flashcards/index.html at main · Louellamatriarchal912/flashcards · GitHub

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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <title>FlashLearn – Flashcard Study App</title>
  <script src="https://unpkg.com/react@18/umd/react.development.js" crossorigin></script>
  <script src="https://unpkg.com/react-dom@18/umd/react-dom.development.js" crossorigin></script>
  <script src="https://unpkg.com/@babel/standalone/babel.min.js"></script>
  <script src="https://cdn.tailwindcss.com"></script>
  <style>
    * { box-sizing: border-box; }
    body { font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif; }
    .flip-card { perspective: 1000px; min-height: 260px; }
    .flip-inner {
      position: relative; width: 100%; min-height: 260px;
      transition: transform 0.55s cubic-bezier(.4,0,.2,1);
      transform-style: preserve-3d;
    }
    .flip-inner.flipped { transform: rotateY(180deg); }
    .flip-face {
      position: absolute; top: 0; left: 0; width: 100%; min-height: 260px;
      backface-visibility: hidden; -webkit-backface-visibility: hidden;
      display: flex; align-items: center; justify-content: center;
    }
    .flip-back { transform: rotateY(180deg); }
    .fade-in { animation: fadeIn .2s ease; }
    @keyframes fadeIn { from { opacity: 0; transform: translateY(6px); } to { opacity: 1; transform: none; } }
    ::-webkit-scrollbar { width: 6px; } ::-webkit-scrollbar-track { background: #f1f5f9; }
    ::-webkit-scrollbar-thumb { background: #cbd5e1; border-radius: 3px; }
  </style>
</head>
<body class="bg-slate-50 min-h-screen">
<div id="root"></div>

<script type="text/babel">
const { useState, useEffect, useCallback, useMemo, useRef } = React;

// ─── Utilities ────────────────────────────────────────────────────────────────
const uid = () => Math.random().toString(36).slice(2) + Date.now().toString(36);
const now = () => new Date().toISOString();
const fmt = (iso) => iso ? new Date(iso).toLocaleDateString() : '—';

// ─── Storage Service ──────────────────────────────────────────────────────────
const storage = {
  getDecks() {
    try { return JSON.parse(localStorage.getItem('fl_decks') || '[]'); } catch { return []; }
  },
  saveDecks(decks) {
    localStorage.setItem('fl_decks', JSON.stringify(decks));
  },
  getCards(deckId) {
    try {
      const all = JSON.parse(localStorage.getItem('fl_cards') || '{}');
      return all[deckId] || [];
    } catch { return []; }
  },
  getAllCards() {
    try { return JSON.parse(localStorage.getItem('fl_cards') || '{}'); } catch { return {}; }
  },
  saveCards(deckId, cards) {
    const all = this.getAllCards();
    all[deckId] = cards;
    localStorage.setItem('fl_cards', JSON.stringify(all));
  },
  deleteCardsByDeck(deckId) {
    const all = this.getAllCards();
    delete all[deckId];
    localStorage.setItem('fl_cards', JSON.stringify(all));
  }
};

// ─── Study Algorithm ──────────────────────────────────────────────────────────
const PRIORITY = { hard: 4, new: 3, medium: 2, easy: 1 };

function getStudyQueue(cards) {
  const scored = cards.map(c => ({
    ...c,
    _priority: PRIORITY[c.difficulty] ?? PRIORITY.new
  }));
  scored.sort((a, b) => b._priority - a._priority || Math.random() - 0.5);
  return scored;
}

// ─── Shared UI helpers ────────────────────────────────────────────────────────
const DIFF_STYLES = {
  new:    'bg-blue-100 text-blue-700',
  easy:   'bg-green-100 text-green-700',
  medium: 'bg-amber-100 text-amber-700',
  hard:   'bg-red-100 text-red-700',
};
const DIFF_LABEL = { new: 'New', easy: 'Easy', medium: 'Medium', hard: 'Hard' };

function Badge({ diff }) {
  return (
    <span className={`text-xs font-medium px-2 py-0.5 rounded-full ${DIFF_STYLES[diff] || DIFF_STYLES.new}`}>
      {DIFF_LABEL[diff] || 'New'}
    </span>
  );
}

function ProgressBar({ value, max, color = 'bg-indigo-500' }) {
  const pct = max === 0 ? 0 : Math.round((value / max) * 100);
  return (
    <div className="w-full bg-slate-200 rounded-full h-2">
      <div className={`${color} h-2 rounded-full transition-all duration-500`} style={{ width: `${pct}%` }} />
    </div>
  );
}

function Modal({ title, onClose, children, wide }) {
  useEffect(() => {
    const handler = (e) => { if (e.key === 'Escape') onClose(); };
    document.addEventListener('keydown', handler);
    return () => document.removeEventListener('keydown', handler);
  }, [onClose]);
  return (
    <div className="fixed inset-0 z-50 flex items-center justify-center p-4 bg-black/40 backdrop-blur-sm" onClick={onClose}>
      <div
        className={`bg-white rounded-2xl shadow-2xl w-full ${wide ? 'max-w-2xl' : 'max-w-md'} fade-in`}
        onClick={e => e.stopPropagation()}
      >
        <div className="flex items-center justify-between px-6 py-4 border-b border-slate-100">
          <h2 className="text-lg font-semibold text-slate-800">{title}</h2>
          <button onClick={onClose} className="p-1.5 rounded-lg hover:bg-slate-100 text-slate-400 hover:text-slate-600 transition-colors">
            <svg className="w-5 h-5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
              <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M6 18L18 6M6 6l12 12" />
            </svg>
          </button>
        </div>
        <div className="px-6 py-5">{children}</div>
      </div>
    </div>
  );
}

function EmptyState({ icon, title, desc }) {
  return (
    <div className="flex flex-col items-center justify-center py-20 text-center">
      <div className="text-5xl mb-4">{icon}</div>
      <h3 className="text-lg font-semibold text-slate-700 mb-1">{title}</h3>
      <p className="text-sm text-slate-400 max-w-xs">{desc}</p>
    </div>
  );
}

