import {
  ChannelIdentityFragment,
  DmIdentityFragment,
} from 'shared/graphql/__generated__';

import { IChannelItemProps } from './components/channel-item';

// -- TYPES

interface IChannelIdentities<
  T extends ChannelIdentityFragment | DmIdentityFragment = ChannelIdentityFragment
> {
  items: T[];
}

type OriginalItem<T extends ChannelIdentityFragment | DmIdentityFragment> = T & {
  channel: NonNullable<T['channel']> & {
    members: NonNullable<NonNullable<T['channel']>['members']>;
  };
};

type ChannelItem = { id: string; channelIdentityId: string } & Pick<
  IChannelItemProps,
  'name' | 'membersCount' | 'hasUnreads'
>;

// -- UTILS

/**
 * Takes user's channel identities and converts them to fit ChannelItemProps
 * @param channelIdentities - User's channel identities
 */
export function toChannelItemProps<
  T extends ChannelIdentityFragment | DmIdentityFragment
>(
  channelIdentities: IChannelIdentities<T>,
  transform?: (item: ChannelItem, originalItem: OriginalItem<T>) => ChannelItem,
) {
  const result: ChannelItem[] = [];
  const { items } = channelIdentities;

  for (const item of items) {
    const { channel, hasUnreads, id } = item;

    if (!channel || !channel.members || !channel.type) {
      continue;
    }

    const entry = {
      id: channel.id as string,
      name: channel.name as string,
      membersCount: channel.members.count,
      hasUnreads,
      channelIdentityId: id as string,
    };

    result.push(
      typeof transform === 'function' ? transform(entry, item as OriginalItem<T>) : entry,
    );
  }

  return result;
}