import type { NextRequest } from 'next/server';
import type { IService } from 'soma-core';
import { AiAssistantRuntime } from '../../../domain/ai-assistant/AiAssistantRuntime';
import { AiApiError, AiErrorCodes } from '../../../domain/ai-shared/AiError';
import { aiErrorResponse } from '../../../domain/ai-shared/AiResponse';
import {
  AI_REQUEST_MAX_BYTES,
  readJsonWithLimit,
  RequestBodyTooLargeError,
} from '../../common/RequestBodyLimit';
import { callerKey, parseRateLimit, sharedRateLimiter } from '../../common/RateLimiter';
import { runService } from '../../common/ServiceRuntime';
import { resolveTrustedRequestContext } from '../../common/TrustedRequestContext';
import { readRequestOrigin } from '../../common/RequestOrigin';

export default class ChatService implements IService {
  async post(req: NextRequest): Promise<Response> {
    return runService(async () => {
      try {
        // 对话同样按调用方限流(缺省 60 次/分钟)——它也是每次都打上游
        const rule = parseRateLimit(process.env.SOMA_AI_CHAT_RATE, { limit: 60, windowMs: 60_000 });
        const actor = await resolveTrustedRequestContext(req);
        const decision = await sharedRateLimiter.hit(`ai-chat:${callerKey(actor)}`, rule);
        if (!decision.allowed) {
          const rejected = aiErrorResponse(new AiApiError(
            AiErrorCodes.AI_RATE_LIMITED,
            `对话请求过于频繁，请 ${decision.retryAfterSeconds} 秒后重试`,
          ));
          return new Response(rejected.body, {
            status: 429,
            headers: {
              ...Object.fromEntries(rejected.headers),
              'retry-after': String(decision.retryAfterSeconds),
            },
          });
        }
        // 合法上界是 80 条 × 32KB(AI_LIMITS),但那是解析之后才判的;
        // 这一道在读之前把内存占用钉住。
        let body: unknown;
        try {
          body = await readJsonWithLimit(req, AI_REQUEST_MAX_BYTES);
        } catch (error) {
          throw error instanceof RequestBodyTooLargeError
            ? new AiApiError(AiErrorCodes.AI_CHAT_INPUT_INVALID, error.message)
            : new AiApiError(AiErrorCodes.AI_CHAT_INPUT_INVALID, '请求 JSON 不合法');
        }
        if (body === null) {
          throw new AiApiError(AiErrorCodes.AI_CHAT_INPUT_INVALID, '请求 JSON 不合法');
        }
        const runtime = AiAssistantRuntime.getInstance();
        const request = await runtime.validateRequest(body);
        // origin 给声明式工具自调宿主接口用:同源、同权、同样过入口网关。
        return await runtime.createChatResponse(request, req.signal, readRequestOrigin(req));
      } catch (error) {
        const response = aiErrorResponse(error);
        if (error instanceof AiApiError && error.code === AiErrorCodes.AI_CHAT_INPUT_INVALID) {
          return new Response(response.body, { status: 400, headers: response.headers });
        }
        return response;
      }
    });
  }
}