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

function Achievement() {
  const [stats, setStats] = useState({
    total_sessions: 0,
    total_focus_time: 0,
    avg_focus_score: 0,
    streak_days: 0
  });
  const [systemStats, setSystemStats] = useState(null);
  const [badges, setBadges] = useState([]);
  const [loading, setLoading] = useState(true);

  // Format total focus time for display.
  const formatTime = (seconds) => {
    const hours = Math.floor(seconds / 3600);
    const minutes = Math.floor((seconds % 3600) / 60);
    if (hours > 0) return `${hours}h ${minutes}m`;
    return `${minutes}m`;
  };

  // Load summary statistics.
  useEffect(() => {
    fetch('/api/stats/summary')
      .then(res => res.json())
      .then(data => {
        setStats(data);
        calculateBadges(data);
        setLoading(false);
      })
      .catch(err => {
        console.error('Failed to load stats:', err);
        setLoading(false);
      });
  }, []);

  // Derive unlocked badges from summary statistics.
  useEffect(() => {
    const fetchSystem = () => {
      fetch('/api/stats/system')
        .then(res => res.json())
        .then(data => setSystemStats(data))
        .catch(() => setSystemStats(null));
    };
    fetchSystem();
    const interval = setInterval(fetchSystem, 3000);
    return () => clearInterval(interval);
  }, []);

  const calculateBadges = (data) => {
    const earnedBadges = [];

    // First-session badge
    if (data.total_sessions >= 1) {
      earnedBadges.push({
        id: 'first-session',
        name: 'First Step',
        description: 'Complete your first focus session',
        icon: '🎯',
        unlocked: true
      });
    }

    // 10-session badge
    if (data.total_sessions >= 10) {
      earnedBadges.push({
        id: 'ten-sessions',
        name: 'Getting Started',
        description: 'Complete 10 focus sessions',
        icon: '⭐',
        unlocked: true
      });
    }

    // 50-session badge
    if (data.total_sessions >= 50) {
      earnedBadges.push({
        id: 'fifty-sessions',
        name: 'Dedicated',
        description: 'Complete 50 focus sessions',
        icon: '🏆',
        unlocked: true
      });
    }

    // Focus Master badge (average focus score > 80%)
    if (data.avg_focus_score >= 0.8 && data.total_sessions >= 5) {
      earnedBadges.push({
        id: 'focus-master',
        name: 'Focus Master',
        description: 'Maintain 80%+ average focus score',
        icon: '🧠',
        unlocked: true
      });
    }

    // Streak badges
    if (data.streak_days >= 7) {
      earnedBadges.push({
        id: 'week-streak',
        name: 'Week Warrior',
        description: '7 day streak',
        icon: '🔥',
        unlocked: true
      });
    }

    if (data.streak_days >= 30) {
      earnedBadges.push({
        id: 'month-streak',
        name: 'Month Master',
        description: '30 day streak',
        icon: '💎',
        unlocked: true
      });
    }

    // Total focus time badge (10+ hours)
    if (data.total_focus_time >= 36000) {
      earnedBadges.push({
        id: 'ten-hours',
        name: 'Endurance',
        description: '10+ hours total focus time',
        icon: '⏱️',
        unlocked: true
      });
    }

