feat: 初始化 Nest 服务骨架与多平台 Chat SSE 网关

- 新增 NestJS + Fastify 入口、配置模块与 Swagger 集成
- 划分 client-app / admin-app 与 shared-domain ai-gateway
- 实现统一 SSE Chat 接口，支持千问、DeepSeek、火山引擎非流式上游与网关分片输出
- 补充项目方案与 JWT 最小实现文档

Made-with: Cursor

src/apps/admin-app/admin-app.module.ts

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+import { Module } from '@nestjs/common';
+
+@Module({
+  imports: [],
+})
+export class AdminAppModule {}
+

src/apps/client-app/chat/application/chat.service.ts

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+// 占位文件，避免 TS include 报错；当前逻辑已直接在 Controller 中调用 ProviderRouterService。
+export {};
+

src/apps/client-app/chat/chat.module.ts

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+import { Module } from '@nestjs/common';
+import { ChatController } from './controllers/chat.controller';
+import { ProviderRouterService } from '@shared/ai-gateway/router/provider-router.service';
+import { QwenProvider } from '@shared/ai-gateway/providers/qwen.provider';
+import { DeepseekProvider } from '@shared/ai-gateway/providers/deepseek.provider';
+import { VolcProvider } from '@shared/ai-gateway/providers/volc.provider';
+
+@Module({
+  controllers: [ChatController],
+  providers: [ProviderRouterService, QwenProvider, DeepseekProvider, VolcProvider],
+})
+export class ChatModule {}
+

src/apps/client-app/chat/controllers/chat.controller.ts

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+import { Body, Controller, Inject, Post, Res } from '@nestjs/common';
+import { FastifyReply } from 'fastify';
+import { StreamChatRequest } from '@shared/ai-gateway/types/chat.types';
+import { ProviderRouterService } from '@shared/ai-gateway/router/provider-router.service';
+
+function formatSse(event: string, data: unknown) {
+  return `event: ${event}\ndata: ${JSON.stringify(data)}\n\n`;
+}
+
+function sleep(ms: number) {
+  return new Promise((resolve) => setTimeout(resolve, ms));
+}
+
+@Controller('client/v1/chat')
+export class ChatController {
+  constructor(
+    @Inject(ProviderRouterService)
+    private readonly router: ProviderRouterService,
+  ) {}
+
+  @Post('completions/stream')
+  async streamChat(
+    @Body() body: StreamChatRequest,
+    @Res() reply: FastifyReply,
+  ) {
+    const response = await this.router.routeAndStream(body);
+
+    reply.raw.setHeader('Content-Type', 'text/event-stream; charset=utf-8');
+    reply.raw.setHeader('Cache-Control', 'no-cache, no-transform');
+    reply.raw.setHeader('Connection', 'keep-alive');
+    reply.raw.setHeader('X-Accel-Buffering', 'no');
+    reply.raw.flushHeaders?.();
+
+    reply.raw.write(
+      formatSse('meta', {
+        requestId: response.requestId,
+        platform: response.providerCode,
+        model: response.model,
+      }),
+    );
+
+    for (const chunk of response.chunks) {
+      reply.raw.write(formatSse('delta', { delta: chunk.content }));
+      await sleep(120);
+    }
+
+    reply.raw.write(formatSse('usage', response.usage));
+    reply.raw.write(formatSse('done', { finishReason: 'stop' }));
+    reply.raw.end();
+  }
+}
+

src/apps/client-app/client-app.module.ts

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+import { Module } from '@nestjs/common';
+import { ChatModule } from './chat/chat.module';
+
+@Module({
+  imports: [ChatModule],
+})
+export class ClientAppModule {}
+

