export type BillingPeriod = "month" | "year";

export function getPublicBetaPresentation(active: boolean) {
  return active
    ? {
        status: "公测期间服务费全免",
        subline: "不绑支付方式 · 不会自动扣款",
        factValue: "¥0",
        factLabel: "公测服务费",
        priceHeading: "当前公测",
        priceValue: "¥0",
        priceDetail: "全部已允许主机",
        cardStatus: "当前有效",
        cardTitle: "公开公测",
        cardDescription: "公测期间，所有已经允许接入的主机槽位不收服务费。",
        cta: "进入公测控制台",
        comparison: "当前公测免费；未来方案未定",
      }
    : {
        status: "公测免费政策已结束",
        subline: "不会自动扣款 · 付费入口仍关闭",
        factValue: "关闭",
        factLabel: "公测免费",
        priceHeading: "公测政策",
        priceValue: "已结束",
        priceDetail: "不会转为自动扣款",
        cardStatus: "已经结束",
        cardTitle: "公开公测",
        cardDescription: "免费政策已结束；付费入口仍由上线门禁关闭，不会自动扣款。",
        cta: "进入控制台",
        comparison: "公测已结束；收费入口未开放",
      };
}

export function getBillingEntitlementPresentation(
  mode: "public_beta" | "grant" | "none",
  publicBetaState: "open" | "gated" | "inactive" = "inactive",
) {
  if (mode === "public_beta") {
    return {
      tone: "good" as const,
      status: "公测免费",
      title: "当前应付 ¥0",
      description: "不需要支付方式；公测结束不会自动生成付款或扣款。",
      emptyOrders: "免费公测不提供报价，也不会生成订单或付款单。",
    };
  }
  if (mode === "grant") {
    return {
      tone: "info" as const,
      status: "闭测邀请",
      title: "当前权益有效",
      description: "当前由有期限的非货币权益覆盖；不会生成付款或自动扣款。",
      emptyOrders: "闭测邀请不会生成报价、订单或付款单。",
    };
  }
  if (publicBetaState === "gated") {
    return {
      tone: "warn" as const,
      status: "公开接入冻结",
      title: "当前没有有效闭测邀请",
      description: "免费政策已经预设，但安全门禁尚未齐全；不会要求付款或自动创建订单。",
      emptyOrders: "公开接入冻结期间不会生成报价、订单或付款单。",
    };
  }
  return {
    tone: "neutral" as const,
    status: "无有效免费资格",
    title: "当前无免费权益",
    description: "公开公测当前未开放，该账户也没有有效闭测邀请；不会自动生成付款或扣款。",
    emptyOrders: "收费功能仍未开放，不会自动生成报价、订单或付款单。",
  };
}

/**
 * Advance a fixed-term order by one calendar billing period while clamping
 * month-end dates. This prevents January 31 from rolling into March and keeps
 * leap-day yearly orders on the final valid day of February.
 */
export function addBillingPeriod(
  startInput: Date | string,
  period: BillingPeriod,
): string {
  const start = new Date(startInput);
  if (Number.isNaN(start.valueOf())) {
    throw new RangeError("Invalid billing term start");
  }

  const requestedDay = start.getUTCDate();
  const result = new Date(start);
  result.setUTCDate(1);

  if (period === "month") {
    result.setUTCMonth(result.getUTCMonth() + 1);
  } else {
    result.setUTCFullYear(result.getUTCFullYear() + 1);
  }

  const lastDay = new Date(
    Date.UTC(result.getUTCFullYear(), result.getUTCMonth() + 1, 0),
  ).getUTCDate();
  result.setUTCDate(Math.min(requestedDay, lastDay));
  return result.toISOString();
}

/** Return the next time the currently summarized entitlement can change. */
export function nextEntitlementExpiry(
  values: Array<string | null>,
): string | null {
  return values
    .filter((value): value is string => Boolean(value))
    .sort()
    .at(0) ?? null;
}

export type EntitlementComponent = {
  source: string;
  capacity: number | null;
  endsAt: string | null;
};

export function summarizeEntitlementComponents(
  components: EntitlementComponent[],
  activeSlots: number,
  reservedSlots: number,
) {
  const unlimitedComponents = components.filter(
    (component) => component.capacity === null,
  );
  const unlimited = unlimitedComponents.length > 0;
  const capacitySlots = unlimited
    ? null
    : components.reduce((sum, component) => sum + (component.capacity ?? 0), 0);
  const effectiveUntil = unlimited
    ? unlimitedComponents.some((component) => component.endsAt === null)
      ? null
      : nextEntitlementExpiry(unlimitedComponents.map((component) => component.endsAt))
    : nextEntitlementExpiry(components.map((component) => component.endsAt));

  return {
    unlimited,
    capacitySlots,
    availableSlots: unlimited
      ? null
      : Math.max(0, (capacitySlots ?? 0) - activeSlots - reservedSlots),
    effectiveUntil,
    sources: [...new Set(components.map((component) => component.source))],
  };
}