BillTracker/services/spendingService.js

'use strict';

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

// Spending = unmatched outflows (amount < 0) that haven't been ignored.
// Bill-matched transactions are excluded so there's no double-counting.
const SPENDING_WHERE = `
  t.amount < 0
  AND t.ignored = 0
  AND t.match_status != 'matched'
  AND t.user_id = ?
`;

function monthRange(year, month) {
  const start = `${year}-${String(month).padStart(2, '0')}-01`;
  const end   = new Date(year, month, 0).toISOString().slice(0, 10); // last day
  return { start, end };
}

function cents(raw) {
  return Math.abs(Number(raw)) / 100;
}

// ── Summary ──────────────────────────────────────────────────────────────────

function getSpendingSummary(db, userId, year, month) {
  const { start, end } = monthRange(year, month);

  // Spending by category
  const rows = db.prepare(`
    SELECT
      c.id        AS category_id,
      c.name      AS category_name,
      SUM(ABS(t.amount)) AS total_cents,
      COUNT(t.id)        AS tx_count
    FROM transactions t
    LEFT JOIN categories c ON c.id = t.spending_category_id AND c.deleted_at IS NULL
    WHERE ${SPENDING_WHERE}
      AND (t.posted_date BETWEEN ? AND ? OR (t.posted_date IS NULL AND t.transacted_at BETWEEN ? AND ?))
    GROUP BY c.id
    ORDER BY total_cents DESC
  `).all(userId, start, end, start + 'T00:00:00', end + 'T23:59:59');

  const budgets = db.prepare(`
    SELECT category_id, amount FROM spending_budgets
    WHERE user_id = ? AND year = ? AND month = ?
  `).all(userId, year, month);
  const budgetMap = new Map(budgets.map(b => [b.category_id, b.amount]));

  let totalCents = 0;
  const byCategory = rows.map(r => {
    totalCents += r.total_cents;
    return {
      category_id:   r.category_id,
      category_name: r.category_name ?? '(Uncategorized)',
      amount:        r.total_cents / 100,
      tx_count:      r.tx_count,
      budget:        r.category_id ? (budgetMap.get(r.category_id) ?? null) : null,
    };
  });

  // Attach pct_of_total
  byCategory.forEach(c => {
    c.pct_of_total = totalCents > 0 ? Math.round(c.amount / (totalCents / 100) * 100) / 100 : 0;
  });

  const uncatRow = byCategory.find(c => !c.category_id);
  const uncategorized_amount = uncatRow?.amount ?? 0;
  const uncategorized_count  = uncatRow?.tx_count ?? 0;

  // Income (positive unmatched transactions this month)
  const incomeRow = db.prepare(`
    SELECT COALESCE(SUM(t.amount), 0) AS total FROM transactions t
    WHERE t.user_id = ? AND t.ignored = 0 AND t.amount > 0
      AND t.match_status != 'matched'
      AND (t.posted_date BETWEEN ? AND ? OR (t.posted_date IS NULL AND t.transacted_at BETWEEN ? AND ?))
  `).get(userId, start, end, start + 'T00:00:00', end + 'T23:59:59');

  return {
    year, month,
    total_spending:        totalCents / 100,
    uncategorized_amount,
    uncategorized_count,
    by_category:           byCategory,
    income:                (incomeRow?.total ?? 0) / 100,
  };
}

// ── Transactions ─────────────────────────────────────────────────────────────

function getSpendingTransactions(db, userId, year, month, {
  categoryId = undefined,
  uncategorizedOnly = false,
  page = 1,
  limit = 50,
} = {}) {
  const { start, end } = monthRange(year, month);
  const offset = (Math.max(1, page) - 1) * limit;

  let filter = '';
  const params = [userId, start, end, start + 'T00:00:00', end + 'T23:59:59'];

  if (uncategorizedOnly) {
    filter = 'AND t.spending_category_id IS NULL';
  } else if (categoryId !== undefined) {
    if (categoryId === null) {
      filter = 'AND t.spending_category_id IS NULL';
    } else {
      filter = 'AND t.spending_category_id = ?';
      params.push(categoryId);
    }
  }

  const rows = db.prepare(`
    SELECT
      t.id, t.amount, t.payee, t.description, t.memo,
      t.posted_date, t.transacted_at, t.spending_category_id,
      c.name AS category_name
    FROM transactions t
    LEFT JOIN categories c ON c.id = t.spending_category_id AND c.deleted_at IS NULL
    WHERE ${SPENDING_WHERE} ${filter}
      AND (t.posted_date BETWEEN ? AND ? OR (t.posted_date IS NULL AND t.transacted_at BETWEEN ? AND ?))
    ORDER BY COALESCE(t.posted_date, DATE(t.transacted_at)) DESC, t.id DESC
    LIMIT ? OFFSET ?
  `).all(...params, limit, offset);

  const total = db.prepare(`
    SELECT COUNT(*) AS n FROM transactions t
    WHERE ${SPENDING_WHERE} ${filter}
      AND (t.posted_date BETWEEN ? AND ? OR (t.posted_date IS NULL AND t.transacted_at BETWEEN ? AND ?))
  `).get(...params).n;

  return {
    transactions: rows.map(r => ({
      id:                  r.id,
      amount:              cents(r.amount),
      payee:               r.payee || r.description || r.memo || '(Unknown)',
      date:                r.posted_date || (r.transacted_at ? String(r.transacted_at).slice(0, 10) : null),
      spending_category_id:   r.spending_category_id,
      spending_category_name: r.category_name ?? null,
    })),
    total,
    page,
    pages: Math.ceil(total / limit),
  };
}

