/**
 * Input validation utilities
 */

/**
 * Date format regex (YYYY-MM-DD)
 */
const DATE_REGEX = /^\d{4}-\d{2}-\d{2}$/;

/**
 * Validate date format (YYYY-MM-DD)
 */
export function isValidDate(date: string): boolean {
  if (!DATE_REGEX.test(date)) {
    return false;
  }

  // Check if it's a valid date
  const d = new Date(date);
  return d instanceof Date && !isNaN(d.getTime());
}

/**
 * Validate date format and throw if invalid
 */
export function validateDate(date: string, fieldName: string): void {
  if (!isValidDate(date)) {
    throw new Error(`${fieldName} must be in YYYY-MM-DD format`);
  }
}

/**
 * Validate date range
 */
export function validateDateRange(startDate: string, endDate: string): void {
  validateDate(startDate, 'start_date');
  validateDate(endDate, 'end_date');

  if (new Date(startDate) >= new Date(endDate)) {
    throw new Error('start_date must be before end_date');
  }
}

/**
 * Validate required field
 */
export function validateRequired<T>(
  value: T | null | undefined,
  fieldName: string
): asserts value is T {
  if (value === null || value === undefined) {
    throw new Error(`${fieldName} is required`);
  }
}

/**
 * Validate array is not empty
 */
export function validateNonEmptyArray<T>(
  value: T[],
  fieldName: string
): asserts value is [T, ...T[]] {
  if (!Array.isArray(value) || value.length === 0) {
    throw new Error(`${fieldName} must be a non-empty array`);
  }
}

/**
 * Validate number is positive
 */
export function validatePositive(value: number, fieldName: string): void {
  if (value <= 0) {
    throw new Error(`${fieldName} must be positive`);
  }
}

/**
 * Validate number is within range
 */
export function validateRange(
  value: number,
  min: number,
  max: number,
  fieldName: string
): void {
  if (value < min || value > max) {
    throw new Error(`${fieldName} must be between ${min} and ${max}`);
  }
}

/**
 * Validate URL format
 */
export function validateUrl(url: string, fieldName: string): void {
  try {
    new URL(url);
  } catch {
    throw new Error(`${fieldName} must be a valid URL`);
  }
}