repl: fix screen refresh in multiline viewport overflow

When multiline REPL input exceeds the terminal height, navigating
the cursor would move the cursor position correctly but fail to
refresh the screen properly, leaving stale content visible.

This implements viewport-based rendering in kRefreshLine() that
displays only the visible portion of input centered around the
cursor position when content exceeds terminal height.

Fixes: #59938

Author: Han5991

lib/internal/readline/interface.js

@@ -16,6 +16,7 @@ const {
   MathFloor,
   MathMax,
   MathMaxApply,
+  MathMin,
   NumberIsFinite,
   ObjectDefineProperty,
   ObjectSetPrototypeOf,
@@ -364,6 +365,11 @@ class Interface extends InterfaceConstructor {
     return Infinity;
   }
 
+  get rows() {
+    if (this.output?.rows) return this.output.rows;
+    return Infinity;
+  }
+
   /**
    * Sets the prompt written to the output.
    * @param {string} prompt
@@ -500,6 +506,10 @@ class Interface extends InterfaceConstructor {
     // cursor position
     const cursorPos = this.getCursorPos();
 
+    const terminalRows = this.rows;
+
+    const exceedsTerminal = lineRows >= terminalRows && terminalRows !== Infinity;
+
     // First move to the bottom of the current line, based on cursor pos
     const prevRows = this.prevRows || 0;
     if (prevRows > 0) {
@@ -513,16 +523,41 @@ class Interface extends InterfaceConstructor {
 
     if (this[kIsMultiline]) {
       const lines = StringPrototypeSplit(this.line, '\n');
-      // Write first line with normal prompt
-      this[kWriteToOutput](this[kPrompt] + lines[0]);
 
-      // For continuation lines, add the "|" prefix
-      for (let i = 1; i < lines.length; i++) {
+      let startLine = 0;
+      let endLine = lines.length;
+      let visibleCursorRow = cursorPos.rows;
+
+      if (exceedsTerminal) {
+        const maxVisibleLines = terminalRows - 2;
+
+        const halfViewport = MathFloor(maxVisibleLines / 2);
+
+        if (cursorPos.rows < halfViewport) {
+          startLine = 0;
+          endLine = MathMin(lines.length, maxVisibleLines);
+        } else if (cursorPos.rows >= lines.length - halfViewport) {
+          startLine = MathMax(0, lines.length - maxVisibleLines);
+          endLine = lines.length;
+          visibleCursorRow = cursorPos.rows - startLine;
+        } else {
+          startLine = cursorPos.rows - halfViewport;
+          endLine = MathMin(lines.length, startLine + maxVisibleLines);
+          visibleCursorRow = halfViewport;
+        }
+      }
+
+      this[kWriteToOutput](this[kPrompt] + lines[startLine]);
+
+      for (let i = startLine + 1; i < endLine; i++) {
         this[kWriteToOutput](`\n${kMultilinePrompt.description}` + lines[i]);
       }
+
+      this.prevRows = exceedsTerminal ? visibleCursorRow : cursorPos.rows;
     } else {
       // Write the prompt and the current buffer content.
       this[kWriteToOutput](line);
+      this.prevRows = cursorPos.rows;
     }
 
     // Force terminal to allocate a new line
@@ -537,8 +572,6 @@ class Interface extends InterfaceConstructor {
     if (diff > 0) {
       moveCursor(this.output, 0, -diff);
     }
-
-    this.prevRows = cursorPos.rows;
   }
 
   /**