// ─── Deck Form Modal ──────────────────────────────────────────────────────────
function DeckFormModal({ deck, onSave, onClose }) {
  const [name, setName] = useState(deck?.name || '');
  const [desc, setDesc] = useState(deck?.description || '');
  const nameRef = useRef(null);
  useEffect(() => { nameRef.current?.focus(); }, []);

  const handleSubmit = (e) => {
    e.preventDefault();
    if (!name.trim()) return;
    onSave({ name: name.trim(), description: desc.trim() });
  };

  return (
    <Modal title={deck ? 'Edit Deck' : 'Create New Deck'} onClose={onClose}>
      <form onSubmit={handleSubmit} className="space-y-4">
        <div>
          <label className="block text-sm font-medium text-slate-700 mb-1">Deck Name <span className="text-red-400">*</span></label>
          <input
            ref={nameRef}
            value={name} onChange={e => setName(e.target.value)}
            placeholder="e.g. Software Metrics Exam"
            className="w-full border border-slate-300 rounded-xl px-3 py-2 text-sm focus:outline-none focus:ring-2 focus:ring-indigo-500 focus:border-transparent"
            maxLength={80}
          />
        </div>
        <div>
          <label className="block text-sm font-medium text-slate-700 mb-1">Description <span className="text-slate-400 font-normal">(optional)</span></label>
          <textarea
            value={desc} onChange={e => setDesc(e.target.value)}
            placeholder="Short description of what this deck covers…"
            rows={3}
            className="w-full border border-slate-300 rounded-xl px-3 py-2 text-sm focus:outline-none focus:ring-2 focus:ring-indigo-500 focus:border-transparent resize-none"
            maxLength={300}
          />
        </div>
        <div className="flex gap-3 pt-1">
          <button type="button" onClick={onClose}
            className="flex-1 px-4 py-2 rounded-xl border border-slate-300 text-sm font-medium text-slate-600 hover:bg-slate-50 transition-colors">
            Cancel
          </button>
          <button type="submit" disabled={!name.trim()}
            className="flex-1 px-4 py-2 rounded-xl bg-indigo-600 text-white text-sm font-medium hover:bg-indigo-700 disabled:opacity-40 disabled:cursor-not-allowed transition-colors">
            {deck ? 'Save Changes' : 'Create Deck'}
          </button>
        </div>
      </form>
    </Modal>
  );
}

// ─── Card Form Modal ──────────────────────────────────────────────────────────
function CardFormModal({ card, onSave, onClose }) {
  const [question, setQuestion] = useState(card?.question || '');
  const [answer, setAnswer] = useState(card?.answer || '');
  const [topic, setTopic] = useState(card?.topic || '');
  const qRef = useRef(null);
  useEffect(() => { qRef.current?.focus(); }, []);

  const handleSubmit = (e) => {
    e.preventDefault();
    if (!question.trim() || !answer.trim()) return;
    onSave({ question: question.trim(), answer: answer.trim(), topic: topic.trim() });
  };

  return (
    <Modal title={card ? 'Edit Flashcard' : 'Add Flashcard'} onClose={onClose} wide>
      <form onSubmit={handleSubmit} className="space-y-4">
        <div>
          <label className="block text-sm font-medium text-slate-700 mb-1">Question <span className="text-red-400">*</span></label>
          <textarea
            ref={qRef}
            value={question} onChange={e => setQuestion(e.target.value)}
            placeholder="Type your question here…"
            rows={3}
            className="w-full border border-slate-300 rounded-xl px-3 py-2 text-sm focus:outline-none focus:ring-2 focus:ring-indigo-500 focus:border-transparent resize-none"
          />
        </div>
        <div>
          <label className="block text-sm font-medium text-slate-700 mb-1">Answer <span className="text-red-400">*</span></label>
          <textarea
            value={answer} onChange={e => setAnswer(e.target.value)}
            placeholder="Type the answer here…"
            rows={4}
            className="w-full border border-slate-300 rounded-xl px-3 py-2 text-sm focus:outline-none focus:ring-2 focus:ring-indigo-500 focus:border-transparent resize-none"
          />
        </div>
        <div>
          <label className="block text-sm font-medium text-slate-700 mb-1">Topic / Category <span className="text-slate-400 font-normal">(optional)</span></label>
          <input
            value={topic} onChange={e => setTopic(e.target.value)}
            placeholder="e.g. Definitions, Formulas…"
            className="w-full border border-slate-300 rounded-xl px-3 py-2 text-sm focus:outline-none focus:ring-2 focus:ring-indigo-500 focus:border-transparent"
            maxLength={60}
          />
        </div>
        <div className="flex gap-3 pt-1">
          <button type="button" onClick={onClose}
            className="flex-1 px-4 py-2 rounded-xl border border-slate-300 text-sm font-medium text-slate-600 hover:bg-slate-50 transition-colors">
            Cancel
          </button>
          <button type="submit" disabled={!question.trim() || !answer.trim()}
            className="flex-1 px-4 py-2 rounded-xl bg-indigo-600 text-white text-sm font-medium hover:bg-indigo-700 disabled:opacity-40 disabled:cursor-not-allowed transition-colors">
            {card ? 'Save Changes' : 'Add Card'}
          </button>
        </div>
      </form>
    </Modal>
  );
}

