import { ApiProperty } from '@nestjs/swagger';
import { Transform } from 'class-transformer';
import {
  IsString,
  MinLength,
  Validate,
  ValidatorConstraint,
} from 'class-validator';

const EMAIL_PART_COUNT = 2;
const FIRST_CHARACTER_INDEX = 0;

const MAX_EMAIL_LENGTH = 254;
const ASCII_SPACE = 32;
const ASCII_DELETE = 127;
const MIN_PASSWORD_LENGTH = 12;
const MAX_PASSWORD_BYTES = 72;

@ValidatorConstraint({ name: 'email' })
class EmailConstraint {
  validate(value: unknown): boolean {
    return (
      typeof value === 'string' &&
      value.length <= MAX_EMAIL_LENGTH &&
      value.split('@').length === EMAIL_PART_COUNT &&
      !value
        .split('')
        .some(
          (character) =>
            /\s/.test(character) ||
            character.charCodeAt(FIRST_CHARACTER_INDEX) < ASCII_SPACE ||
            character.charCodeAt(FIRST_CHARACTER_INDEX) === ASCII_DELETE,
        ) &&
        value.split('@').every(Boolean)
    );
  }

  defaultMessage(): string {
    return 'must be a valid email address';
  }
}

@ValidatorConstraint({ name: 'passwordBytes' })
class PasswordBytesConstraint {
  validate(value: unknown): boolean {
    return (
      typeof value === 'string' &&
      Buffer.byteLength(value, 'utf8') <= MAX_PASSWORD_BYTES
    );
  }

  defaultMessage(): string {
    return 'must not exceed 72 UTF-8 bytes';
  }
}

export class CredentialsDto {
  @ApiProperty({ example: 'user@example.com' })
  @IsString()
  @Transform(({ value }: { value: unknown }) =>
    typeof value === 'string' ? value.trim().toLowerCase() : value,
  )
  @Validate(EmailConstraint)
  declare email: string;

  @ApiProperty({
    minLength: MIN_PASSWORD_LENGTH,
    maxLength: MAX_PASSWORD_BYTES,
    example: 'a secure password',
  })
  @IsString()
  @MinLength(MIN_PASSWORD_LENGTH)
  @Validate(PasswordBytesConstraint)
  declare password: string;
}