const
	pageJSONParser = require( '../mobile.startup/page/pageJSONParser' ),
	util = require( '../mobile.startup/util' ),
	extendSearchParams = require( '../mobile.startup/extendSearchParams' );

/**
 * API for interacting with watchlist.
 *
 * @param {mw.Api} api
 * @param {string} lastTitle of page listed in Watchlist to be used as a continuation parameter
 * @private
 */
function WatchListGateway( api, lastTitle ) {
	this.api = api;
	// Try to keep it in sync with SpecialMobileEditWatchlist::LIMIT (php)
	this.limit = 50;

	if ( lastTitle ) {
		this.continueParams = {
			continue: 'gwrcontinue||',
			gwrcontinue: '0|' + lastTitle.replace( / /g, '_' )
		};
		this.shouldSkipFirstTitle = true;
	} else {
		this.continueParams = {
			continue: ''
		};
		this.shouldSkipFirstTitle = false;
	}

	this.canContinue = true;
}

WatchListGateway.prototype = {
	/**
	 * Load the list of items on the watchlist
	 *
	 * @return {jQuery.Deferred}
	 */
	loadWatchlist: function () {
		const self = this,
			params = extendSearchParams( 'watchlist', {
				prop: [ 'info', 'revisions' ],
				rvprop: 'timestamp|user',
				generator: 'watchlistraw',
				gwrnamespace: '0',
				gwrlimit: this.limit
			}, this.continueParams );

		if ( this.canContinue === false ) {
			return util.Deferred().resolve( [] );
		}
		return this.api.get( params ).then( function ( data ) {
			if ( data.continue !== undefined ) {
				self.continueParams = data.continue;
			} else {
				self.canContinue = false;
			}

			return self.parseData( data );
		} );
	},

	/**
	 * Parse api response data into pagelist item format
	 *
	 * @param {Object[]} data
	 * @return {Page[]}
	 */
	parseData: function ( data ) {
		let pages;

		if ( !data.query || !data.query.pages ) {
			return [];
		}

		pages = data.query.pages;

		// Sort results alphabetically (the api map doesn't have any order). The
		// watchlist is ordered alphabetically right now.
		pages.sort( function ( p1, p2 ) {
			return p1.title === p2.title ? 0 : ( p1.title < p2.title ? -1 : 1 );
		} );

		// If we requested from the last item of the previous page, we shall
		// remove the first result (to avoid it being repeated)
		if ( this.shouldSkipFirstTitle ) {
			pages = pages.slice( 1 );
			this.shouldSkipFirstTitle = false;
		}

		// Transform the items to a sensible format
		return pages.map( pageJSONParser.parse );
	}

};

module.exports = WatchListGateway;