// ─── Confirm Modal ────────────────────────────────────────────────────────────
function ConfirmModal({ title, message, confirmLabel = 'Delete', onConfirm, onClose }) {
  return (
    <Modal title={title} onClose={onClose}>
      <p className="text-sm text-slate-600 mb-6">{message}</p>
      <div className="flex gap-3">
        <button onClick={onClose}
          className="flex-1 px-4 py-2 rounded-xl border border-slate-300 text-sm font-medium text-slate-600 hover:bg-slate-50 transition-colors">
          Cancel
        </button>
        <button onClick={onConfirm}
          className="flex-1 px-4 py-2 rounded-xl bg-red-600 text-white text-sm font-medium hover:bg-red-700 transition-colors">
          {confirmLabel}
        </button>
      </div>
    </Modal>
  );
}

// ─── Home Screen – Deck List ──────────────────────────────────────────────────
function DeckListScreen({ decks, onSelectDeck, onCreateDeck, onEditDeck, onDeleteDeck, onImport }) {
  const [showCreate, setShowCreate] = useState(false);
  const [showImport, setShowImport] = useState(false);
  const [editTarget, setEditTarget] = useState(null);
  const [deleteTarget, setDeleteTarget] = useState(null);
  const [search, setSearch] = useState('');

  const filtered = useMemo(() =>
    decks.filter(d => d.name.toLowerCase().includes(search.toLowerCase()) ||
      d.description?.toLowerCase().includes(search.toLowerCase())),
    [decks, search]
  );

  const getDeckStats = (deckId) => {
    const cards = storage.getCards(deckId);
    const total = cards.length;
    const reviewed = cards.filter(c => c.timesReviewed > 0).length;
    const byDiff = { easy: 0, medium: 0, hard: 0, new: 0 };
    cards.forEach(c => { byDiff[c.difficulty] = (byDiff[c.difficulty] || 0) + 1; });
    return { total, reviewed, ...byDiff };
  };

  return (
    <div className="max-w-3xl mx-auto px-4 py-8 fade-in">
      {/* Header */}
      <div className="flex items-center justify-between mb-8">
        <div>
          <h1 className="text-2xl font-bold text-slate-800 flex items-center gap-2">
            <span className="text-3xl">🧠</span> FlashLearn
          </h1>
          <p className="text-sm text-slate-500 mt-0.5">Your personal flashcard study app</p>
        </div>
        <div className="flex items-center gap-2">
          <button onClick={() => setShowImport(true)}
            className="flex items-center gap-2 px-4 py-2 border border-slate-300 text-slate-600 text-sm font-medium rounded-xl hover:bg-slate-50 transition-colors">
            <svg className="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
              <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M4 16v1a3 3 0 003 3h10a3 3 0 003-3v-1m-4-8l-4-4m0 0L8 8m4-4v12" />
            </svg>
            Import
          </button>
          <button onClick={() => setShowCreate(true)}
            className="flex items-center gap-2 px-4 py-2 bg-indigo-600 text-white text-sm font-medium rounded-xl hover:bg-indigo-700 transition-colors shadow-sm">
            <svg className="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
              <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M12 4v16m8-8H4" />
            </svg>
            New Deck
          </button>
        </div>
      </div>

      {/* Search */}
      {decks.length > 0 && (
        <div className="relative mb-6">
          <svg className="absolute left-3 top-1/2 -translate-y-1/2 w-4 h-4 text-slate-400" fill="none" stroke="currentColor" viewBox="0 0 24 24">
            <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M21 21l-6-6m2-5a7 7 0 11-14 0 7 7 0 0114 0z" />
          </svg>
          <input value={search} onChange={e => setSearch(e.target.value)}
            placeholder="Search decks…"
            className="w-full pl-9 pr-4 py-2 border border-slate-200 rounded-xl text-sm bg-white focus:outline-none focus:ring-2 focus:ring-indigo-400"
          />
        </div>
      )}

      {/* Deck Grid */}
      {decks.length === 0 ? (
        <EmptyState icon="📚" title="No decks yet" desc="Create your first deck to start adding flashcards and studying." />
      ) : filtered.length === 0 ? (
        <EmptyState icon="🔍" title="No decks found" desc="Try a different search term." />
      ) : (
        <div className="grid gap-4">
          {filtered.map(deck => {
            const stats = getDeckStats(deck.id);
            const pct = stats.total === 0 ? 0 : Math.round((stats.reviewed / stats.total) * 100);
            return (
              <div key={deck.id}
                className="bg-white rounded-2xl border border-slate-200 p-5 hover:shadow-md hover:border-indigo-200 transition-all cursor-pointer group"
                onClick={() => onSelectDeck(deck.id)}
              >
                <div className="flex items-start justify-between mb-3">
                  <div className="flex-1 min-w-0 pr-4">
                    <h2 className="font-semibold text-slate-800 truncate text-lg group-hover:text-indigo-700 transition-colors">{deck.name}</h2>
                    {deck.description && (
                      <p className="text-sm text-slate-500 mt-0.5 truncate">{deck.description}</p>
                    )}
                    <p className="text-xs text-slate-400 mt-1">Created {fmt(deck.createdAt)}</p>
                  </div>
                  <div className="flex items-center gap-1 shrink-0" onClick={e => e.stopPropagation()}>
                    <button onClick={() => setEditTarget(deck)}
                      className="p-1.5 rounded-lg hover:bg-slate-100 text-slate-400 hover:text-slate-600 transition-colors">
                      <svg className="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
                        <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M15.232 5.232l3.536 3.536m-2.036-5.036a2.5 2.5 0 113.536 3.536L6.5 21.036H3v-3.572L16.732 3.732z" />
                      </svg>
                    </button>
                    <button onClick={() => setDeleteTarget(deck)}
                      className="p-1.5 rounded-lg hover:bg-red-50 text-slate-400 hover:text-red-500 transition-colors">
                      <svg className="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
                        <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M19 7l-.867 12.142A2 2 0 0116.138 21H7.862a2 2 0 01-1.995-1.858L5 7m5 4v6m4-6v6m1-10V4a1 1 0 00-1-1h-4a1 1 0 00-1 1v3M4 7h16" />
                      </svg>
                    </button>
                  </div>
                </div>

