/**
 * Renders a profile's "follow" tab, which shows the users the user follows at
 * `/@name/follow` and the playlists at `/@name/follow/playlists`.
 *
 * @module
 */

import { useCallback } from "react";
import { useNavigate } from "react-router";
import { Trans } from "@lingui/react/macro";
import { API_URL } from "../../config/api.ts";
import type { Wire } from "../../../shared/api.ts";
import type { Playlist } from "../../../shared/playlist.ts";
import type { PublicUser } from "../../../shared/user.ts";
import { type FollowView, userPath } from "../../../shared/paths.ts";
import { canLoadMore, pageUrl, readPage } from "../../utils/feed/pagedList.ts";
import {
  deserializePlaylist,
  deserializePublicUser,
} from "../../utils/shared/deserialize.ts";
import { usePagedList } from "../../hooks/feed/usePagedList.ts";
import { useInfiniteScroll } from "../../hooks/feed/useInfiniteScroll.ts";
import { usePlaylistListSync } from "../../hooks/playlist/usePlaylistListSync.ts";
import { ListState } from "../shared/ListState.tsx";
import { TabBar } from "../shared/TabBar.tsx";
import { FeedFooter } from "../feed/FeedFooter.tsx";
import { UserCard } from "../social/UserCard.tsx";
import { PlaylistCardList } from "../playlist/PlaylistCardList.tsx";
import { ProfileSection } from "./ProfileSection.tsx";

/** Passed to {@link ProfileFollowTab} by `UserPublicProfile`. */
export interface ProfileFollowTabProps {
  user: PublicUser;
  /** The view the path names, after `/follow`. */
  view: FollowView;
}

/**
 * Returns page after page of what `userId` follows, from
 * `GET /api/users/:userId/follow/<view>`, and the sentinel that loads the
 * next.
 */
function useFollowList<T>(
  userId: string,
  view: FollowView,
  deserialize: (wire: Wire<T>) => T,
) {
  const url = `${API_URL}/api/users/${userId}/follow/${view}`;
  const paged = usePagedList<T>(
    url,
    useCallback(
      (page: number, signal?: AbortSignal) =>
        fetch(pageUrl(url, page), { signal })
          .then((res) => readPage(res, deserialize)),
      [url, deserialize],
    ),
  );
  const loaded = paged.state.status === "loaded" ? paged.state.data : null;
  const sentinelRef = useInfiniteScroll(paged.loadMore, canLoadMore(loaded));
  return { ...paged, sentinelRef };
}

/** Renders the users `userId` follows, the latest followed first. */
function FollowedUsers({ userId }: { userId: string }) {
  const { state, sentinelRef } = useFollowList(
    userId,
    "users",
    deserializePublicUser,
  );
  return (
    <ListState
      state={state}
      isEmpty={({ data }) => data.items.length === 0}
      empty={
        <p className="empty-state">
          <Trans>Not following anyone yet.</Trans>
        </p>
      }
    >
      {({ data }) => (
        <>
          <ul className="user-card-list">
            {data.items.map((u) => <UserCard key={u.id} user={u} />)}
          </ul>
          <FeedFooter
            hasMore={data.hasMore}
            loadingMore={data.loadingMore}
            sentinelRef={sentinelRef}
          />
        </>
      )}
    </ListState>
  );
}

/**
 * Renders the public playlists `userId` follows, which the socket keeps
 * current but never adds to.
 */
function FollowedPlaylists({ userId }: { userId: string }) {
  const { state, setItems, sentinelRef } = useFollowList<Playlist>(
    userId,
    "playlists",
    deserializePlaylist,
  );
  usePlaylistListSync(setItems, { noNewEntries: true });
  return (
    <ListState
      state={state}
      isEmpty={({ data }) => data.items.length === 0}
      empty={
        <p className="empty-state">
          <Trans>No followed playlists yet.</Trans>
        </p>
      }
    >
      {({ data }) => (
        <>
          <PlaylistCardList playlists={data.items} />
          <FeedFooter
            hasMore={data.hasMore}
            loadingMore={data.loadingMore}
            sentinelRef={sentinelRef}
          />
        </>
      )}
    </ListState>
  );
}

/**
 * Renders the two views under a row of tabs that switch between their paths,
 * each view loading its list when first shown.
 */
export function ProfileFollowTab(
  { user, view }: ProfileFollowTabProps,
): React.JSX.Element {
  const navigate = useNavigate();
  return (
    <ProfileSection title={<Trans>Followed</Trans>}>
      <TabBar
        tabs={[
          { key: "users" as FollowView, label: <Trans>Users</Trans> },
          { key: "playlists" as FollowView, label: <Trans>Playlists</Trans> },
        ]}
        activeTab={view}
        onChange={(v) =>
          navigate(userPath(user.username, "follow", v), { replace: true })}
        innerClassName="followed-sub-nav"
      />
      {view === "users"
        ? <FollowedUsers userId={user.id} />
        : <FollowedPlaylists userId={user.id} />}
    </ProfileSection>
  );
}