Function deleteRange

packages/core/src/widgets/codeEditor.ts:101–136

(lines: readonly string[], selection: EditorSelection)

 * @returns Edit result with updated lines and cursor
 */
export function deleteRange(lines: readonly string[], selection: EditorSelection): EditResult {
  const newLines = [...lines];

  // Normalize selection (anchor before active)
  const [start, end] = normalizeSelection(selection);

  // Clamp to valid positions
  const startRow = Math.max(0, Math.min(start.line, newLines.length - 1));
  const endRow = Math.max(0, Math.min(end.line, newLines.length - 1));

  const startLine = newLines[startRow] ?? "";
  const endLine = newLines[endRow] ?? "";

  const startCol = Math.max(0, Math.min(start.column, startLine.length));
  const endCol = Math.max(0, Math.min(end.column, endLine.length));

  // Same line
  if (startRow === endRow) {
    newLines[startRow] = startLine.slice(0, startCol) + startLine.slice(endCol);
    return Object.freeze({
      lines: Object.freeze(newLines),
      cursor: { line: startRow, column: startCol },
      selection: null,
    });
  }

  // Multi-line delete
  const newLine = startLine.slice(0, startCol) + endLine.slice(endCol);
  newLines.splice(startRow, endRow - startRow + 1, newLine);

  return Object.freeze({
    lines: Object.freeze(newLines),
    cursor: { line: startRow, column: startCol },
    selection: null,
  });
}

/**
 * Delete character before cursor (backspace).