export abstract class TokenFlow {
  /**
   * The required number of children for this flow type, or null if there is no fixed requirement.
   */
  get requiredLength(): number | null {
    return null;
  }

  /**
   * If a selection range extends from within one child to within another child,
   * this function determines whether a third child is considered to be "within"
   * those two children (inclusive of those two) for the purposes of selection highlighting.
   * @param anchorIndex The index of the first child in the selection range
   * @param headIndex The index of the second child in the selection range
   * @param otherIndex The index of the child to test
   * @returns Whether the child at otherIndex is between the children at anchorIndex and headIndex
   */
  isWithin(
    anchorIndex: number,
    headIndex: number,
    otherIndex: number
  ): boolean {
    const minIndex = Math.min(anchorIndex, headIndex);
    const maxIndex = Math.max(anchorIndex, headIndex);
    return otherIndex >= minIndex && otherIndex <= maxIndex;
  }

  /**
   * When navigating vertically (e.g., with the up/down arrow keys), this function provides a list of candidate child indices
   * to move to from a given child index in the specified direction.
   * @param direction The direction of navigation ("up" or "down")
   * @param fromIndex The current child index
   * @returns An array of candidate child indices to navigate to
   */
  verticalCandidates(
    _direction: "up" | "down",
    _fromIndex: number,
    _length: number
  ): number[] {
    return [];
  }
}