import { BadRequestException } from '@nestjs/common';
import { ErrorMessages } from '../constants/error-messages';

/**
 * Validate UUID format
 */
export function isValidUUID(id: string): boolean {
  const uuidRegex = /^[0-9a-f]{8}-[0-9a-f]{4}-[1-5][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i;
  return uuidRegex.test(id);
}

/**
 * Validate and throw if UUID is invalid
 */
export function validateUUID(id: string, fieldName: string = 'ID'): void {
  if (!isValidUUID(id)) {
    throw new BadRequestException(`Некорректный формат ${fieldName}`);
  }
}

/**
 * Validate email format
 */
export function isValidEmail(email: string): boolean {
  const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
  return emailRegex.test(email);
}

/**
 * Validate date string format (YYYY-MM-DD)
 */
export function isValidDateString(dateStr: string): boolean {
  const dateRegex = /^\d{4}-\d{2}-\d{2}$/;
  if (!dateRegex.test(dateStr)) return false;
  
  const date = new Date(dateStr);
  return !isNaN(date.getTime());
}

/**
 * Validate pagination parameters
 */
export interface PaginationParams {
  page: number;
  limit: number;
}

export function validatePagination(page?: number, limit?: number): PaginationParams {
  const validPage = Math.max(1, page || 1);
  const validLimit = Math.min(100, Math.max(1, limit || 20));
  
  return { page: validPage, limit: validLimit };
}

/**
 * Calculate pagination offset
 */
export function calculateOffset(page: number, limit: number): number {
  return (page - 1) * limit;
}

/**
 * Create pagination response metadata
 */
export interface PaginationMeta {
  page: number;
  limit: number;
  total: number;
  totalPages: number;
  hasNext: boolean;
  hasPrev: boolean;
}

export function createPaginationMeta(
  page: number,
  limit: number,
  total: number,
): PaginationMeta {
  const totalPages = Math.ceil(total / limit);
  
  return {
    page,
    limit,
    total,
    totalPages,
    hasNext: page < totalPages,
    hasPrev: page > 1,
  };
}

/**
 * Validate date range
 */
export function validateDateRange(startDate: string, endDate: string): void {
  if (!isValidDateString(startDate)) {
    throw new BadRequestException('Некорректная дата начала');
  }
  
  if (!isValidDateString(endDate)) {
    throw new BadRequestException('Некорректная дата окончания');
  }
  
  if (new Date(startDate) > new Date(endDate)) {
    throw new BadRequestException('Дата начала не может быть позже даты окончания');
  }
}

/**
 * Validate transaction amount
 */
export function validateTransactionAmount(amount: number): void {
  if (typeof amount !== 'number' || isNaN(amount)) {
    throw new BadRequestException(ErrorMessages.INVALID_AMOUNT);
  }
  
  if (amount <= 0) {
    throw new BadRequestException(ErrorMessages.AMOUNT_MUST_BE_POSITIVE);
  }
  
  if (amount > 1_000_000_000) {
    throw new BadRequestException(ErrorMessages.AMOUNT_TOO_LARGE);
  }
}