(.+?)</label>%s';

		if ( preg_match_all( $pattern, $content, $matches ) ) {
			$form_tags_manager = WPCF7_FormTagsManager::get_instance();

			foreach ( $matches[1] as $insidelabel ) {
				$tags = $form_tags_manager->scan( $insidelabel );
				$fields_count = 0;

				foreach ( $tags as $tag ) {
					$is_multiple_controls_container = wpcf7_form_tag_supports(
						$tag->type, 'multiple-controls-container' );
					$is_zero_controls_container = wpcf7_form_tag_supports(
						$tag->type, 'zero-controls-container' );

					if ( $is_multiple_controls_container ) {
						$fields_count += count( $tag->values );

						if ( $tag->has_option( 'free_text' ) ) {
							$fields_count += 1;
						}
					} elseif ( $is_zero_controls_container ) {
						$fields_count += 0;
					} elseif ( ! empty( $tag->name ) ) {
						$fields_count += 1;
					}

					if ( 1 < $fields_count ) {
						return $this->add_error( $section,
							self::error_multiple_controls_in_label, array(
								'link' => self::get_doc_link( 'multiple_controls_in_label' ),
							)
						);
					}
				}
			}
		}

		return false;
	}

	public function detect_unavailable_names( $section, $content ) {
		$public_query_vars = array( 'm', 'p', 'posts', 'w', 'cat',
			'withcomments', 'withoutcomments', 's', 'search', 'exact', 'sentence',
			'calendar', 'page', 'paged', 'more', 'tb', 'pb', 'author', 'order',
			'orderby', 'year', 'monthnum', 'day', 'hour', 'minute', 'second',
			'name', 'category_name', 'tag', 'feed', 'author_name', 'static',
			'pagename', 'page_id', 'error', 'attachment', 'attachment_id',
			'subpost', 'subpost_id', 'preview', 'robots', 'taxonomy', 'term',
			'cpage', 'post_type', 'embed' );

		$form_tags_manager = WPCF7_FormTagsManager::get_instance();
		$ng_named_tags = $form_tags_manager->filter( $content,
			array( 'name' => $public_query_vars ) );

		$ng_names = array();

		foreach ( $ng_named_tags as $tag ) {
			$ng_names[] = sprintf( '"%s"', $tag->name );
		}

		if ( $ng_names ) {
			$ng_names = array_unique( $ng_names );

			return $this->add_error( $section,
				self::error_unavailable_names,
				array(
					'message' =>
						/* translators: %names%: a list of form control names */
						__( "Unavailable names (%names%) are used for form controls.", 'contact-form-7' ),
					'params' => array( 'names' => implode( ', ', $ng_names ) ),
					'link' => self::get_doc_link( 'unavailable_names' ),
				)
			);
		}

		return false;
	}

	public function detect_unavailable_html_elements( $section, $content ) {
		$pattern = '%(?:<form[\s\t>]|</form>)%i';

		if ( preg_match( $pattern, $content ) ) {
			return $this->add_error( $section,
				self::error_unavailable_html_elements,
				array(
					'message' => __( "Unavailable HTML elements are used in the form template.", 'contact-form-7' ),
					'link' => self::get_doc_link( 'unavailable_html_elements' ),
				)
			);
		}

		return false;
	}

	public function validate_mail( $template = 'mail' ) {
		$components = (array) $this->contact_form->prop( $template );

		if ( ! $components ) {
			return;
		}

		if ( 'mail' != $template
		and empty( $components['active'] ) ) {
			return;
		}

		$components = wp_parse_args( $components, array(
			'subject' => '',
			'sender' => '',
			'recipient' => '',
			'additional_headers' => '',
			'body' => '',
			'attachments' => '',
		) );

		$callback = array( $this, 'replace_mail_tags_with_minimum_input' );