src/apps/shared-domain/ai-gateway/providers/deepseek.provider.ts

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+import { Injectable, InternalServerErrorException } from '@nestjs/common';
+import { request } from 'undici';
+import { ProviderStreamResult, StreamChatRequest } from '../types/chat.types';
+import { AiProvider } from './provider.interface';
+
+@Injectable()
+export class DeepseekProvider implements AiProvider {
+  readonly code = 'deepseek';
+
+  supports(model?: string): boolean {
+    if (!model) return true;
+    return model.toLowerCase().includes('deepseek');
+  }
+
+  async streamChat(req: StreamChatRequest): Promise<ProviderStreamResult> {
+    const apiKey = process.env.DEEPSEEK_API_KEY;
+    const baseUrl = process.env.DEEPSEEK_BASE_URL || 'https://api.deepseek.com/v1';
+
+    if (!apiKey) {
+      throw new InternalServerErrorException('DEEPSEEK_API_KEY 未配置');
+    }
+
+    const model = req.model || 'deepseek-chat';
+    const upstreamBody = {
+      model,
+      stream: false,
+      messages: (req.messages || []).map((m) => ({
+        role: m.role,
+        content: m.content,
+      })),
+    };
+
+    const { statusCode, body } = await request(`${baseUrl}/chat/completions`, {
+      method: 'POST',
+      body: JSON.stringify(upstreamBody),
+      headers: {
+        'Content-Type': 'application/json',
+        Authorization: `Bearer ${apiKey}`,
+      },
+    });
+
+    if (statusCode < 200 || statusCode >= 300) {
+      const text = await body.text();
+      throw new InternalServerErrorException(
+        `DeepSeek 调用失败: ${statusCode} - ${text}`,
+      );
+    }
+
+    const json = (await body.json()) as any;
+    const content: string =
+      json.choices?.[0]?.message?.content ??
+      '[DeepSeek] 未返回内容，请检查请求参数或模型配置。';
+
+    const promptTokens: number = json.usage?.prompt_tokens ?? 0;
+    const completionTokens: number = json.usage?.completion_tokens ?? 0;
+    const totalTokens: number =
+      json.usage?.total_tokens ?? Math.max(1, promptTokens + completionTokens);
+
+    const chunks = this.splitText(content, 24).map((c) => ({ content: c }));
+
+    return {
+      requestId: json.id || `deepseek_${Date.now()}`,
+      providerCode: this.code,
+      model,
+      chunks,
+      usage: { promptTokens, completionTokens, totalTokens },
+    };
+  }
+
+  private splitText(text: string, size: number) {
+    const result: string[] = [];
+    for (let i = 0; i < text.length; i += size) {
+      result.push(text.slice(i, i + size));
+    }
+    return result;
+  }
+}
+

src/apps/shared-domain/ai-gateway/providers/provider.interface.ts

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+import { StreamChatRequest, ProviderStreamResult } from '../types/chat.types';
+
+export interface AiProvider {
+  readonly code: string; // qwen | deepseek | volc | demo
+
+  supports(model?: string): boolean;
+
+  streamChat(req: StreamChatRequest): Promise<ProviderStreamResult>;
+}
+

