wp-discourse/admin/settings-validator.php

<?php
/**
 * Validation methods for the settings page.
 *
 * @link    https://github.com/discourse/wp-discourse/blob/master/lib/settings-validator.php
 * @package WPDiscourse
 */

namespace WPDiscourse\Admin;

use WPDiscourse\Shared\PluginUtilities;

/**
 * Class SettingsValidator
 *
 * @package WPDiscourse\Validator
 */
class SettingsValidator {

	use PluginUtilities;

	/**
	 * Indicates whether or not the "discourse_sso_common['sso-secret']" option has been set.
	 *
	 * @access protected
	 * @var    bool|void
	 */
	protected $sso_secret_set;

	/**
	 * Indicates whether or not the "discourse_sso_provider['enable-sso']" option is enabled.
	 *
	 * @access protected
	 * @var    bool|void
	 */
	protected $sso_provider_enabled;

	/**
	 * Indicates whether or not the "discourse_sso_client['sso-client-enabled']" option is enabled.
	 *
	 * @access protected
	 * @var    bool|void
	 */
	protected $sso_client_enabled;

	/**
	 * Indicates whether or not 'use_discourse_comments' is enabled.
	 *
	 * @access protected
	 * @var    bool
	 */
	protected $use_discourse_comments = false;

	/**
	 * Indicates whether or not 'use_discourse_webhook' is enabled.
	 *
	 * @access protected
	 * @var    bool
	 */
	protected $use_discourse_webhook;

	/**
	 * Indicates whether or not 'use_discourse_user_webhook' is enabled.
	 *
	 * @access protected
	 * @var    bool
	 */
	protected $use_discourse_user_webhook;

	/**
	 * Gives access to the plugin options.
	 *
	 * @access protected
	 * @var    array|void
	 */
	protected $options;

	/**
	 * SettingsValidator constructor.
	 *
	 * Adds the callback function for each of the validator filters that are applied
	 * in `admin.php`.
	 */
	public function __construct() {
		add_action( 'admin_init', array( $this, 'setup_options' ) );

		add_filter( 'wpdc_validate_url', array( $this, 'validate_url' ) );
		add_filter( 'wpdc_validate_api_key', array( $this, 'validate_api_key' ) );
		add_filter( 'wpdc_validate_publish_username', array( $this, 'validate_publish_username' ) );

		add_filter( 'wpdc_validate_publish_category', array( $this, 'validate_publish_category' ) );
		add_filter( 'wpdc_validate_publish_category_update', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_allow_tags', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_max_tags', array( $this, 'validate_max_tags' ) );
		add_filter( 'wpdc_validate_publish_as_unlisted', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_full_post_content', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_auto_publish', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_force_publish', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_force_publish_max_age', array( $this, 'validate_force_publish_max_age' ) );
		add_filter( 'wpdc_validate_add_featured_link', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_auto_track', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_allowed_post_types', array( $this, 'validate_allowed_post_types' ) );
		add_filter( 'wpdc_validate_publish_failure_notice', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_publish_failure_email', array( $this, 'validate_email' ) );
		add_filter( 'wpdc_validate_hide_discourse_name_field', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_discourse_username_editable', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_discourse_direct_db_publication_flags', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_discourse_verbose_publication_logs', array( $this, 'validate_checkbox' ) );

		add_filter( 'wpdc_validate_enable_discourse_comments', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_comment_type', array( $this, 'validate_radio_string_value' ) );
		add_filter( 'wpdc_validate_cache_html', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_clear_cached_comment_html', array( $this, 'validate_clear_comments_html' ) );
		add_filter( 'wpdc_validate_ajax_load', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_load_comment_css', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_discourse_new_tab', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_hide_wordpress_comments', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_show_existing_comments', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_existing_comments_heading', array( $this, 'validate_existing_comments_heading' ) );
		add_filter( 'wpdc_validate_max_comments', array( $this, 'validate_max_comments' ) );
		add_filter( 'wpdc_validate_min_replies', array( $this, 'validate_min_replies' ) );
		add_filter( 'wpdc_validate_min_score', array( $this, 'validate_min_score' ) );
		add_filter( 'wpdc_validate_min_trust_level', array( $this, 'validate_min_trust_level' ) );
		add_filter( 'wpdc_validate_bypass_trust_level_score', array( $this, 'validate_bypass_trust_level_score' ) );
		add_filter( 'wpdc_validate_custom_excerpt_length', array( $this, 'validate_custom_excerpt_length' ) );
		add_filter( 'wpdc_validate_custom_datetime_format', array( $this, 'validate_text_input' ) );
		add_filter( 'wpdc_validate_only_show_moderator_liked', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_display_subcategories', array( $this, 'validate_checkbox' ) );

