import { getTokenKeySessionStorage } from "@/utils/auth";
/**
 * 创建聊天流式连接
 * @param {Object} params 请求参数
 * @param {string} params.prompt 用户输入
 * @param {string} params.userId 用户ID
 * @param {string} params.userName 用户名
 * @param {string} [params.conversationId] 会话ID
 * @returns {Object} 包含stream和cancel方法的对象
 */
export function createChatStream(params) {
  const requestId = `req-${Date.now()}-${Math.random()
    .toString(36)
    .slice(2, 8)}`;
  const url = `${process.env.VUE_APP_BASE_API}/aitutor/aichat/stream`;
  const token = getTokenKeySessionStorage();

  if (!token) {
    throw new Error("请先登录");
  }

  const controller = new AbortController();

  const fetchPromise = fetch(url, {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      Authorization: `Bearer ${token}`,
      "X-Request-ID": requestId,
    },
    body: JSON.stringify({
      query: params.prompt,
      user_id: params.userId,
      user_name: params.userName,
      user_token: params.user_token || "123",
      user_role: "student",
      conversation_id: params.conversationId || null,
    }),
    signal: controller.signal,
  }).then((response) => {
    if (!response.ok) {
      throw new Error(`HTTP ${response.status}`);
    }
    if (!response.body) {
      throw new Error("Response body is null");
    }
    return {
      reader: response.body.getReader(),
      decoder: new TextDecoder("utf-8"),
    };
  });

  return {
    stream: fetchPromise,
    cancel: (reason) => {
      if (!controller.signal.aborted) {
        controller.abort(reason);
      }
    },
  };
}

/**
 * 处理流式响应
 * @param {ReadableStreamDefaultReader} reader 读取器
 * @param {TextDecoder} decoder 文本解码器
 * @param {Function} onMessage 消息回调
 * @param {Function} onError 错误回调
 * @param {Function} onComplete 完成回调
 */
export async function processStream(
  reader,
  decoder,
  { onMessage, onError, onComplete }
) {
  let buffer = "";

  try {
    while (true) {
      const { done, value } = await reader.read();
      if (done) break;

      buffer += decoder.decode(value, { stream: true });
      const lines = buffer.split("\n");
      buffer = lines.pop() || "";

      for (const line of lines) {
        if (!line.trim()) continue;

        try {
          const data = JSON.parse(line);
          if (typeof onMessage === "function") {
            onMessage(data);
          }
        } catch (e) {
          console.warn("解析消息失败:", line, e);
        }
      }
    }

    if (typeof onComplete === "function") {
      onComplete();
    }
  } catch (error) {
    if (error.name !== "AbortError" && typeof onError === "function") {
      onError(error);
    }
  } finally {
    reader.releaseLock();
  }
}