'use strict';

const crypto = require('crypto');
const { getResponseDataUsage } = require('../utils/fastgptResponseData');

const DOC_KIND = {
   BID: 'bid',
   PLAN: 'plan',
};

const EVENT_TYPE = {
   CREATE: 'create',
   REWRITE: 'rewrite',
   GENERATE: 'generate',
};

const BILLING_STATUS = {
   FREE: 'free',
   PENDING: 'pending',
   CONFIRMED: 'confirmed',
   ROLLED_BACK: 'rolled_back',
   SKIP: 'skip',
};

const QUOTA_ERROR_CODE = {
   CREATE_LIMIT_REACHED: 'CREATE_LIMIT_REACHED',
   REWRITE_LIMIT_REACHED: 'REWRITE_LIMIT_REACHED',
   RECHARGE_REQUIRED: 'RECHARGE_REQUIRED',
   CHARGE_CONFIRM_REQUIRED: 'CHARGE_CONFIRM_REQUIRED',
   CHARGE_CONFIRM_INVALID: 'CHARGE_CONFIRM_INVALID',
   BILLING_SERVICE_UNAVAILABLE: 'BILLING_SERVICE_UNAVAILABLE',
};
const QUOTA_ENFORCED_REGISTER_SOURCES = new Set(['OFFICIALWEBSITE', 'PHONE']);
const CHARGEABLE_REGISTER_SOURCES = new Set(['OFFICIALWEBSITE']);

const toSafePositiveNumber = (value, fallback) => {
   const n = Number(value);
   return Number.isFinite(n) && n > 0 ? n : fallback;
};

const buildQuotaError = (code, message) => {
   const error = new Error(message);
   error.code = code;
   return error;
};

const normalizeUserId = (value) => {
   const text = String(value ?? '').trim();
   if (!text) return null;
   if (!/^\d+$/.test(text)) return null;
   const n = Number(text);
   if (!Number.isSafeInteger(n) || n <= 0) return null;
   return n;
};

const normalizeBoolean = (value) => {
   if (value === true || value === false) return value;
   const text = String(value ?? '').trim().toLowerCase();
   return text === '1' || text === 'true' || text === 'yes' || text === 'on';
};

const toUsageFromResponse = (responseBody = {}) => {
   // FastGPT top-level usage may be a placeholder. Only detail=true responseData is trusted.
   return getResponseDataUsage(responseBody);
};

const buildService = (app) => {
   const getOrm = () => {
      const orm = app?.fs?.dc?.orm;
      if (!orm) {
         throw buildQuotaError(
            QUOTA_ERROR_CODE.BILLING_SERVICE_UNAVAILABLE,
            '计费服务未初始化：数据库连接未就绪'
         );
      }
      return orm;
   };

   // 延迟获取 orm，避免服务初始化时机早于 sequelize 注入导致启动报错。
   const orm = new Proxy({}, {
      get(_target, prop) {
         const ormInstance = getOrm();
         const raw = ormInstance[prop];
         return typeof raw === 'function' ? raw.bind(ormInstance) : raw;
      },
   });
   const QueryTypes = new Proxy({}, {
      get(_target, prop) {
         return getOrm()?.QueryTypes?.[prop];
      },
   });
   const billingConfig = app.fs.config.billing || {};
   const tokenPerYuan = toSafePositiveNumber(billingConfig.tokenPerYuan, 10000);
   const createChargeYuan = toSafePositiveNumber(
      process.env.BILLING_CREATE_CHARGE_YUAN ?? billingConfig.createChargeYuan,
      5
   );
   const rewriteLimitPerHour = Math.max(
      1,
      Number(process.env.BILLING_REWRITE_LIMIT_PER_HOUR || 20) || 20
   );
   const rewriteWindowMinutes = Math.max(
      1,
      Number(process.env.BILLING_REWRITE_WINDOW_MINUTES || 60) || 60
   );
   const confirmTokenTtlMs = Math.max(
      30 * 1000,
      Number(billingConfig.confirmTokenTtlMs || billingConfig.confirmTokenTtl || 5 * 60 * 1000) || (5 * 60 * 1000)
   );
   const chargeConfirmStore = new Map();