		add_filter( 'wpdc_validate_discourse_link_text', array( $this, 'validate_text_input' ) );
		add_filter( 'wpdc_validate_start_discussion_text', array( $this, 'validate_text_input' ) );
		add_filter( 'wpdc_validate_continue_discussion_text', array( $this, 'validate_text_input' ) );
		add_filter( 'wpdc_validate_join_discussion_text', array( $this, 'validate_text_input' ) );
		add_filter( 'wpdc_validate_comments_singular_text', array( $this, 'validate_text_input' ) );
		add_filter( 'wpdc_validate_comments_plural_text', array( $this, 'validate_text_input' ) );
		add_filter( 'wpdc_validate_no_comments_text', array( $this, 'validate_text_input' ) );
		add_filter( 'wpdc_validate_notable_replies_text', array( $this, 'validate_text_input' ) );
		add_filter( 'wpdc_validate_comments_not_available_text', array( $this, 'validate_text_input' ) );
		add_filter( 'wpdc_validate_participants_text', array( $this, 'validate_text_input' ) );
		add_filter( 'wpdc_validate_published_at_text', array( $this, 'validate_text_input' ) );
		add_filter( 'wpdc_validate_single_reply_text', array( $this, 'validate_text_input' ) );
		add_filter( 'wpdc_validate_many_replies_text', array( $this, 'validate_text_input' ) );
		add_filter( 'wpdc_validate_more_replies_more_text', array( $this, 'validate_text_input' ) );
		add_filter( 'wpdc_validate_external_login_text', array( $this, 'validate_text_input' ) );
		add_filter( 'wpdc_validate_link_to_discourse_text', array( $this, 'validate_text_input' ) );
		add_filter( 'wpdc_validate_linked_to_discourse_text', array( $this, 'validate_text_input' ) );

		add_filter( 'wpdc_validate_use_discourse_webhook', array( $this, 'validate_use_discourse_webhook' ) );
		add_filter( 'wpdc_validate_webhook_match_old_topics', array( $this, 'validate_webhook_match_old_topics' ) );
		add_filter( 'wpdc_validate_use_discourse_user_webhook', array( $this, 'validate_use_discourse_user_webhook' ) );
		add_filter( 'wpdc_validate_webhook_match_user_email', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_webhook_secret', array( $this, 'validate_webhook_secret' ) );

		add_filter( 'wpdc_validate_sso_client_enabled', array( $this, 'validate_sso_client_enabled' ) );
		add_filter( 'wpdc_validate_sso_client_login_form_change', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_sso_client_login_form_redirect', array( $this, 'validate_sso_client_login_form_redirect' ) );
		add_filter( 'wpdc_validate_sso_client_sync_by_email', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_sso_client_sync_logout', array( $this, 'validate_checkbox' ) );

		add_filter( 'wpdc_validate_enable_sso', array( $this, 'validate_enable_sso' ) );
		add_filter( 'wpdc_validate_auto_create_sso_user', array( $this, 'validate_checkbox' ) );

		add_filter( 'wpdc_validate_sso_secret', array( $this, 'validate_sso_secret' ) );
		add_filter( 'wpdc_validate_login_path', array( $this, 'validate_login_path' ) );
		add_filter( 'wpdc_validate_real_name_as_discourse_name', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_force_avatar_update', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_redirect_without_login', array( $this, 'validate_checkbox' ) );

		add_filter( 'wpdc_validate_site_multisite_configuration_enabled', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_site_url', array( $this, 'validate_url' ) );
		add_filter( 'wpdc_validate_site_api_key', array( $this, 'validate_api_key' ) );
		add_filter( 'wpdc_validate_site_publish_username', array( $this, 'validate_publish_username' ) );
		add_filter( 'wpdc_validate_site_use_discourse_webhook', array( $this, 'validate_use_discourse_webhook' ) );
		add_filter( 'wpdc_validate_site_webhook_match_old_topics', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_site_webhook_secret', array( $this, 'validate_webhook_secret' ) );
		add_filter( 'wpdc_validate_site_webhook_match_user_email', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_site_use_discourse_user_webhook', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_site_hide_discourse_name_field', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_site_sso_secret', array( $this, 'validate_sso_secret' ) );
		add_filter( 'wpdc_validate_site_enable_sso', array( $this, 'validate_checkbox' ) );
		add_filter( 'wpdc_validate_site_sso_client_enabled', array( $this, 'validate_checkbox' ) );
	}

