const { all, audit, now, one, run } = require('../db');

let cache = null;

function clearCache() {
  cache = null;
}

function lookup() {
  if (!cache) {
    cache = {};
    for (const row of all('SELECT * FROM depreciation_zones')) cache[row.code] = row;
  }
  return cache;
}

// Raw row (incl. dates) for the engine; null when unknown or disabled.
function getZone(code) {
  if (!code) return null;
  const zone = lookup()[code];
  return zone && zone.enabled ? zone : null;
}

function slugify(value) {
  return String(value || '').trim().toLowerCase().replace(/[^a-z0-9]+/g, '_').replace(/^_+|_+$/g, '').slice(0, 40);
}

function fromRow(row) {
  if (!row) return null;
  return {
    id: row.id,
    code: row.code,
    name: row.name,
    allowance_percent: row.allowance_percent,
    pis_start: row.pis_start,
    pis_end: row.pis_end,
    real_property_end: row.real_property_end,
    max_recovery_years: row.max_recovery_years,
    leasehold_life_years: row.leasehold_life_years,
    notes: row.notes,
    enabled: Boolean(row.enabled),
    asset_count: one('SELECT COUNT(*) AS c FROM assets WHERE special_zone = ?', [row.code]).c
  };
}

function list() {
  return all('SELECT * FROM depreciation_zones ORDER BY name').map(fromRow);
}

function normalize(body) {
  const num = (v) => (v === '' || v === null || v === undefined ? null : Number(v));
  return {
    name: String(body.name || '').trim(),
    allowance_percent: Number(body.allowance_percent) || 0,
    pis_start: body.pis_start || null,
    pis_end: body.pis_end || null,
    real_property_end: body.real_property_end || null,
    max_recovery_years: num(body.max_recovery_years),
    leasehold_life_years: num(body.leasehold_life_years),
    notes: body.notes || null,
    enabled: body.enabled === false ? 0 : 1
  };
}

function createZone(body, userId) {
  const input = normalize(body);
  if (!input.name) throw Object.assign(new Error('A zone name is required'), { status: 400 });
  const code = slugify(body.code || input.name);
  if (!code) throw Object.assign(new Error('A valid zone code is required'), { status: 400 });
  if (one('SELECT id FROM depreciation_zones WHERE code = ?', [code])) {
    throw Object.assign(new Error('A zone with that code already exists'), { status: 400 });
  }
  const ts = now();
  run(
    `INSERT INTO depreciation_zones (code, name, allowance_percent, pis_start, pis_end, real_property_end, max_recovery_years, leasehold_life_years, notes, enabled, created_at, updated_at)
     VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
    [code, input.name, input.allowance_percent, input.pis_start, input.pis_end, input.real_property_end, input.max_recovery_years, input.leasehold_life_years, input.notes, input.enabled, ts, ts]
  );
  clearCache();
  audit(userId, 'create', 'depreciation_zone', code, null, input);
  return fromRow(one('SELECT * FROM depreciation_zones WHERE code = ?', [code]));
}

function updateZone(code, body, userId) {
  const before = one('SELECT * FROM depreciation_zones WHERE code = ?', [code]);
  if (!before) return null;
  const input = normalize({ ...before, ...body, enabled: body.enabled === undefined ? Boolean(before.enabled) : body.enabled });
  run(
    `UPDATE depreciation_zones SET name = ?, allowance_percent = ?, pis_start = ?, pis_end = ?, real_property_end = ?,
       max_recovery_years = ?, leasehold_life_years = ?, notes = ?, enabled = ?, updated_at = ? WHERE code = ?`,
    [input.name, input.allowance_percent, input.pis_start, input.pis_end, input.real_property_end, input.max_recovery_years, input.leasehold_life_years, input.notes, input.enabled, now(), code]
  );
  clearCache();
  audit(userId, 'update', 'depreciation_zone', code, before, input);
  return fromRow(one('SELECT * FROM depreciation_zones WHERE code = ?', [code]));
}

function deleteZone(code, userId) {
  const before = one('SELECT * FROM depreciation_zones WHERE code = ?', [code]);
  if (!before) return false;
  run('DELETE FROM depreciation_zones WHERE code = ?', [code]);
  clearCache();
  audit(userId, 'delete', 'depreciation_zone', code, before, null);
  return true;
}

module.exports = {
  clearCache,
  createZone,
  deleteZone,
  getZone,
  list,
  updateZone
};