import { useRef, useState, useEffect, useMemo } from 'react';
import Layout from '@/components/layout';
import styles from '@/styles/Home.module.css';
import { Message } from '@/types/chat';
import { fetchEventSource } from '@microsoft/fetch-event-source';
import Image from 'next/image';
import ReactMarkdown from 'react-markdown';
import LoadingDots from '@/components/ui/LoadingDots';

export default function Home() {
  const [query, setQuery] = useState<string>('');
  const [loading, setLoading] = useState<boolean>(false);
  const [messageState, setMessageState] = useState<{
    messages: Message[];
    pending?: string;
    history: [string, string][];
  }>({
    messages: [
      {
        message: 'Hi there its Tom! What would like to learn about notion?',
        type: 'apiMessage',
      },
    ],
    history: [],
  });

  const { messages, pending, history } = messageState;

  const messageListRef = useRef<HTMLDivElement>(null);
  const textAreaRef = useRef<HTMLTextAreaElement>(null);

  useEffect(() => {
    textAreaRef.current?.focus();
  }, []);

  //handle form submission
  async function handleSubmit(e: any) {
    e.preventDefault();

    if (!query) {
      alert('Please input a question');
      return;
    }

    const question = query.trim();

    setMessageState((state) => ({
      ...state,
      messages: [
        ...state.messages,
        {
          type: 'userMessage',
          message: question,
        },
      ],
      pending: undefined,
    }));

    setLoading(true);
    setQuery('');
    setMessageState((state) => ({ ...state, pending: '' }));

    const ctrl = new AbortController();

    try {
      fetchEventSource('/api/chat', {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
        },
        body: JSON.stringify({
          question,
          history,
        }),
        signal: ctrl.signal,
        onmessage: (event) => {
          if (event.data === '[DONE]') {
            setMessageState((state) => ({
              history: [...state.history, [question, state.pending ?? '']],
              messages: [
                ...state.messages,
                {
                  type: 'apiMessage',
                  message: state.pending ?? '',
                },
              ],
              pending: undefined,
            }));
            setLoading(false);
            ctrl.abort();
          } else {
            const data = JSON.parse(event.data);
            setMessageState((state) => ({
              ...state,
              pending: (state.pending ?? '') + data.data,
            }));
          }
        },
      });
    } catch (error) {
      setLoading(false);
      console.log('error', error);
    }
  }

  //prevent empty submissions
  const handleEnter = (e: any) => {
    if (e.key === 'Enter' && query) {
      handleSubmit(e);
    } else if (e.key == 'Enter') {
      e.preventDefault();
    }
  };

  const chatMessages = useMemo(() => {
    return [
      ...messages,
      ...(pending ? [{ type: 'apiMessage', message: pending }] : []),
    ];
  }, [messages, pending]);

  return (
    <>
      <Layout>
        <div className="mx-auto flex flex-col gap-4">
          <h1 className="text-2xl font-bold leading-[1.1] tracking-tighter text-center">
            Thomas Frank Notion Guide ChatBot
          </h1>
          <main className={styles.main}>
            <div className={styles.cloud}>
              <div ref={messageListRef} className={styles.messagelist}>
                {chatMessages.map((message, index) => {
                  let icon;
                  let className;
                  if (message.type === 'apiMessage') {
                    icon = (
                      <Image
                        src="/Thomas-Frank-Avatar.jpg"
                        alt="AI"
                        width="40"
                        height="40"
                        className={styles.boticon}
                        priority
                      />
                    );
                    className = styles.apimessage;
                  } else {
                    icon = (
                      <Image
                        src="/usericon.png"
                        alt="Me"
                        width="30"
                        height="30"
                        className={styles.usericon}
                        priority
                      />
                    );
                    // The latest message sent by the user will be animated while waiting for a response
                    className =
                      loading && index === chatMessages.length - 1
                        ? styles.usermessagewaiting
                        : styles.usermessage;
                  }
                  return (
                    <div key={index} className={className}>
                      {icon}
                      <div className={styles.markdownanswer}>
                        <ReactMarkdown linkTarget="_blank">
                          {message.message}
                        </ReactMarkdown>
                      </div>
                    </div>
                  );
                })}
              </div>
            </div>
            <div className={styles.center}>
              <div className={styles.cloudform}>
                <form onSubmit={handleSubmit}>
                  <textarea
                    disabled={loading}
                    onKeyDown={handleEnter}
                    ref={textAreaRef}
                    autoFocus={false}
                    rows={1}
                    maxLength={512}
                    id="userInput"
                    name="userInput"
                    placeholder={
                      loading
                        ? 'Waiting for response...'
                        : 'How does notion api work?'
                    }
                    value={query}
                    onChange={(e) => setQuery(e.target.value)}
                    className={styles.textarea}
                  />
                  <button
                    type="submit"
                    disabled={loading}
                    className={styles.generatebutton}
                  >
                    {loading ? (
                      <div className={styles.loadingwheel}>
                        <LoadingDots color="#000" />
                      </div>
                    ) : (
                      // Send icon SVG in input field
                      <svg
                        viewBox="0 0 20 20"
                        className={styles.svgicon}
                        xmlns="http://www.w3.org/2000/svg"
                      >
                        <path d="M10.894 2.553a1 1 0 00-1.788 0l-7 14a1 1 0 001.169 1.409l5-1.429A1 1 0 009 15.571V11a1 1 0 112 0v4.571a1 1 0 00.725.962l5 1.428a1 1 0 001.17-1.408l-7-14z"></path>
                      </svg>
                    )}
                  </button>
                </form>
              </div>
            </div>
          </main>
        </div>
        <footer className="m-auto">
          <a href="https://twitter.com/mayowaoshin">
            Powered by LangChain. Demo built by Mayo (Twitter: @mayowaoshin).
          </a>
        </footer>
      </Layout>
    </>
  );
}