	/**
	 * Setup options.
	 */
	public function setup_options() {
		$this->options = $this->get_options();

		$this->sso_provider_enabled = ! empty( $this->options['enable-sso'] );
		$this->sso_client_enabled   = ! empty( $this->options['sso-client-enabled'] );
		$this->sso_secret_set       = ! empty( $this->options['sso-secret'] );
	}

	/**
	 * Validates the Discourse URL.
	 *
	 * @param string $input The input to be validated.
	 *
	 * @return string
	 */
	public function validate_url( $input ) {
		$regex = '/^(http:|https:)/';

		// Make sure the url starts with a valid protocol.
		if ( ! preg_match( $regex, $input ) ) {
			add_settings_error( 'discourse', 'discourse_url', __( 'The Discourse URL needs to be set to a valid URL that begins with either \'http:\' or \'https:\'.', 'wp-discourse' ) );

			$url = '';
		} else {
			$url = untrailingslashit( esc_url_raw( $input ) );

			if ( ! filter_var( $url, FILTER_VALIDATE_URL ) ) {
				add_settings_error( 'discourse', 'discourse_url', __( 'The Discourse URL you provided is not a valid URL.', 'wp-discourse' ) );

			}
		}

		return $url;
	}

	/**
	 * Validates the api key.
	 *
	 * @param string $input The input to be validated.
	 *
	 * @return string
	 */
	public function validate_api_key( $input ) {
		$regex = '/^\s*([0-9]*[a-z]*|[a-z]*[0-9]*)*\s*$/';

		if ( empty( $input ) ) {
			add_settings_error( 'discourse', 'api_key', __( 'You must provide an API key.', 'wp-discourse' ) );

			$api_key = '';
		} else {
			$api_key = trim( $input );

			if ( ! preg_match( $regex, $input ) ) {
				add_settings_error( 'discourse', 'api_key', __( 'The API key you provided is not valid.', 'wp-discourse' ) );
			}
		}

		return $api_key;
	}

	/**
	 * Validates the publish_username.
	 *
	 * @param string $input The input to be validated.
	 *
	 * @return string
	 */
	public function validate_publish_username( $input ) {
		if ( ! empty( $input ) ) {
			$publish_username = $this->sanitize_text( $input );
		} else {
			add_settings_error( 'discourse', 'publish_username', __( 'You need to provide a Discourse username.', 'wp-discourse' ) );

			$publish_username = '';
		}

		return $publish_username;
	}

	/**
	 * Validates the 'publish_category' select input.
	 *
	 * Returns the category id.
	 *
	 * @param string $input The input to be validated.
	 *
	 * @return string
	 */
	public function validate_publish_category( $input ) {
		return $this->sanitize_int( $input );
	}

	/**
	 * Validates the 'allowed_post_types' multi-select.
	 *
	 * @param array $input The array of allowed post-types.
	 *
	 * @return array
	 */
	public function validate_allowed_post_types( $input ) {
		$output = array();
		foreach ( $input as $post_type ) {
			$output[] = sanitize_text_field( $post_type );
		}

		return $output;
	}

	/**
	 * Validates the 'clear_cached_comment_html input.
	 *
	 * @param string $input The input to be validated.
	 *
	 * @return int
	 */
	public function validate_clear_comments_html( $input ) {
		if ( 1 === intval( $input ) ) {
			$this->clear_cached_html();
		}

		return 0;
	}

	/**
	 * Validates the 'existing_comments_heading' input.
	 *
	 * @param string $input The input to be validated.
	 *
	 * @return string
	 */
	public function validate_existing_comments_heading( $input ) {
		return $this->sanitize_html( $input );
	}

	/**
	 * Validates the 'max_comments' number input.
	 *
	 * @param int $input The input to be validated.
	 *
	 * @return mixed
	 */
	public function validate_max_comments( $input ) {
		return $this->validate_int(
			$input,
			'max_comments',
			0,
			null,
			__( 'The max visible comments must be set to at least 0.', 'wp-discourse' ),
			$this->use_discourse_comments
		);
	}

