var sharpmap = {};

sharpmap.queue = (function () {

var queued = [], active = 0, size = 6;

function init() {

webdb.check();

}

function process() {

if ((active >= size) || !queued.length)

return;

active++;

queued.pop()();

}

function dequeue(send) {

for (var i = 0; i < queued.length; i++) {

if (queued[i] == send) {

queued.splice(i, 1);

return true;

}

}

return false;

}

function request(url, callback, mimeType) {

var req;

function send() {

req = new XMLHttpRequest();

if (mimeType && req.overrideMimeType) {

req.overrideMimeType(mimeType);

}

req.open("GET", url, true);

req.onreadystatechange = function () {

if (req.readyState == 4) {

active--;

if (req.status < 300)

callback(req);

process();

}

};

req.send(null);

}

function abort(hard) {

if (dequeue(send))

return true;

if (hard && req) {

req.abort();

return true;

}

return false;

}

queued.push(send);

process();

return { abort: abort };

}

function json(url, callback) {

var data = webdb.get(url), parse;

if (data) {

parse = JSON.parse(data);

console.log('retrieved from webdb ' + url);

return callback(parse);

}

return request(url, function (req) {

var text;

if (req.responseText) {

text = req.responseText;

webdb.add(url, text);

data = JSON.parse(text);

console.log('added to webdb ' + url);

callback(data);

}

}, "application/json");

}

return { init: init, json: json };

})();