gemini-cli/packages/cli/src/ui/utils/textUtils.ts

/**
 * @license
 * Copyright 2025 Google LLC
 * SPDX-License-Identifier: Apache-2.0
 */

import stripAnsi from 'strip-ansi';
import { stripVTControlCharacters } from 'node:util';

/**
 * Calculates the maximum width of a multi-line ASCII art string.
 * @param asciiArt The ASCII art string.
 * @returns The length of the longest line in the ASCII art.
 */
export const getAsciiArtWidth = (asciiArt: string): number => {
  if (!asciiArt) {
    return 0;
  }
  const lines = asciiArt.split('\n');
  return Math.max(...lines.map((line) => line.length));
};

/*
 * -------------------------------------------------------------------------
 *  Unicode‑aware helpers (work at the code‑point level rather than UTF‑16
 *  code units so that surrogate‑pair emoji count as one "column".)
 * ---------------------------------------------------------------------- */

export function toCodePoints(str: string): string[] {
  // [...str] or Array.from both iterate by UTF‑32 code point, handling
  // surrogate pairs correctly.
  return Array.from(str);
}

export function cpLen(str: string): number {
  return toCodePoints(str).length;
}

export function cpSlice(str: string, start: number, end?: number): string {
  // Slice by code‑point indices and re‑join.
  const arr = toCodePoints(str).slice(start, end);
  return arr.join('');
}

/**
 * Strip characters that can break terminal rendering.
 *
 * Uses Node.js built-in stripVTControlCharacters to handle VT sequences,
 * then filters remaining control characters that can disrupt display.
 *
 * Characters stripped:
 * - ANSI escape sequences (via strip-ansi)
 * - VT control sequences (via Node.js util.stripVTControlCharacters)
 * - C0 control chars (0x00-0x1F) except CR/LF which are handled elsewhere
 * - C1 control chars (0x80-0x9F) that can cause display issues
 *
 * Characters preserved:
 * - All printable Unicode including emojis
 * - DEL (0x7F) - handled functionally by applyOperations, not a display issue
 * - CR/LF (0x0D/0x0A) - needed for line breaks
 */
export function stripUnsafeCharacters(str: string): string {
  const strippedAnsi = stripAnsi(str);
  const strippedVT = stripVTControlCharacters(strippedAnsi);

  return toCodePoints(strippedVT)
    .filter((char) => {
      const code = char.codePointAt(0);
      if (code === undefined) return false;

      // Preserve CR/LF for line handling
      if (code === 0x0a || code === 0x0d) return true;

      // Remove C0 control chars (except CR/LF) that can break display
      // Examples: BELL(0x07) makes noise, BS(0x08) moves cursor, VT(0x0B), FF(0x0C)
      if (code >= 0x00 && code <= 0x1f) return false;

      // Remove C1 control chars (0x80-0x9f) - legacy 8-bit control codes
      if (code >= 0x80 && code <= 0x9f) return false;

      // Preserve DEL (0x7f) - it's handled functionally by applyOperations as backspace
      // and doesn't cause rendering issues when displayed

      // Preserve all other characters including Unicode/emojis
      return true;
    })
    .join('');
}