                {/* Stats row */}
                <div className="flex items-center gap-4 text-xs text-slate-500 mb-3">
                  <span className="font-medium">{stats.total} card{stats.total !== 1 ? 's' : ''}</span>
                  {stats.hard > 0 && <span className="text-red-500 font-medium">🔴 {stats.hard} hard</span>}
                  {stats.medium > 0 && <span className="text-amber-500 font-medium">🟡 {stats.medium} medium</span>}
                  {stats.easy > 0 && <span className="text-green-500 font-medium">🟢 {stats.easy} easy</span>}
                  {stats.new > 0 && <span className="text-blue-500 font-medium">🔵 {stats.new} new</span>}
                </div>

                {/* Progress */}
                {stats.total > 0 && (
                  <div>
                    <div className="flex justify-between text-xs text-slate-400 mb-1">
                      <span>Progress</span>
                      <span>{pct}% reviewed</span>
                    </div>
                    <ProgressBar value={stats.reviewed} max={stats.total} />
                  </div>
                )}
              </div>
            );
          })}
        </div>
      )}

      {/* Modals */}
      {showImport && (
        <ImportModal
          existingDeckNames={decks.map(d => d.name)}
          onImport={(data) => { onImport(data); setShowImport(false); }}
          onClose={() => setShowImport(false)}
        />
      )}
      {showCreate && (
        <DeckFormModal
          onSave={(data) => { onCreateDeck(data); setShowCreate(false); }}
          onClose={() => setShowCreate(false)}
        />
      )}
      {editTarget && (
        <DeckFormModal
          deck={editTarget}
          onSave={(data) => { onEditDeck(editTarget.id, data); setEditTarget(null); }}
          onClose={() => setEditTarget(null)}
        />
      )}
      {deleteTarget && (
        <ConfirmModal
          title="Delete Deck"
          message={`Are you sure you want to delete "${deleteTarget.name}" and all its cards? This cannot be undone.`}
          onConfirm={() => { onDeleteDeck(deleteTarget.id); setDeleteTarget(null); }}
          onClose={() => setDeleteTarget(null)}
        />
      )}
    </div>
  );
}

// ─── Import Modal ─────────────────────────────────────────────────────────────
function ImportModal({ existingDeckNames, onImport, onClose }) {
  const [text, setText] = useState('');
  const [error, setError] = useState('');
  const [preview, setPreview] = useState(null);
  const fileRef = useRef(null);

  const parse = (raw) => {
    const data = JSON.parse(raw);
    if (!Array.isArray(data)) throw new Error('JSON must be an array of deck objects.');
    data.forEach((d, i) => {
      if (!d.deckName) throw new Error(`Item ${i + 1} is missing "deckName".`);
      if (!Array.isArray(d.cards)) throw new Error(`Deck "${d.deckName}" is missing "cards" array.`);
      d.cards.forEach((c, j) => {
        if (!c.question || !c.answer) throw new Error(`Card ${j + 1} in "${d.deckName}" is missing "question" or "answer".`);
      });
    });
    return data;
  };

  const handleText = (val) => {
    setText(val);
    setError('');
    setPreview(null);
    if (!val.trim()) return;
    try { setPreview(parse(val)); }
    catch (e) { setError(e.message); }
  };

  const handleFile = (e) => {
    const file = e.target.files?.[0];
    if (!file) return;
    const reader = new FileReader();
    reader.onload = (ev) => handleText(ev.target.result);
    reader.readAsText(file);
  };

  const duplicates = preview ? preview.filter(d => existingDeckNames.includes(d.deckName)) : [];
  const totalCards = preview ? preview.reduce((sum, d) => sum + d.cards.length, 0) : 0;

  return (
    <Modal title="Import Decks from JSON" onClose={onClose} wide>
      <div className="space-y-4">
        {/* File upload */}
        <div>
          <p className="text-sm font-medium text-slate-700 mb-2">Upload a JSON file</p>
          <label className="flex items-center gap-3 cursor-pointer border-2 border-dashed border-slate-300 hover:border-indigo-400 rounded-xl px-4 py-3 transition-colors group">
            <svg className="w-5 h-5 text-slate-400 group-hover:text-indigo-500 shrink-0" fill="none" stroke="currentColor" viewBox="0 0 24 24">
              <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M4 16v1a3 3 0 003 3h10a3 3 0 003-3v-1m-4-8l-4-4m0 0L8 8m4-4v12" />
            </svg>
            <span className="text-sm text-slate-500 group-hover:text-indigo-600">
              {fileRef.current?.files?.[0]?.name || 'Click to choose a .json file'}
            </span>
            <input ref={fileRef} type="file" accept=".json,application/json" className="sr-only" onChange={handleFile} />
          </label>
        </div>

        <div className="flex items-center gap-3">
          <hr className="flex-1 border-slate-200" />
          <span className="text-xs text-slate-400 font-medium">or paste JSON</span>
          <hr className="flex-1 border-slate-200" />
        </div>

        {/* Textarea */}
        <div>
          <textarea
            value={text}
            onChange={e => handleText(e.target.value)}
            placeholder={'[\n  {\n    "deckName": "My Deck",\n    "deckDescription": "...",\n    "cards": [\n      { "question": "...", "answer": "...", "topic": "..." }\n    ]\n  }\n]'}
            rows={7}
            className="w-full border border-slate-300 rounded-xl px-3 py-2 text-xs font-mono focus:outline-none focus:ring-2 focus:ring-indigo-500 focus:border-transparent resize-none"
          />
        </div>