src/apps/shared-domain/ai-gateway/providers/qwen.provider.ts

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+import { Injectable, InternalServerErrorException } from '@nestjs/common';
+import { ProviderStreamResult, StreamChatRequest } from '../types/chat.types';
+import { AiProvider } from './provider.interface';
+import { request } from 'undici';
+
+@Injectable()
+export class QwenProvider implements AiProvider {
+  readonly code = 'qwen';
+
+  supports(model?: string): boolean {
+    if (!model) return true;
+    return model.toLowerCase().includes('qwen');
+  }
+
+  async streamChat(req: StreamChatRequest): Promise<ProviderStreamResult> {
+    const apiKey = process.env.QWEN_API_KEY;
+    const baseUrl =
+      process.env.QWEN_BASE_URL ||
+      'https://dashscope.aliyuncs.com/compatible-mode/v1';
+
+    if (!apiKey) {
+      throw new InternalServerErrorException('QWEN_API_KEY 未配置');
+    }
+
+    const model = req.model || 'qwen-plus';
+
+    const upstreamBody = {
+      model,
+      stream: false, // 先用非流式，统一在网关层拆分为 SSE
+      messages: (req.messages || []).map((m) => ({
+        role: m.role,
+        content: m.content,
+      })),
+    };
+
+    const { statusCode, body } = await request(
+      `${baseUrl}/chat/completions`,
+      {
+        method: 'POST',
+        body: JSON.stringify(upstreamBody),
+        headers: {
+          'Content-Type': 'application/json',
+          Authorization: `Bearer ${apiKey}`,
+        },
+      },
+    );
+
+    if (statusCode < 200 || statusCode >= 300) {
+      const text = await body.text();
+      throw new InternalServerErrorException(
+        `Qwen 调用失败: ${statusCode} - ${text}`,
+      );
+    }
+
+    const json = (await body.json()) as any;
+
+    const choice = json.choices?.[0];
+    const content: string =
+      choice?.message?.content ??
+      '[Qwen] 未返回内容，请检查请求参数或模型配置。';
+
+    const promptTokens: number = json.usage?.prompt_tokens ?? 0;
+    const completionTokens: number = json.usage?.completion_tokens ?? 0;
+    const totalTokens: number =
+      json.usage?.total_tokens ??
+      Math.max(1, promptTokens + completionTokens);
+
+    const chunks = this.splitText(content, 24).map((c) => ({ content: c }));
+
+    return {
+      requestId: json.id || `qwen_${Date.now()}`,
+      providerCode: this.code,
+      model,
+      chunks,
+      usage: {
+        promptTokens,
+        completionTokens,
+        totalTokens,
+      },
+    };
+  }
+
+  private splitText(text: string, size: number) {
+    const result: string[] = [];
+    for (let i = 0; i < text.length; i += size) {
+      result.push(text.slice(i, i + size));
+    }
+    return result;
+  }
+}
+
+

src/apps/shared-domain/ai-gateway/providers/volc.provider.ts

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+import { Injectable, InternalServerErrorException } from '@nestjs/common';
+import { request } from 'undici';
+import { ProviderStreamResult, StreamChatRequest } from '../types/chat.types';
+import { AiProvider } from './provider.interface';
+
+@Injectable()
+export class VolcProvider implements AiProvider {
+  readonly code = 'volc';
+
+  supports(model?: string): boolean {
+    if (!model) return true;
+    return (
+      model.toLowerCase().includes('volc') ||
+      model.toLowerCase().includes('ark')
+    );
+  }
+
+  async streamChat(req: StreamChatRequest): Promise<ProviderStreamResult> {
+    const apiKey = process.env.VOLC_API_KEY;
+    const baseUrl =
+      process.env.VOLC_BASE_URL || 'https://ark.cn-beijing.volces.com/api/v3';
+
+    if (!apiKey) {
+      throw new InternalServerErrorException('VOLC_API_KEY 未配置');
+    }
+
+    const model = req.model || 'ep-default';
+    const upstreamBody = {
+      model,
+      stream: false,
+      messages: (req.messages || []).map((m) => ({
+        role: m.role,
+        content: m.content,
+      })),
+    };
+
+    const { statusCode, body } = await request(`${baseUrl}/chat/completions`, {
+      method: 'POST',
+      body: JSON.stringify(upstreamBody),
+      headers: {
+        'Content-Type': 'application/json',
+        Authorization: `Bearer ${apiKey}`,
+      },
+    });
+
+    if (statusCode < 200 || statusCode >= 300) {
+      const text = await body.text();
+      throw new InternalServerErrorException(
+        `火山引擎调用失败: ${statusCode} - ${text}`,
+      );
+    }
+
+    const json = (await body.json()) as any;
+    const content: string =
+      json.choices?.[0]?.message?.content ??
+      '[Volc] 未返回内容，请检查请求参数或模型配置。';
+
+    const promptTokens: number = json.usage?.prompt_tokens ?? 0;
+    const completionTokens: number = json.usage?.completion_tokens ?? 0;
+    const totalTokens: number =
+      json.usage?.total_tokens ?? Math.max(1, promptTokens + completionTokens);
+
+    const chunks = this.splitText(content, 24).map((c) => ({ content: c }));
+
+    return {
+      requestId: json.id || `volc_${Date.now()}`,
+      providerCode: this.code,
+      model,
+      chunks,
+      usage: { promptTokens, completionTokens, totalTokens },
+    };
+  }
+
+  private splitText(text: string, size: number) {
+    const result: string[] = [];
+    for (let i = 0; i < text.length; i += size) {
+      result.push(text.slice(i, i + size));
+    }
+    return result;
+  }
+}
+

