tag.
	 *
	 * @see `AP_Form::sanitize_description`
	 *
	 * @param array $matches Matches.
	 * @return string
	 */
	private static function pre_content( $matches ) {
		return '
' . esc_html( $matches[1] ) . '
';
	}

	/**
	 * Callback for replacing contents inside  tag.
	 *
	 * @see `AP_Form::sanitize_description`
	 *
	 * @param array $matches Matches.
	 * @return string
	 */
	private static function code_content( $matches ) {
		return '' . esc_html( $matches[1] ) . '';
	}

	/**
	 * Sanitize tags field.
	 *
	 * Sanitize keys and values. Exclude new tags if not allowed.
	 * Only include numbers of max tags allowed in field option.
	 *
	 * @param null|array $value      Arrays of tags to sanitize.
	 * @param array      $options    Tags options.
	 * @param array      $js_options Tags JavaScript options.
	 *
	 * @return array|null Return sanitized tag array.
	 */
	public static function sanitize_tags_field( $value = null, $options, $js_options ) {
		if ( ! empty( $value ) ) {
			$i = 0;
			$sanitized = [];
			foreach ( (array) $value as $tag_slug => $tag_label ) {
				$i++;

				// Include new tags only if add_tag option is true.
				if ( true === $js_options['add_tag'] || ( false === $js_options['add_tag'] && in_array( $tag_slug, array_keys( $options ), true ) ) ) {
					$sanitized[ sanitize_title( $tag_slug ) ] = sanitize_text_field( $tag_label );

					// Only output max numbers of tags allowed.
					if ( $js_options['max_tags'] === $i ) {
						break;
					}
				}
			}

			return $sanitized;
		}
	}

	/**
	 * Sanitize upload field.
	 *
	 * @param  null|array $value          Array of uploads.
	 * @param  array      $upload_options Upload options.
	 * @return null|array
	 */
	public static function sanitize_upload( $value = null, $upload_options ) {
		if ( ! empty( $value ) && is_array( $value ) ) {
			if ( true === $upload_options['multiple'] && wp_is_numeric_array( $value ) ) {
				$value = array_slice( $value, 0, $upload_options['max_files'] );

				foreach ( $value as $key => $file ) {
					$value[ $key ]['error'] = (int) $file['error'];
					$value[ $key ]['name']  = sanitize_file_name( $file['name'] );
				}

				return $value;
			} elseif ( false === $upload_options['multiple'] && ! wp_is_numeric_array( $value ) ) {
				$value['error'] = (int) $value['error'];
				$value['name']  = sanitize_file_name( $value['name'] );

				return $value;
			}
		}
	}

	/**
	 * Validate `required` field.
	 *
	 * @param object $field Instance of @see `AP_Field` object.
	 * @return void
	 */
	public static function validate_required( $field ) {
		if ( '' === $field->value() || is_null( $field->value() ) ) {
			$field->add_error( 'required', sprintf(
				// Translators: placeholder contain field label.
				__( '%s field is required.', 'anspress-question-answer' ),
				$field->get( 'label' )
			) );
		}
	}

	/**
	 * Validate if value is not zero.
	 *
	 * @param object $field Instance of @see `AP_Field` object.
	 * @return void
	 */
	public static function validate_not_zero( $field ) {
		if ( '0' == $field->value() ) {
			$field->add_error( 'is-zero', sprintf(
				// Translators: placeholder contain field label.
				__( '%s field is required.', 'anspress-question-answer' ),
				$field->get( 'label' )
			) );
		}
	}

	/**
	 * Validate `is_email` field.
	 *
	 * @param object $field Instance of @see `AP_Field` object.
	 * @return void
	 */
	public static function validate_is_email( $field ) {
		if ( ! empty( $field->value() ) && ! is_email( $field->value() ) ) {
			$field->add_error( 'is-email', sprintf(
				// Translators: placeholder contain field label.
				__( 'Value provided in field %s is not a valid email.', 'anspress-question-answer' ),
				$field->get( 'label' )
			) );
		}
	}

	/**
	 * Validate `is_url` field.
	 *
	 * @param object $field Instance of @see `AP_Field` object.
	 * @return void
	 */
	public static function validate_is_url( $field ) {
		if ( ! empty( $field->unsafe_value() ) && false === filter_var( $field->unsafe_value(), FILTER_VALIDATE_URL ) ) {
			$field->add_error( 'is-url', sprintf(
				// Translators: placeholder contain field label.
				__( 'Value provided in field %s is not a valid URL.', 'anspress-question-answer' ),
				$field->get( 'label' )
			) );
		}
	}

	/**
	 * Validate `is_url` field.
	 *
	 * @param object $field Instance of @see `AP_Field` object.
	 * @return void
	 */
	public static function validate_is_numeric( $field ) {
		if ( ! empty( $field->unsafe_value() ) && ! is_numeric( $field->unsafe_value() ) ) {
			$field->add_error( 'is-numeric', sprintf(
				// Translators: placeholder contain field label.
				__( 'Value provided in field %s is not numeric.', 'anspress-question-answer' ),
				$field->get( 'label' )
			) );
		}
	}