	/**
	 * Validates the 'min_replies' number input.
	 *
	 * @param int $input The input to be validated.
	 *
	 * @return mixed
	 */
	public function validate_min_replies( $input ) {
		return $this->validate_int(
			$input,
			'min_replies',
			0,
			null,
			__( 'The min number of replies setting requires a number greater than or equal to 0.', 'wp-discourse' ),
			$this->use_discourse_comments
		);
	}

	/**
	 * Validates the 'min_score' number input.
	 *
	 * @param int $input The input to be validated.
	 *
	 * @return mixed
	 */
	public function validate_min_score( $input ) {
		return $this->validate_int(
			$input,
			'min_score',
			0,
			null,
			__( 'The min score of posts setting requires a number greater than or equal to 0.', 'wp-discourse' ),
			$this->use_discourse_comments
		);
	}

	/**
	 * Validates the 'min_trust_level' number input.
	 *
	 * @param int $input The input to be validated.
	 *
	 * @return mixed
	 */
	public function validate_min_trust_level( $input ) {
		return $this->validate_int(
			$input,
			'min_trust_level',
			0,
			5,
			__( 'The trust level setting requires a number between 0 and 5.', 'wp-discourse' ),
			$this->use_discourse_comments
		);
	}

	/**
	 * Validates the 'bypass_trust_level_score' number input.
	 *
	 * @param int $input The input to be validated.
	 *
	 * @return mixed
	 */
	public function validate_bypass_trust_level_score( $input ) {
		return $this->validate_int(
			$input,
			'bypass_trust_level',
			0,
			null,
			__( 'The bypass trust level score setting requires an integer greater than or equal to 0.', 'wp-discourse' ),
			$this->use_discourse_comments
		);
	}

	/**
	 * Validates the 'custom_excerpt_length' number input.
	 *
	 * @param int $input The input to be validated.
	 *
	 * @return mixed
	 */
	public function validate_custom_excerpt_length( $input ) {

		return $this->validate_int(
			$input,
			'excerpt_length',
			0,
			null,
			__( 'The custom excerpt length setting requires a positive integer.', 'wp-discourse' ),
			true
		);
	}

	/**
	 * Validates the 'max_tags' input.
	 *
	 * @param int $input The input to be validated.
	 *
	 * @return mixed
	 */
	public function validate_max_tags( $input ) {
		return $this->validate_int( $input );
	}

	/**
	 * Validates use_discourse_webhook.
	 *
	 * @param string $input The input to be validated.
	 *
	 * @return bool|int
	 */
	public function validate_use_discourse_webhook( $input ) {
		$this->use_discourse_webhook = $this->validate_checkbox( $input );

		return $this->use_discourse_webhook;
	}

	/**
	 * Validates user_discourse_user_webhook.
	 *
	 * @param string $input The input to be validated.
	 *
	 * @return bool|int
	 */
	public function validate_use_discourse_user_webhook( $input ) {
		$this->use_discourse_user_webhook = $this->validate_checkbox( $input );

		return $this->use_discourse_user_webhook;
	}

	/**
	 * Validates the webhook_secret input.
	 *
	 * @param string $input The input to be validated.
	 *
	 * @return string
	 */
	public function validate_webhook_secret( $input ) {
		if ( ( $this->use_discourse_webhook || $this->use_discourse_user_webhook ) && strlen( $input ) < 12 ) {
			add_settings_error( 'discourse', 'webhook_secret', __( 'To use a Discourse webhook, the secret must be set to a value at least 12 characters long.', 'wp-discourse' ) );

			return '';
		}

		return $input;
	}

	/**
	 * Validates the webhook_match_old_topics input.
	 *
	 * @param string $input The input to be validated.
	 *
	 * @return int
	 */
	public function validate_webhook_match_old_topics( $input ) {
		$match_old_topics = $this->validate_checkbox( $input );

		return $match_old_topics;
	}

	/**
	 * Validates the 'enable_sso'checkbox.
	 *
	 * @param string $input The input to be validated.
	 *
	 * @return int
	 */
	public function validate_enable_sso( $input ) {
		$new_value = $this->sanitize_checkbox( $input );

		if ( 1 === $new_value && $this->sso_client_enabled ) {
			add_settings_error(
				'discourse',
				'sso_client_enabled',
				__(
					"You have the 'SSO Client' option enabled. Visit the 'SSO Client' settings tab
			to disable it before enabling your site to function as the SSO provider.",
					'wp-discourse'
				)
			);

