Display slash commands outcome when previewing Markdown

Remove slash commands from Markdown preview and display their outcome next to
the text field.
Introduce new "explanation" block to our slash commands DSL.
Introduce optional "parse_params" block to slash commands DSL that allows to
process a parameter before it is passed to "explanation" or "command" blocks.
Pass path for previewing Markdown as "data" attribute instead of setting
a variable on "window".

1 files changed, 40 insertions, 8 deletions

diff --git a/app/assets/javascripts/preview_markdown.js b/app/assets/javascripts/preview_markdown.js
index 07eea98e737..4a3df2fd465 100644
--- a/app/assets/javascripts/preview_markdown.js
+++ b/app/assets/javascripts/preview_markdown.js
@@ -2,8 +2,9 @@
 
 // MarkdownPreview
 //
-// Handles toggling the "Write" and "Preview" tab clicks, rendering the preview,
-// and showing a warning when more than `x` users are referenced.
+// Handles toggling the "Write" and "Preview" tab clicks, rendering the preview
+// (including the explanation of slash commands), and showing a warning when
+// more than `x` users are referenced.
 //
 (function () {
   var lastTextareaPreviewed;
@@ -17,32 +18,45 @@
 
     // Minimum number of users referenced before triggering a warning
     MarkdownPreview.prototype.referenceThreshold = 10;
+    MarkdownPreview.prototype.emptyMessage = 'Nothing to preview.';
 
     MarkdownPreview.prototype.ajaxCache = {};
 
     MarkdownPreview.prototype.showPreview = function ($form) {
       var mdText;
       var preview = $form.find('.js-md-preview');
+      var url = preview.data('url');
       if (preview.hasClass('md-preview-loading')) {
         return;
       }
       mdText = $form.find('textarea.markdown-area').val();
 
       if (mdText.trim().length === 0) {
-        preview.text('Nothing to preview.');
+        preview.text(this.emptyMessage);
         this.hideReferencedUsers($form);
       } else {
         preview.addClass('md-preview-loading').text('Loading...');
-        this.fetchMarkdownPreview(mdText, (function (response) {
-          preview.removeClass('md-preview-loading').html(response.body);
+        this.fetchMarkdownPreview(mdText, url, (function (response) {
+          var body;
+          if (response.body.length > 0) {
+            body = response.body;
+          } else {
+            body = this.emptyMessage;
+          }
+
+          preview.removeClass('md-preview-loading').html(body);
           preview.renderGFM();
           this.renderReferencedUsers(response.references.users, $form);
+
+          if (response.references.commands) {
+            this.renderReferencedCommands(response.references.commands, $form);
+          }
         }).bind(this));
       }
     };
 
-    MarkdownPreview.prototype.fetchMarkdownPreview = function (text, success) {
-      if (!window.preview_markdown_path) {
+    MarkdownPreview.prototype.fetchMarkdownPreview = function (text, url, success) {
+      if (!url) {
         return;
       }
       if (text === this.ajaxCache.text) {
@@ -51,7 +65,7 @@
       }
       $.ajax({
         type: 'POST',
-        url: window.preview_markdown_path,
+        url: url,
         data: {
           text: text
         },
@@ -83,6 +97,22 @@
       }
     };
 
+    MarkdownPreview.prototype.hideReferencedCommands = function ($form) {
+      $form.find('.referenced-commands').hide();
+    };
+
+    MarkdownPreview.prototype.renderReferencedCommands = function (commands, $form) {
+      var referencedCommands;
+      referencedCommands = $form.find('.referenced-commands');
+      if (commands.length > 0) {
+        referencedCommands.html(commands);
+        referencedCommands.show();
+      } else {
+        referencedCommands.html('');
+        referencedCommands.hide();
+      }
+    };
+
     return MarkdownPreview;
   }());
 
@@ -137,6 +167,8 @@
     $form.find('.md-write-holder').show();
     $form.find('textarea.markdown-area').focus();
     $form.find('.md-preview-holder').hide();
+
+    markdownPreview.hideReferencedCommands($form);
   });
 
   $(document).on('markdown-preview:toggle', function (e, keyboardEvent) {