	/**
	 * Validate if length of a string is at least as defined.
	 *
	 * @param object $field Instance of @see `AP_Field` object.
	 * @return void
	 */
	public static function validate_min_string_length( $field ) {
		$value = $field->value();

		if ( ! empty( $value ) && $field->get( 'min_length' ) ) {
			$min_length = $field->get( 'min_length', 0 );
			$value = wp_strip_all_tags( $value );
			$value = html_entity_decode( $value, ENT_XML1, 'UTF-8' );

			if ( mb_strlen( $value, 'utf-8' ) < $min_length ) {
				$field->add_error( 'min-string-length', sprintf(
					// Translators: placeholder contain field label.
					__( 'Value provided in field %1$s must be at least %2$d characters long.', 'anspress-question-answer' ),
					$field->get( 'label' ), $min_length
				) );
			}
		}
	}

	/**
	 * Validate if length of a string is at least as defined.
	 *
	 * @param object $field Instance of @see `AP_Field` object.
	 * @return void
	 */
	public static function validate_max_string_length( $field ) {
		$value = $field->value();

		if ( ! empty( $value ) && $field->get( 'max_length' ) ) {
			$max_length = $field->get( 'max_length', 10 );
			$value = wp_strip_all_tags( $value );
			$value = html_entity_decode( $value, ENT_XML1, 'UTF-8' );

			if ( mb_strlen( $value, 'utf-8' ) > $max_length ) {
				$field->add_error( 'max-string-length', sprintf(
					// Translators: placeholder contain field label.
					__( 'Value provided in field %1$s must not exceeds %2$d characters.', 'anspress-question-answer' ),
					$field->get( 'label' ), $max_length
				) );
			}
		} // End if().
	}

	/**
	 * Validate if field is array.
	 *
	 * @param object $field Instance of @see `AP_Field` object.
	 * @return void
	 */
	public static function validate_is_array( $field ) {
		$value = $field->value();

		if ( ! empty( $value ) && ! is_array( $value ) ) {
			$field->add_error( 'is-array', sprintf(
				// Translators: placeholder contain field label.
				__( 'Value provided in field %s is not an array.', 'anspress-question-answer' ),
				$field->get( 'label' )
			) );
		}
	}

	/**
	 * Validate if there are minimum items in an array.
	 *
	 * @param object $field Instance of @see `AP_Field` object.
	 * @return void
	 */
	public static function validate_array_min( $field ) {
		$min_arr = $field->get( 'array_min', 0 );
		$value = $field->value();

		if ( empty( $value ) || ! is_array( $value ) || $min_arr > count( $value ) ) {
			$field->add_error( 'array-min', sprintf(
				// Translators: placeholder contain field label.
				__( 'Minimum %1$d values are required in field %2$s.', 'anspress-question-answer' ),
				$min_arr, $field->get( 'label' )
			) );
		}
	}

	/**
	 * Validate if there are minimum items in an array.
	 *
	 * @param object $field Instance of @see `AP_Field` object.
	 * @return void
	 */
	public static function validate_array_max( $field ) {
		$max_arr = (int) $field->get( 'array_max', 0 );
		$value   = $field->value();

		if ( ! empty( $value ) && count( $value ) > $max_arr ) {
			$field->add_error( 'array-max', sprintf(
				// Translators: placeholder contain field label.
				__( 'Maximum values allowed in field %2$s is %1$d.', 'anspress-question-answer' ),
				$max_arr, $field->get( 'label' )
			) );
		}
	}

	/**
	 * Check if checking for bad word is enabled.
	 *
	 * @return array
	 * @since  4.0.0
	 */
	public static function get_bad_words() {
		$bad_word_file = ap_get_theme_location( 'badwords.txt' );

		// Return if badwords.txt file does not exists.
		if ( file_exists( $bad_word_file ) ) {
			return  file( $bad_word_file, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES );
		}

		$option = ap_opt( 'bad_words' );

		if ( ! empty( $option ) ) {
			return explode( ',', $option );
		}

		return [];
	}

	/**
	 * Validate if there are minimum items in an array.
	 *
	 * @param object $field Instance of @see `AP_Field` object.
	 * @return void
	 */
	public static function validate_badwords( $field ) {
		$value = $field->unsafe_value();
		$found = [];

		foreach ( (array) SELF::get_bad_words() as $w ) {
			$w = trim( $w );
			$count = preg_match_all( '/\b' . preg_quote( $w ) . '\b/i', $value );

			if ( $count > 0 ) {
				$found[ $w ] = $count;
			}
		}

		if ( ! empty( $found ) ) {
			$field->add_error( 'bad-words', sprintf(
				// Translators: placeholder contain field label.
				__( 'Found bad words in field %s. Remove them and try again.', 'anspress-question-answer' ),
				$field->get( 'label' )
			) );
		}
	}

