import { NextRequest, NextResponse } from "next/server";
import { getApiUrlFromRequest, getPaymentConfig } from "@/config/services.config";
import {
  checkPaymentsByUserId,
  checkSiteVipByUserId,
  findLinkedMemberFromOrder,
  findVipEmailLinkByAnonymousUserId,
  getAdminToken,
  isAnonymousUserId,
  upsertVipEmailLink,
} from "@/app/api/vip/_helpers";

type PayjsVipResult = {
  vip: boolean;
  email?: string;
  linkedUserId?: string;
};

const inflightUserChecks = new Map<string, Promise<PayjsVipResult | null>>();
type UserCheckPayload = {
  ok: boolean;
  vip: boolean;
  alreadyLinked: boolean;
  /** 服务端异常/超时时为 true，前端勿据此清空本地已登录 VIP */
  uncertain?: boolean;
  email?: string;
  linkedUserId?: string;
};
const inflightUserRequests = new Map<
  string,
  Promise<UserCheckPayload>
>();
const userCheckResultCache = new Map<
  string,
  {
    expiresAt: number;
    payload: UserCheckPayload;
  }
>();
const USER_CHECK_CACHE_TTL_MS = Number(process.env.CHECK_BY_USER_CACHE_TTL_MS) || 10_000;

async function fetchPayjsVipWithRetry(
  url: string,
  timeoutMs: number,
  retries: number
): Promise<Response | null> {
  let lastError: unknown = null;
  for (let i = 0; i <= retries; i += 1) {
    try {
      const res = await fetch(url, {
        cache: "no-store",
        signal: AbortSignal.timeout(timeoutMs),
      });
      return res;
    } catch (error) {
      lastError = error;
      if (i < retries) {
        await new Promise((resolve) => setTimeout(resolve, 250 * (i + 1)));
      }
    }
  }
  throw lastError instanceof Error ? lastError : new Error("payjsapi fetch failed");
}

function resolvePayApiUrl(request: NextRequest): string {
  const payConfig = getPaymentConfig();
  const hostHeader = request.headers.get("host") || request.headers.get("x-forwarded-host");
  return (
    (hostHeader ? getApiUrlFromRequest(hostHeader) : null) ||
    payConfig.apiUrl
  ).replace(/\/$/, "");
}

async function checkVipFromPayjsapi(
  request: NextRequest,
  userId: string
): Promise<PayjsVipResult | null> {
  const existed = inflightUserChecks.get(userId);
  if (existed) {
    return existed;
  }

  const task = (async () => {
  try {
    const apiUrl = resolvePayApiUrl(request);
    const url = `${apiUrl}/nomadvip/check_vip?user_id=${encodeURIComponent(
      userId
    )}`;
    console.log("[check-by-user] payjsapi request user_id=%s url=%s", userId, url);
    const checkTimeout = Number(process.env.PAYJSAPI_CHECK_TIMEOUT) || 15_000;
    const retries = Math.max(0, Number(process.env.PAYJSAPI_CHECK_RETRIES) || 1);
    const res = await fetchPayjsVipWithRetry(url, checkTimeout, retries);
    if (!res) {
      return null;
    }
    if (!res.ok) {
      console.log(
        "[check-by-user] payjsapi non-ok user_id=%s status=%s",
        userId,
        res.status
      );
      return null;
    }

    const data = await res.json().catch(() => ({}));
    const result = {
      vip: !!data?.vip,
      email:
        typeof data?.email === "string" && data.email.trim()
          ? data.email.trim().toLowerCase()
          : undefined,
      linkedUserId:
        typeof data?.linked_user_id === "string" && data.linked_user_id.trim()
          ? data.linked_user_id.trim()
          : undefined,
    };
    console.log(
      "[check-by-user] payjsapi response user_id=%s vip=%s email=%s",
      userId,
      result.vip,
      result.email ?? "(none)"
    );
    return result;
  } catch (error) {
    console.log(
      "[check-by-user] payjsapi request failed user_id=%s error=%s",
      userId,
      error instanceof Error ? error.message : String(error)
    );
    return null;
  }
  })();

  inflightUserChecks.set(userId, task);
  try {
    return await task;
  } finally {
    inflightUserChecks.delete(userId);
  }
}

export async function POST(request: NextRequest) {
  const body = await request.json().catch(() => ({}));
  const userId = String(body?.user_id ?? body?.userId ?? "").trim();

  console.log("[check-by-user] request user_id=%s", userId || "(empty)");

  if (!userId) {
    return NextResponse.json(
      { ok: false, vip: false, error: "缺少 user_id" },
      { status: 400 }
    );
  }

  const cached = userCheckResultCache.get(userId);
  if (cached && cached.expiresAt > Date.now()) {
    return NextResponse.json(cached.payload);
  }
  if (cached) {
    userCheckResultCache.delete(userId);
  }

  const inflight = inflightUserRequests.get(userId);
  if (inflight) {
    const payload = await inflight;
    return NextResponse.json(payload);
  }

