progress reimplementing 'j' motion to pass new tests

fcore/normal-mode/normal-move.sml

@@ -275,21 +275,45 @@ struct
 
           val buffer = LineGap.goToLine (newCursorLineNumber, buffer)
           val lineIdx = LineGap.lineNumberToIdx (newCursorLineNumber, buffer)
-
           val buffer = LineGap.goToIdx (lineIdx, buffer)
-
-          val lineIdx =
-            if Cursor.isPrevChrStartOfLine (buffer, lineIdx) then lineIdx
-            else lineIdx + 1
-
-          val lineIdx =
-            if lineIdx >= #textLength buffer - 1 then
-              Int.max (0, #textLength buffer - 1)
-            else
-              lineIdx
         in
-          finishMoveCursorUpDown
-            (app, newCursorLineNumber, buffer, column, lineIdx)
+          if lineIdx >= #textLength buffer then
+            (* we reached last line *)
+            let
+              val lineIdx = Int.max (#textLength buffer - 1, 0)
+              val buffer = LineGap.goToIdx (lineIdx, buffer)
+              val startOfLine = Cursor.vi0 (buffer, lineIdx)
+            in
+              if cursorIdx >= startOfLine then
+                (* we are already on last line so don't move *)
+                NormalFinish.buildTextAndClear
+                  (app, buffer, cursorIdx, searchList, [], bufferModifyTime)
+              else
+                finishMoveCursorUpDown
+                  (app, newCursorLineNumber, buffer, column, startOfLine)
+            end
+          else if lineIdx = #textLength buffer - 1 then
+            (* last line in buffer ends with \n
+             * and we just reached it *)
+            let val () = print "296\n"
+            in raise Fail ""
+            end
+          else
+            let
+              val lineIdx =
+                if lineIdx >= #textLength buffer - 2 then
+                  Int.max (0, #textLength buffer - 2)
+                else
+                  lineIdx
+
+              val buffer = LineGap.goToIdx (lineIdx, buffer)
+              val lineIdx =
+                if Cursor.isOnNewlineAfterChr (buffer, lineIdx) then lineIdx + 1
+                else lineIdx
+            in
+              finishMoveCursorUpDown
+                (app, newCursorLineNumber, buffer, column, lineIdx)
+            end
         end
     end