   const calculateAmountYuan = (totalTokens) => {
      // 按 TOKEN_PER_YUAN 换算金额，并固定保留 6 位小数作为账务精度。
      const tokens = Number(totalTokens || 0);
      if (!Number.isFinite(tokens) || tokens <= 0) return 0;
      return Number((tokens / tokenPerYuan).toFixed(6));
   };

   const extractFirstRow = (queryResult) => {
      if (!Array.isArray(queryResult)) return null;
      if (Array.isArray(queryResult[0])) return queryResult[0][0] || null;
      if (queryResult[0] && typeof queryResult[0] === 'object') return queryResult[0];
      return null;
   };

   const lockByKey = async (transaction, lockKey) => {
      await orm.query(
         'SELECT pg_advisory_xact_lock(hashtext(:lockKey));',
         {
            replacements: { lockKey: String(lockKey || '') },
            type: QueryTypes.SELECT,
            transaction,
         }
      );
   };

   const pruneExpiredConfirmToken = () => {
      const now = Date.now();
      for (const [token, item] of chargeConfirmStore.entries()) {
         if (!item?.expireAt || item.expireAt <= now) {
            chargeConfirmStore.delete(token);
         }
      }
   };

   const createChargeConfirmToken = ({ userId, docKind, action, aideductUserId }) => {
      pruneExpiredConfirmToken();
      const token = crypto.randomBytes(24).toString('hex');
      const expireAt = Date.now() + confirmTokenTtlMs;
      chargeConfirmStore.set(token, {
         userId: Number(userId),
         docKind: String(docKind || ''),
         action: String(action || ''),
         aideductUserId: String(aideductUserId || ''),
         expireAt,
      });
      return {
         token,
         expireAt,
      };
   };

   const consumeChargeConfirmToken = ({
      token,
      userId,
      docKind,
      action,
      aideductUserId,
   }) => {
      pruneExpiredConfirmToken();
      const key = String(token || '').trim();
      if (!key) return false;
      const payload = chargeConfirmStore.get(key);
      if (!payload) return false;
      const valid = (
         Number(payload.userId) === Number(userId)
         && String(payload.docKind || '') === String(docKind || '')
         && String(payload.action || '') === String(action || '')
         && String(payload.aideductUserId || '') === String(aideductUserId || '')
      );
      if (!valid) return false;
      chargeConfirmStore.delete(key);
      return true;
   };

   const resolveAideductUserId = async ({ transaction, userId, externalUserId = '' }) => {
      const preferredExternalUserId = String(externalUserId || '').trim();
      if (preferredExternalUserId && preferredExternalUserId !== String(userId)) {
         return preferredExternalUserId;
      }
      const [userRow] = await orm.query(
         'SELECT external_user_id FROM tender_user WHERE id = :userId LIMIT 1;',
         {
            replacements: { userId },
            type: QueryTypes.SELECT,
            transaction,
         }
      );
      const external = String(userRow?.external_user_id || '').trim();
      if (external) return external;
      return String(userId);
   };

   const resolveUserBillingMode = async ({ transaction, userId }) => {
      const normalizedUserId = normalizeUserId(userId);
      if (!normalizedUserId) {
         return {
            registerSource: '',
            quotaEnabled: false,
            chargeable: false,
         };
      }
      const replacements = { userId: normalizedUserId };
      const queryOptions = transaction
         ? { replacements, type: QueryTypes.SELECT, transaction }
         : { replacements, type: QueryTypes.SELECT };
      const [userRow] = await orm.query(
         'SELECT register_source FROM tender_user WHERE id = :userId LIMIT 1;',
         queryOptions
      );
      const registerSource = String(userRow?.register_source || '').trim().toUpperCase();
      return {
         registerSource,
         quotaEnabled: QUOTA_ENFORCED_REGISTER_SOURCES.has(registerSource),
         chargeable: CHARGEABLE_REGISTER_SOURCES.has(registerSource),
      };
   };

