define(function(require) {
    'use strict';

    var util = require('js/crypto/util');

    var dl = {};

    dl.createDownload = function(options, callback) {
        var contentType = options.contentType || 'application/octet-stream';
        var filename = options.filename || 'file';
        var content = options.content;
        var a = document.createElement('a');
        var supportsBlob;

        try {
            supportsBlob = !!new Blob();
        } catch (e) {}

        if (window.chrome && window.chrome.fileSystem) {
            // chrome app
            chrome.fileSystem.chooseEntry({
                type: 'saveFile',
                suggestedName: filename
            }, function(file) {
                if (!file) {
                    callback();
                    return;
                }
                file.createWriter(function(writer) {
                    writer.onerror = callback;
                    writer.onwriteend = function() {
                        callback();
                    };
                    writer.write(new Blob([content], {
                        type: contentType
                    }));
                }, callback);
            });
            return;
        } else if (typeof a.download !== "undefined" && supportsBlob) {
            // ff 30+, chrome 27+ (android: 37+)
            document.body.appendChild(a);
            a.style = "display: none";
            a.href = window.URL.createObjectURL(new Blob([content], {
                type: contentType
            }));
            a.download = filename;
            a.click();
            setTimeout(function() {
                window.URL.revokeObjectURL(a.href);
                document.body.removeChild(a);
            }, 10); // arbitrary, just get it off the main thread
        } else if (window.navigator.msSaveBlob) {
            // ie 10+
            window.navigator.msSaveBlob(new Blob([content], {
                type: contentType
            }), filename);
        } else if (supportsBlob) {
            // safari actually makes no sense:
            // - you can't open a new window
            // - the file system api is dead
            // - download attribute doesn't work
            // - behaves randomly (opens a new tab or doesn't, downloads stuff or doesn't, ...)
            var url = window.URL.createObjectURL(new Blob([content], {
                type: contentType
            }));
            var newTab = window.open(url, "_blank");
            if (!newTab) {
                window.location.href = url;
            }
        } else {
            // anything else, where anything at all is better than nothing
            if (typeof content !== "string" && content.buffer) {
                content = util.arrBuf2BinStr(content.buffer);
            }
            window.open('data:' + contentType + ';base64,' + btoa(content), "_blank");
        }
    };

    return dl;
});