import { getToken } from '../utils/user';
import { SYSTEM_PROMPT_PREFIX } from '@/constants/chat';

interface StreamFetchProps {
  url: string;
  data: any;
  onMessage: (text: string) => void;
  abortSignal: AbortController;
}
export const streamFetch = ({ url, data, onMessage, abortSignal }: StreamFetchProps) =>
  new Promise<{ responseText: string; systemPrompt: string }>(async (resolve, reject) => {
    try {
      const res = await fetch(url, {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
          Authorization: getToken() || ''
        },
        body: JSON.stringify(data),
        signal: abortSignal.signal
      });
      const reader = res.body?.getReader();
      if (!reader) return;

      const decoder = new TextDecoder();
      let responseText = '';
      let systemPrompt = '';

      const read = async () => {
        try {
          const { done, value } = await reader?.read();
          if (done) {
            if (res.status === 200) {
              resolve({ responseText, systemPrompt });
            } else {
              const parseError = JSON.parse(responseText);
              reject(parseError?.message || '请求异常');
            }

            return;
          }
          let text = decoder.decode(value).replace(/<br\/>/g, '\n');
          // check system prompt
          if (text.includes(SYSTEM_PROMPT_PREFIX)) {
            const arr = text.split(SYSTEM_PROMPT_PREFIX);
            systemPrompt = arr.pop() || '';

            text = arr.join('');
          }
          responseText += text;
          onMessage(text);

          read();
        } catch (err: any) {
          if (err?.message === 'The user aborted a request.') {
            return resolve({ responseText, systemPrompt });
          }
          reject(typeof err === 'string' ? err : err?.message || '请求异常');
        }
      };

      read();
    } catch (err: any) {
      console.log(err, '====');
      reject(typeof err === 'string' ? err : err?.message || '请求异常');
    }
  });