const { insertBill, validateBillData } = require('./billsService');

const SUBSCRIPTION_TYPES = ['streaming', 'software', 'cloud', 'music', 'news', 'fitness', 'gaming', 'utilities', 'insurance', 'other'];

const MONTHLY_FACTORS = {
  weekly: 52 / 12,
  biweekly: 26 / 12,
  monthly: 1,
  quarterly: 1 / 3,
  annual: 1 / 12,
  annually: 1 / 12,
  irregular: 1,
};

const TYPE_KEYWORDS = [
  ['streaming', ['netflix', 'hulu', 'disney', 'max', 'paramount', 'peacock', 'youtube tv', 'sling']],
  ['music', ['spotify', 'apple music', 'tidal', 'pandora']],
  ['software', ['adobe', 'microsoft', 'github', 'notion', 'linear', 'figma', 'canva', 'openai', 'chatgpt']],
  ['cloud', ['dropbox', 'icloud', 'google storage', 'backblaze', 'aws', 'cloudflare']],
  ['news', ['nyt', 'new york times', 'economist', 'athletic', 'washington post']],
  ['fitness', ['peloton', 'planet fitness', 'gym', 'fitbit']],
  ['gaming', ['xbox', 'playstation', 'steam', 'nintendo']],
  ['utilities', ['verizon', 'at t', 'comcast', 'xfinity', 'spectrum', 'tmobile']],
  ['insurance', ['insurance', 'geico', 'progressive', 'state farm', 'allstate']],
];

function normalizeMerchant(value) {
  return String(value || '')
    .toLowerCase()
    .replace(/[^a-z0-9\s]/g, ' ')
    .replace(/\b(pos|debit|card|payment|purchase|recurring|online|inc|llc|co)\b/g, ' ')
    .replace(/\s+/g, ' ')
    .trim();
}

function titleCase(value) {
  return String(value || 'Subscription')
    .split(/\s+/)
    .filter(Boolean)
    .map(word => word.charAt(0).toUpperCase() + word.slice(1))
    .join(' ');
}

function inferType(text) {
  const haystack = normalizeMerchant(text);
  for (const [type, words] of TYPE_KEYWORDS) {
    if (words.some(word => haystack.includes(word))) return type;
  }
  return 'other';
}

function monthlyEquivalent(amount, cycleType, billingCycle) {
  const key = String(cycleType || billingCycle || 'monthly').toLowerCase();
  const fallback = String(billingCycle || '').toLowerCase() === 'quarterly'
    ? 'quarterly'
    : String(billingCycle || '').toLowerCase() === 'annually'
      ? 'annual'
      : key;
  const factor = MONTHLY_FACTORS[key] ?? MONTHLY_FACTORS[fallback] ?? 1;
  return Math.round(Number(amount || 0) * factor * 100) / 100;
}

function nextDueDate(bill, now = new Date()) {
  const dueDay = Math.min(Math.max(Number(bill.due_day) || 1, 1), 31);
  const cycle = String(bill.cycle_type || bill.billing_cycle || 'monthly').toLowerCase();
  let date = new Date(now.getFullYear(), now.getMonth(), dueDay);
  if (date < new Date(now.getFullYear(), now.getMonth(), now.getDate())) {
    date = new Date(now.getFullYear(), now.getMonth() + 1, dueDay);
  }

  if (cycle === 'quarterly' || cycle === 'annual') {
    const startMonth = Math.min(Math.max(Number(bill.cycle_day) || 1, 1), 12) - 1;
    const step = cycle === 'quarterly' ? 3 : 12;
    date = new Date(now.getFullYear(), startMonth, dueDay);
    while (date < new Date(now.getFullYear(), now.getMonth(), now.getDate())) {
      date = new Date(date.getFullYear(), date.getMonth() + step, dueDay);
    }
  }

  return date.toISOString().slice(0, 10);
}

function decorateSubscription(bill) {
  const monthly = monthlyEquivalent(bill.expected_amount, bill.cycle_type, bill.billing_cycle);
  return {
    ...bill,
    is_subscription: !!bill.is_subscription,
    active: !!bill.active,
    monthly_equivalent: monthly,
    yearly_equivalent: Math.round(monthly * 12 * 100) / 100,
    next_due_date: nextDueDate(bill),
    subscription_type: bill.subscription_type || inferType(`${bill.name} ${bill.category_name || ''}`),
  };
}