        {/* Error */}
        {error && (
          <div className="flex items-start gap-2 bg-red-50 border border-red-200 rounded-xl px-3 py-2.5">
            <svg className="w-4 h-4 text-red-500 shrink-0 mt-0.5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
              <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M12 8v4m0 4h.01M21 12a9 9 0 11-18 0 9 9 0 0118 0z" />
            </svg>
            <p className="text-xs text-red-700">{error}</p>
          </div>
        )}

        {/* Preview */}
        {preview && (
          <div className="bg-slate-50 border border-slate-200 rounded-xl p-4 space-y-3">
            <div className="flex items-center justify-between">
              <p className="text-sm font-semibold text-slate-700">Ready to import</p>
              <span className="text-xs bg-indigo-100 text-indigo-700 px-2 py-0.5 rounded-full font-medium">
                {preview.length} deck{preview.length !== 1 ? 's' : ''} · {totalCards} cards
              </span>
            </div>
            <div className="space-y-1.5 max-h-44 overflow-y-auto pr-1">
              {preview.map((d, i) => {
                const isDup = existingDeckNames.includes(d.deckName);
                return (
                  <div key={i} className="flex items-center justify-between bg-white rounded-lg border border-slate-200 px-3 py-2">
                    <div className="flex items-center gap-2 min-w-0">
                      <span className="text-sm font-medium text-slate-700 truncate">{d.deckName}</span>
                      {isDup && (
                        <span className="text-xs bg-amber-100 text-amber-700 px-1.5 py-0.5 rounded-full shrink-0">duplicate name</span>
                      )}
                    </div>
                    <span className="text-xs text-slate-400 shrink-0 ml-2">{d.cards.length} cards</span>
                  </div>
                );
              })}
            </div>
            {duplicates.length > 0 && (
              <p className="text-xs text-amber-600">
                ⚠ {duplicates.length} deck{duplicates.length !== 1 ? 's' : ''} with the same name already exist — they will be imported as separate decks.
              </p>
            )}
          </div>
        )}

        <div className="flex gap-3 pt-1">
          <button type="button" onClick={onClose}
            className="flex-1 px-4 py-2 rounded-xl border border-slate-300 text-sm font-medium text-slate-600 hover:bg-slate-50 transition-colors">
            Cancel
          </button>
          <button onClick={() => onImport(preview)} disabled={!preview}
            className="flex-1 px-4 py-2 rounded-xl bg-indigo-600 text-white text-sm font-medium hover:bg-indigo-700 disabled:opacity-40 disabled:cursor-not-allowed transition-colors flex items-center justify-center gap-2">
            <svg className="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
              <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M4 16v1a3 3 0 003 3h10a3 3 0 003-3v-1m-4-8l-4-4m0 0L8 8m4-4v12" />
            </svg>
            Import {preview ? `${preview.length} Deck${preview.length !== 1 ? 's' : ''}` : ''}
          </button>
        </div>
      </div>
    </Modal>
  );
}

// ─── Deck Detail Screen ────────────────────────────────────────────────────────
function DeckDetailScreen({ deck, onBack, onStartStudy, onViewProgress }) {
  const [cards, setCards] = useState(() => storage.getCards(deck.id));
  const [showAdd, setShowAdd] = useState(false);
  const [editCard, setEditCard] = useState(null);
  const [deleteCard, setDeleteCard] = useState(null);
  const [search, setSearch] = useState('');
  const [filterDiff, setFilterDiff] = useState('all');
  const [filterTopic, setFilterTopic] = useState('all');

  const reload = () => setCards(storage.getCards(deck.id));

  const addCard = (data) => {
    const newCard = {
      id: uid(), deckId: deck.id,
      question: data.question, answer: data.answer, topic: data.topic,
      difficulty: 'new', timesReviewed: 0, lastReviewedAt: null,
      createdAt: now()
    };
    const updated = [...cards, newCard];
    storage.saveCards(deck.id, updated);
    setCards(updated);
    setShowAdd(false);
  };

  const updateCard = (id, data) => {
    const updated = cards.map(c => c.id === id ? { ...c, ...data } : c);
    storage.saveCards(deck.id, updated);
    setCards(updated);
    setEditCard(null);
  };

  const removeCard = (id) => {
    const updated = cards.filter(c => c.id !== id);
    storage.saveCards(deck.id, updated);
    setCards(updated);
    setDeleteCard(null);
  };

  const topics = useMemo(() => ['all', ...new Set(cards.map(c => c.topic).filter(Boolean))], [cards]);

  const filtered = useMemo(() => cards.filter(c => {
    const matchSearch = !search || c.question.toLowerCase().includes(search.toLowerCase()) ||
      c.answer.toLowerCase().includes(search.toLowerCase()) ||
      c.topic?.toLowerCase().includes(search.toLowerCase());
    const matchDiff = filterDiff === 'all' || c.difficulty === filterDiff;
    const matchTopic = filterTopic === 'all' || c.topic === filterTopic;
    return matchSearch && matchDiff && matchTopic;
  }), [cards, search, filterDiff, filterTopic]);

  const stats = useMemo(() => {
    const reviewed = cards.filter(c => c.timesReviewed > 0).length;
    const byDiff = { easy: 0, medium: 0, hard: 0, new: 0 };
    cards.forEach(c => { byDiff[c.difficulty] = (byDiff[c.difficulty] || 0) + 1; });
    return { total: cards.length, reviewed, ...byDiff };
  }, [cards]);

  return (
    <div className="max-w-3xl mx-auto px-4 py-8 fade-in">
      {/* Header */}
      <div className="flex items-center gap-3 mb-6">
        <button onClick={onBack}
          className="p-2 rounded-xl hover:bg-slate-200 text-slate-500 transition-colors">
          <svg className="w-5 h-5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
            <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M15 19l-7-7 7-7" />
          </svg>
        </button>
        <div className="flex-1 min-w-0">
          <h1 className="text-xl font-bold text-slate-800 truncate">{deck.name}</h1>
          {deck.description && <p className="text-sm text-slate-500 truncate">{deck.description}</p>}
        </div>
      </div>