			return 0;
		}

		if ( 1 === $new_value && ! $this->sso_secret_set ) {
			add_settings_error(
				'discourse',
				'sso_provider_no_secret',
				__(
					'Before enabling your site to function as the SSO provider,
            you need to set the SSO Secret Key.',
					'wp-discourse'
				)
			);

			return 0;
		}

		// When the SSO Provider option is updated, clear the comment cache to update links to Discourse.
		$this->clear_cached_html();

		return $new_value;
	}

	/**
	 * Validates the 'sso_client_enabled' checkbox.
	 *
	 * @param string $input The input to be validated.
	 *
	 * @return int
	 */
	public function validate_sso_client_enabled( $input ) {
		$new_value = $this->sanitize_checkbox( $input );

		if ( 1 === $new_value && $this->sso_provider_enabled ) {
			add_settings_error(
				'discourse',
				'sso_provider_enabled',
				__(
					"You have the 'SSO Provider' option enabled. Click on the 'SSO Provider' settings tab
			to disable it before enabling your site to function as an SSO client.",
					'wp-discourse'
				)
			);

			return 0;
		}

		if ( 1 === $new_value && ! $this->sso_secret_set ) {
			add_settings_error(
				'discourse',
				'sso_client_no_secret',
				__(
					'Before enabling your site to function as an SSO client,
            you need to set the SSO Secret Key.',
					'wp-discourse'
				)
			);

			return 0;
		}

		return $this->sanitize_checkbox( $input );
	}

	/**
	 * Validates the sso_client_login_form_redirect redirect text input.
	 *
	 * @param string $input The input to be validated.
	 *
	 * @return string
	 */
	public function validate_sso_client_login_form_redirect( $input ) {
		if ( empty( $input ) ) {

			return '';
		}
		$regex = '/^(http:|https:)/';

		// Make sure the url starts with a valid protocol.
		if ( ! preg_match( $regex, $input ) ) {
			add_settings_error( 'discourse', 'sso_client_login_redirect', __( 'The redirect URL needs to be set to a valid URL that begins with either \'http:\' or \'https:\'.', 'wp-discourse' ) );

			$url = '';
		} else {
			$url = untrailingslashit( esc_url_raw( $input ) );

			if ( ! filter_var( $url, FILTER_VALIDATE_URL ) ) {
				add_settings_error( 'discourse', 'sso_client_login_redirect', __( 'The redirect URL you provided is not a valid URL.', 'wp-discourse' ) );
			}
		}

		return $url;
	}

	/**
	 * Validates the 'sso_secret' text input.
	 *
	 * @param string $input The input to be validated.
	 *
	 * @return string
	 */
	public function validate_sso_secret( $input ) {
		$secret = trim( $input );
		if ( strlen( $secret ) < 10 ) {
			add_settings_error( 'discourse', 'sso_secret', __( 'The SSO secret key must be at least 10 characters long.', 'wp-discourse' ) );

			return '';
		}

		return $secret;
	}

	/**
	 * Validates the 'login_path' text input.
	 *
	 * @param string $input The input to be validated.
	 *
	 * @return string
	 */
	public function validate_login_path( $input ) {
		if ( $this->sso_provider_enabled && $input ) {

			$regex = '/^\//';
			if ( ! preg_match( $regex, $input ) ) {
				add_settings_error( 'discourse', 'login_path', __( 'The path to login page setting needs to be a valid file path, starting with \'/\'.', 'wp-discourse' ) );
			}

			// It's valid.
			return $this->sanitize_text( $input );
		}

		// Sanitize, but don't validate. SSO is not enabled.
		return $this->sanitize_text( $input );
	}

	/**
	 * Validates the 'auto-create-login-redirect' field.
	 *
	 * @param string $input The input to be validated.
	 *
	 * @return string
	 */
	public function validate_auto_create_login_redirect( $input ) {
		if ( $this->sso_provider_enabled && $input ) {

			$regex = '/^\//';
			if ( ! preg_match( $regex, $input ) ) {
				add_settings_error( 'discourse', 'auto_create_login_redirect', __( 'The path to the login redirect page setting needs to be a valid file path, starting with \'/\'.', 'wp-discourse' ) );
			}

			// It's valid.
			return $this->sanitize_text( $input );
		}

		// Sanitize, but don't validate. SSO is not enabled.
		return $this->sanitize_text( $input );
	}

