From d7f3462929f827705699ef5cc7c16fba43414fcc Mon Sep 17 00:00:00 2001
From: Tarun Batra <tarun.batra00@gmail.com>
Date: Sat, 11 Oct 2025 20:32:07 -0700
Subject: [PATCH] repl: handle screen refresh for multiline input

Fixes an issue where when navigating a multiline input which exceeds
terminal height, pressing UP arrow would not update the visible data
when the cursor reaches the top.

Fixes: https://github.com/nodejs/node/issues/59938
---
 lib/internal/readline/interface.js | 35 ++++++++++++++++++++++++++----
 1 file changed, 31 insertions(+), 4 deletions(-)

diff --git a/lib/internal/readline/interface.js b/lib/internal/readline/interface.js
index 46674883381392..bf32d6cdb80f72 100644
--- a/lib/internal/readline/interface.js
+++ b/lib/internal/readline/interface.js
@@ -364,6 +364,11 @@ 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
@@ -496,6 +501,7 @@ class Interface extends InterfaceConstructor {
     const dispPos = this[kGetDisplayPos](line);
     const lineCols = dispPos.cols;
     const lineRows = dispPos.rows;
+    const terminalRows = this.rows;
 
     // cursor position
     const cursorPos = this.getCursorPos();
@@ -513,11 +519,32 @@ 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]);
-
+      // Normal case - display line from the first row to the last
+      let startLine = 0;
+      let endLine = lineRows;
+
+      const exceedsTerminal = lineRows >= terminalRows && terminalRows !== Infinity;
+      if (exceedsTerminal) {
+        const topOfVisibleData = lineRows - terminalRows;
+        // The cursor starts from the last row. If it is within the
+        // visible data segment, show the last part of the multiline data
+        if (cursorPos.rows > topOfVisibleData) {
+          startLine = topOfVisibleData;
+        } else {
+          // Cursor has traveled through the visible rows
+          // Start displaying the data that the cursor is on
+          // up until the terminal size allows
+          startLine = cursorPos.rows;
+          endLine = cursorPos.rows + terminalRows - 1;
+        }
+      }
+      // If the first row is visible, show the normal prompt
+      if (startLine === 0) {
+        this[kWriteToOutput](this[kPrompt] + lines[0]);
+        startLine++;
+      }
       // For continuation lines, add the "|" prefix
-      for (let i = 1; i < lines.length; i++) {
+      for (let i = startLine; i <= endLine; i++) {
         this[kWriteToOutput](`\n${kMultilinePrompt.description}` + lines[i]);
       }
     } else {