<?php
/**
 * Settings storage, defaults and saving rules.
 *
 * @package DevLab_Image_Alt
 */

defined( 'ABSPATH' ) || exit;

/**
 * Registers the plugin option.
 *
 * Everything lives in ONE option (devlab_alt_settings), loaded with the other
 * autoloaded options, so the front end needs no extra database query.
 */
class DevLab_ALT_Settings {

	/**
	 * Name of the option that stores everything.
	 */
	const OPTION = 'devlab_alt_settings';

	/**
	 * Settings API option group.
	 */
	const GROUP = 'devlab_alt_group';

	/**
	 * Alt source: the attachment title.
	 */
	const SOURCE_TITLE = 'title';

	/**
	 * Alt source: the attachment caption.
	 */
	const SOURCE_CAPTION = 'caption';

	/**
	 * Alt source: the attachment description.
	 */
	const SOURCE_DESCRIPTION = 'description';

	/**
	 * Alt source: the cleaned-up file name.
	 */
	const SOURCE_FILENAME = 'filename';

	/**
	 * Valid source values. Kept apart from the labels so reading the settings
	 * never loads translations (which must wait for the 'init' action).
	 *
	 * @var string[]
	 */
	const SOURCES = array( 'title', 'caption', 'description', 'filename' );

	/**
	 * Per-request cache of the normalised settings.
	 *
	 * @var array|null
	 */
	private static $cache = null;

	/**
	 * Notice codes already queued in this request (the sanitize callback can
	 * run twice when the option is created for the first time).
	 *
	 * @var array
	 */
	private static $notices_added = array();

	/**
	 * Hooks the settings into WordPress.
	 */
	public function __construct() {
		add_action( 'admin_init', array( $this, 'register' ) );

		// Keep the in-memory copy fresh if the option changes during a request.
		add_action( 'add_option_' . self::OPTION, array( __CLASS__, 'flush_cache' ) );
		add_action( 'update_option_' . self::OPTION, array( __CLASS__, 'flush_cache' ) );
		add_action( 'delete_option_' . self::OPTION, array( __CLASS__, 'flush_cache' ) );
	}

	/**
	 * Default values: the attachment title, on content and on attachment images.
	 *
	 * @return array
	 */
	public static function defaults() {
		return array(
			'source'            => self::SOURCE_TITLE,
			'apply_content'     => 1,
			'apply_attachments' => 1,
		);
	}

	/**
	 * The alt text sources, as value => label.
	 *
	 * @return string[]
	 */
	public static function get_sources() {
		return array(
			self::SOURCE_TITLE       => __( 'Attachment title', 'devlab-image-alt' ),
			self::SOURCE_CAPTION     => __( 'Caption', 'devlab-image-alt' ),
			self::SOURCE_DESCRIPTION => __( 'Description', 'devlab-image-alt' ),
			self::SOURCE_FILENAME    => __( 'File name (cleaned up)', 'devlab-image-alt' ),
		);
	}

	/**
	 * Returns the current settings (cached for the request).
	 *
	 * @return array {
	 *     @type string $source            One of the SOURCE_* values.
	 *     @type int    $apply_content     1 to fill alt text inside post content.
	 *     @type int    $apply_attachments 1 to fill alt text on attachment images
	 *                                     (featured images, template images).
	 * }
	 */
	public static function get() {
		if ( null === self::$cache ) {
			self::$cache = self::normalise( get_option( self::OPTION, array() ) );
		}

		return self::$cache;
	}

	/**
	 * Clears the in-memory copy.
	 *
	 * @return void
	 */
	public static function flush_cache() {
		self::$cache = null;
	}

	/**
	 * Fills in defaults and forces the right type on every key.
	 *
	 * The database value is re-validated on every read, because it may have
	 * been written by WP-CLI, another plugin or a restore.
	 *
	 * @param mixed $stored Value read from the database.
	 * @return array Normalised settings.
	 */
	public static function normalise( $stored ) {
		$stored   = is_array( $stored ) ? $stored : array();
		$defaults = self::defaults();
		$out      = $defaults;

		if ( isset( $stored['source'] ) && is_string( $stored['source'] )
			&& in_array( $stored['source'], self::SOURCES, true ) ) {
			$out['source'] = $stored['source'];
		}

		foreach ( array( 'apply_content', 'apply_attachments' ) as $key ) {
			if ( array_key_exists( $key, $stored ) ) {
				$out[ $key ] = self::to_flag( $stored[ $key ] );
			}
		}

		return $out;
	}

	/**
	 * Turns a stored or submitted value into 1 or 0.
	 *
	 * @param mixed $value Raw value.
	 * @return int
	 */
	private static function to_flag( $value ) {
		if ( is_string( $value ) ) {
			$value = strtolower( trim( $value ) );

			return in_array( $value, array( '1', 'true', 'on', 'yes' ), true ) ? 1 : 0;
		}

		return empty( $value ) ? 0 : 1;
	}

	/**
	 * Registers the option with the Settings API.
	 *
	 * The Settings API form posts to options.php, which checks the nonce and
	 * the manage_options capability before this option is touched.
	 *
	 * @return void
	 */
	public function register() {
		register_setting(
			self::GROUP,
			self::OPTION,
			array(
				'type'              => 'array',
				'sanitize_callback' => array( $this, 'sanitize' ),
				'default'           => self::defaults(),
				'show_in_rest'      => false,
			)
		);
	}

	/**
	 * Sanitize callback for the option.
	 *
	 * The file options.php has already run wp_unslash() on the submitted data.
	 * A key that is missing from the submission keeps its current value.
	 *
	 * @param mixed $input Submitted value.
	 * @return array Value to store.
	 */
	public function sanitize( $input ) {
		$new   = self::normalise( get_option( self::OPTION, array() ) );
		$input = is_array( $input ) ? $input : array();

		if ( isset( $input['source'] ) && is_string( $input['source'] ) ) {
			$source = sanitize_key( $input['source'] );

			if ( in_array( $source, self::SOURCES, true ) ) {
				$new['source'] = $source;
			}
		}

		foreach ( array( 'apply_content', 'apply_attachments' ) as $key ) {
			if ( array_key_exists( $key, $input ) ) {
				$new[ $key ] = self::to_flag( $input[ $key ] );
			}
		}

		if ( ! $new['apply_content'] && ! $new['apply_attachments'] ) {
			$this->add_notice_once(
				'devlab_alt_all_off',
				__( 'Both options are off, so no alt text is filled in until you switch one on.', 'devlab-image-alt' ),
				'warning'
			);
		}

		$this->add_notice_once(
			'devlab_alt_saved',
			__( 'Settings saved.', 'devlab-image-alt' ),
			'success'
		);

		return $new;
	}

	/**
	 * Queues a Settings API notice only once per request.
	 *
	 * @param string $code    Unique notice code.
	 * @param string $message Already translated, plain-text message.
	 * @param string $type    error|warning|success|info.
	 * @return void
	 */
	private function add_notice_once( $code, $message, $type ) {
		// add_settings_error() is an admin-only function; skip the notice if the
		// callback is ever reached from a context where it is not loaded.
		if ( isset( self::$notices_added[ $code ] ) || ! function_exists( 'add_settings_error' ) ) {
			return;
		}

		self::$notices_added[ $code ] = true;
		add_settings_error( 'devlab_alt_messages', $code, $message, $type );
	}
}