function getSubscriptions(db, userId) {
  return db.prepare(`
    SELECT b.*, c.name AS category_name
    FROM bills b
    LEFT JOIN categories c ON c.id = b.category_id AND c.user_id = b.user_id AND c.deleted_at IS NULL
    WHERE b.user_id = ?
      AND b.deleted_at IS NULL
      AND b.is_subscription = 1
    ORDER BY b.active DESC, b.due_day ASC, b.name COLLATE NOCASE ASC
  `).all(userId).map(decorateSubscription);
}

function getSubscriptionSummary(subscriptions) {
  const active = subscriptions.filter(item => item.active);
  const monthlyTotal = active.reduce((sum, item) => sum + Number(item.monthly_equivalent || 0), 0);
  const typeTotals = new Map();
  for (const item of active) {
    const type = item.subscription_type || 'other';
    typeTotals.set(type, (typeTotals.get(type) || 0) + Number(item.monthly_equivalent || 0));
  }
  const topType = [...typeTotals.entries()].sort((a, b) => b[1] - a[1])[0] || null;
  return {
    active_count: active.length,
    paused_count: subscriptions.length - active.length,
    monthly_total: Math.round(monthlyTotal * 100) / 100,
    yearly_total: Math.round(monthlyTotal * 12 * 100) / 100,
    top_type: topType ? { type: topType[0], monthly_total: Math.round(topType[1] * 100) / 100 } : null,
  };
}

function existingBillNames(db, userId) {
  return db.prepare('SELECT name FROM bills WHERE user_id = ? AND deleted_at IS NULL')
    .all(userId)
    .map(row => normalizeMerchant(row.name))
    .filter(Boolean);
}

function dollarsFromTransactionAmount(amount) {
  return Math.round((Math.abs(Number(amount || 0)) / 100) * 100) / 100;
}

function billingCycleForCycleType(cycleType) {
  if (cycleType === 'quarterly') return 'quarterly';
  if (cycleType === 'annual') return 'annually';
  if (cycleType === 'monthly') return 'monthly';
  return 'irregular';
}

function getSubscriptionRecommendations(db, userId) {
  const existingNames = existingBillNames(db, userId);
  const rows = db.prepare(`
    SELECT
      t.id, t.amount, t.currency, t.description, t.payee, t.memo, t.category,
      COALESCE(t.posted_date, substr(t.transacted_at, 1, 10)) AS tx_date,
      ds.provider AS data_source_provider,
      ds.name AS data_source_name
    FROM transactions t
    LEFT JOIN data_sources ds ON ds.id = t.data_source_id AND ds.user_id = t.user_id
    WHERE t.user_id = ?
      AND t.ignored = 0
      AND t.match_status = 'unmatched'
      AND t.amount < 0
      AND COALESCE(t.posted_date, substr(t.transacted_at, 1, 10)) >= date('now', '-420 days')
      AND (ds.provider = 'simplefin' OR t.source_type = 'provider_sync')
    ORDER BY tx_date ASC
  `).all(userId);

  const groups = new Map();
  for (const tx of rows) {
    const merchant = normalizeMerchant(tx.payee || tx.description || tx.memo);
    if (!merchant || merchant.length < 3) continue;
    const amount = dollarsFromTransactionAmount(tx.amount);
    if (amount < 1) continue;
    const key = `${merchant}:${Math.round(amount)}`;
    const group = groups.get(key) || { merchant, amountBucket: Math.round(amount), items: [] };
    group.items.push({ ...tx, amount_dollars: amount });
    groups.set(key, group);
  }

  const recommendations = [];
  for (const group of groups.values()) {
    if (group.items.length < 2) continue;
    if (existingNames.some(name => name.includes(group.merchant) || group.merchant.includes(name))) continue;