   const checkWalletChargeDecision = async ({
      transaction,
      userId,
      docKind,
      action,
      chargeAmountYuan = 0,
      confirmCharge = false,
      confirmToken = '',
      externalUserId = '',
   }) => {
      const billingMode = await resolveUserBillingMode({ transaction, userId });
      if (!billingMode.chargeable) {
         const isRewriteAction = String(action || '') === EVENT_TYPE.REWRITE;
         return {
            passed: false,
            code: isRewriteAction
               ? QUOTA_ERROR_CODE.REWRITE_LIMIT_REACHED
               : QUOTA_ERROR_CODE.CREATE_LIMIT_REACHED,
            message: isRewriteAction
               ? `重编试用次数已达上限，请${rewriteWindowMinutes}分钟后再试`
               : '今日试用次数已用完，请明日再试',
         };
      }
      const aideductService = app.fs?.aideductService;
      if (!aideductService?.getBalance) {
         return {
            passed: false,
            code: QUOTA_ERROR_CODE.BILLING_SERVICE_UNAVAILABLE,
            message: '扣费服务暂不可用，请稍后重试',
         };
      }

      const aideductUserId = await resolveAideductUserId({
         transaction,
         userId,
         externalUserId,
      });
      let balance = 0;
      try {
         const balanceRes = await aideductService.getBalance({ userId: aideductUserId });
         balance = Number(balanceRes?.data?.balance || 0);
      } catch (error) {
         app?.logger?.log?.(error);
         return {
            passed: false,
            code: QUOTA_ERROR_CODE.BILLING_SERVICE_UNAVAILABLE,
            message: '扣费服务暂不可用，请稍后重试',
         };
      }

      if (!Number.isFinite(balance) || balance <= 0) {
         return {
            passed: false,
            code: QUOTA_ERROR_CODE.RECHARGE_REQUIRED,
            message: '免费次数已用完，请充值后继续使用',
         };
      }

      const isConfirmed = normalizeBoolean(confirmCharge);
      if (!isConfirmed) {
         const confirmInfo = createChargeConfirmToken({
            userId,
            docKind,
            action,
            aideductUserId,
         });
         return {
            passed: false,
            code: QUOTA_ERROR_CODE.CHARGE_CONFIRM_REQUIRED,
            message: chargeAmountYuan > 0
               ? `免费次数已用完，继续使用将扣费${Number(chargeAmountYuan)}元`
               : '免费次数已用完，继续使用将进行扣费',
            confirmToken: confirmInfo.token,
            confirmExpireAt: new Date(confirmInfo.expireAt).toISOString(),
         };
      }

      const validConfirm = consumeChargeConfirmToken({
         token: confirmToken,
         userId,
         docKind,
         action,
         aideductUserId,
      });
      if (!validConfirm) {
         return {
            passed: false,
            code: QUOTA_ERROR_CODE.CHARGE_CONFIRM_INVALID,
            message: '扣费确认已失效，请重新操作',
         };
      }

      return {
         passed: true,
         chargeRequired: chargeAmountYuan > 0,
         chargeAmountYuan: chargeAmountYuan > 0 ? Number(chargeAmountYuan) : 0,
      };
   };

   const ensureUserProfileAndPolicy = async (transaction, userId) => {
      const [userRow] = await orm.query(
         'SELECT pep_id FROM tender_user WHERE id = :userId LIMIT 1;',
         {
            replacements: { userId },
            type: QueryTypes.SELECT,
            transaction,
         }
      );

      const policyCode = userRow?.pep_id ? 'default' : 'non_project_enterprise';

