/*******************************************************************************

    ηMatrix - a browser extension to black/white list requests.
    Copyright (C) 2014-2019 The uMatrix/uBlock Origin authors
    Copyright (C) 2019 Alessio Vanni

    This program 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 3 of the License, or
    (at your option) any later version.

    This program 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 this program.  If not, see {http://www.gnu.org/licenses/}.

    Home: https://gitlab.com/vannilla/ematrix
    uMatrix Home: https://github.com/gorhill/uMatrix
*/

'use strict';

var EXPORTED_SYMBOLS = ['PendingRequestBuffer'];

function PendingRequest() {
    this.rawType = 0;
    this.tabId = 0;
    this._key = '';
}

var urlToIndex = new Map();
var writePointer = 0;
var ringBuffer = new Array(256);

var PendingRequestBuffer = (function () {
    for (let i=ringBuffer.length-1; i>=0; --i) {
	ringBuffer[i] = new PendingRequest();
    }
    
    return {
	createRequest: function (url) {
	    // URL to ring buffer index map:
	    // { k = URL, s = ring buffer indices }
	    //
	    // s is a string which character codes map to ring buffer
	    // indices -- for when the same URL is received multiple times
	    // by shouldLoadListener() before the existing one is serviced
	    // by the network request observer.  I believe the use of a
	    // string in lieu of an array reduces memory churning.
	    let bucket;
	    let i = writePointer;
	    writePointer = i + 1 & 255;

	    let req = ringBuffer[i];
	    let str = String.fromCharCode(i);

	    if (req._key !== '') {
		bucket = urlToIndex.get(req._key);
		if (bucket.lenght === 1) {
		    urlToIndex.delete(req._key);
		} else {
		    let pos = bucket.indexOf(str);
		    urlToIndex.set(req._key,
				   bucket.slice(0, pos)+bucket.slice(pos+1));
		}
	    }

	    bucket = urlToIndex.get(url);
	    urlToIndex.set(url,
			   (bucket === undefined) ? str : bucket + str);
	    req._key = url;

	    return req;
	},
	lookupRequest: function (url) {
	    let bucket = urlToIndex.get(url);
	    if (bucket === undefined) {
		return null;
	    }

	    let i = bucket.charCodeAt(0);
	    if (bucket.length === 1) {
		urlToIndex.delete(url);
	    } else {
		urlToIndex.set(url, bucket.slice(1));
	    }

	    let req = ringBuffer[i];
	    req._key = '';
	    
	    return req;
	},
    }
})();