Function getTreeLinePrefix

packages/core/src/widgets/tree.ts:171–205

(
  flatNode: FlattenedNode<T>,
  showLines: boolean,
  indentSize: number,
)

 * @returns String prefix for the node
 */
export function getTreeLinePrefix<T>(
  flatNode: FlattenedNode<T>,
  showLines: boolean,
  indentSize: number,
): string {
  if (flatNode.depth === 0) {
    return "";
  }

  if (!showLines) {
    // Simple indentation without lines
    return " ".repeat(flatNode.depth * indentSize);
  }

  // Build tree line prefix
  const parts: string[] = [];

  // Add ancestor lines (excluding the last which is for current node)
  for (let i = 0; i < flatNode.depth - 1; i++) {
    const isLast = flatNode.ancestorIsLast[i];
    if (isLast) {
      // Ancestor was last child, no continuing line
      parts.push(TREE_CHARS.space);
    } else {
      // Ancestor has siblings below, show continuing line
      parts.push(`${TREE_CHARS.vertical}  `);
    }
  }

  // Add branch for current node
  const isLast = flatNode.siblingIndex === flatNode.siblingCount - 1;
  parts.push(isLast ? TREE_CHARS.lastBranch : TREE_CHARS.branch);

  return parts.join("");
}

/* ========== Navigation ========== */