"use client";

import { useState, useEffect, useCallback } from 'react';

const MEDALS = ['🥇', '🥈', '🥉'];

export default function Leaderboard({ isOpen, onClose }) {
    const [data, setData] = useState(null);
    const [loading, setLoading] = useState(false);

    const fetchLeaderboard = useCallback(() => {
        setLoading(true);
        fetch(`/api/leaderboard?t=${Date.now()}`) // cache-bust
            .then(res => res.json())
            .then(d => { setData(d); setLoading(false); })
            .catch(() => setLoading(false));
    }, []);

    // Fetch on first open
    useEffect(() => {
        if (isOpen && !data) {
            fetchLeaderboard();
        }
    }, [isOpen, data, fetchLeaderboard]);

    if (!isOpen) return null;

    return (
        <>
            <div className="panel-backdrop" onClick={onClose} />
            <div className="leaderboard-modal">
                <div className="leaderboard-header">
                    <h3>🏆 Annotation Leaderboard</h3>
                    <div className="leaderboard-header-actions">
                        <button
                            className="btn-refresh"
                            onClick={fetchLeaderboard}
                            disabled={loading}
                            title="Refresh"
                        >
                            {loading ? '⏳' : '🔄'}
                        </button>
                        <button className="panel-close" onClick={onClose}>&times;</button>
                    </div>
                </div>

                <div className="leaderboard-body">
                    {loading && !data ? (
                        <div className="leaderboard-loading">
                            <div className="spinner" />
                            <p>Tallying scores...</p>
                        </div>
                    ) : !data?.leaderboard?.length ? (
                        <p className="leaderboard-empty">No annotations yet. Be the first! 🚀</p>
                    ) : (
                        <table className="leaderboard-table">
                            <thead>
                                <tr>
                                    <th>#</th>
                                    <th>Annotator</th>
                                    <th title="Total verifications">✅ Verified</th>
                                    <th title="Manually added mentions">✍️ Added</th>
                                    <th title="Documents worked on">📄 Docs</th>
                                    <th title="Total score">⭐ Score</th>
                                </tr>
                            </thead>
                            <tbody>
                                {data.leaderboard.map((entry, i) => (
                                    <tr key={entry.annotator} className={i < 3 ? `rank-${i + 1}` : ''}>
                                        <td className="rank-cell">
                                            {i < 3 ? MEDALS[i] : i + 1}
                                        </td>
                                        <td className="annotator-cell">
                                            {entry.annotator}
                                        </td>
                                        <td>
                                            <span className="stat-verified">{entry.verified}</span>
                                            {entry.incorrect > 0 && (
                                                <span className="stat-detail"> ({entry.correct}✓ {entry.incorrect}✕)</span>
                                            )}
                                        </td>
                                        <td>{entry.humanAdded}</td>
                                        <td>{entry.docsWorked}</td>
                                        <td className="score-cell">{entry.score}</td>
                                    </tr>
                                ))}
                            </tbody>
                        </table>
                    )}
                </div>

                <div className="leaderboard-footer">
                    <p>Score = Verified + Added</p>
                </div>
            </div>
        </>
    );
}