      {/* Stats summary */}
      <div className="grid grid-cols-4 gap-3 mb-6">
        {[
          { label: 'Total', value: stats.total, color: 'text-slate-700', bg: 'bg-slate-50' },
          { label: 'Hard', value: stats.hard, color: 'text-red-600', bg: 'bg-red-50' },
          { label: 'Medium', value: stats.medium, color: 'text-amber-600', bg: 'bg-amber-50' },
          { label: 'Easy', value: stats.easy, color: 'text-green-600', bg: 'bg-green-50' },
        ].map(s => (
          <div key={s.label} className={`${s.bg} rounded-xl p-3 text-center`}>
            <div className={`text-2xl font-bold ${s.color}`}>{s.value}</div>
            <div className="text-xs text-slate-500 mt-0.5">{s.label}</div>
          </div>
        ))}
      </div>

      {/* Action buttons */}
      <div className="flex gap-3 mb-6">
        <button onClick={() => onStartStudy(deck.id)}
          disabled={cards.length === 0}
          className="flex-1 flex items-center justify-center gap-2 py-2.5 bg-indigo-600 text-white rounded-xl font-medium text-sm hover:bg-indigo-700 disabled:opacity-40 disabled:cursor-not-allowed transition-colors shadow-sm">
          <svg className="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
            <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M14.752 11.168l-3.197-2.132A1 1 0 0010 9.87v4.263a1 1 0 001.555.832l3.197-2.132a1 1 0 000-1.664z" />
            <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M21 12a9 9 0 11-18 0 9 9 0 0118 0z" />
          </svg>
          Study Now
        </button>
        <button onClick={() => onViewProgress(deck.id)}
          disabled={stats.reviewed === 0}
          className="flex items-center justify-center gap-2 px-4 py-2.5 border border-slate-300 text-slate-600 rounded-xl font-medium text-sm hover:bg-slate-50 disabled:opacity-40 disabled:cursor-not-allowed transition-colors">
          <svg className="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
            <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M9 19v-6a2 2 0 00-2-2H5a2 2 0 00-2 2v6a2 2 0 002 2h2a2 2 0 002-2zm0 0V9a2 2 0 012-2h2a2 2 0 012 2v10m-6 0a2 2 0 002 2h2a2 2 0 002-2m0 0V5a2 2 0 012-2h2a2 2 0 012 2v14a2 2 0 01-2 2h-2a2 2 0 01-2-2z" />
          </svg>
          Progress
        </button>
        <button onClick={() => setShowAdd(true)}
          className="flex items-center justify-center gap-2 px-4 py-2.5 border border-indigo-300 text-indigo-600 rounded-xl font-medium text-sm hover:bg-indigo-50 transition-colors">
          <svg className="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
            <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M12 4v16m8-8H4" />
          </svg>
          Add Card
        </button>
      </div>

      {/* Filters */}
      {cards.length > 0 && (
        <div className="flex flex-wrap gap-2 mb-4">
          <div className="relative flex-1 min-w-48">
            <svg className="absolute left-3 top-1/2 -translate-y-1/2 w-3.5 h-3.5 text-slate-400" fill="none" stroke="currentColor" viewBox="0 0 24 24">
              <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M21 21l-6-6m2-5a7 7 0 11-14 0 7 7 0 0114 0z" />
            </svg>
            <input value={search} onChange={e => setSearch(e.target.value)}
              placeholder="Search cards…"
              className="w-full pl-8 pr-3 py-1.5 border border-slate-200 rounded-lg text-sm bg-white focus:outline-none focus:ring-2 focus:ring-indigo-400"
            />
          </div>
          <select value={filterDiff} onChange={e => setFilterDiff(e.target.value)}
            className="border border-slate-200 rounded-lg text-sm px-3 py-1.5 bg-white focus:outline-none focus:ring-2 focus:ring-indigo-400">
            <option value="all">All Difficulties</option>
            <option value="new">New</option>
            <option value="easy">Easy</option>
            <option value="medium">Medium</option>
            <option value="hard">Hard</option>
          </select>
          {topics.length > 1 && (
            <select value={filterTopic} onChange={e => setFilterTopic(e.target.value)}
              className="border border-slate-200 rounded-lg text-sm px-3 py-1.5 bg-white focus:outline-none focus:ring-2 focus:ring-indigo-400">
              <option value="all">All Topics</option>
              {topics.slice(1).map(t => <option key={t} value={t}>{t}</option>)}
            </select>
          )}
        </div>
      )}

      {/* Card list */}
      {cards.length === 0 ? (
        <EmptyState icon="🃏" title="No cards yet" desc='Click "Add Card" to start building your flashcard deck.' />
      ) : filtered.length === 0 ? (
        <EmptyState icon="🔍" title="No cards match your filters" desc="Try adjusting your search or filters." />
      ) : (
        <div className="space-y-3">
          {filtered.map(card => (
            <div key={card.id}
              className="bg-white rounded-xl border border-slate-200 p-4 hover:shadow-sm transition-shadow">
              <div className="flex items-start justify-between gap-3">
                <div className="flex-1 min-w-0">
                  <p className="text-sm font-medium text-slate-800 line-clamp-2">{card.question}</p>
                  <p className="text-sm text-slate-500 mt-1 line-clamp-2">{card.answer}</p>
                  <div className="flex items-center gap-2 mt-2 flex-wrap">
                    <Badge diff={card.difficulty} />
                    {card.topic && (
                      <span className="text-xs bg-slate-100 text-slate-600 px-2 py-0.5 rounded-full">{card.topic}</span>
                    )}
                    {card.timesReviewed > 0 && (
                      <span className="text-xs text-slate-400">Reviewed {card.timesReviewed}×</span>
                    )}
                  </div>
                </div>
                <div className="flex items-center gap-1 shrink-0">
                  <button onClick={() => setEditCard(card)}
                    className="p-1.5 rounded-lg hover:bg-slate-100 text-slate-400 hover:text-slate-600 transition-colors">
                    <svg className="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
                      <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M15.232 5.232l3.536 3.536m-2.036-5.036a2.5 2.5 0 113.536 3.536L6.5 21.036H3v-3.572L16.732 3.732z" />
                    </svg>
                  </button>
                  <button onClick={() => setDeleteCard(card)}
                    className="p-1.5 rounded-lg hover:bg-red-50 text-slate-400 hover:text-red-500 transition-colors">
                    <svg className="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
                      <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M19 7l-.867 12.142A2 2 0 0116.138 21H7.862a2 2 0 01-1.995-1.858L5 7m5 4v6m4-6v6m1-10V4a1 1 0 00-1-1h-4a1 1 0 00-1 1v3M4 7h16" />
                    </svg>
                  </button>
                </div>
              </div>
            </div>
          ))}
        </div>
      )}

