feat(API): 集成 Gemini 图片生成能力

- 添加 Gemini 模型类型检测和初始化
- 实现图片生成请求处理逻辑
- 支持流式返回生成的图片数据
- 将生成的图片保存到数据库

src/app/api/chat/route.ts

@@ -1,6 +1,6 @@
 import { NextResponse } from 'next/server';
 import { db } from '@/drizzle/db';
-import { conversations, messages, userSettings } from '@/drizzle/schema';
+import { conversations, messages, userSettings, type GeneratedImageData } from '@/drizzle/schema';
 import { eq } from 'drizzle-orm';
 import { nanoid } from 'nanoid';
 import { executeTool } from '@/services/tools';
@@ -94,6 +94,19 @@ function isCodexModel(modelId: string): boolean {
   return modelId.startsWith('gpt-') && modelId.includes('codex');
 }
 
+// 判断是否为 Gemini 图片生成模型
+function isGeminiImageModel(modelId: string): boolean {
+  // 支持的图片生成模型列表
+  const imageModels = [
+    'gemini-2.0-flash-preview-image-generation',
+    'gemini-3-pro-image-preview',
+    'imagen-3.0-generate-002',
+  ];
+  return imageModels.some(model => modelId.includes(model)) ||
+         modelId.includes('image-generation') ||
+         modelId.includes('imagen');
+}
+
 // 规范化 URL（移除末尾斜杠，避免拼接时出现双斜杠）
 function normalizeBaseUrl(url: string): string {
   return url.replace(/\/+$/, '');
@@ -359,6 +372,7 @@ export async function POST(request: Request) {
     // 判断使用的模型类型
     const useModel = model || conversation.model;
     const isCodex = isCodexModel(useModel);
+    const isGeminiImage = isGeminiImageModel(useModel);
 
     // 创建 SSE 响应
     const encoder = new TextEncoder();
@@ -420,6 +434,7 @@ export async function POST(request: Request) {
           let totalInputTokens = 0;
           let totalOutputTokens = 0;
           let usedTools: string[] = []; // 收集使用过的工具名称
+          let generatedImages: GeneratedImageData[] = []; // Gemini 生成的图片
 
           // 如果有文档解析失败，将警告添加到内容开头
           if (documentParseErrors.length > 0) {
@@ -433,13 +448,35 @@ export async function POST(request: Request) {
           }
 
           // 【重要】处理器选择优先级说明：
-          // 1. 首先检查 apiFormat === 'openai'：如果用户选择了 "OpenAI 兼容" 格式，
+          // 0. 首先检查 isGeminiImage：Gemini 图片生成模型有专门的处理逻辑
+          // 1. 然后检查 apiFormat === 'openai'：如果用户选择了 "OpenAI 兼容" 格式，
           //    则所有模型（包括 Codex 模型）都统一使用 /v1/chat/completions 端点
           //    这是因为第三方中转站通常只支持 OpenAI 兼容的 /v1/chat/completions 端点
           // 2. 然后检查 isCodex：如果是 Claude 原生格式 + Codex 模型，才使用 /v1/responses 端点
           // 3. 最后是普通的 Claude 原生格式，使用 /v1/messages 端点
 
-          if (apiFormat === 'openai') {
+          if (isGeminiImage) {
+            // ==================== Gemini 图片生成模型处理 ====================
+            // Gemini 图片生成模型使用专门的 Gemini API 端点
+            console.log('[API/chat] 使用 Gemini 图片生成模型:', useModel);
+            const result = await handleGeminiImageChat({
+              cchUrl,
+              apiKey: decryptedApiKey,
+              model: useModel,
+              systemPrompt,
+              temperature,
+              historyMessages,
+              message,
+              controller,
+              encoder,
+              images,
+            });
+
+            fullContent = result.fullContent;
+            generatedImages = result.generatedImages;
+            totalInputTokens = result.inputTokens;
+            totalOutputTokens = result.outputTokens;
+          } else if (apiFormat === 'openai') {
             // ==================== OpenAI 兼容格式处理 ====================
             // 当用户选择 "OpenAI 兼容" 时，无论什么模型都走这个分支
             // 第三方中转站统一使用 /v1/chat/completions 端点
@@ -528,6 +565,7 @@ export async function POST(request: Request) {
             content: fullContent,
             thinkingContent: thinkingContent || null,
             usedTools: usedTools.length > 0 ? usedTools : null,
+            generatedImages: generatedImages.length > 0 ? generatedImages : null,
             inputTokens: totalInputTokens,
             outputTokens: totalOutputTokens,
             status: 'completed',
@@ -1974,6 +2012,203 @@ async function handleOpenAICompatibleChat(params: OpenAICompatibleChatParams): P
   };
 }
 
