/**
 * Stripe webhook 事件处理器
 *
 * 4 个核心事件：
 *   - `checkout.session.completed`     订阅首次购买 / 续费成功（返回 session URL 时 Stripe 触发）
 *   - `customer.subscription.deleted`  订阅取消（用户在 Portal 取消 / 不续费）
 *   - `customer.subscription.updated`  订阅状态变化（plan 升级 / 降级 / 重新激活）
 *   - `invoice.payment_succeeded`      续费周期扣款成功（每个计费周期触发）
 *
 * 设计：handler 返回 `Promise<void>`，幂等（用 event.id 去重）—— Stripe 保留重试权利
 *
 * 注：本轮handler 暂不调后端 API（因为后端 Stripe 接入可能还没完成）——
 *   只记录 event 到服务端 console，并 TODO 注释后续接入位置。
 *   webhook 验签 + 分发在 `/api/payment/webhook` API route 里处理（见 route.ts）。
 */
import type Stripe from "stripe";
import { getStripeClient } from "./stripe-client";
import { Logger } from "@/utils";

const log = new Logger("LibStripeStripeEvents");

/**
 * 4 个事件的主分发器
 * @returns true 如果事件已处理；false 如果忽略
 */
export async function dispatchStripeEvent(
  event: Stripe.Event,
): Promise<boolean> {
  switch (event.type) {
    case "checkout.session.completed":
      await handleCheckoutCompleted(event);
      return true;
    case "customer.subscription.deleted":
      await handleSubscriptionDeleted(event);
      return true;
    case "customer.subscription.updated":
    case "customer.subscription.created":
      await handleSubscriptionUpdated(event);
      return true;
    case "invoice.payment_succeeded":
      await handleInvoicePaymentSucceeded(event);
      return true;
    default:
      // 其他事件不关心（如 `payment_intent.succeeded`、试用结束警告等）
      return false;
  }
}

// ============================================================
// Handler 1: checkout.session.completed
// ============================================================
/**
 * 首次购买 / 续费成功 → 设置 user.isVip=true，补充 voiceMinutesRemaining
 *
 * 业务事实：
 *   - mode: "subscription" 的 Checkout Session 完成即代表订阅生效
 *   - 可以从 event.data.object 取到 customer + subscription 字段
 *   - 如果是续费（`subscription` 已存在）→ 同样处理（补充配额）
 */
async function handleCheckoutCompleted(
  event: Stripe.CheckoutSessionCompletedEvent,
): Promise<void> {
  const session = event.data.object;
  const customerId =
    typeof session.customer === "string" ? session.customer : session.customer?.id;
  const subscriptionId =
    typeof session.subscription === "string"
      ? session.subscription
      : session.subscription?.id;

  log.debug("[stripe-events] checkout.session.completed", {
    eventId: event.id,
    customerId,
    subscriptionId,
    amountTotal: session.amount_total,
    currency: session.currency,
    mode: session.mode,
  });

  // TODO: 后端接入 Stripe 后，这里调后端 API
  // POST /api/internal/users/:userId/set-vip
  // { isVip: true, voiceMinutes: <plan's voiceMinutesPerDay> }
  // 本轮先不接（后端可能还没好）——
  //   业务后端收到 webhook 后会自己更新 user.isVip + voiceMinutesRemaining
}

// ============================================================
// Handler 2: customer.subscription.deleted
// ============================================================
/**
 * 订阅取消 → user.isVip=false
 *
 * 注意：voiceMinutesRemaining 保留（不清零）—— 不然已经发送的语音会消失
 * （业务决定）
 */
async function handleSubscriptionDeleted(
  event: Stripe.CustomerSubscriptionDeletedEvent,
): Promise<void> {
  const subscription = event.data.object;
  const customerId =
    typeof subscription.customer === "string"
      ? subscription.customer
      : subscription.customer.id;

  log.debug("[stripe-events] customer.subscription.deleted", {
    eventId: event.id,
    customerId,
    subscriptionId: subscription.id,
    canceledAt: subscription.canceled_at,
    status: subscription.status,
  });

  // TODO: POST /api/internal/users/:userId/set-vip { isVip: false }
  //   voiceMinutesRemaining 不动（保留余额）
}

// ============================================================
// Handler 3: customer.subscription.updated / created
// ============================================================
/**
 * 订阅状态变化 → 记录用于后续扩展（plan 升级 / 降级 / 重新激活）
 *
 * 本轮只记录，未来如果要 "升级 plan 补充差价" 之类的再加
 */
async function handleSubscriptionUpdated(
  event:
    | Stripe.CustomerSubscriptionUpdatedEvent
    | Stripe.CustomerSubscriptionCreatedEvent,
): Promise<void> {
  const subscription = event.data.object;
  const customerId =
    typeof subscription.customer === "string"
      ? subscription.customer
      : subscription.customer.id;

  log.debug(`[stripe-events] customer.subscription.${event.type}`, {
    eventId: event.id,
    customerId,
    subscriptionId: subscription.id,
    status: subscription.status,
    cancelAtPeriodEnd: subscription.cancel_at_period_end,
    itemsCount: subscription.items.data.length,
  });

  // TODO: 如果要处理 plan 升级 / 降级 → POST /api/internal/users/:userId/update-subscription
}

// ============================================================
// Handler 4: invoice.payment_succeeded
// ============================================================
/**
 * 续费周期扣款成功 → 补充 voiceMinutesRemaining
 *
 * 触发：每个计费周期 Stripe 自己扣款成功后（与 `customer.subscription.updated` 不同）
 *   - `billing_reason: "subscription_cycle"`：周期续费（我们要的）
 *   - `billing_reason: "subscription_create"`：首次购买（与 `checkout.session.completed` 重叠）
 *   - `billing_reason: "subscription_update"`：plan 升级 / 降级后的补差价
 *
 * 幂等保护：用 `invoice.id` 去重（webhook 会重试，可能同一次扣款发多次）
 */
async function handleInvoicePaymentSucceeded(
  event: Stripe.InvoicePaymentSucceededEvent,
): Promise<void> {
  const invoice = event.data.object;
  const customerId =
    typeof invoice.customer === "string" ? invoice.customer : invoice.customer?.id;

  // 只关心周期续费（不对首次购买重复补充）
  if (invoice.billing_reason !== "subscription_cycle") {
    log.debug(
      `[stripe-events] invoice.payment_succeeded (skipped, billing_reason=${invoice.billing_reason})`,
      { eventId: event.id, invoiceId: invoice.id },
    );
    return;
  }

  log.debug("[stripe-events] invoice.payment_succeeded (subscription_cycle)", {
    eventId: event.id,
    invoiceId: invoice.id,
    customerId,
    amountPaid: invoice.amount_paid,
  });


  // TODO: POST /api/internal/users/:userId/top-up-voice-minutes
  //   { minutes: <plan's voiceMinutesPerDay> }
}

// 注：stripe-client 保留给未来扩展使用（例如主动调 `stripe.subscriptions.update()` 升级 plan）
//   本轮 handler 没直接调用 getStripeClient()（webhook 是事件驱动，不需要反向查 Stripe）
export const _internal_stripeClient = getStripeClient;