      await orm.query(
         `INSERT INTO user_billing_profile (user_id, policy_code, activated_at, created_at, updated_at)
          VALUES (:userId, :policyCode, now(), now(), now())
          ON CONFLICT (user_id)
          DO UPDATE SET policy_code = EXCLUDED.policy_code, updated_at = now();`,
         {
            replacements: { userId, policyCode },
            type: QueryTypes.INSERT,
            transaction,
         }
      );

      const [policy] = await orm.query(
         `SELECT bp.*
          FROM user_billing_profile ubp
          JOIN billing_policy bp ON bp.code = ubp.policy_code
          WHERE ubp.user_id = :userId
          LIMIT 1;`,
         {
            replacements: { userId },
            type: QueryTypes.SELECT,
            transaction,
         }
      );

      if (!policy) {
         throw new Error('用户计费策略不存在');
      }
      return policy;
   };

   const getUserQuotaSnapshot = async ({ userId }) => {
      const normalizedUserId = normalizeUserId(userId);
      if (!normalizedUserId) return null;
      const billingMode = await resolveUserBillingMode({ userId: normalizedUserId });
      if (!billingMode.quotaEnabled) return null;

      const transaction = await orm.transaction();
      try {
         const policy = await ensureUserProfileAndPolicy(transaction, normalizedUserId);
         const createRows = await orm.query(
            `SELECT doc_kind, COUNT(*)::BIGINT AS used_count
             FROM quota_event
             WHERE user_id = :userId
               AND event_type = 'create'
             GROUP BY doc_kind;`,
            {
               replacements: { userId: normalizedUserId },
               type: QueryTypes.SELECT,
               transaction,
            }
         );
         const [rewriteRow] = await orm.query(
            `SELECT COUNT(*)::BIGINT AS rewrite_count
             FROM quota_event
             WHERE user_id = :userId
               AND event_type = 'rewrite'
               AND created_at >= now() - make_interval(mins => :windowMinutes);`,
            {
               replacements: {
                  userId: normalizedUserId,
                  windowMinutes: rewriteWindowMinutes,
               },
               type: QueryTypes.SELECT,
               transaction,
            }
         );
         await transaction.commit();

         const createCountMap = new Map(
            (Array.isArray(createRows) ? createRows : []).map((row) => [
               String(row?.doc_kind || '').trim().toLowerCase(),
               Number(row?.used_count || 0),
            ])
         );
         const bidLimit = Number(policy?.seed_bid_limit || 0);
         const planLimit = Number(policy?.seed_plan_limit || 0);
         const bidUsed = Number(createCountMap.get(DOC_KIND.BID) || 0);
         const planUsed = Number(createCountMap.get(DOC_KIND.PLAN) || 0);
         const rewriteUsed = Number(rewriteRow?.rewrite_count || 0);

         return {
            policyCode: String(policy?.code || ''),
            policyName: String(policy?.name || ''),
            create: {
               bid: {
                  limit: bidLimit,
                  used: bidUsed,
                  remaining: Math.max(0, bidLimit - bidUsed),
               },
               plan: {
                  limit: planLimit,
                  used: planUsed,
                  remaining: Math.max(0, planLimit - planUsed),
               },
            },
            rewrite: {
               limitPerHour: rewriteLimitPerHour,
               windowMinutes: rewriteWindowMinutes,
               used: rewriteUsed,
               remaining: Math.max(0, rewriteLimitPerHour - rewriteUsed),
            },
            generatedAt: new Date().toISOString(),
         };
      } catch (error) {
         await transaction.rollback();
         throw error;
      }
   };

   const checkCreateQuota = async ({
      transaction,
      userId,
      docKind,
      confirmCharge = false,
      confirmToken = '',
      externalUserId = '',
   }) => {
      if (!userId || !docKind) {
         return { passed: true };
      }
      const billingMode = await resolveUserBillingMode({ transaction, userId });
      if (!billingMode.quotaEnabled) {
         return {
            passed: true,
            chargeRequired: false,
            chargeAmountYuan: 0,
         };
      }
      // 创建配额并发敏感，按 user+docKind 加事务级 advisory lock。
      await lockByKey(transaction, `create:${userId}:${docKind}`);
      const policy = await ensureUserProfileAndPolicy(transaction, userId);