		$subject = $components['subject'];
		$subject = new WPCF7_MailTaggedText( $subject,
			array( 'callback' => $callback ) );
		$subject = $subject->replace_tags();
		$subject = wpcf7_strip_newline( $subject );
		$this->detect_maybe_empty( sprintf( '%s.subject', $template ), $subject );

		$sender = $components['sender'];
		$sender = new WPCF7_MailTaggedText( $sender,
			array( 'callback' => $callback ) );
		$sender = $sender->replace_tags();
		$sender = wpcf7_strip_newline( $sender );

		if ( ! $this->detect_invalid_mailbox_syntax( sprintf( '%s.sender', $template ), $sender )
		and ! wpcf7_is_email_in_site_domain( $sender ) ) {
			$this->add_error( sprintf( '%s.sender', $template ),
				self::error_email_not_in_site_domain, array(
					'link' => self::get_doc_link( 'email_not_in_site_domain' ),
				)
			);
		}

		$recipient = $components['recipient'];
		$recipient = new WPCF7_MailTaggedText( $recipient,
			array( 'callback' => $callback ) );
		$recipient = $recipient->replace_tags();
		$recipient = wpcf7_strip_newline( $recipient );

		$this->detect_invalid_mailbox_syntax(
			sprintf( '%s.recipient', $template ), $recipient );

		$additional_headers = $components['additional_headers'];
		$additional_headers = new WPCF7_MailTaggedText( $additional_headers,
			array( 'callback' => $callback ) );
		$additional_headers = $additional_headers->replace_tags();
		$additional_headers = explode( "\n", $additional_headers );
		$mailbox_header_types = array( 'reply-to', 'cc', 'bcc' );
		$invalid_mail_header_exists = false;

		foreach ( $additional_headers as $header ) {
			$header = trim( $header );

			if ( '' === $header ) {
				continue;
			}

			if ( ! preg_match( '/^([0-9A-Za-z-]+):(.*)$/', $header, $matches ) ) {
				$invalid_mail_header_exists = true;
			} else {
				$header_name = $matches[1];
				$header_value = trim( $matches[2] );

				if ( in_array( strtolower( $header_name ), $mailbox_header_types ) ) {
					$this->detect_invalid_mailbox_syntax(
						sprintf( '%s.additional_headers', $template ),
						$header_value, array(
							'message' =>
								__( "Invalid mailbox syntax is used in the %name% field.", 'contact-form-7' ),
							'params' => array( 'name' => $header_name ) ) );
				} elseif ( empty( $header_value ) ) {
					$invalid_mail_header_exists = true;
				}
			}
		}

		if ( $invalid_mail_header_exists ) {
			$this->add_error( sprintf( '%s.additional_headers', $template ),
				self::error_invalid_mail_header, array(
					'link' => self::get_doc_link( 'invalid_mail_header' ),
				)
			);
		}

		$body = $components['body'];
		$body = new WPCF7_MailTaggedText( $body,
			array( 'callback' => $callback ) );
		$body = $body->replace_tags();
		$this->detect_maybe_empty( sprintf( '%s.body', $template ), $body );

		if ( '' !== $components['attachments'] ) {
			$attachables = array();

			$tags = $this->contact_form->scan_form_tags(
				array( 'type' => array( 'file', 'file*' ) )
			);

			foreach ( $tags as $tag ) {
				$name = $tag->name;

				if ( false === strpos( $components['attachments'], "[{$name}]" ) ) {
					continue;
				}

				$limit = (int) $tag->get_limit_option();

				if ( empty( $attachables[$name] )
				or $attachables[$name] < $limit ) {
					$attachables[$name] = $limit;
				}
			}

			$total_size = array_sum( $attachables );

