// Finish → Co-teachers: let other accounts edit this study with you. You make a single-use invite link;
// whoever opens it (signed in) can edit the study, and you can remove them any time. Edits from both of you
// sync through the account; if you both change the same study, "Combine both" keeps everything.
import { useCallback, useEffect, useState } from 'react';
import { createEditInvite, getCollaborators, removeCollaborator } from '../syncService.js';

const btn = 'rounded-xl border border-[var(--r-line)] px-4 py-2 text-sm hover:bg-black/5 disabled:opacity-50';

export default function CoTeachers({ projectId, sharedBy, onLeave }) {
  const [state, setState] = useState({ status: 'loading', collaborators: [], pendingInvites: 0 });
  const [invite, setInvite] = useState(null); // { url, expiresAt }
  const [busy, setBusy] = useState(false);
  const [copied, setCopied] = useState(false);
  const [error, setError] = useState('');

  const load = useCallback(async () => {
    if (!projectId || sharedBy !== undefined) return;
    const r = await getCollaborators(projectId);
    setState(r.ok ? { status: 'ready', ...r.data } : { status: 'unavailable', collaborators: [], pendingInvites: 0 });
  }, [projectId, sharedBy]);
  useEffect(() => { setInvite(null); load(); }, [load]);

  // Someone else's study that you were invited to edit
  if (sharedBy !== undefined) {
    return (
      <section className="rounded-2xl border border-[var(--r-line)] bg-[var(--r-bar)] p-5" aria-label="Co-teachers">
        <h2 className="text-sm font-medium">Shared with you</h2>
        <p className="mb-3 mt-1 text-xs text-[var(--r-sub)]">{sharedBy || 'Its owner'} invited you to edit this study. Your changes sync to them, and theirs to you.</p>
        <button type="button" onClick={onLeave} className={btn}>Leave this study</button>
      </section>
    );
  }

  const makeInvite = async () => {
    setBusy(true); setError('');
    const r = await createEditInvite(projectId);
    setBusy(false);
    if (!r.ok) { setError(r.error ?? 'Could not make the link.'); return; }
    setInvite({ url: `${window.location.origin}${window.location.pathname}?join=${r.data.token}`, expiresAt: r.data.expiresAt });
    load();
  };
  const copy = async () => {
    try { await navigator.clipboard.writeText(invite.url); setCopied(true); window.setTimeout(() => setCopied(false), 1800); } catch { setError('Couldn’t copy. Select the link and copy it.'); }
  };
  const remove = async (userId, email) => {
    if (!window.confirm(`Remove ${email}? They will no longer be able to edit this study.`)) return;
    const r = await removeCollaborator(projectId, userId);
    if (r.ok) load(); else setError(r.error ?? 'Could not remove them.');
  };

  return (
    <section className="rounded-2xl border border-[var(--r-line)] bg-[var(--r-bar)] p-5" aria-label="Co-teachers">
      <h2 className="text-sm font-medium">Co-teachers</h2>
      <p className="mb-3 mt-1 text-xs text-[var(--r-sub)]">Let someone else edit this study with you. They need an account here. Each invite link works once and lasts 7 days.</p>
      {state.status === 'unavailable' && <p className="text-xs text-[var(--r-sub)]">Invites need your account and a connection, and the study has to have synced once. Try again in a moment.</p>}
      {state.status === 'ready' && (
        <>
          {state.collaborators.length > 0 && (
            <ul className="mb-3 divide-y divide-[var(--r-line)] text-sm">
              {state.collaborators.map((c) => (
                <li key={c.userId} className="flex items-center justify-between gap-3 py-2">
                  <span>{c.email}</span>
                  <button type="button" onClick={() => remove(c.userId, c.email)} className="text-xs text-[var(--r-danger,#b42318)] hover:underline">Remove</button>
                </li>
              ))}
            </ul>
          )}
          {invite ? (
            <div className="space-y-2">
              <div className="flex items-center gap-2">
                <input readOnly aria-label="Invite link" value={invite.url} onFocus={(e) => e.target.select()} className="min-w-0 flex-1 truncate rounded-lg border border-[var(--r-line)] bg-[var(--r-bg)] px-3 py-2 text-xs text-[var(--r-sub)]" />
                <button type="button" onClick={copy} className="shrink-0 rounded-lg bg-[var(--r-accent)] px-4 py-2 text-xs font-medium text-[var(--r-on)]">{copied ? 'Copied!' : 'Copy'}</button>
              </div>
              <p className="text-[11px] text-[var(--r-sub)]">Send it to one person. It stops working once they use it, or on {new Date(invite.expiresAt).toLocaleDateString()}.</p>
            </div>
          ) : (
            <button type="button" onClick={makeInvite} disabled={busy} className={btn}>{busy ? 'Making a link…' : 'Invite a co-teacher'}</button>
          )}
          {state.pendingInvites > 0 && !invite && <p className="mt-2 text-[11px] text-[var(--r-sub)]">{state.pendingInvites} invite{state.pendingInvites === 1 ? '' : 's'} waiting to be used.</p>}
        </>
      )}
      {error && <p role="alert" className="mt-2 text-xs text-[var(--r-danger,#b42318)]">{error}</p>}
    </section>
  );
}