/* ────────────────────────────────────────────────────────────────
   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';

const WRITE_RE = /^\s*(insert|update|replace)\s/i;

/* ── 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',
    'career_name','start_date','retirement_start_date','scenario_title'
  ],
  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'],
  reminders         : ['phone_e164','message_body'],
  milestone_impacts : ['amount','impact_type', 'direction'],
  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(); }

// choose cap per-process from env (server1/2/3 each have their own DB_POOL_SIZE)
const cap = Number(process.env.DB_POOL_SIZE || 5);
console.log(`[db] mysql pool connectionLimit=${cap}`);

/* ── 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    : cap,
  ssl : {
    ca   : process.env.DB_SSL_CA,
    key  : process.env.DB_SSL_KEY,
    cert : process.env.DB_SSL_CERT,
    servername: ''
  }
});

/* ── 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 s = sql.replace(/\s+/g, ' ').toLowerCase();

  // INSERT INTO t (c1, c2, ...) VALUES (?, ?, ...)
  const ins = s.match(/insert\s+into\s+[`\w]+\s*\(([^)]+)\)\s*values\s*\(([^)]+)\)/i);
  if (ins) {
    const cols = ins[1].split(',').map(c => c.replace(/`/g, '').trim());
    return cols[paramIndex] || null;  // only VALUES params exist here
  }

  // UPDATE t SET c1 = ?, c2 = ? WHERE ...
  const upd = s.match(/update\s+[`\w]+\s+set\s+(.+?)(?:\s+where|\s*$)/i);
  if (upd) {
    const setPart = upd[1];

    // Build a list of columns in the same order as the '?'s in SET only
    const pairs = setPart.split(',').map(p => p.trim());
    const colsForQs = [];
    for (const p of pairs) {
      const col = p.split('=')[0].replace(/`/g, '').trim();
      const qCnt = (p.match(/\?/g) || []).length;
      for (let i = 0; i < qCnt; i++) colsForQs.push(col);
    }

    const setQCount = colsForQs.length;
    if (paramIndex < setQCount) return colsForQs[paramIndex];

    // params after SET (WHERE/LIMIT/etc.) → no mapping
    return null;
  }

  // SELECT/DELETE/etc. → we don’t map WHERE/LIMIT params
  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 isWrite = WRITE_RE.test(sql);
  const tables  = extractTables(sql);

  const encryptNeeded = (col) =>
    tables.some(t => (TABLE_MAP[t] || []).some(c =>
      c.toLowerCase() === String(col || '').toLowerCase()
    ));

  const encParams = isWrite
    ? params.map((v, i) => {
        const col = extractColumn(sql, i);
        return (col && encryptNeeded(col) && v != null && !isEncrypted(v))
          ? encrypt(v)
          : v;
      })
    : params; // SELECT path: never touch params

  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