/**
 * Shared export utilities for OData, CSV, and Excel.
 * Centralizes filter fields, order-by parsing, and row flattening.
 */

/** Allowed filter fields per object type for OData/CSV/Excel exports */
export const EXPORT_FILTER_BY_TYPE = {
  note: ['parent._id', 'noteType', 'user'],
  notification: ['user'],
  userNotifier: ['user', 'object', 'objectType'],
  printer: ['host'],
  job: ['printer', 'gcodeFile'],
  subJob: ['job'],
  filamentStock: ['filamentSku'],
  filament: ['material', 'material._id', 'name', 'diameter', 'cost'],
  filamentSku: ['filament', 'vendor', 'costTaxRate'],
  material: ['name', 'tags'],
  partStock: ['partSku'],
  partSku: ['part', 'vendor', 'priceTaxRate', 'costTaxRate'],
  productStock: ['productSku'],
  productSku: ['product', 'vendor', 'priceTaxRate', 'costTaxRate'],
  purchaseOrder: ['vendor'],
  orderItem: ['order._id', 'orderType', 'item._id', 'itemType', 'sku._id', 'shipment._id'],
  shipment: ['order._id', 'orderType', 'courierService._id'],
  stockEvent: ['parent._id', 'parentType', 'owner._id', 'ownerType'],
  stockLocation: ['name'],
  stockTransfer: ['state.type', 'postedAt'],
  stockAudit: ['filamentStock._id', 'partStock._id'],
  documentJob: ['documentTemplate', 'documentPrinter', 'object._id', 'objectType'],
  documentTemplate: ['parent._id', 'documentSize._id'],
  salesOrder: ['client'],
  invoice: ['to._id', 'from._id', 'order._id', 'orderType'],
  auditLog: ['parent._id', 'parentType', 'owner._id', 'ownerType'],
  appPassword: ['name', 'user', 'active'],
};

/**
 * Get allowed filter fields for a given object type.
 * @param {string} objectType - Model type (e.g. 'filament', 'material')
 * @returns {string[]} Allowed filter field names
 */
export function getModelFilterFields(objectType) {
  const base = ['_id'];
  const extra = EXPORT_FILTER_BY_TYPE[objectType] || [];
  return [...base, ...extra];
}

/**
 * Parse OData $orderby or orderby string into sort and order.
 * Supports "field asc", "field desc", or just "field" (defaults asc).
 * @param {string} [orderby] - Orderby string (e.g. "createdAt desc")
 * @returns {{ sort: string, order: 'ascend'|'descend' }}
 */
export function parseOrderBy(orderby) {
  if (!orderby || typeof orderby !== 'string') {
    return { sort: 'createdAt', order: 'ascend' };
  }
  const trimmed = orderby.trim();
  const parts = trimmed.split(/\s+/);
  const sort = parts[0] || 'createdAt';
  const dir = (parts[1] || 'asc').toLowerCase();
  const order = dir === 'desc' ? 'descend' : 'ascend';
  return { sort, order };
}

/**
 * Flatten nested objects for export display.
 * Objects become "key.subkey: value"; arrays become comma-separated strings.
 * @param {*} obj - Value to flatten
 * @param {string} [prefix=''] - Key prefix for nested values
 * @returns {Object} Flat key-value object
 */
export function flattenForExport(obj, prefix = '') {
  if (obj === null || obj === undefined) return {};
  if (typeof obj !== 'object') return { [prefix]: obj };
  if (obj instanceof Date) return { [prefix]: obj };
  if (Array.isArray(obj)) {
    const str = obj
      .map((v) => (v && typeof v === 'object' && !(v instanceof Date) ? JSON.stringify(v) : v))
      .join(', ');
    return { [prefix]: str };
  }
  const result = {};
  for (const [k, v] of Object.entries(obj)) {
    const key = prefix ? `${prefix}.${k}` : k;
    if (v !== null && typeof v === 'object' && !(v instanceof Date) && !Array.isArray(v)) {
      Object.assign(result, flattenForExport(v, key));
    } else {
      result[key] = v;
    }
  }
  return result;
}

/**
 * Convert a row (e.g. OData value item) to flat key-value for CSV/Excel.
 * Nested objects are flattened; @odata.* keys are skipped.
 * @param {Object} row - Row object
 * @returns {Object} Flat key-value object
 */
export function rowToFlat(row) {
  const flat = {};
  for (const [key, val] of Object.entries(row)) {
    if (key.startsWith('@')) continue;
    if (val !== null && typeof val === 'object' && !(val instanceof Date) && !Array.isArray(val)) {
      Object.assign(flat, flattenForExport(val, key));
    } else {
      flat[key] = val;
    }
  }
  return flat;
}