    const sorted = group.items.filter(item => item.tx_date).sort((a, b) => String(a.tx_date).localeCompare(String(b.tx_date)));
    if (sorted.length < 2) continue;
    const gaps = [];
    for (let i = 1; i < sorted.length; i++) {
      gaps.push(Math.round((new Date(`${sorted[i].tx_date}T00:00:00`) - new Date(`${sorted[i - 1].tx_date}T00:00:00`)) / 86400000));
    }
    const avgGap = gaps.reduce((sum, gap) => sum + gap, 0) / gaps.length;
    const cycleType = avgGap >= 320 ? 'annual' : avgGap >= 75 ? 'quarterly' : avgGap >= 10 && avgGap <= 18 ? 'biweekly' : avgGap <= 9 ? 'weekly' : 'monthly';
    if (cycleType === 'monthly' && (avgGap < 24 || avgGap > 38)) continue;
    if (cycleType === 'quarterly' && (avgGap < 75 || avgGap > 105)) continue;

    const averageAmount = sorted.reduce((sum, item) => sum + item.amount_dollars, 0) / sorted.length;
    const maxDelta = Math.max(...sorted.map(item => Math.abs(item.amount_dollars - averageAmount)));
    if (maxDelta > Math.max(3, averageAmount * 0.18)) continue;

    const last = sorted[sorted.length - 1];
    recommendations.push({
      id: Buffer.from(`${group.merchant}:${group.amountBucket}:${last.tx_date}`).toString('base64url'),
      name: titleCase(group.merchant),
      subscription_type: inferType(group.merchant),
      expected_amount: Math.round(averageAmount * 100) / 100,
      monthly_equivalent: monthlyEquivalent(averageAmount, cycleType, cycleType),
      cycle_type: cycleType,
      billing_cycle: billingCycleForCycleType(cycleType),
      due_day: Number(String(last.tx_date).slice(8, 10)) || 1,
      last_seen_date: last.tx_date,
      occurrence_count: sorted.length,
      confidence: Math.min(96, 58 + sorted.length * 9 + (maxDelta <= 1 ? 10 : 0)),
      transaction_ids: sorted.map(item => item.id),
      merchant: group.merchant,
      source: last.data_source_name || 'SimpleFIN',
      reasons: [
        `${sorted.length} similar SimpleFIN charges`,
        `About ${Math.round(avgGap)} days apart`,
        `${last.currency || 'USD'} ${averageAmount.toFixed(2)} average charge`,
      ],
    });
  }

  return recommendations.sort((a, b) => b.confidence - a.confidence || b.occurrence_count - a.occurrence_count).slice(0, 20);
}

function createSubscriptionFromRecommendation(db, userId, payload = {}) {
  const seenDate = payload.last_seen_date || new Date().toISOString().slice(0, 10);
  const draft = {
    name: payload.name,
    category_id: payload.category_id || null,
    due_day: payload.due_day,
    expected_amount: payload.expected_amount,
    billing_cycle: billingCycleForCycleType(payload.cycle_type || 'monthly'),
    cycle_type: payload.cycle_type || 'monthly',
    cycle_day: payload.cycle_type === 'annual' || payload.cycle_type === 'quarterly'
      ? String(new Date(`${seenDate}T00:00:00`).getMonth() + 1)
      : String(payload.due_day || 1),
    is_subscription: 1,
    subscription_type: SUBSCRIPTION_TYPES.includes(payload.subscription_type) ? payload.subscription_type : 'other',
    reminder_days_before: 3,
    subscription_source: 'simplefin_recommendation',
    subscription_detected_at: new Date().toISOString(),
    notes: payload.merchant ? `Detected from recurring SimpleFIN merchant: ${payload.merchant}` : null,
  };

  const validation = validateBillData(draft);
  if (validation.errors.length > 0) {
    const err = new Error(validation.errors[0].message);
    err.field = validation.errors[0].field;
    err.status = 400;
    throw err;
  }

  const created = insertBill(db, userId, validation.normalized);
  const ids = Array.isArray(payload.transaction_ids)
    ? payload.transaction_ids.map(id => Number(id)).filter(Number.isInteger).slice(0, 50)
    : [];
  if (ids.length > 0) {
    const update = db.prepare(`
      UPDATE transactions
      SET matched_bill_id = ?, match_status = 'matched', updated_at = CURRENT_TIMESTAMP
      WHERE user_id = ? AND id = ? AND ignored = 0
    `);
    for (const id of ids) update.run(created.id, userId, id);
  }

  return decorateSubscription(created);
}

module.exports = {
  SUBSCRIPTION_TYPES,
  createSubscriptionFromRecommendation,
  decorateSubscription,
  getSubscriptionRecommendations,
  getSubscriptionSummary,
  getSubscriptions,
  monthlyEquivalent,
};