import { Body, Controller, Inject, Post, Res, UseGuards } 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';
import { ClientJwtAuthGuard } from '../../auth/client-jwt-auth.guard';
import {
  ApiBearerAuth,
  ApiBody,
  ApiConsumes,
  ApiOkResponse,
  ApiOperation,
  ApiProduces,
  ApiTags,
} from '@nestjs/swagger';

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));
}

@ApiTags('Client Chat')
@ApiBearerAuth('access-token')
@Controller('client/v1/chat')
export class ChatController {
  constructor(
    @Inject(ProviderRouterService)
    private readonly router: ProviderRouterService,
  ) {}

  @Post('completions/stream')
  @UseGuards(ClientJwtAuthGuard)
  @ApiOperation({ summary: '统一流式 Chat 接口（SSE）' })
  @ApiConsumes('application/json')
  @ApiProduces('text/event-stream')
  @ApiBody({
    schema: {
      type: 'object',
      description: '统一 chat 请求体，支持指定平台或自动路由',
      properties: {
        model: {
          type: 'string',
          description: '模型名（不传时 provider 使用默认模型）',
          example: 'qwen-plus',
        },
        platform: {
          type: 'string',
          description: '目标平台（auto 或不传表示自动路由）',
          enum: ['auto', 'qwen', 'deepseek', 'volc'],
          example: 'qwen',
        },
        messages: {
          type: 'array',
          description: '聊天消息列表',
          items: {
            type: 'object',
            properties: {
              role: {
                type: 'string',
                description: '消息角色',
                enum: ['system', 'user', 'assistant'],
                example: 'user',
              },
              content: {
                type: 'string',
                description: '消息文本内容',
                example: '你是谁',
              },
            },
            required: ['role', 'content'],
          },
        },
      },
      required: ['messages'],
    },
  })
  @ApiOkResponse({
    description: 'SSE 流式响应：meta -> delta -> usage -> done',
    schema: {
      type: 'string',
      example:
        'event: meta\\ndata: {"requestId":"chatcmpl_xxx","platform":"qwen","model":"qwen-plus"}\\n\\n' +
        'event: delta\\ndata: {"delta":"你好"}\\n\\n' +
        'event: usage\\ndata: {"promptTokens":10,"completionTokens":20,"totalTokens":30}\\n\\n' +
        'event: done\\ndata: {"finishReason":"stop"}\\n\\n',
    },
  })
  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();
  }
}