Function buildHeaderRows

packages/react-stately/src/table/TableCollection.ts:46–200

(
  keyMap: Map<Key, GridNode<T>>,
  columnNodes: GridNode<T>[]
)

/** @private */
export function buildHeaderRows<T>(
  keyMap: Map<Key, GridNode<T>>,
  columnNodes: GridNode<T>[]
): GridNode<T>[] {
  if (columnNodes.length === 0) {
    return [];
  }

  let columns: GridNode<T>[][] = [];
  let seen = new Map();
  for (let column of columnNodes) {
    let parentKey = column.parentKey;
    let col = [column];

    while (parentKey != null) {
      let parent: GridNode<T> | undefined = keyMap.get(parentKey);
      if (!parent) {
        break;
      }

      // If we've already seen this parent, than it is shared
      // with a previous column. If the current column is taller
      // than the previous column, than we need to shift the parent
      // in the previous column so it's level with the current column.
      if (seen.has(parent)) {
        parent.colSpan ??= 0;
        parent.colSpan++;
        parent.colspan = parent.colSpan;

        let {column, index} = seen.get(parent);
        if (index > col.length) {
          break;
        }

        for (let i = index; i < col.length; i++) {
          column.splice(i, 0, null);
        }

        // Adjust shifted indices
        for (let i = col.length; i < column.length; i++) {
          // eslint-disable-next-line max-depth
          if (column[i] && seen.has(column[i])) {
            seen.get(column[i]).index = i;
          }
        }
      } else {
        parent.colSpan = 1;
        parent.colspan = 1;
        col.push(parent);
        seen.set(parent, {column: col, index: col.length - 1});
      }

      parentKey = parent.parentKey;
    }

    columns.push(col);
    column.index = columns.length - 1;
  }