'use strict';

const { getDb } = require('../db/database');

// Lazy-loaded in-memory cache — loaded once on first use
let _patterns = null;
let _overrideTerms = null;

function normalize(text) {
  if (!text) return '';
  return String(text)
    .toLowerCase()
    .replace(/&/g, 'and')
    .replace(/\s+/g, ' ')
    .trim();
}

function loadCache() {
  if (_patterns !== null) return;
  const db = getDb();
  _patterns = db.prepare(
    'SELECT pattern, confidence, category, rationale FROM advisory_non_bill_filters'
  ).all();
  _overrideTerms = db.prepare(
    'SELECT term FROM advisory_bill_like_overrides'
  ).all().map(r => r.term);
}

/**
 * Check a transaction title against advisory filter patterns.
 * Returns null if Create Bill should be shown normally, or
 * { confidence: 'high'|'medium', category, rationale } if it should be suppressed.
 */
function checkTransaction(title) {
  if (!title) return null;
  try {
    loadCache();
  } catch {
    return null;
  }

  const normalized = normalize(title);
  if (!normalized) return null;

  // Bill-like override terms take priority — always show Create Bill
  for (const term of _overrideTerms) {
    if (normalized.includes(term)) return null;
  }

  // Find the highest-confidence matching pattern
  let highMatch = null;
  let mediumMatch = null;

  for (const row of _patterns) {
    if (normalized.includes(row.pattern)) {
      if (row.confidence === 'high') {
        highMatch = row;
        break; // high confidence — no need to keep looking
      } else if (!mediumMatch) {
        mediumMatch = row;
      }
    }
  }

  const match = highMatch || mediumMatch;
  if (!match) return null;

  return {
    confidence: match.confidence,
    category: match.category,
    rationale: match.rationale || null,
  };
}

/** Clear the in-memory cache (used after re-seeding in tests). */
function clearCache() {
  _patterns = null;
  _overrideTerms = null;
}

module.exports = { checkTransaction, clearCache };