/* ────────────────────────────────────────────────────────────────
   Drop‑in replacement for mysql2 that transparently encrypts /
   decrypts selected columns, using helpers above.
   ---------------------------------------------------------------- */

import mysql from 'mysql2/promise';
import {
  encrypt,
  decrypt,
  isEncrypted,
  initEncryption
} from '../crypto/encryption.js';

/* ── map of columns that must be protected ─────────────────── */
const TABLE_MAP = {
  user_profile : [
    'username', 'firstname', 'lastname', 'email', 'phone_e164',
    'zipcode',  'stripe_customer_id',
    'interest_inventory_answers', 'riasec_scores',
    'career_priorities', 'career_list'
  ],
  financial_profiles : [
    'current_salary','additional_income','monthly_expenses',
    'monthly_debt_payments','retirement_savings','emergency_fund',
    'retirement_contribution','emergency_contribution',
    'extra_cash_emergency_pct','extra_cash_retirement_pct'
  ],
  career_profiles : [
    'planned_monthly_expenses','planned_monthly_debt_payments',
    'planned_monthly_retirement_contribution','planned_monthly_emergency_contribution',
    'planned_surplus_emergency_pct','planned_surplus_retirement_pct',
    'planned_additional_income','career_goals','desired_retirement_income_monthly'
  ],
  college_profiles : [
    'selected_school','selected_program','annual_financial_aid',
    'existing_college_debt','tuition','tuition_paid','loan_deferral_until_graduation',
    'loan_term','interest_rate','extra_payment','expected_salary'
  ],
  milestones        : ['title','description','date','progress'],
  tasks             : ['title','description','due_date','status'],
  reminders         : ['phone_e164','message_body'],
  milestone_impacts : ['amount','impact_type'],
  ai_risk_analysis  : ['reasoning','risk_level'],
  ai_generated_ksa  : ['knowledge_json','abilities_json','skills_json'],
  context_cache     : ['ctx_text']
};

/* ── initialise KMS unwrap once ─────────────────────────────── */
async function ensureCryptoReady () { await initEncryption(); }

/* ── mysql connection pool (uses env injected by docker) ────── */
export const pool = mysql.createPool({
  host               : process.env.DB_HOST,
  port               : process.env.DB_PORT,
  user               : process.env.DB_USER,
  password           : process.env.DB_PASSWORD,
  database           : process.env.DB_NAME,
  waitForConnections : true,
  connectionLimit    : 5,
  ssl : {
    ca   : process.env.DB_SSL_CA,
    key  : process.env.DB_SSL_KEY,
    cert : process.env.DB_SSL_CERT
  }
});

/* ── tiny helpers to parse SQL (works for *your* queries) ───── */
function extractTables (sql) {
  return [...new Set(
    [...sql.matchAll(/\b(?:from|join|into|update)\s+`?([a-z0-9_]+)`?/ig)]
      .map(m => m[1].toLowerCase())
  )];
}

function extractColumn(sql, paramIndex) {
  const normalized = sql.replace(/\s+/g, ' ').toLowerCase();

  // INSERT INTO table (col1, col2, ...) VALUES (?, ?, ...)
  if (normalized.includes('insert into')) {
    const m = normalized.match(/\(\s*([^)]+?)\s*\)\s*values/i);
    if (!m || !m[1]) {
      console.warn(`[DAO] INSERT column extraction failed for param ${paramIndex}`);
      return null;
    }
    const colList = m[1].split(',').map(s => s.replace(/`/g, '').trim());
    const col = colList[paramIndex] ?? null;
    console.log(`[DAO] Param ${paramIndex} maps to column: ${col}`);
    return col;
  }

  // UPDATE table SET col1 = ?, col2 = ? WHERE ...
  if (normalized.includes('update')) {
    const m = normalized.match(/set\s+(.*?)\s*(where|$)/);
    if (!m || !m[1]) {
      console.warn(`[DAO] UPDATE column extraction failed for param ${paramIndex}`);
      return null;
    }
    const colList = m[1].split(',').map(s =>
      s.split('=')[0].replace(/`/g, '').trim()
    );
    const col = colList[paramIndex] ?? null;
    console.log(`[DAO] Param ${paramIndex} maps to column: ${col}`);
    return col;
  }

  // SELECT ... WHERE col = ?
  if (normalized.includes('where')) {
    const m = normalized.match(/where\s+([a-z0-9_]+)\s*=/i);
    const col = m?.[1]?.trim() ?? null;
    console.log(`[DAO] Param ${paramIndex} maps to column (WHERE clause): ${col}`);
    return col;
  }

  console.log(`[DAO] No column mapping for param ${paramIndex} — unsupported SQL`);
  return null;
}


function decryptRow (row, tables) {
  for (const t of tables) {
    const encSet = new Set((TABLE_MAP[t] ?? []).map(c => c.toLowerCase()));
    for (const k of Object.keys(row)) {
      if (!encSet.has(k.toLowerCase())) continue;
      const val = row[k];
      if (val != null && isEncrypted(val)) row[k] = decrypt(val);
    }
  }
}

/* ─────────────────────────────────────────────────────────────
   Replacement for pool.execute / pool.query
   ──────────────────────────────────────────────────────────── */
export async function exec (sql, params = []) {
  await ensureCryptoReady();

  const tables        = extractTables(sql);
  const encryptNeeded = (col) => tables.some(t => TABLE_MAP[t]?.includes(col));

  const encParams = params.map((v, i) => {
    const col = extractColumn(sql, i);
    return (col && encryptNeeded(col) && v != null && !isEncrypted(v))
           ? encrypt(v)
           : v;
  });

  const [rows, fields] = await pool.execute(sql, encParams);

  if (Array.isArray(rows)) {
    for (const row of rows) decryptRow(row, tables);
  }
  return [rows, fields];
}

/* ── mysql‑like façade so existing code keeps working ───────── */
export const query         = exec;
export const getConnection = () => pool.getConnection();
export const end           = () => pool.end();
export const poolRaw       = pool;          // escape hatch