	/**
	 * Validates the 'auto-create-welcome-redirect' field.
	 *
	 * @param string $input The input to be validated.
	 *
	 * @return string
	 */
	public function validate_auto_create_welcome_redirect( $input ) {
		if ( $this->sso_provider_enabled && $input ) {

			$regex = '/^\//';
			if ( ! preg_match( $regex, $input ) ) {
				add_settings_error( 'discourse', 'auto_create_welcome_redirect', __( 'The path to the welcome page setting needs to be a valid file path, starting with \'/\'.', 'wp-discourse' ) );
			}

			// It's valid.
			return $this->sanitize_text( $input );
		}

		// Sanitize, but don't validate. SSO is not enabled.
		return $this->sanitize_text( $input );
	}

	/**
	 * Validates the `force-publish-max-age` input.
	 *
	 * @param string $input The input to be validated.
	 *
	 * @return int
	 */
	public function validate_force_publish_max_age( $input ) {
		return $this->sanitize_int( $input );
	}

	/**
	 * Validate a checkbox input.
	 *
	 * @param string $input The input to be validated.
	 *
	 * @return int
	 */
	public function validate_checkbox( $input ) {
		return $this->sanitize_checkbox( $input );
	}

	/**
	 * Validate a radio input that returns a string.
	 *
	 * @param string $input The input to be validated.
	 *
	 * @return string
	 */
	public function validate_radio_string_value( $input ) {
		return $this->validate_text_input( $input );
	}

	/**
	 * Validate a text input.
	 *
	 * @param string $input The input to be validated.
	 *
	 * @return string
	 */
	public function validate_text_input( $input ) {
		if ( ! empty( $input ) ) {
			return $this->sanitize_text( $input );
		} else {
			return '';
		}
	}

	/**
	 * Validates an email input.
	 *
	 * @param string $input The input to be validated.
	 *
	 * @return string
	 */
	public function validate_email( $input ) {
		if ( ! empty( $input ) ) {

			return sanitize_email( $input );
		} else {

			return '';
		}
	}

	/**
	 * Helper methods
	 ******************************/

	/**
	 * A helper method to sanitize text inputs.
	 *
	 * @param string $input The input to be sanitized.
	 *
	 * @return string
	 */
	protected function sanitize_text( $input ) {
		return sanitize_text_field( $input );
	}

	/**
	 * A helper method to sanitize the value returned from checkbox inputs.
	 *
	 * @param string $input The value returned from the checkbox.
	 *
	 * @return int
	 */
	protected function sanitize_checkbox( $input ) {
		return 1 === intval( $input ) ? 1 : 0;
	}

	/**
	 * A helper function to sanitize HTML.
	 *
	 * @param string $input HTML input to be sanitized.
	 *
	 * @return string
	 */
	protected function sanitize_html( $input ) {
		return wp_kses_post( $input );
	}

	/**
	 * A helper function to sanitize an int.
	 *
	 * @param mixed|int $input The input to be validated.
	 *
	 * @return int
	 */
	protected function sanitize_int( $input ) {
		return intval( $input );
	}

	/**
	 * A helper function to validate and sanitize integers.
	 *
	 * @param int    $input         The input to be validated.
	 * @param string $option_id     The option being validated.
	 * @param null   $min           The minimum allowed value.
	 * @param null   $max           The maximum allowed value.
	 * @param string $error_message The error message to return.
	 * @param bool   $add_error     Whether or not to add a setting error.
	 *
	 * @return mixed
	 */
	protected function validate_int( $input, $option_id = null, $min = null, $max = null, $error_message = '', $add_error = false ) {
		$options = array();

		if ( isset( $min ) ) {
			$options['min_range'] = $min;
		}
		if ( isset( $max ) ) {
			$options['max_range'] = $max;
		}

		$input = filter_var(
			$input,
			FILTER_VALIDATE_INT,
			array(
				'options' => $options,
			)
		);

		if ( false === $input ) {
			if ( $add_error ) {
				add_settings_error( 'discourse', $option_id, $error_message );
			}

			// The input is not valid, but the setting's section is not being used, sanitize the input and return it.
			return null;
		} else {
			// Valid input.
			return $input;
		}
	}

	/**
	 * Clears all cached comment HTML.
	 */
	protected function clear_cached_html() {
		$transient_keys = get_option( 'wpdc_cached_html_keys' );
		if ( ! empty( $transient_keys ) ) {
			foreach ( $transient_keys as $transient_key ) {
				delete_transient( $transient_key );
			}
		}
	}
}