Function insertText

packages/core/src/widgets/codeEditor.ts:44–92

(
  lines: readonly string[],
  cursor: CursorPosition,
  text: string,
)

 * @returns Edit result with updated lines and cursor
 */
export function insertText(
  lines: readonly string[],
  cursor: CursorPosition,
  text: string,
): EditResult {
  const newLines = [...lines];
  const { line, column } = cursor;

  // Ensure we have at least one line
  if (newLines.length === 0) {
    newLines.push("");
  }

  // Clamp cursor to valid position
  const safeRow = Math.max(0, Math.min(line, newLines.length - 1));
  const currentLine = newLines[safeRow] ?? "";
  const safeCol = Math.max(0, Math.min(column, currentLine.length));

  // Split text into lines
  const insertLines = text.split("\n");
  const beforeCursor = currentLine.slice(0, safeCol);
  const afterCursor = currentLine.slice(safeCol);

  if (insertLines.length === 1) {
    // Single line insert
    newLines[safeRow] = beforeCursor + insertLines[0] + afterCursor;
    return Object.freeze({
      lines: Object.freeze(newLines),
      cursor: { line: safeRow, column: safeCol + (insertLines[0]?.length ?? 0) },
      selection: null,
    });
  }

  // Multi-line insert
  const firstLine = beforeCursor + (insertLines[0] ?? "");
  const lastInsertLine = insertLines[insertLines.length - 1] ?? "";
  const lastLine = lastInsertLine + afterCursor;

  newLines.splice(safeRow, 1, firstLine, ...insertLines.slice(1, -1), lastLine);

  return Object.freeze({
    lines: Object.freeze(newLines),
    cursor: {
      line: safeRow + insertLines.length - 1,
      column: lastInsertLine.length,
    },
    selection: null,
  });
}

/**
 * Delete text in a selection range.