// ── Categorize ───────────────────────────────────────────────────────────────

function categorizeTransaction(db, userId, txId, categoryId, saveMerchantRule = false) {
  const tx = db.prepare('SELECT * FROM transactions WHERE id = ? AND user_id = ?').get(txId, userId);
  if (!tx) throw Object.assign(new Error('Transaction not found'), { status: 404 });

  db.prepare("UPDATE transactions SET spending_category_id=?, updated_at=datetime('now') WHERE id=? AND user_id=?")
    .run(categoryId ?? null, txId, userId);

  if (saveMerchantRule && categoryId) {
    const merchant = normalizeMerchant(tx.payee || tx.description || tx.memo || '');
    if (merchant && merchant.length >= 3) {
      try {
        db.prepare(`
          INSERT INTO spending_category_rules (user_id, category_id, merchant)
          VALUES (?, ?, ?)
          ON CONFLICT(user_id, merchant) DO UPDATE SET category_id=excluded.category_id
        `).run(userId, categoryId, merchant);
        // Apply this rule to all existing matching transactions
        applySpendingCategoryRules(db, userId, merchant);
      } catch { /* safe to ignore */ }
    }
  }
}

// ── Auto-categorization ──────────────────────────────────────────────────────

function applySpendingCategoryRules(db, userId, onlyMerchant = null) {
  let rules;
  try {
    const q = onlyMerchant
      ? db.prepare('SELECT merchant, category_id FROM spending_category_rules WHERE user_id=? AND merchant=?')
          .all(userId, onlyMerchant)
      : db.prepare('SELECT merchant, category_id FROM spending_category_rules WHERE user_id=?')
          .all(userId);
    rules = q;
  } catch { return 0; }
  if (!rules.length) return 0;

  let applied = 0;
  const update = db.prepare("UPDATE transactions SET spending_category_id=?, updated_at=datetime('now') WHERE id=? AND user_id=?");

  const txRows = db.prepare(`
    SELECT id, payee, description, memo FROM transactions
    WHERE user_id=? AND amount<0 AND ignored=0 AND match_status!='matched' AND spending_category_id IS NULL
  `).all(userId);

  db.transaction(() => {
    for (const tx of txRows) {
      const merchant = normalizeMerchant(tx.payee || tx.description || tx.memo || '');
      if (!merchant) continue;
      const rule = rules.find(r => merchantMatches(merchant, r.merchant));
      if (rule) { update.run(rule.category_id, tx.id, userId); applied++; }
    }
  })();

  return applied;
}

function merchantMatches(txMerchant, ruleMerchant) {
  if (!txMerchant || !ruleMerchant) return false;
  if (txMerchant === ruleMerchant) return true;
  const esc = s => s.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
  const wb  = s => new RegExp(`(^|\\s)${esc(s)}(\\s|$)`);
  return wb(ruleMerchant).test(txMerchant) || wb(txMerchant).test(ruleMerchant);
}

// ── Budgets ──────────────────────────────────────────────────────────────────

function getSpendingBudgets(db, userId, year, month) {
  return db.prepare(`
    SELECT sb.category_id, sb.amount, c.name AS category_name
    FROM spending_budgets sb
    JOIN categories c ON c.id = sb.category_id AND c.deleted_at IS NULL
    WHERE sb.user_id=? AND sb.year=? AND sb.month=?
  `).all(userId, year, month);
}

function setSpendingBudget(db, userId, categoryId, year, month, amount) {
  if (amount === null || amount === undefined) {
    db.prepare('DELETE FROM spending_budgets WHERE user_id=? AND category_id=? AND year=? AND month=?')
      .run(userId, categoryId, year, month);
  } else {
    db.prepare(`
      INSERT INTO spending_budgets (user_id, category_id, year, month, amount, updated_at)
      VALUES (?, ?, ?, ?, ?, datetime('now'))
      ON CONFLICT(user_id, category_id, year, month) DO UPDATE SET
        amount=excluded.amount, updated_at=datetime('now')
    `).run(userId, categoryId, year, month, Number(amount));
  }
}

// ── Category rules ───────────────────────────────────────────────────────────

function getSpendingCategoryRules(db, userId) {
  return db.prepare(`
    SELECT r.id, r.merchant, r.category_id, c.name AS category_name
    FROM spending_category_rules r
    JOIN categories c ON c.id = r.category_id AND c.deleted_at IS NULL
    WHERE r.user_id=?
    ORDER BY r.merchant ASC
  `).all(userId);
}

function addSpendingCategoryRule(db, userId, categoryId, merchant) {
  const normalized = normalizeMerchant(merchant);
  if (!normalized || normalized.length < 2) throw Object.assign(new Error('Merchant name too short'), { status: 400 });
  db.prepare(`
    INSERT INTO spending_category_rules (user_id, category_id, merchant)
    VALUES (?, ?, ?)
    ON CONFLICT(user_id, merchant) DO UPDATE SET category_id=excluded.category_id
  `).run(userId, categoryId, normalized);
  applySpendingCategoryRules(db, userId, normalized);
}

function deleteSpendingCategoryRule(db, userId, ruleId) {
  db.prepare('DELETE FROM spending_category_rules WHERE id=? AND user_id=?').run(ruleId, userId);
}

module.exports = {
  getSpendingSummary,
  getSpendingTransactions,
  categorizeTransaction,
  applySpendingCategoryRules,
  getSpendingBudgets,
  setSpendingBudget,
  getSpendingCategoryRules,
  addSpendingCategoryRule,
  deleteSpendingCategoryRule,
};