Add prepare_ajax_request and preview_sql to modular code.

Signed-Off-By: Piyush Vijay <piyushvijay.1997@gmail.com>

js/src/functions/AjaxRequest.js

@@ -0,0 +1,11 @@
+/**
+ * Add a hidden field to the form to indicate that this will be an
+ * Ajax request (only if this hidden field does not exist)
+ *
+ * @param $form object   the form
+ */
+export function PMA_prepareForAjaxRequest ($form) {
+    if (! $form.find('input:hidden').is('#ajax_request_hidden')) {
+        $form.append('<input type="hidden" id="ajax_request_hidden" name="ajax_request" value="true" />');
+    }
+}

js/src/functions/Sql/PreviewSql.js

@@ -0,0 +1,54 @@
+import { PMA_Messages as PMA_messages } from '../../variables/export_variables';
+import PMA_commonParams from '../../variables/common_params';
+import { PMA_ajaxShowMessage, PMA_ajaxRemoveMessage } from '../../utils/show_ajax_messages';
+/**
+ * Requests SQL for previewing before executing.
+ *
+ * @param jQuery Object $form Form containing query data
+ *
+ * @return void
+ */
+export function PMA_previewSQL ($form) {
+    var form_url = $form.attr('action');
+    var sep = PMA_commonParams.get('arg_separator');
+    var form_data = $form.serialize() +
+        sep + 'do_save_data=1' +
+        sep + 'preview_sql=1' +
+        sep + 'ajax_request=1';
+    var $msgbox = PMA_ajaxShowMessage();
+    $.ajax({
+        type: 'POST',
+        url: form_url,
+        data: form_data,
+        success: function (response) {
+            PMA_ajaxRemoveMessage($msgbox);
+            if (response.success) {
+                var $dialog_content = $('<div/>')
+                    .append(response.sql_data);
+                var button_options = {};
+                button_options[PMA_messages.strClose] = function () {
+                    $(this).dialog('close');
+                };
+                var $response_dialog = $dialog_content.dialog({
+                    minWidth: 550,
+                    maxHeight: 400,
+                    modal: true,
+                    buttons: button_options,
+                    title: PMA_messages.strPreviewSQL,
+                    close: function () {
+                        $(this).remove();
+                    },
+                    open: function () {
+                        // Pretty SQL printing.
+                        PMA_highlightSQL($(this));
+                    }
+                });
+            } else {
+                PMA_ajaxShowMessage(response.message);
+            }
+        },
+        error: function () {
+            PMA_ajaxShowMessage(PMA_messages.strErrorProcessingRequest);
+        }
+    });
+}