var sim = {};

(function() {
var alphabet = "abcdefghijklmnopqrstuvwxyz234567";
var N_shares = 10;
var K_required = 3;
var encryptionRelativeSize = 3.0;

sim.onEncrypt = function() {
    var cleartext = $('cleartext').value;
    var fakeHash = simpleHash(cleartext);

    $('url').update("http://localhost:8123/uri/URI%3ACHK%3A" + 
		    randomHex(fakeHash + 1234, 128) + ":" + 
		    randomHex(fakeHash + 5678, 256) + ":" + 
		    K_required + ":" + N_shares + ":" + cleartext.length);

    $('encrypted').value = randomHex(fakeHash + 9876, 
				     cleartext.length * 8 * encryptionRelativeSize, 
				     100);
    sim.updateActiveSteps();
}

sim.onStore = function() {
    var cleartext = $('cleartext').value;
    var fakeHash = simpleHash(cleartext);
    $('shares').update('');
    for (var row=0; row < Math.ceil(N_shares / 4); row++) {
	var rowElem = new Element('tr');
	for (var col=0; col < 4 && (row * 4 + col < N_shares); col++) {
	    var shareNum = row*4+col + 1;
	    var td = new Element('td');

	    td.appendChild(new Element('div').update(
		'#' + shareNum));
	    var data = randomHex(fakeHash + shareNum, 
		                 cleartext.length * 8 / K_required, 25);
	    td.appendChild(new Element('textarea', 
				       {class: 'encrypted share', 
					id: 'share'+shareNum,
					correctValue: data,
					cols: '26', rows: '4'}).update(data));

	    rowElem.appendChild(td);
	}
	$('shares').appendChild(rowElem);
    }
    sim.updateActiveSteps();
}

sim.onRecover = function() {
    var usableShares = new Array();
    for (var i=1; i <= N_shares; i++) {
	var cell = $('share' + i);

	cell.removeClassName('share-used');
	cell.removeClassName('share-errored');

	if (usableShares.length >= K_required) {
	    continue;
	}

	if (cell.value == cell.getAttribute('correctValue')) {
	    usableShares.push(i);
	    cell.addClassName('share-used');
	} else {
	    cell.addClassName('share-errored');
	}
    }
    if (usableShares.length == K_required) {
	$('recovered').value = $('cleartext').value; // sssh!
	$('recover-report').update("Recovery used these shares: " + usableShares);
    } else {
	$('recovered').value = "";
	$('recover-report').update("Recovery failed");
    }
}

sim.updateActiveSteps = function() {
    $('active-encrypt').addClassName('disabled');
    $('active-store').addClassName('disabled');
    $('active-recover').addClassName('disabled');

    if ($('cleartext').value != '') {
	$('active-encrypt').removeClassName('disabled');

	if ($('encrypted').value != '') {
	    $('active-store').removeClassName('disabled');

	    if ($('shares').descendants().length > 3) {
		$('active-recover').removeClassName('disabled');
	    }
	}
    }
}

var _seed = 0;
function awfulRandSeed(seed) {
    _seed = seed;
}
function awfulRand() {
    _seed = (_seed * 93485039485) % 1029480192;
    return (_seed % 10000) / 10000;
}

function randomHex(seed, bits, width) {
    var result = "";
    awfulRandSeed(seed);
    var chars = charsNeeded(bits, alphabet.length);
    for (var i=0; i < chars; i++) {
	result += alphabet[Math.floor(awfulRand() * alphabet.length)];
	if (!(width == undefined) && (i + 1) % width == 0) {
	    result += "\n";
	}
    }
    return result;
}

function simpleHash(s) {
    var result = 0;
    for (var i=0; i < s.length; i++) {
	result += s.charCodeAt(i);
    }
    return (result * 95739387523) % 100000000;
}

function charsNeeded(bits, alphabetSize) {
    var bitsPerChar = Math.log(alphabetSize) / Math.log(2);
    return Math.ceil(bits / bitsPerChar)
}
})();