      const [counter] = await orm.query(
         `SELECT
             COUNT(*)::BIGINT AS total_created,
             COUNT(*) FILTER (
               WHERE created_at >= now() - make_interval(hours => :rollingHours)
             )::BIGINT AS rolling_created,
             COUNT(*) FILTER (
               WHERE created_at >= date_trunc('day', now())
             )::BIGINT AS today_created
          FROM quota_event
          WHERE user_id = :userId
            AND event_type = 'create'
            AND doc_kind = :docKind;`,
         {
            replacements: {
               userId,
               docKind,
               rollingHours: Number(policy.rolling_create_hours || 24),
            },
            type: QueryTypes.SELECT,
            transaction,
         }
      );

      const totalCreated = Number(counter?.total_created || 0);
      const todayCreated = Number(counter?.today_created || 0);
      const seedLimitRaw = docKind === DOC_KIND.BID ? policy.seed_bid_limit : policy.seed_plan_limit;
      const seedLimit = Number.isFinite(Number(seedLimitRaw)) ? Number(seedLimitRaw) : 3;

      // 先消耗永久种子额度。
      if (totalCreated < seedLimit) return { passed: true };
      // 超过免费总额度后，每日首次创建继续免费。
      if (todayCreated === 0) return { passed: true };
      // 手机号用户仅走试用次数逻辑，超限后需等待，不进入扣费链路。
      if (!billingMode.chargeable) {
         return {
            passed: false,
            code: QUOTA_ERROR_CODE.CREATE_LIMIT_REACHED,
            message: '今日试用次数已用完，请明日再试',
         };
      }

      return checkWalletChargeDecision({
         transaction,
         userId,
         docKind,
         action: EVENT_TYPE.CREATE,
         chargeAmountYuan: createChargeYuan,
         confirmCharge,
         confirmToken,
         externalUserId,
      });
   };

   const recordCreateEvent = async ({
      transaction,
      userId,
      docKind,
      docId,
      source = 'manual',
      billingStatus = BILLING_STATUS.SKIP,
      amountYuan = 0,
      requestId = null,
   }) => {
      if (!userId || !docKind || !docId) return null;
      const billingMode = await resolveUserBillingMode({ transaction, userId });
      if (!billingMode.quotaEnabled) return null;
      // 删除不回退额度，因此用事件流水统计，且同文档创建事件幂等写入。
      const result = await orm.query(
         `INSERT INTO quota_event (
            user_id, doc_id, doc_kind, event_type, source,
            amount_yuan, billing_status, request_id, created_at
          )
          VALUES (
            :userId, :docId, :docKind, 'create', :source,
            :amountYuan, :billingStatus, :requestId, now()
         )
          ON CONFLICT DO NOTHING
          RETURNING id;`,
         {
            replacements: {
               userId,
               docId,
               docKind,
               source,
               amountYuan,
               billingStatus,
               requestId,
            },
            transaction,
         }
      );
      return extractFirstRow(result)?.id || null;
   };

   const checkAndRecordRewrite = async ({
      transaction,
      userId,
      docId,
      docKind,
      chapterKey = null,
      action = 'rewrite',
      consumeCount = 1,
      confirmCharge = false,
      confirmToken = '',
      externalUserId = '',
   }) => {
      if (!userId || !docId) {
         return { passed: true };
      }
      const billingMode = await resolveUserBillingMode({ transaction, userId });
      if (!billingMode.quotaEnabled) {
         return {
            passed: true,
            overLimit: false,
            chargeRequired: false,
            chargeAmountYuan: 0,
         };
      }
      const normalizedConsumeCount = Math.max(1, Math.floor(Number(consumeCount || 1)));