			$has_file_not_found = false;
			$has_file_not_in_content_dir = false;

			foreach ( explode( "\n", $components['attachments'] ) as $line ) {
				$line = trim( $line );

				if ( '' === $line
				or '[' == substr( $line, 0, 1 ) ) {
					continue;
				}

				$has_file_not_found = $this->detect_file_not_found(
					sprintf( '%s.attachments', $template ), $line
				);

				if ( ! $has_file_not_found
				and ! $has_file_not_in_content_dir ) {
					$has_file_not_in_content_dir = $this->detect_file_not_in_content_dir(
						sprintf( '%s.attachments', $template ), $line
					);
				}

				if ( ! $has_file_not_found ) {
					$path = path_join( WP_CONTENT_DIR, $line );
					$total_size += (int) @filesize( $path );
				}
			}

			$max = 25 * 1024 * 1024; // 25 MB

			if ( $max < $total_size ) {
				$this->add_error( sprintf( '%s.attachments', $template ),
					self::error_attachments_overweight,
					array(
						'message' => __( "The total size of attachment files is too large.", 'contact-form-7' ),
						'link' => self::get_doc_link( 'attachments_overweight' ),
					)
				);
			}
		}
	}

	public function detect_invalid_mailbox_syntax( $section, $content, $args = '' ) {
		$args = wp_parse_args( $args, array(
			'link' => self::get_doc_link( 'invalid_mailbox_syntax' ),
			'message' => '',
			'params' => array(),
		) );

		if ( ! wpcf7_is_mailbox_list( $content ) ) {
			return $this->add_error( $section,
				self::error_invalid_mailbox_syntax, $args );
		}

		return false;
	}

	public function detect_maybe_empty( $section, $content ) {
		if ( '' === $content ) {
			return $this->add_error( $section,
				self::error_maybe_empty, array(
					'link' => self::get_doc_link( 'maybe_empty' ),
				)
			);
		}

		return false;
	}

	public function detect_file_not_found( $section, $content ) {
		$path = path_join( WP_CONTENT_DIR, $content );

		if ( ! is_readable( $path )
		or ! is_file( $path ) ) {
			return $this->add_error( $section,
				self::error_file_not_found,
				array(
					'message' =>
						__( "Attachment file does not exist at %path%.", 'contact-form-7' ),
					'params' => array( 'path' => $content ),
					'link' => self::get_doc_link( 'file_not_found' ),
				)
			);
		}

		return false;
	}

	public function detect_file_not_in_content_dir( $section, $content ) {
		$path = path_join( WP_CONTENT_DIR, $content );

		if ( ! wpcf7_is_file_path_in_content_dir( $path ) ) {
			return $this->add_error( $section,
				self::error_file_not_in_content_dir,
				array(
					'message' =>
						__( "It is not allowed to use files outside the wp-content directory.", 'contact-form-7' ),
					'link' => self::get_doc_link( 'file_not_in_content_dir' ),
				)
			);
		}

		return false;
	}

	public function validate_messages() {
		$messages = (array) $this->contact_form->prop( 'messages' );

		if ( ! $messages ) {
			return;
		}

		if ( isset( $messages['captcha_not_match'] )
		and ! wpcf7_use_really_simple_captcha() ) {
			unset( $messages['captcha_not_match'] );
		}

		foreach ( $messages as $key => $message ) {
			$section = sprintf( 'messages.%s', $key );
			$this->detect_html_in_message( $section, $message );
		}
	}

	public function detect_html_in_message( $section, $content ) {
		$stripped = wp_strip_all_tags( $content );

		if ( $stripped != $content ) {
			return $this->add_error( $section,
				self::error_html_in_message,
				array(
					'link' => self::get_doc_link( 'html_in_message' ),
				)
			);
		}

		return false;
	}

	public function validate_additional_settings() {
		$deprecated_settings_used =
			$this->contact_form->additional_setting( 'on_sent_ok' ) ||
			$this->contact_form->additional_setting( 'on_submit' );

		if ( $deprecated_settings_used ) {
			return $this->add_error( 'additional_settings.body',
				self::error_deprecated_settings,
				array(
					'link' => self::get_doc_link( 'deprecated_settings' ),
				)
			);
		}
	}

}