      {/* Modals */}
      {showAdd && <CardFormModal onSave={addCard} onClose={() => setShowAdd(false)} />}
      {editCard && (
        <CardFormModal
          card={editCard}
          onSave={(data) => updateCard(editCard.id, data)}
          onClose={() => setEditCard(null)}
        />
      )}
      {deleteCard && (
        <ConfirmModal
          title="Delete Card"
          message={`Delete this card? "${deleteCard.question.slice(0, 60)}${deleteCard.question.length > 60 ? '…' : ''}"`}
          onConfirm={() => removeCard(deleteCard.id)}
          onClose={() => setDeleteCard(null)}
        />
      )}
    </div>
  );
}

// ─── Study Mode Screen ────────────────────────────────────────────────────────
function StudyModeScreen({ deck, onFinish }) {
  const [queue, setQueue] = useState(() => getStudyQueue(storage.getCards(deck.id)));
  const [index, setIndex] = useState(0);
  const [revealed, setRevealed] = useState(false);
  const [sessionStats, setSessionStats] = useState({ easy: 0, medium: 0, hard: 0 });
  const [done, setDone] = useState(false);
  const [flipped, setFlipped] = useState(false);

  const total = queue.length;
  const card = queue[index];

  const revealAnswer = () => {
    setFlipped(true);
    setTimeout(() => setRevealed(true), 280);
  };

  const rate = (diff) => {
    // Update card in storage
    const allCards = storage.getCards(deck.id);
    const updated = allCards.map(c =>
      c.id === card.id
        ? { ...c, difficulty: diff, timesReviewed: c.timesReviewed + 1, lastReviewedAt: now() }
        : c
    );
    storage.saveCards(deck.id, updated);

    setSessionStats(s => ({ ...s, [diff]: s[diff] + 1 }));

    if (index + 1 >= total) {
      setDone(true);
    } else {
      setFlipped(false);
      setRevealed(false);
      setTimeout(() => setIndex(i => i + 1), 50);
    }
  };

  if (done) {
    const reviewed = sessionStats.easy + sessionStats.medium + sessionStats.hard;
    return (
      <div className="max-w-lg mx-auto px-4 py-16 text-center fade-in">
        <div className="text-6xl mb-4">🎉</div>
        <h1 className="text-2xl font-bold text-slate-800 mb-2">Session Complete!</h1>
        <p className="text-slate-500 mb-8">You reviewed {reviewed} card{reviewed !== 1 ? 's' : ''} from <strong>{deck.name}</strong>.</p>

        <div className="grid grid-cols-3 gap-4 mb-8">
          <div className="bg-green-50 rounded-2xl p-4">
            <div className="text-3xl font-bold text-green-600">{sessionStats.easy}</div>
            <div className="text-xs text-green-700 mt-1 font-medium">Easy</div>
          </div>
          <div className="bg-amber-50 rounded-2xl p-4">
            <div className="text-3xl font-bold text-amber-600">{sessionStats.medium}</div>
            <div className="text-xs text-amber-700 mt-1 font-medium">Medium</div>
          </div>
          <div className="bg-red-50 rounded-2xl p-4">
            <div className="text-3xl font-bold text-red-600">{sessionStats.hard}</div>
            <div className="text-xs text-red-700 mt-1 font-medium">Hard</div>
          </div>
        </div>

        <div className="flex gap-3 justify-center">
          <button onClick={onFinish}
            className="px-6 py-2.5 border border-slate-300 rounded-xl text-sm font-medium text-slate-600 hover:bg-slate-50 transition-colors">
            Back to Deck
          </button>
          <button onClick={() => {
            const fresh = getStudyQueue(storage.getCards(deck.id));
            setQueue(fresh);
            setIndex(0);
            setRevealed(false);
            setFlipped(false);
            setSessionStats({ easy: 0, medium: 0, hard: 0 });
            setDone(false);
          }}
            className="px-6 py-2.5 bg-indigo-600 text-white rounded-xl text-sm font-medium hover:bg-indigo-700 transition-colors">
            Study Again
          </button>
        </div>
      </div>
    );
  }

  return (
    <div className="max-w-xl mx-auto px-4 py-8 fade-in">
      {/* Header */}
      <div className="flex items-center gap-3 mb-6">
        <button onClick={onFinish}
          className="p-2 rounded-xl hover:bg-slate-200 text-slate-500 transition-colors">
          <svg className="w-5 h-5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
            <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M15 19l-7-7 7-7" />
          </svg>
        </button>
        <div className="flex-1">
          <div className="flex justify-between text-xs text-slate-500 mb-1.5">
            <span>{deck.name}</span>
            <span>{index + 1} / {total}</span>
          </div>
          <ProgressBar value={index} max={total} />
        </div>
      </div>

