export type OptimisticTimelineEntryLike = {
  id: string;
  startDate: Date | string;
  endDate: Date | string;
};

export type OptimisticTimelineOverrideLike = {
  startDate: Date;
  endDate: Date;
};

export function reconcileOptimisticEntries(
  optimisticAllocations: ReadonlyMap<string, OptimisticTimelineOverrideLike>,
  entries: readonly OptimisticTimelineEntryLike[],
  pendingOptimisticAllocationId: string | null,
): {
  optimisticAllocations: Map<string, OptimisticTimelineOverrideLike>;
  pendingOptimisticAllocationId: string | null;
  changed: boolean;
} {
  if (optimisticAllocations.size === 0) {
    return {
      optimisticAllocations: new Map(optimisticAllocations),
      pendingOptimisticAllocationId,
      changed: false,
    };
  }

  const next = new Map(optimisticAllocations);
  let nextPendingId = pendingOptimisticAllocationId;

  for (const entry of entries) {
    const override = next.get(entry.id);
    if (!override) continue;

    const startTime = new Date(entry.startDate).getTime();
    const endTime = new Date(entry.endDate).getTime();
    if (startTime === override.startDate.getTime() && endTime === override.endDate.getTime()) {
      next.delete(entry.id);
      if (nextPendingId === entry.id) {
        nextPendingId = null;
      }
    }
  }

  return {
    optimisticAllocations: next,
    pendingOptimisticAllocationId: nextPendingId,
    changed: next.size !== optimisticAllocations.size || nextPendingId !== pendingOptimisticAllocationId,
  };
}