	/**
	 * Check if a upload field's value array have error.
	 *
	 * @param object $field Instance of @see `AP_Field` object.
	 * @return false|string Return error message if exists.
	 */
	private static function file_have_error( $field ) {
		$args  = $field->get( 'upload_options' );
		$value = $field->value();

		$errors = array(
			0 => __( 'There is no error, the file uploaded with success', 'anspress-question-answer' ),
			1 => __( 'The uploaded file exceeds the upload_max_filesize directive in php.ini', 'anspress-question-answer' ),
			2 => __( 'The uploaded file exceeds the MAX_FILE_SIZE directive that was specified in the HTML form', 'anspress-question-answer' ),
			3 => __( 'The uploaded file was only partially uploaded', 'anspress-question-answer' ),
			4 => __( 'No file was uploaded', 'anspress-question-answer' ),
			6 => __( 'Missing a temporary folder', 'anspress-question-answer' ),
			7 => __( 'Failed to write file to disk.', 'anspress-question-answer' ),
			8 => __( 'A PHP extension stopped the file upload.', 'anspress-question-answer' ),
		);

		$have_error = false;

		if ( true === $args['multiple'] && wp_is_numeric_array( $value ) ) {
			foreach ( $value as $key => $file ) {
				if ( 0 !== $file['error'] ) {
					$have_error = $errors[ $file['error'] ];
				}
			}
		} else {
			if ( 0 !== $value['error'] ) {
				$have_error = $errors[ $value['error'] ];
			}
		}

		return $have_error;
	}

	/**
	 * Check if upload field file size is greater then allowed.
	 *
	 * @param object $field Instance of @see `AP_Field` object.
	 * @return false
	 */
	private static function file_size_error( $field ) {
		$args       = $field->get( 'upload_options' );
		$value      = $field->value();
		$have_error = false;
		$is_numeric = wp_is_numeric_array( $value );

		if ( true === $args['multiple'] && $is_numeric ) {
			foreach ( $value as $key => $file ) {
				if ( $file['size'] > ap_opt( 'max_upload_size' ) ) {
					$have_error = true;
				}
			}
		} elseif ( ! $is_numeric && $value['size'] > ap_opt( 'max_upload_size' ) ) {
			$have_error = true;
		}

		return $have_error;
	}

	/**
	 * Check file array contain allowed mime types.
	 *
	 * @param object $field Instance of @see `AP_Field` object.
	 * @return boolean
	 */
	private static function file_valid_type( $field ) {
		$args       = $field->get( 'upload_options' );
		$value      = $field->value();
		$have_error = true;
		$is_numeric = wp_is_numeric_array( $value );

		if ( true === $args['multiple'] && $is_numeric ) {
			foreach ( $value as $key => $file ) {
				$actual_mime = mime_content_type( $file['tmp_name'] );

				if ( in_array( $actual_mime, $args['allowed_mimes'], true ) ) {
					$have_error = false;
				}
			}
		} elseif ( ! $is_numeric ) {
			$actual_mime = mime_content_type( $value['tmp_name'] );

			if ( in_array( $actual_mime, $args['allowed_mimes'], true ) ) {
				$have_error = false;
			}
		}

		return $have_error;
	}

	/**
	 * Validate an upload field.
	 *
	 * @param object $field Instance of @see `AP_Field` object.
	 * @return void
	 */
	public static function validate_upload( $field ) {
		$args  = $field->get( 'upload_options' );
		$value = $field->unsafe_value();

		if ( ! empty( $value ) ) {

			// Check if user have permission to upload files.
			if ( ! ap_user_can_upload() ) {
				$field->add_error( 'deny-upload', __( 'You are not allowed to upload file(s)', 'anspress-question-answer' ) );
			}

			$is_numeric = wp_is_numeric_array( $value );

			if ( ( false === $args['multiple'] && $is_numeric ) ||
					 ( true === $args['multiple'] && count( $value ) > $args['max_files'] ) ) {
				$field->add_error( 'max-uploads', sprintf(
					// Translators: %1$d contain maximum files user can upload, %2$s contain label of field.
					__( 'You cannot upload more than %1$d file in field %2$s', 'anspress-question-answer' ),  $args['max_files'], $field->get( 'label' )
				) );
			}

			// Check if allowed mimes.
			$valid_mimes = self::file_valid_type( $field );
			if ( false !== $valid_mimes ) {
				$field->add_error( 'mimes-not-allowed', __( 'File type is not allowed to upload.', 'anspress-question-answer' ) );
			}

			// Check if file have any error.
			$error = self::file_have_error( $field );
			if ( false !== $error ) {
				$field->add_error( 'upload-file-error', $error );
			}

			// Check file size.
			$file_size = self::file_size_error( $field );
			if ( false !== $file_size ) {
				$field->add_error( 'max-size-upload', sprintf(
					// Translators: %s contain maximum file size user can upload.
					__( 'File(s) size is bigger then %s MB', 'anspress-question-answer' ),
					round( ap_opt( 'max_upload_size' ) / ( 1024 * 1024 ), 2 )
				) );
			}
		} // End if().
	}
}