'use strict';

const { normalizeMerchant } = require('./subscriptionService');

// Persist a merchant→bill rule so future synced transactions auto-match.
function addMerchantRule(db, userId, billId, merchant) {
  const normalized = normalizeMerchant(merchant);
  if (!normalized || normalized.length < 3) return;
  try {
    db.prepare(`
      INSERT INTO bill_merchant_rules (user_id, bill_id, merchant)
      VALUES (?, ?, ?)
      ON CONFLICT(user_id, bill_id, merchant) DO NOTHING
    `).run(userId, billId, normalized);
  } catch {
    // Table may not exist yet on legacy DBs — safe to skip
  }
}

// Scan all unmatched negative transactions for this user, apply any stored
// merchant rules, create payments, and mark the transactions matched.
// Returns { matched: number }.
function applyMerchantRules(db, userId) {
  let rules;
  try {
    rules = db.prepare(`
      SELECT bmr.bill_id, bmr.merchant
      FROM bill_merchant_rules bmr
      JOIN bills b ON b.id = bmr.bill_id AND b.user_id = bmr.user_id AND b.deleted_at IS NULL
      WHERE bmr.user_id = ?
    `).all(userId);
  } catch {
    return { matched: 0 };
  }

  if (rules.length === 0) return { matched: 0 };

  const txRows = db.prepare(`
    SELECT id, amount, payee, description, memo, posted_date, transacted_at
    FROM transactions
    WHERE user_id = ?
      AND match_status = 'unmatched'
      AND ignored = 0
      AND amount < 0
  `).all(userId);

  if (txRows.length === 0) return { matched: 0 };

  const insertPayment = db.prepare(`
    INSERT OR IGNORE INTO payments (bill_id, amount, paid_date, payment_source, transaction_id)
    VALUES (?, ?, ?, 'auto_match', ?)
  `);
  const updateTx = db.prepare(`
    UPDATE transactions
    SET matched_bill_id = ?, match_status = 'matched', updated_at = datetime('now')
    WHERE id = ? AND user_id = ? AND match_status = 'unmatched'
  `);

  let matched = 0;

  db.transaction(() => {
    for (const tx of txRows) {
      const txMerchant = normalizeMerchant(tx.payee || tx.description || tx.memo || '');
      if (!txMerchant) continue;

      const rule = rules.find(r =>
        txMerchant.includes(r.merchant) || r.merchant.includes(txMerchant)
      );
      if (!rule) continue;

      const paidDate = tx.posted_date || (tx.transacted_at ? String(tx.transacted_at).slice(0, 10) : null);
      if (!paidDate) continue;

      const amount = Math.round(Math.abs(tx.amount)) / 100;
      insertPayment.run(rule.bill_id, amount, paidDate, tx.id);
      updateTx.run(rule.bill_id, tx.id, userId);
      matched++;
    }
  })();

  return { matched };
}

// Sync all unmatched SimpleFIN transactions for a single bill using its stored
// merchant rules. If no rule exists yet but the bill has a detected merchant in
// its notes, the rule is created on the fly.
// Returns { added: number }.
function syncBillPaymentsFromSimplefin(db, userId, billId) {
  // Load rules for this specific bill
  let rules;
  try {
    rules = db.prepare(`
      SELECT merchant FROM bill_merchant_rules
      WHERE user_id = ? AND bill_id = ?
    `).all(userId, billId).map(r => r.merchant);
  } catch {
    return { added: 0 };
  }

  // Fallback: extract merchant from notes "Detected from recurring merchant: X"
  if (rules.length === 0) {
    const bill = db.prepare('SELECT notes FROM bills WHERE id = ? AND user_id = ? AND deleted_at IS NULL').get(billId, userId);
    const match = bill?.notes?.match(/Detected from recurring merchant:\s*(.+)/i);
    if (match) {
      const extracted = normalizeMerchant(match[1].trim());
      if (extracted && extracted.length >= 3) {
        addMerchantRule(db, userId, billId, extracted);
        rules = [extracted];
      }
    }
    if (rules.length === 0) return { added: 0 };
  }

  const txRows = db.prepare(`
    SELECT id, amount, payee, description, memo, posted_date, transacted_at
    FROM transactions
    WHERE user_id = ?
      AND match_status = 'unmatched'
      AND ignored = 0
      AND amount < 0
  `).all(userId);

  if (txRows.length === 0) return { added: 0 };

  const insertPayment = db.prepare(`
    INSERT OR IGNORE INTO payments (bill_id, amount, paid_date, payment_source, transaction_id)
    VALUES (?, ?, ?, 'auto_match', ?)
  `);
  const updateTx = db.prepare(`
    UPDATE transactions
    SET matched_bill_id = ?, match_status = 'matched', updated_at = datetime('now')
    WHERE id = ? AND user_id = ? AND match_status = 'unmatched'
  `);

  let added = 0;
  db.transaction(() => {
    for (const tx of txRows) {
      const txMerchant = normalizeMerchant(tx.payee || tx.description || tx.memo || '');
      if (!txMerchant) continue;
      const matches = rules.some(r => txMerchant.includes(r) || r.includes(txMerchant));
      if (!matches) continue;
      const paidDate = tx.posted_date || (tx.transacted_at ? String(tx.transacted_at).slice(0, 10) : null);
      if (!paidDate) continue;
      const amount = Math.round(Math.abs(tx.amount)) / 100;
      insertPayment.run(billId, amount, paidDate, tx.id);
      updateTx.run(billId, tx.id, userId);
      added++;
    }
  })();

  return { added };
}

module.exports = { addMerchantRule, applyMerchantRules, syncBillPaymentsFromSimplefin };