import type { AcquisitionMode } from "./mode";

/** 默认:用户明确立即处理 > 追更补缺 > 新作品 > 已有版本升级(REQ §6.8) */
export type PriorityClass = "immediate" | "catch_up" | "new_title" | "upgrade";
export const DEFAULT_PRIORITY_ORDER: readonly PriorityClass[] = ["immediate", "catch_up", "new_title", "upgrade"];

export interface QueueItem {
  id: string;
  priorityClass: PriorityClass;
  /** 入队时间 ISO;同优先级先进先出,避免饥饿 */
  enqueuedAt: string;
}

export function priorityOf(mode: AcquisitionMode, immediate = false): PriorityClass {
  return immediate ? "immediate" : mode;
}

export function validatePriorityOrder(order: readonly PriorityClass[]): void {
  const all = new Set<PriorityClass>(DEFAULT_PRIORITY_ORDER);
  if (order.length !== all.size || new Set(order).size !== all.size || !order.every((o) => all.has(o)))
    throw new Error(`优先级配置必须恰好包含 ${[...all].join("/")} 各一次`);
}

/** 按优先级排序(稳定、纯函数)。优先级只影响资源分配,不越过阈值/HR/权限 */
export function sortByPriority<T extends QueueItem>(
  items: readonly T[],
  order: readonly PriorityClass[] = DEFAULT_PRIORITY_ORDER,
): T[] {
  validatePriorityOrder(order);
  const rank = new Map(order.map((c, i) => [c, i]));
  return [...items].sort(
    (a, b) =>
      rank.get(a.priorityClass)! - rank.get(b.priorityClass)! ||
      a.enqueuedAt.localeCompare(b.enqueuedAt) ||
      a.id.localeCompare(b.id),
  );
}