/**
 * The user a profile page is about comes through this hook, which loads them
 * by the name in the URL and keeps them live. Each tab of the profile loads
 * its own lists, by the user's id.
 *
 * @module
 */

import { useEffect, useState } from "react";

import type { PublicUser } from "../../../shared/user.ts";
import { fetchPublicUser } from "../../utils/shared/fetchPublicUser.ts";
import { useAuth } from "../auth/useAuth.ts";
import { useWS } from "../ws/useWS.ts";
import { type FetchState, useFetchState } from "../shared/useFetchState.ts";

/** Returned by {@link useProfile} to `UserPublicProfile`. */
export interface UseProfileResult {
  state: FetchState<PublicUser>;
  /** It is false while the profile loads. */
  isOwnProfile: boolean;
  /** It shows the header's edits, which the server echoes to other browsers. */
  setUser: (fn: (user: PublicUser) => PublicUser) => void;
}

/**
 * Returns the user named `username`, from `GET /api/users/@:username`, which
 * answers a former name or another case too. The profile then puts the
 * current name in its URL, and that path, naming the user on screen, fetches
 * nothing; another user's does. The socket's `user_updated` keeps them live.
 */
export function useProfile(username: string | undefined): UseProfileResult {
  const { user: me } = useAuth();
  const { lastUserEvent } = useWS();

  // The name last fetched, which the URL may leave for the current one.
  const [target, setTarget] = useState(username);
  const { state, setData } = useFetchState(
    target,
    (signal) => fetchPublicUser(target!, signal),
  );
  const user = state.status === "loaded" ? state.data : null;
  if (
    target !== username &&
    user?.username.toLowerCase() !== username?.toLowerCase()
  ) {
    setTarget(username);
  }

  useEffect(() => {
    if (!lastUserEvent) return;
    setData((u) => u.id === lastUserEvent.user.id ? lastUserEvent.user : u);
  }, [lastUserEvent, setData]);

  return {
    state,
    isOwnProfile: !!me && me.id === user?.id,
    setUser: setData,
  };
}