tTab"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var mc MessageContent
+			err := json.Unmarshal([]byte(tt.json), &mc)
+			require.NoError(t, err)
+			assert.Equal(t, tt.expected, mc.String())
+			assert.True(t, mc.isString)
+		})
+	}
+}
+
+func TestMessageContent_UnmarshalJSON_Array(t *testing.T) {
+	tests := []struct {
+		name     string
+		json     string
+		expected string
+	}{
+		{
+			"single text part",
+			`[{"type":"text","text":"Hello"}]`,
+			"Hello",
+		},
+		{
+			"multiple text parts",
+			`[{"type":"text","text":"Hello"},{"type":"text","text":"World"}]`,
+			"Hello World",
+		},
+		{
+			"mixed types with image",
+			`[{"type":"text","text":"Look at this"},{"type":"image_url","image_url":{"url":"https://example.com/img.png"}},{"type":"text","text":"image"}]`,
+			"Look at this image",
+		},
+		{
+			"empty array",
+			`[]`,
+			"",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var mc MessageContent
+			err := json.Unmarshal([]byte(tt.json), &mc)
+			require.NoError(t, err)
+			assert.Equal(t, tt.expected, mc.String())
+			assert.False(t, mc.isString)
+		})
+	}
+}
+
+func TestMessageContent_UnmarshalJSON_Invalid(t *testing.T) {
+	tests := []struct {
+		name string
+		json string
+	}{
+		{"number", `123`},
+		{"boolean", `true`},
+		{"object", `{"key":"value"}`},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var mc MessageContent
+			err := json.Unmarshal([]byte(tt.json), &mc)
+			assert.Error(t, err)
+			assert.Contains(t, err.Error(), "content must be string or array")
+		})
+	}
+}
+
+func TestMessageContent_UnmarshalJSON_Null(t *testing.T) {
+	var mc *MessageContent
+	err := json.Unmarshal([]byte(`null`), &mc)
+	assert.NoError(t, err)
+	assert.Nil(t, mc)
+}
+
+func TestMessageContent_MarshalJSON_String(t *testing.T) {
+	mc := NewStringContent("Hello World")
+	data, err := json.Marshal(mc)
+	require.NoError(t, err)
+	assert.Equal(t, `"Hello World"`, string(data))
+}
+
+func TestMessageContent_MarshalJSON_Array(t *testing.T) {
+	mc := NewArrayContent([]OpenAIContentPart{
+		{Type: "text", Text: "Hello"},
+		{Type: "text", Text: "World"},
+	})
+	data, err := json.Marshal(mc)
+	require.NoError(t, err)
+	assert.JSONEq(t, `[{"type":"text","text":"Hello"},{"type":"text","text":"World"}]`, string(data))
+}
+
+func TestMessageContent_Roundtrip_String(t *testing.T) {
+	original := NewStringContent("Test message with \"quotes\" and \nnewlines")
+
+	// Marshal
+	data, err := json.Marshal(original)
+	require.NoError(t, err)
+
+	// Unmarshal
+	var decoded MessageContent
+	err = json.Unmarshal(data, &decoded)
+	require.NoError(t, err)
+
+	// Verify
+	assert.Equal(t, original.String(), decoded.String())
+	assert.Equal(t, original.isString, decoded.isString)
+}
+
+func TestMessageContent_Roundtrip_Array(t *testing.T) {
+	parts := []OpenAIContentPart{
+		{Type: "text", Text: "Part 1"},
+		{Type: "text", Text: "Part 2"},
+	}
+	original := NewArrayContent(parts)
+
+	// Marshal
+	data, err := json.Marshal(original)
+	require.NoError(t, err)
+
+	// Unmarshal
+	var decoded MessageContent
+	err = json.Unmarshal(data, &decoded)
+	require.NoError(t, err)
+
+	// Verify
+	assert.Equal(t, original.String(), decoded.String())
+	assert.Equal(t, original.isString, decoded.isString)
+}
+
+func TestNewStringContent(t *testing.T) {
+	mc := NewStringContent("test")
+	assert.NotNil(t, mc)
+	assert.True(t, mc.isString)
+	assert.Equal(t, "test", mc.strValue)
+	assert.Equal(t, "test", mc.String())
+}
+
+func TestNewArrayContent(t *testing.T) {
+	parts := []OpenAIContentPart{
+		{Type: "text", Text: "Hello"},
+	}
+	mc := NewArrayContent(parts)
+	assert.NotNil(t, mc)
+	assert.False(t, mc.isString)
+	assert.Equal(t, parts, mc.arrValue)
+	assert.Equal(t, "Hello", mc.String())
+}
+
+func TestMessageContent_String_EmptyArray(t *testing.T) {
+	mc := NewArrayContent([]OpenAIContentPart{})
+	assert.Equal(t, "", mc.String())
+}
+
+func TestMessageContent_String_NoTextParts(t *testing.T) {
+	mc := NewArrayContent([]OpenAIContentPart{
+		{Type: "image_url", Text: ""},
+	})
+	assert.Equal(t, "", mc.String())
+}

