"use client";

import type { UseChatHelpers } from "@ai-sdk/react";
import { useEffect } from "react";
import { useDataStream } from "@/components/chat/data-stream-provider";
import type { ChatMessage } from "@/lib/types";

export type UseAutoResumeParams = {
  autoResume: boolean;
  initialMessages: ChatMessage[];
  resumeStream: UseChatHelpers<ChatMessage>["resumeStream"];
  setMessages: UseChatHelpers<ChatMessage>["setMessages"];
};

export function useAutoResume({
  autoResume,
  initialMessages,
  resumeStream: _resumeStream,
  setMessages,
}: UseAutoResumeParams) {
  const { dataStream } = useDataStream();

  // Stream resumption is disabled because the server does not persist
  // streams or expose a GET /api/chat/:id/stream endpoint.  Calling
  // resumeStream() would hit a 404 in production.
  useEffect(() => {
    if (!autoResume) {
      return;
    }
    // no-op: server does not support stream resumption
  }, [autoResume]);

  useEffect(() => {
    if (!dataStream) {
      return;
    }
    if (dataStream.length === 0) {
      return;
    }

    const dataPart = dataStream[0];

    if (dataPart.type === "data-appendMessage") {
      const message = JSON.parse(dataPart.data);
      setMessages([...initialMessages, message]);
    }
  }, [dataStream, initialMessages, setMessages]);
}