src/apps/shared-domain/ai-gateway/router/provider-router.service.ts

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+import { Inject, Injectable } from '@nestjs/common';
+import {
+  ProviderStreamResult,
+  StreamChatRequest,
+} from '../types/chat.types';
+import { AiProvider } from '../providers/provider.interface';
+import { QwenProvider } from '../providers/qwen.provider';
+import { DeepseekProvider } from '../providers/deepseek.provider';
+import { VolcProvider } from '../providers/volc.provider';
+
+@Injectable()
+export class ProviderRouterService {
+  private readonly providers: AiProvider[];
+
+  constructor(
+    @Inject(QwenProvider)
+    private readonly qwen: QwenProvider,
+    @Inject(DeepseekProvider)
+    private readonly deepseek: DeepseekProvider,
+    @Inject(VolcProvider)
+    private readonly volc: VolcProvider,
+  ) {
+    this.providers = [qwen, deepseek, volc];
+  }
+
+  async routeAndStream(req: StreamChatRequest): Promise<ProviderStreamResult> {
+    const platform = (req.platform || 'auto').toLowerCase();
+
+    if (platform !== 'auto') {
+      const target = this.providers.find((p) => p.code === platform);
+      if (!target) {
+        return this.buildFallback(req, `未知平台：${platform}`);
+      }
+      return target.streamChat(req);
+    }
+
+    const candidate =
+      this.providers.find((p) => p.supports(req.model)) || this.qwen;
+    return candidate.streamChat(req);
+  }
+
+  private async buildFallback(
+    req: StreamChatRequest,
+    reason: string,
+  ): Promise<ProviderStreamResult> {
+    const lastUserMessage =
+      [...(req.messages || [])].reverse().find((m) => m.role === 'user')
+        ?.content || '';
+
+    const text = `【路由降级】${reason}。直接返回 demo 内容：${lastUserMessage}`;
+    const chunks = this.splitText(text, 12).map((c) => ({ content: c }));
+
+    return {
+      requestId: `fallback_${Date.now()}`,
+      providerCode: 'demo',
+      model: req.model || 'demo-model',
+      chunks,
+      usage: {
+        promptTokens: Math.max(1, lastUserMessage.length),
+        completionTokens: Math.max(1, text.length),
+        totalTokens: Math.max(2, lastUserMessage.length + text.length),
+      },
+    };
+  }
+
+  private splitText(text: string, size: number) {
+    const result: string[] = [];
+    for (let i = 0; i < text.length; i += size) {
+      result.push(text.slice(i, i + size));
+    }
+    return result;
+  }
+}
+

src/apps/shared-domain/ai-gateway/types/chat.types.ts

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+export type ChatRole = 'system' | 'user' | 'assistant';
+
+export interface ChatMessage {
+  role: ChatRole;
+  content: string;
+}
+
+export interface StreamChatRequest {
+  model?: string;
+  platform?: string; // qwen | deepseek | volc | auto | demo
+  messages: ChatMessage[];
+}
+
+export interface ProviderStreamChunk {
+  content: string;
+}
+
+export interface ProviderUsage {
+  promptTokens: number;
+  completionTokens: number;
+  totalTokens: number;
+}
+
+export interface ProviderStreamResult {
+  requestId: string;
+  providerCode: string;
+  model: string;
+  chunks: ProviderStreamChunk[];
+  usage: ProviderUsage;
+}
+