backend/go.mod

@@ -49,6 +49,7 @@ require (
 	github.com/sbzhu/weworkapi_golang v0.0.0-20210525081115-1799804a7c8d
 	github.com/silenceper/wechat/v2 v2.1.9
 	github.com/spf13/viper v1.20.1
+	github.com/stretchr/testify v1.10.0
 	github.com/swaggo/echo-swagger v1.4.1
 	github.com/swaggo/swag v1.16.5
 	github.com/tidwall/gjson v1.14.1
@@ -98,6 +99,7 @@ require (
 	github.com/cloudwego/eino-ext/components/model/openai v0.0.0-20250710065240-482d48888f25 // indirect
 	github.com/cloudwego/eino-ext/libs/acl/openai v0.0.0-20250626133421-3c142631c961 // indirect
 	github.com/cohesion-org/deepseek-go v1.2.8 // indirect
+	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f // indirect
 	github.com/dlclark/regexp2 v1.11.4 // indirect
 	github.com/dustin/go-humanize v1.0.1 // indirect
@@ -165,6 +167,7 @@ require (
 	github.com/pelletier/go-toml/v2 v2.2.4 // indirect
 	github.com/perimeterx/marshmallow v1.1.5 // indirect
 	github.com/pkg/errors v0.9.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/rs/xid v1.6.0 // indirect
 	github.com/sagikazarmark/locafero v0.9.0 // indirect
 	github.com/sirupsen/logrus v1.9.3 // indirect

backend/handler/share/chat.go

@@ -268,7 +268,9 @@ func (h *ShareChatHandler) ChatCompletions(c echo.Context) error {
 	var lastUserMessage string
 	for i := len(req.Messages) - 1; i >= 0; i-- {
 		if req.Messages[i].Role == "user" {
-			lastUserMessage = req.Messages[i].Content
+			if req.Messages[i].Content != nil {
+				lastUserMessage = req.Messages[i].Content.String()
+			}
 			break
 		}
 	}
@@ -345,11 +347,12 @@ func (h *ShareChatHandler) handleOpenAIStreamResponse(c echo.Context, eventCh <-
 						Index: 0,
 						Delta: domain.OpenAIMessage{
 							Role:    "assistant",
-							Content: event.Content,
+							Content: domain.NewStringContent(event.Content),
 						},
 					},
 				},
 			}
+
 			if err := h.writeOpenAIStreamEvent(c, streamResp); err != nil {
 				return err
 			}
@@ -397,7 +400,7 @@ func (h *ShareChatHandler) handleOpenAINonStreamResponse(c echo.Context, eventCh
 						Index: 0,
 						Message: domain.OpenAIMessage{
 							Role:    "assistant",
-							Content: content,
+							Content: domain.NewStringContent(content),
 						},
 						FinishReason: "stop",
 					},