import { useCallback, useEffect, useState } from 'react';
import type { Conversation } from '@altricade/core';
import { userChannel } from '@altricade/core';
import { listConversations, createDirect, createGroup } from '@altricade/core/api';
import { apiConfig } from '../../shared/api';
import { useRealtime } from '../realtime';

export interface UseConversations {
  conversations: Conversation[];
  loading: boolean;
  startDirect: (username: string) => Promise<Conversation>;
  createGroupChat: (title: string, members: string[]) => Promise<Conversation>;
}

const isConversationNew = (
  data: unknown,
): data is { type: 'conversation.new'; conversation: Conversation } => {
  if (typeof data !== 'object' || data === null) {
    return false;
  }
  return 'type' in data && data.type === 'conversation.new' && 'conversation' in data;
};

const upsert = (list: Conversation[], conversation: Conversation): Conversation[] => {
  const rest = list.filter((item) => item.id !== conversation.id);
  return [conversation, ...rest];
};

export const useConversations = (userId: string): UseConversations => {
  const { subscribe } = useRealtime();
  const [conversations, setConversations] = useState<Conversation[]>([]);
  const [loading, setLoading] = useState(true);

  useEffect(() => {
    let cancelled = false;
    const load = async (): Promise<void> => {
      try {
        const list = await listConversations(apiConfig);
        if (!cancelled) {
          setConversations(list);
        }
      } finally {
        if (!cancelled) {
          setLoading(false);
        }
      }
    };
    void load();
    return () => {
      cancelled = true;
    };
  }, []);

  // New conversations (a DM someone started with me, or a group I was added to)
  // arrive on my personal channel.
  useEffect(() => {
    return subscribe(userChannel(userId), (event) => {
      if (isConversationNew(event.data)) {
        const { conversation } = event.data;
        setConversations((prev) => upsert(prev, conversation));
      }
    });
  }, [subscribe, userId]);

  const startDirect = useCallback(async (username: string): Promise<Conversation> => {
    const conversation = await createDirect(apiConfig, { username });
    setConversations((prev) => upsert(prev, conversation));
    return conversation;
  }, []);

  const createGroupChat = useCallback(
    async (title: string, members: string[]): Promise<Conversation> => {
      const conversation = await createGroup(apiConfig, { title, members });
      setConversations((prev) => upsert(prev, conversation));
      return conversation;
    },
    [],
  );

  return { conversations, loading, startDirect, createGroupChat };
};