If editing an HTML page, show that in the preview instead of just the index.

index.html

@@ -21,7 +21,7 @@
         {"path": "src/poo.js", "is_dir": false, "name": "poo.js"},
         {"path": "src/poo.py", "is_dir": false, "name": "poo.py"}
       ],
-      "file_path": "src/poo.js",
+      "file_path": "src/poo.html",
       "is_dir": false,
       "file_content": "function x() {\n  return 1;\n}",
       "csrf_token": "arg",

src/App.elm

@@ -87,6 +87,9 @@ type alias Model =
   , elm_packages : List ElmPackage
   }
 
+suffix : String -> String
+suffix = String.split "." >> List.reverse >> List.head >> Maybe.withDefault ""
+
 init_model : Model
 init_model =
   { show_preview = True
@@ -689,26 +692,37 @@ log_pane model =
     ]
 
 preview_pane model =
-  H.details
-    [ HA.attribute "open" ""
-    , HA.id "preview"
-    , HE.on "toggle" (JD.at ["target", "open"] JD.bool |> JD.map TogglePreview)
-    ]
-    ( [ H.summary
-        []
-        [ H.text "Preview"
-        ]
-      ]
-    ++ if model.show_preview then
-        [ H.iframe
-          [ HA.id "preview-frame" 
-          , HA.src model.preview_url
-          ]
-          []
-        ]
+  let
+    file_suffix = suffix model.file_path
+
+    page_suffixes = ["html", "php"]
+    
+    preview_url = 
+      if List.member file_suffix page_suffixes then
+        model.preview_url ++ "/" ++ model.file_path
       else
-        []
-    )
+        model.preview_url
+  in
+    H.details
+      [ HA.attribute "open" ""
+      , HA.id "preview"
+      , HE.on "toggle" (JD.at ["target", "open"] JD.bool |> JD.map TogglePreview)
+      ]
+      ( [ H.summary
+          []
+          [ H.text <| "Preview"
+          ]
+        ]
+      ++ if model.show_preview then
+          [ H.iframe
+            [ HA.id "preview-frame" 
+            , HA.src preview_url
+            ]
+            []
+          ]
+        else
+          []
+      )
 
 commit_modal model = 
   let