  const task = (async () => {
    let payjsResult: PayjsVipResult | null = null;
    let vip = false;
    let email: string | null = null;
    let linkedUserId: string | undefined;
    let vipFromSite = false;
    let vipFromPayments = false;
    let vipSource = "none";

    try {
      const adminToken = await getAdminToken().catch((error) => {
        console.error("[check-by-user] getAdminToken failed:", error);
        return null;
      });
      if (!adminToken) {
        payjsResult = await checkVipFromPayjsapi(request, userId);
        vip = !!payjsResult?.vip;
        email = payjsResult?.email ?? null;
        console.error("[check-by-user] missing PocketBase admin token, fallback to payjs result");
        return {
          ok: true,
          vip,
          alreadyLinked: !!email,
          email: email ?? undefined,
        };
      }

      if (!vip) {
        vipFromSite = await checkSiteVipByUserId(adminToken, userId);
        vip = vipFromSite;
        if (!vip) {
          vipFromPayments = await checkPaymentsByUserId(adminToken, userId);
          vip = vipFromPayments;
        }
        if (vipFromSite) {
          vipSource = "pocketbase:site_vip";
        } else if (vipFromPayments) {
          vipSource = "pocketbase:payments";
        }
        console.log(
          "[check-by-user] pb fallback user_id=%s site_vip=%s payments=%s",
          userId,
          vipFromSite,
          vipFromPayments
        );
      }

      // 同机 PB 命中则不再打 payjsapi；仅未命中时再走 payjs（与线上极致路径一致）
      if (!vip) {
        payjsResult = await checkVipFromPayjsapi(request, userId);
        if (payjsResult?.vip) {
          vip = true;
          email = payjsResult.email ?? null;
          linkedUserId = payjsResult.linkedUserId;
          vipSource = "payjsapi";
        }
      }

      if (isAnonymousUserId(userId)) {
        const linkRecord = await findVipEmailLinkByAnonymousUserId(adminToken, userId);
        const linkEmail =
          typeof linkRecord?.email === "string"
            ? linkRecord.email.trim().toLowerCase()
            : "";
        const linkUserId =
          typeof linkRecord?.user_id === "string" ? linkRecord.user_id.trim() : "";

        // 匿名 user_id 本身可能已迁移到真实用户，需补查映射用户的 VIP
        if (!vip && linkUserId && linkUserId !== userId) {
          const linkedVip = await checkSiteVipByUserId(adminToken, linkUserId);
          const linkedPaymentVip = linkedVip
            ? true
            : await checkPaymentsByUserId(adminToken, linkUserId);
          if (linkedVip || linkedPaymentVip) {
            vip = true;
            linkedUserId = linkUserId;
            vipSource = linkedVip ? "vip_email_link:site_vip" : "vip_email_link:payments";
          }
        }

        if (vip && linkEmail) {
          email = linkEmail;
          if (linkUserId && !isAnonymousUserId(linkUserId)) {
            linkedUserId = linkUserId;
          }
          if (!vipSource || vipSource === "none") {
            vipSource = "vip_email_link";
          }
          console.log(
            "[check-by-user] linked by vip_email_link user_id=%s linkedUserId=%s email=%s",
            userId,
            linkedUserId || "(none)",
            email
          );
        } else if (vip) {
          const linkedMember = await findLinkedMemberFromOrder(adminToken, userId);
          if (linkedMember) {
            email = linkedMember.email;
            linkedUserId = linkedMember.userId;
            await upsertVipEmailLink(
              adminToken,
              linkedMember.email,
              linkedMember.userId,
              userId
            );
            vipSource = "linked_from_order";
            console.log(
              "[check-by-user] linked by order user_id=%s linkedUserId=%s email=%s",
              userId,
              linkedUserId,
              email
            );
          }
        }
      }

      console.log(
        "[check-by-user] result user_id=%s vip=%s source=%s alreadyLinked=%s linkedUserId=%s",
        userId,
        vip,
        vipSource,
        !!email,
        linkedUserId || "(none)"
      );

      return {
        ok: true,
        vip,
        alreadyLinked: !!email,
        email: email ?? undefined,
        linkedUserId,
      };
    } catch (error) {
      console.error("[check-by-user] failed:", error);
      // 勿伪装成「确定非 VIP」，否则微信/H5 弱网会误清本地态
      return {
        ok: false,
        vip: false,
        alreadyLinked: false,
        uncertain: true,
      };
    }
  })();

  inflightUserRequests.set(userId, task);
  try {
    const payload = await task;
    // 只缓存命中结果，避免绑定邮箱后的短时 false 缓存导致需要多次刷新才恢复
    if (!payload.uncertain && payload.vip) {
      userCheckResultCache.set(userId, {
        payload,
        expiresAt: Date.now() + USER_CHECK_CACHE_TTL_MS,
      });
    }
    return NextResponse.json(payload);
  } finally {
    inflightUserRequests.delete(userId);
  }
}