extract reusable function containing common code previously used in both 'NormalMove.moveCursorUp' and 'NormalMove.moveCursorDown' functions, and make them call the reusable function instead

fcore/normal-mode/normal-move.sml

@@ -106,34 +106,20 @@ struct
         )
     end
 
-  fun moveCursorUp (app: app_type, count) =
+  fun finishMoveCursorUpDown
+    (app: app_type, newCursorLineNumber, buffer, column) =
     let
       val
         { windowWidth
         , windowHeight
-        , cursorIdx
+        , visualScrollColumn = prevScrollColumn
-        , buffer
         , startLine = prevLineNumber
         , searchList
         , searchString
         , bufferModifyTime
-        , visualScrollColumn = prevScrollColumn
         , ...
         } = app
 
-      (* calculate new idx to move to *)
-      val buffer = LineGap.goToIdx (cursorIdx, buffer)
-      val startOfLine = Cursor.vi0 (buffer, cursorIdx)
-      val column = cursorIdx - startOfLine
-
-      val cursorLineNumber =
-        if Cursor.isNextChrEndOfLine (buffer, cursorIdx) then
-          LineGap.idxToLineNumber (cursorIdx + 1, buffer)
-        else
-          LineGap.idxToLineNumber (cursorIdx, buffer)
-      val newCursorLineNumber = Int.max (cursorLineNumber - count, 0)
-      val column = if newCursorLineNumber = 0 then column - 1 else column
-
       val buffer = LineGap.goToLine (newCursorLineNumber, buffer)
       val lineIdx = LineGap.lineNumberToIdx (newCursorLineNumber, buffer)
       val buffer = LineGap.goToIdx (lineIdx, buffer)
@@ -188,6 +174,26 @@ struct
         )
     end
 
+  fun moveCursorUp (app: app_type, count) =
+    let
+      val {cursorIdx, buffer, ...} = app
+
+      (* calculate new idx to move to *)
+      val buffer = LineGap.goToIdx (cursorIdx, buffer)
+      val startOfLine = Cursor.vi0 (buffer, cursorIdx)
+      val column = cursorIdx - startOfLine
+
+      val cursorLineNumber =
+        if Cursor.isNextChrEndOfLine (buffer, cursorIdx) then
+          LineGap.idxToLineNumber (cursorIdx + 1, buffer)
+        else
+          LineGap.idxToLineNumber (cursorIdx, buffer)
+      val newCursorLineNumber = Int.max (cursorLineNumber - count, 0)
+      val column = if newCursorLineNumber = 0 then column - 1 else column
+    in
+      finishMoveCursorUpDown (app, newCursorLineNumber, buffer, column)
+    end
+
   fun moveCursorDown (app: app_type, count) =
     let
       val
@@ -220,62 +226,10 @@ struct
           Int.max (0, #lineLength buffer - 2)
         else
           newCursorLineNumber
-
-      val buffer = LineGap.goToLine (newCursorLineNumber, buffer)
-      val lineIdx = LineGap.lineNumberToIdx (newCursorLineNumber, buffer)
-      val buffer = LineGap.goToIdx (lineIdx, buffer)
-      val lineIdx =
-        if Cursor.isNextChrEndOfLine (buffer, lineIdx) then lineIdx
-        else lineIdx + 1
-
-      val buffer = LineGap.goToIdx (lineIdx, buffer)
-      val endOfLineIdx = Cursor.viDlr (buffer, lineIdx, 1)
-
-      val cursorIdx = Int.min (endOfLineIdx, lineIdx + column)
-
-      val buffer = LineGap.goToIdx (cursorIdx, buffer)
-
-      (* create draw message *)
-      val visualScrollColumn =
-        TextScroll.getScrollColumn
-          (buffer, cursorIdx, windowWidth, prevScrollColumn)
-
-      val startLine =
-        TextScroll.getStartLine
-          (prevLineNumber, newCursorLineNumber, windowHeight)
-
-      val buffer = LineGap.goToLine (startLine, buffer)
-
-      val drawMsg = NormalModeTextBuilder.build
-        ( startLine
-        , cursorIdx
-        , buffer
-        , windowWidth
-        , windowHeight
-        , searchList
-        , searchString
-        , visualScrollColumn
-        )
-      val drawMsg = Vector.concat drawMsg
-      val drawMsg = DrawMsg.DRAW_TEXT drawMsg
-      val drawMsg = [MailboxType.DRAW drawMsg]
-
-      val mode = NORMAL_MODE ""
     in
-      NormalModeWith.bufferAndCursorIdx
+      finishMoveCursorUpDown (app, newCursorLineNumber, buffer, column)
-        ( app
-        , buffer
-        , cursorIdx
-        , mode
-        , startLine
-        , searchList
-        , drawMsg
-        , bufferModifyTime
-        , visualScrollColumn
-        )
     end
 
-
   fun moveToLine (app: app_type, reqLine) =
     let
       val reqLine = reqLine - 1