fix(cli): Add delimiter before printing tool response in non-interactive mode (#11351)

packages/cli/src/ui/utils/textOutput.ts

@@ -0,0 +1,54 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * A utility to manage writing text to stdout, ensuring that newlines
+ * are handled consistently and robustly across the application.
+ */
+
+import stripAnsi from 'strip-ansi';
+
+export class TextOutput {
+  private atStartOfLine = true;
+
+  /**
+   * Writes a string to stdout.
+   * @param str The string to write.
+   */
+  write(str: string): void {
+    if (str.length === 0) {
+      return;
+    }
+    process.stdout.write(str);
+    const strippedStr = stripAnsi(str);
+    if (strippedStr.length > 0) {
+      this.atStartOfLine = strippedStr.endsWith('\n');
+    }
+  }
+
+  /**
+   * Writes a string to stdout, ensuring it starts on a new line.
+   * If the previous output did not end with a newline, one will be added.
+   * This prevents adding extra blank lines if a newline already exists.
+   * @param str The string to write.
+   */
+  writeOnNewLine(str: string): void {
+    if (!this.atStartOfLine) {
+      this.write('\n');
+    }
+    this.write(str);
+  }
+
+  /**
+   * Ensures that the output ends with a newline. If the last character
+   * written was not a newline, one will be added.
+   */
+  ensureTrailingNewline(): void {
+    if (!this.atStartOfLine) {
+      this.write('\n');
+    }
+  }
+}