/*
 * This file is part of the MediaWiki extension MediaViewer.
 *
 * MediaViewer is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * MediaViewer is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with MediaViewer.  If not, see <http://www.gnu.org/licenses/>.
 */

const { isMediaViewerEnabledOnClick } = require( 'mmv.head' );
const api = new mw.Api();

/**
 * Contains/retrieves configuration/environment information for MediaViewer.
 */
class Config {
	/**
	 * @param {Object} viewerConfig
	 * @param {mw.Api} api
	 */
	constructor( viewerConfig = mw.config.get( 'wgMultimediaViewer', {} ) ) {
		/**
		 * A plain object storing MediaViewer-specific settings
		 *
		 * @type {Object}
		 */
		this.viewerConfig = viewerConfig;
	}

	/**
	 * Get value from local storage or fail gracefully.
	 *
	 * @param {string} key
	 * @param {any} [fallback] value to return when key is not set or localStorage is not supported
	 * @return {string|null} stored value or fallback or null if neither exists
	 */
	getFromLocalStorage( key, fallback ) {
		const value = mw.storage.get( key );

		// localStorage will only store strings; if values `null`, `false` or
		// `0` are set, they'll come out as `"null"`, `"false"` or `"0"`, so we
		// can be certain that an actual null is a failure to locate the item,
		// and false is an issue with localStorage itself
		if ( value !== null && value !== false ) {
			return value;
		}

		if ( value === null ) {
			mw.log( `Failed to fetch item ${ key } from localStorage` );
		}

		return fallback !== undefined ? fallback : null;
	}

	/**
	 * Set item in local storage or fail gracefully.
	 *
	 * @param {string} key
	 * @param {any} value
	 * @return {boolean} whether storing the item was successful
	 */
	setInLocalStorage( key, value ) {
		return mw.storage.set( key, value );
	}

	/**
	 * Remove item from local storage or fail gracefully.
	 *
	 * @param {string} key
	 * @return {boolean} whether storing the item was successful
	 */
	removeFromLocalStorage( key ) {
		mw.storage.remove( key );

		// mw.storage.remove catches all exceptions and returns false if any
		// occur, so we can't distinguish between actual issues, and
		// localStorage not being supported - however, localStorage.removeItem
		// is not documented to throw any errors, so nothing to worry about;
		// when localStorage is not supported, we'll consider removal successful
		// (it can't have been there in the first place)
		return true;
	}

	/**
	 * (Semi-)permanently stores the setting whether MediaViewer should handle thumbnail clicks.
	 * - for logged-in users, we use preferences
	 * - for anons, we use localStorage
	 * - for anons with old browsers, we don't do anything
	 *
	 * @param {boolean} enabled
	 * @return {jQuery.Promise} a deferred which resolves/rejects on success/failure respectively
	 */
	setMediaViewerEnabledOnClick( enabled ) {
		const defaultPrefValue = mw.config.get( 'wgMediaViewerEnabledByDefault' );
		let deferred;
		let newPrefValue;
		let success = true;

		if ( !mw.user.isNamed() ) {
			if ( !enabled ) {
				success = this.setInLocalStorage( 'wgMediaViewerOnClick', '0' ); // localStorage stringifies everything, best use strings in the first place
			} else {
				success = this.removeFromLocalStorage( 'wgMediaViewerOnClick' );
			}
			if ( success ) {
				deferred = $.Deferred().resolve();
			} else {
				deferred = $.Deferred().reject();
			}
		} else {
			// Simulate changing the option in Special:Preferences. Turns out this is quite hard (bug 69942):
			// we need to delete the user_properties row if the new setting is the same as the default,
			// otherwise set '1' for enabled, '' for disabled. In theory the pref API will delete the row
			// if the new value equals the default, but this does not always work.
			if ( defaultPrefValue === true ) {
				newPrefValue = enabled ? '1' : '';
			} else {
				// undefined will cause the API call to omit the optionvalue parameter
				// which in turn will cause the options API to delete the row and revert the pref to default
				newPrefValue = enabled ? '1' : undefined;
			}
			deferred = api.saveOption( 'multimediaviewer-enable', newPrefValue );
		}

		return deferred.done( () => {
			// make the change work without a reload
			mw.config.set( 'wgMediaViewerOnClick', enabled );
			if ( !enabled ) {
				// set flag for showing a popup if this was a first-time disable
				this.maybeEnableStatusInfo();
			}
		} );
	}

	/**
	 * True if info about enable/disable status should be displayed (mingle #719).
	 *
	 * @return {boolean}
	 */
	shouldShowStatusInfo() {
		return !isMediaViewerEnabledOnClick( mw.config, mw.user, mw.storage ) && this.getFromLocalStorage( 'mmv-showStatusInfo' ) === '1';
	}

	/**
	 * Called when MediaViewer is disabled. If status info was never displayed before, future
	 * shouldShowStatusInfo() calls will return true.
	 *
	 * @private
	 */
	maybeEnableStatusInfo() {
		const currentShowStatusInfo = this.getFromLocalStorage( 'mmv-showStatusInfo' );
		if ( currentShowStatusInfo === null ) {
			this.setInLocalStorage( 'mmv-showStatusInfo', '1' );
		}
	}

	/**
	 * Called when status info is displayed. Future shouldShowStatusInfo() calls will return false.
	 */
	disableStatusInfo() {
		this.setInLocalStorage( 'mmv-showStatusInfo', '0' );
	}

	/**
	 * Returns file extensions handled by Media Viewer.
	 *
	 * The object's keys are the file extensions.
	 * The object's values are either 'default' when Media Viewer handles that file extension
	 * directly or the name of a ResourceLoader module to load when such a file is opened.
	 *
	 * @return {Object}
	 */
	extensions() {
		return this.viewerConfig.extensions;
	}

	/**
	 * Returns UI language
	 *
	 * @return {string} Language code
	 */
	language() {
		return mw.config.get( 'wgUserLanguage', false ) || mw.config.get( 'wgContentLanguage', 'en' );
	}

	/**
	 * Returns URI of virtual view beacon or false if not set
	 *
	 * @return {string|boolean} URI
	 */
	recordVirtualViewBeaconURI() {
		return this.viewerConfig.recordVirtualViewBeaconURI;
	}

	/**
	 * Returns useThumbnailGuessing flag
	 *
	 * @return {boolean}
	 */
	useThumbnailGuessing() {
		return this.viewerConfig.useThumbnailGuessing;
	}

	/**
	 * Returns imageQueryParameter, if set
	 *
	 * @return {string|boolean}
	 */
	imageQueryParameter() {
		return this.viewerConfig.imageQueryParameter;
	}
}

module.exports = Config;