Function reorderProjects

apps/web/src/uiStateStore.ts:370–412

(
  state: UiState,
  currentProjectOrder: readonly string[],
  draggedProjectIds: readonly string[],
  targetProjectIds: readonly string[],
)

}

export function reorderProjects(
  state: UiState,
  currentProjectOrder: readonly string[],
  draggedProjectIds: readonly string[],
  targetProjectIds: readonly string[],
): UiState {
  if (draggedProjectIds.length === 0) {
    return state;
  }
  const draggedSet = new Set(draggedProjectIds);
  const targetSet = new Set(targetProjectIds);
  if (draggedProjectIds.every((id) => targetSet.has(id))) {
    return state;
  }

  const originalTargetIndex = currentProjectOrder.findIndex((id) => targetSet.has(id));
  if (originalTargetIndex < 0) {
    return state;
  }

  const projectOrder = [...currentProjectOrder];

  const removed: string[] = [];
  let draggedBeforeTarget = 0;
  for (let i = projectOrder.length - 1; i >= 0; i--) {
    if (draggedSet.has(projectOrder[i]!)) {
      removed.unshift(projectOrder.splice(i, 1)[0]!);
      if (i < originalTargetIndex) {
        draggedBeforeTarget++;
      }
    }
  }
  if (removed.length === 0) {
    return state;
  }

  const insertIndex = originalTargetIndex - Math.max(0, draggedBeforeTarget - 1);
  projectOrder.splice(insertIndex, 0, ...removed);
  return {
    ...state,
    projectOrder,
  };
}

interface UiStateStore extends UiState {
  markThreadVisited: (threadId: string, visitedAt: string) => void;