      {/* Session stats bar */}
      <div className="flex justify-center gap-4 text-xs mb-6">
        <span className="text-green-600 font-medium">✔ {sessionStats.easy} easy</span>
        <span className="text-amber-600 font-medium">~ {sessionStats.medium} medium</span>
        <span className="text-red-600 font-medium">✗ {sessionStats.hard} hard</span>
      </div>

      {/* Flip Card */}
      <div className="flip-card mb-6">
        <div className={`flip-inner ${flipped ? 'flipped' : ''}`}>
          {/* Front – Question */}
          <div className="flip-face bg-white rounded-2xl border-2 border-indigo-200 shadow-lg p-8 flex flex-col items-center justify-center min-h-64">
            <div className="text-xs font-semibold text-indigo-400 uppercase tracking-wider mb-4">Question</div>
            {card?.topic && (
              <span className="text-xs bg-slate-100 text-slate-600 px-2 py-0.5 rounded-full mb-3">{card.topic}</span>
            )}
            <p className="text-lg font-medium text-slate-800 text-center leading-relaxed">{card?.question}</p>
            <div className="mt-4">
              <Badge diff={card?.difficulty || 'new'} />
            </div>
          </div>

          {/* Back – Answer */}
          <div className="flip-face flip-back bg-indigo-600 rounded-2xl shadow-lg p-8 flex flex-col items-center justify-center min-h-64">
            <div className="text-xs font-semibold text-indigo-200 uppercase tracking-wider mb-4">Answer</div>
            <p className="text-lg font-medium text-white text-center leading-relaxed">{card?.answer}</p>
          </div>
        </div>
      </div>

      {/* Actions */}
      {!revealed ? (
        <button onClick={revealAnswer}
          className="w-full py-3 bg-indigo-600 text-white font-medium rounded-xl hover:bg-indigo-700 transition-colors shadow-sm text-sm">
          Reveal Answer
        </button>
      ) : (
        <div className="space-y-3">
          <p className="text-center text-sm text-slate-500 font-medium">How well did you remember it?</p>
          <div className="grid grid-cols-3 gap-3">
            <button onClick={() => rate('hard')}
              className="py-3 bg-red-50 border-2 border-red-200 text-red-700 font-semibold rounded-xl hover:bg-red-100 hover:border-red-400 transition-all text-sm">
              <div className="text-lg mb-0.5">😰</div>
              Hard
            </button>
            <button onClick={() => rate('medium')}
              className="py-3 bg-amber-50 border-2 border-amber-200 text-amber-700 font-semibold rounded-xl hover:bg-amber-100 hover:border-amber-400 transition-all text-sm">
              <div className="text-lg mb-0.5">🤔</div>
              Medium
            </button>
            <button onClick={() => rate('easy')}
              className="py-3 bg-green-50 border-2 border-green-200 text-green-700 font-semibold rounded-xl hover:bg-green-100 hover:border-green-400 transition-all text-sm">
              <div className="text-lg mb-0.5">😊</div>
              Easy
            </button>
          </div>
        </div>
      )}
    </div>
  );
}

// ─── Progress Summary Screen ───────────────────────────────────────────────────
function ProgressScreen({ deck, onBack }) {
  const cards = storage.getCards(deck.id);
  const total = cards.length;
  const reviewed = cards.filter(c => c.timesReviewed > 0).length;
  const byDiff = { easy: 0, medium: 0, hard: 0, new: 0 };
  cards.forEach(c => { byDiff[c.difficulty] = (byDiff[c.difficulty] || 0) + 1; });
  const pct = total === 0 ? 0 : Math.round((reviewed / total) * 100);

  const topics = {};
  cards.forEach(c => {
    const t = c.topic || 'Uncategorized';
    if (!topics[t]) topics[t] = { easy: 0, medium: 0, hard: 0, new: 0 };
    topics[t][c.difficulty]++;
  });

  const totalReviews = cards.reduce((sum, c) => sum + c.timesReviewed, 0);

  return (
    <div className="max-w-2xl mx-auto px-4 py-8 fade-in">
      <div className="flex items-center gap-3 mb-8">
        <button onClick={onBack}
          className="p-2 rounded-xl hover:bg-slate-200 text-slate-500 transition-colors">
          <svg className="w-5 h-5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
            <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M15 19l-7-7 7-7" />
          </svg>
        </button>
        <div>
          <h1 className="text-xl font-bold text-slate-800">Progress – {deck.name}</h1>
          <p className="text-sm text-slate-500">Your study statistics</p>
        </div>
      </div>

      {/* Overall progress */}
      <div className="bg-white rounded-2xl border border-slate-200 p-6 mb-5">
        <h2 className="font-semibold text-slate-700 mb-4">Overall Progress</h2>
        <div className="flex items-end gap-4 mb-3">
          <div className="text-4xl font-bold text-indigo-600">{pct}%</div>
          <div className="text-sm text-slate-500 pb-1">{reviewed} of {total} cards reviewed</div>
        </div>
        <ProgressBar value={reviewed} max={total} />
        <p className="text-xs text-slate-400 mt-2">{totalReviews} total review{totalReviews !== 1 ? 's' : ''}</p>
      </div>

      {/* Difficulty breakdown */}
      <div className="bg-white rounded-2xl border border-slate-200 p-6 mb-5">
        <h2 className="font-semibold text-slate-700 mb-4">Difficulty Breakdown</h2>
        <div className="space-y-3">
          {[
            { key: 'hard', label: 'Hard', color: 'bg-red-500', textColor: 'text-red-600' },
            { key: 'medium', label: 'Medium', color: 'bg-amber-500', textColor: 'text-amber-600' },
            { key: 'easy', label: 'Easy', color: 'bg-green-500', textColor: 'text-green-600' },
            { key: 'new', label: 'Not yet reviewed', color: 'bg-blue-400', textColor: 'text-blue-600' },