+// ==================== Gemini 图片生成模型处理函数 ====================
+interface GeminiImageChatParams {
+  cchUrl: string;
+  apiKey: string;
+  model: string;
+  systemPrompt: string;
+  temperature: number;
+  historyMessages: { role: string; content: string }[];
+  message: string;
+  controller: ReadableStreamDefaultController;
+  encoder: TextEncoder;
+  // 用户上传的图片
+  images?: {
+    type: 'image';
+    media_type: string;
+    data: string;
+  }[];
+}
+
+async function handleGeminiImageChat(params: GeminiImageChatParams): Promise<{
+  fullContent: string;
+  generatedImages: GeneratedImageData[];
+  inputTokens: number;
+  outputTokens: number;
+}> {
+  const {
+    cchUrl,
+    apiKey,
+    model,
+    systemPrompt,
+    temperature,
+    historyMessages,
+    message,
+    controller,
+    encoder,
+    images,
+  } = params;
+
+  // 创建安全的 stream 写入器
+  const safeWriter = createSafeStreamWriter(controller, encoder);
+
+  // 发送生成开始事件
+  safeWriter.write({
+    type: 'image_generation_start',
+    model,
+  });
+
+  // 构建 Gemini API 请求内容
+  // Gemini 使用 contents 数组格式
+  const contents: Array<{
+    role: 'user' | 'model';
+    parts: Array<{ text?: string; inlineData?: { mimeType: string; data: string } }>;
+  }> = [];
+
+  // 添加历史消息
+  for (const msg of historyMessages) {
+    if (msg.content && msg.content.trim() !== '') {
+      contents.push({
+        role: msg.role === 'assistant' ? 'model' : 'user',
+        parts: [{ text: msg.content }],
+      });
+    }
+  }
+
+  // 构建当前用户消息（支持多模态）
+  const currentParts: Array<{ text?: string; inlineData?: { mimeType: string; data: string } }> = [];
+
+  // 如果有图片，先添加图片
+  if (images && images.length > 0) {
+    for (const img of images) {
+      currentParts.push({
+        inlineData: {
+          mimeType: img.media_type,
+          data: img.data,
+        },
+      });
+    }
+  }
+
+  // 添加文本消息
+  if (message) {
+    currentParts.push({ text: message });
+  }
+
+  contents.push({
+    role: 'user',
+    parts: currentParts,
+  });
+
+  // 构建请求体
+  const requestBody = {
+    contents,
+    systemInstruction: systemPrompt ? { parts: [{ text: systemPrompt }] } : undefined,
+    generationConfig: {
+      temperature,
+      responseModalities: ['TEXT', 'IMAGE'], // 请求同时返回文本和图片
+    },
+  };
+
+  console.log('[handleGeminiImageChat] Sending request to Gemini API:', {
+    model,
+    contentsCount: contents.length,
+    hasImages: images && images.length > 0,
+  });
+
+  // 发送请求到 Gemini API
+  // Gemini API 端点格式: /v1beta/models/{model}:generateContent
+  const geminiEndpoint = `${normalizeBaseUrl(cchUrl)}/v1beta/models/${model}:generateContent`;
+
+  const response = await fetch(geminiEndpoint, {
+    method: 'POST',
+    headers: {
+      'Content-Type': 'application/json',
+      'x-goog-api-key': apiKey,
+    },
+    body: JSON.stringify(requestBody),
+  });
+
+  if (!response.ok) {
+    const errorText = await response.text();
+    throw new Error(`Gemini API error: ${response.status} - ${errorText}`);
+  }
+
+  // 解析 Gemini 响应
+  const geminiResponse = await response.json();
+
+  let fullContent = '';
+  const generatedImages: GeneratedImageData[] = [];
+  let totalInputTokens = 0;
+  let totalOutputTokens = 0;
+
+  // 提取 usage 信息
+  if (geminiResponse.usageMetadata) {
+    totalInputTokens = geminiResponse.usageMetadata.promptTokenCount || 0;
+    totalOutputTokens = geminiResponse.usageMetadata.candidatesTokenCount || 0;
+  }
+
+  // 解析候选响应
+  if (geminiResponse.candidates && geminiResponse.candidates.length > 0) {
+    const candidate = geminiResponse.candidates[0];
+
+    if (candidate.content && candidate.content.parts) {
+      for (const part of candidate.content.parts) {
+        // 处理文本内容
+        if (part.text) {
+          fullContent += part.text;
+          safeWriter.write({
+            type: 'text',
+            content: part.text,
+          });
+        }
+
+        // 处理生成的图片
+        if (part.inlineData) {
+          const imageData: GeneratedImageData = {
+            mimeType: part.inlineData.mimeType,
+            data: part.inlineData.data,
+          };
+          generatedImages.push(imageData);
+
+          // 发送生成图片事件
+          safeWriter.write({
+            type: 'generated_image',
+            image: imageData,
+            index: generatedImages.length - 1,
+          });
+
+          console.log('[handleGeminiImageChat] Generated image:', {
+            mimeType: imageData.mimeType,
+            dataLength: imageData.data.length,
+          });
+        }
+      }
+    }
+  }
+
+  // 发送生成完成事件
+  safeWriter.write({
+    type: 'image_generation_complete',
+    imageCount: generatedImages.length,
+  });
+
+  console.log('[handleGeminiImageChat] Response processed:', {
+    textLength: fullContent.length,
+    imageCount: generatedImages.length,
+    inputTokens: totalInputTokens,
+    outputTokens: totalOutputTokens,
+  });
+
+  return {
+    fullContent,
+    generatedImages,
+    inputTokens: totalInputTokens,
+    outputTokens: totalOutputTokens,
+  };
+}
+
 // 构建 Claude 工具定义
 function buildClaudeToolDefinitions(toolIds: string[]) {
   const toolMap: Record<string, object> = {