'use strict';

const { categorizeTransaction } = require('./spendingService');

// Mirrors the pack's match_order_recommendation: regional descriptor variants
// (most specific — tied to a city/county) are checked first, then online
// billing descriptors (PAYPAL/STRIPE/APPLE.COM/BILL/etc.), then canonical
// national merchants as the fallback.
const ENTRY_KIND_ORDER = {
  regional_descriptor_variant: 0,
  online_billing_descriptor_variant: 1,
  canonical_merchant: 2,
};

let _entries = null;

function maxPatternLength(patterns) {
  return patterns.reduce((max, p) => Math.max(max, p.length), 0);
}

// Lazily load and pre-sort all merchant_store_matches rows. Cached for the
// lifetime of the process — this is static reference data seeded once by the
// v1.05 migration.
function loadMerchantMatchEntries(db) {
  if (_entries) return _entries;

  const rows = db.prepare(`
    SELECT id, entry_kind, canonical_merchant_id, canonical_name, display_name,
           category, merchant_type, scope, priority, match_patterns, negative_patterns,
           locality_city, locality_state
    FROM merchant_store_matches
  `).all();

  _entries = rows.map(row => ({
    ...row,
    match_patterns: JSON.parse(row.match_patterns || '[]'),
    negative_patterns: JSON.parse(row.negative_patterns || '[]'),
  }));

  _entries.sort((a, b) => {
    const orderA = ENTRY_KIND_ORDER[a.entry_kind] ?? 99;
    const orderB = ENTRY_KIND_ORDER[b.entry_kind] ?? 99;
    if (orderA !== orderB) return orderA - orderB;
    if (b.priority !== a.priority) return b.priority - a.priority;
    return maxPatternLength(b.match_patterns) - maxPatternLength(a.match_patterns);
  });

  return _entries;
}

// Apply the pack's normalization rules: uppercase, "&" -> "AND", strip
// apostrophes/punctuation, collapse whitespace. match_patterns in the pack
// are pre-normalized to this same shape (e.g. "THE CHILDREN S PLACE").
function normalizeForMatch(value) {
  return String(value || '')
    .toUpperCase()
    .replace(/&/g, ' AND ')
    .replace(/['’]/g, '')
    .replace(/[^A-Z0-9\s]/g, ' ')
    .replace(/\s+/g, ' ')
    .trim();
}

// Find the best merchant/store match for a raw transaction description.
// Returns { entry_id, canonical_name, display_name, category, scope, priority } or null.
function findMerchantMatch(db, description) {
  const normalized = normalizeForMatch(description);
  if (!normalized) return null;

  const entries = loadMerchantMatchEntries(db);
  for (const entry of entries) {
    if (entry.negative_patterns.some(p => normalized.includes(p))) continue;
    if (entry.match_patterns.some(p => p && normalized.includes(p))) {
      return {
        entry_id: entry.id,
        canonical_name: entry.canonical_name,
        display_name: entry.display_name,
        category: entry.category,
        scope: entry.scope,
        priority: entry.priority,
      };
    }
  }
  return null;
}

// Find-or-create a spending category by name for this user, matching the
// COLLATE NOCASE convention used by ensureUserDefaultCategories (db/database.js).
function findOrCreateCategory(db, userId, name) {
  const existing = db.prepare('SELECT id FROM categories WHERE user_id = ? AND name = ? COLLATE NOCASE')
    .get(userId, name);
  if (existing) return existing.id;
  const result = db.prepare('INSERT INTO categories (user_id, name) VALUES (?, ?)').run(userId, name);
  return result.lastInsertRowid;
}

// Scan the user's uncategorized outflows, apply merchant/store pack matches,
// and categorize them (writing spending_category_rules so future syncs hit
// the cheaper rule path instead of rescanning the full pack).
//
// With { dryRun: true }, computes the same matches without writing anything
// (no categories created, no transactions updated) — used to preview an
// auto-categorize run before applying it.
//
// Returns { updated: number, categories: [{ name, count }], changes: [{ transaction_id, display_name, category }] }.
function applyMerchantStoreMatches(db, userId, { dryRun = false } = {}) {
  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);

  if (txRows.length === 0) return { updated: 0, categories: [], changes: [] };

  const categoryCounts = new Map(); // category name -> count
  const changes = [];
  let updated = 0;

  const apply = () => {
    for (const tx of txRows) {
      const match = findMerchantMatch(db, tx.payee || tx.description || tx.memo || '');
      if (!match) continue;

      if (!dryRun) {
        const categoryId = findOrCreateCategory(db, userId, match.category);
        categorizeTransaction(db, userId, tx.id, categoryId, true);
      }
      updated++;
      changes.push({ transaction_id: tx.id, display_name: match.display_name, category: match.category });
      categoryCounts.set(match.category, (categoryCounts.get(match.category) || 0) + 1);
    }
  };

  if (dryRun) {
    apply();
  } else {
    db.transaction(apply)();
  }

  return {
    updated,
    categories: [...categoryCounts.entries()].map(([name, count]) => ({ name, count })),
    changes,
  };
}

module.exports = {
  loadMerchantMatchEntries,
  normalizeForMatch,
  findMerchantMatch,
  findOrCreateCategory,
  applyMerchantStoreMatches,
};