<script>
       jQuery.extend({
           postJSON: function(url, data, callback) {
               return jQuery.ajax({
                   type: "POST",
                   url: url,
                   data: JSON.stringify(data),
                   success: callback,
                   dataType: "json",
                   contentType: "application/json",
                   processData: false
               });
           }
       });

       function fileSelected(o) {
           $(o).parent().parent().find('.form-control').html($(o).val().split(/[\\|/]/).pop());
           hideError();

           var reader = new FileReader();
           reader.onload = function() {
               var arrayBuffer = this.result;
               bytes = new Uint8Array(arrayBuffer);
               csr_data = '';
               for(i=0; i<bytes.length; i++) {
                   csr_data += ("0" + bytes[i].toString(16)).substr(-2);
               }

               if (csr_data.substr(0x40, 0x40) == "0".repeat(0x40)) {
                   $("#license-code-form").show();
               } else {
                   $("#license-code-form").hide();
                   sign_csr(csr_data, null);
               }
           }
           reader.readAsArrayBuffer(o.files[0]);
       }

       function manualRetrieve() {
           hideError();

           license_code = $("#redeem-code")[0].value;

           if (license_code.length != 8) {
               showError("Invalid license code");
               return;
           }

           license_code = license_code.toUpperCase();

           if (/^[0-9A-Z]{8}$/.test(license_code) != true) {
               showError("Invalid license code");
               return;
           }

           sign_csr(csr_data, license_code);
       }

       function hideError() {
           $("#license_error").hide();
       }

       function showError(txt) {
           $("#license_error_text").html(txt);
           $("#license_error").show();
       }

       function sign_csr(csr_data, code) {
           if (code != null) {
               o = { csr_data: csr_data, redeem_code: code };
           } else {
               o = { csr_data: csr_data };
           }

           $.postJSON("server.php?u=sign", o, function(r) {
               if ('error' in r) {
                   showError(r.error);
               } else {
                   get_license(csr_data, code);
               }
           });
       }

       function get_license(csr_data, code) {
           if (code != null) {
               o = { csr_data: csr_data, redeem_code: code };
           } else {
               o = { csr_data: csr_data };
           }

           $.postJSON("server.php?u=retrieve", o, function(r) {
               if ('error' in r) {
                   showError(r.error);
               } else {
                   license_file = new Uint8Array(r.license.length/2);
                   for(i=0; i<r.license.length/2; i++) {
                       license_file[i] = parseInt(r.license.substr(i*2,2),16);
                   }
                   download(license_file, "license.dat");
                   license_success();
               }
           });
       }

       function license_success() {
           $("#upload_form").hide();
           $("#license-code-form").hide();
           $("#license_success").show();
       }

       function download(content, filename, contentType) {
           if(!contentType) { contentType = 'application/octet-stream'; }
           var a = document.createElement('a');
           var blob = new Blob([content], {'type':contentType});
           a.href = window.URL.createObjectURL(blob);
           a.download = filename;
           a.click();
       }
       </script>