    // Full badge catalog, including locked examples
    const allBadges = [
      {
        id: 'first-session',
        name: 'First Step',
        description: 'Complete your first focus session',
        icon: '🎯',
        unlocked: data.total_sessions >= 1
      },
      {
        id: 'ten-sessions',
        name: 'Getting Started',
        description: 'Complete 10 focus sessions',
        icon: '⭐',
        unlocked: data.total_sessions >= 10
      },
      {
        id: 'fifty-sessions',
        name: 'Dedicated',
        description: 'Complete 50 focus sessions',
        icon: '🏆',
        unlocked: data.total_sessions >= 50
      },
      {
        id: 'focus-master',
        name: 'Focus Master',
        description: 'Maintain 80%+ average focus score',
        icon: '🧠',
        unlocked: data.avg_focus_score >= 0.8 && data.total_sessions >= 5
      },
      {
        id: 'week-streak',
        name: 'Week Warrior',
        description: '7 day streak',
        icon: '🔥',
        unlocked: data.streak_days >= 7
      },
      {
        id: 'month-streak',
        name: 'Month Master',
        description: '30 day streak',
        icon: '💎',
        unlocked: data.streak_days >= 30
      },
      {
        id: 'ten-hours',
        name: 'Endurance',
        description: '10+ hours total focus time',
        icon: '⏱️',
        unlocked: data.total_focus_time >= 36000
      },
      {
        id: 'hundred-sessions',
        name: 'Centurion',
        description: 'Complete 100 focus sessions',
        icon: '👑',
        unlocked: data.total_sessions >= 100
      }
    ];

    setBadges(allBadges);
  };

  return (
    <main id="page-c" className="page">
      <h1 className="page-title">My Achievement</h1>

      {loading ? (
        <div style={{ textAlign: 'center', padding: '40px', color: '#888' }}>
          Loading stats...
        </div>
      ) : (
        <>
          {systemStats && systemStats.cpu_percent != null && (
            <div style={{
              textAlign: 'center',
              marginBottom: '12px',
              padding: '8px 12px',
              background: 'rgba(0,0,0,0.2)',
              borderRadius: '8px',
              fontSize: '13px',
              color: '#aaa'
            }}>
              Server: CPU <strong style={{ color: '#8f8' }}>{systemStats.cpu_percent}%</strong>
              {' · '}
              RAM <strong style={{ color: '#8af' }}>{systemStats.memory_percent}%</strong>
              {systemStats.memory_used_mb != null && ` (${systemStats.memory_used_mb}/${systemStats.memory_total_mb} MB)`}
            </div>
          )}
          <div className="stats-grid">
            <div className="stat-card">
              <div className="stat-number" id="total-sessions">{stats.total_sessions}</div>
              <div className="stat-label">Total Sessions</div>
            </div>
            <div className="stat-card">
              <div className="stat-number" id="total-hours">{formatTime(stats.total_focus_time)}</div>
              <div className="stat-label">Total Focus Time</div>
            </div>
            <div className="stat-card">
              <div className="stat-number" id="avg-focus">{(stats.avg_focus_score * 100).toFixed(1)}%</div>
              <div className="stat-label">Average Focus</div>
            </div>
            <div className="stat-card">
              <div className="stat-number" id="current-streak">{stats.streak_days}</div>
              <div className="stat-label">Day Streak</div>
            </div>
          </div>

          <div className="achievements-section">
            <h2>Badges</h2>
            <div id="badges-container" className="badges-grid">
              {badges.map(badge => (
                <div
                  key={badge.id}
                  className={`badge ${badge.unlocked ? 'unlocked' : 'locked'}`}
                  style={{
                    padding: '20px',
                    textAlign: 'center',
                    border: '2px solid',
                    borderColor: badge.unlocked ? '#00FF00' : '#444',
                    borderRadius: '10px',
                    backgroundColor: badge.unlocked ? 'rgba(0, 255, 0, 0.1)' : 'rgba(68, 68, 68, 0.1)',
                    opacity: badge.unlocked ? 1 : 0.5,
                    transition: 'all 0.3s'
                  }}
                >
                  <div style={{ fontSize: '48px', marginBottom: '10px' }}>
                    {badge.unlocked ? badge.icon : '🔒'}
                  </div>
                  <div style={{ fontWeight: 'bold', marginBottom: '5px' }}>
                    {badge.name}
                  </div>
                  <div style={{ fontSize: '12px', color: '#888' }}>
                    {badge.description}
                  </div>
                </div>
              ))}
            </div>
          </div>
        </>
      )}
    </main>
  );
}

export default Achievement;