      // 重写限流按 user 粒度，全文档共享每小时次数。
      await lockByKey(transaction, `rewrite:${userId}`);

      const [counter] = await orm.query(
         `SELECT COUNT(*)::BIGINT AS rewrite_count
          FROM quota_event
          WHERE user_id = :userId
            AND event_type = 'rewrite'
            AND created_at >= now() - make_interval(mins => :windowMinutes);`,
         {
            replacements: {
               userId,
               windowMinutes: rewriteWindowMinutes,
            },
            type: QueryTypes.SELECT,
            transaction,
         }
      );

      const rewriteCount = Number(counter?.rewrite_count || 0);
      const overLimit = rewriteCount + normalizedConsumeCount > rewriteLimitPerHour;
      if (overLimit) {
         if (!billingMode.chargeable) {
            return {
               passed: false,
               code: QUOTA_ERROR_CODE.REWRITE_LIMIT_REACHED,
               message: `重编试用次数已达上限，请${rewriteWindowMinutes}分钟后再试`,
            };
         }
         const decision = await checkWalletChargeDecision({
            transaction,
            userId,
            docKind,
            action: EVENT_TYPE.REWRITE,
            confirmCharge,
            confirmToken,
            externalUserId,
         });
         if (decision?.passed === false) return decision;
         return {
            ...decision,
            passed: true,
            overLimit: true,
         };
      }

      await orm.query(
         `INSERT INTO quota_event (
            user_id, doc_id, doc_kind, chapter_key, event_type, action,
            billing_status, created_at
          )
          SELECT
            :userId, :docId, :docKind, :chapterKey, 'rewrite', :action,
            'skip', now()
          FROM generate_series(1, :consumeCount);`,
         {
            replacements: {
               userId,
               docId,
               docKind: docKind || null,
               chapterKey,
               action,
               consumeCount: normalizedConsumeCount,
            },
            type: QueryTypes.INSERT,
            transaction,
         }
      );

      return {
         passed: true,
         overLimit: false,
      };
   };

   const markChapterFirstFree = async ({ userId, docId, chapterKey }) => {
      if (!userId || !docId || !chapterKey) return false;
      // 首次章节免费：唯一键冲突即表示“已免过”，无需额外读查询。
      const result = await orm.query(
         `INSERT INTO quota_chapter_first_free (
            user_id, doc_id, chapter_key, first_generated_at
          ) VALUES (
            :userId, :docId, :chapterKey, now()
          )
          ON CONFLICT DO NOTHING
          RETURNING user_id;`,
         {
            replacements: { userId, docId, chapterKey },
         }
      );
      return !!extractFirstRow(result);
   };

   const isDocGenerateBillingExemptByCreate = async ({ userId, docId, docKind }) => {
      if (!userId || !docId || !docKind) return false;
      const billingMode = await resolveUserBillingMode({ userId });
      if (!billingMode.quotaEnabled || !billingMode.chargeable) return true;
      const [row] = await orm.query(
         `SELECT billing_status
          FROM quota_event
          WHERE user_id = :userId
            AND doc_id = :docId
            AND doc_kind = :docKind
            AND event_type = 'create'
          ORDER BY id DESC
          LIMIT 1;`,
         {
            replacements: { userId, docId, docKind },
            type: QueryTypes.SELECT,
         }
      );
      const status = String(row?.billing_status || '').trim().toLowerCase();
      // 免费创建（skip/free）文档：目录与正文生成统一免扣费。
      return status === BILLING_STATUS.SKIP || status === BILLING_STATUS.FREE;
   };

   const recordGenerateEvent = async ({
      userId,
      docId,
      docKind,
      chapterKey = null,
      usage = {},
      billingStatus = BILLING_STATUS.SKIP,
      tokenPerYuanSnapshot = tokenPerYuan,
      amountYuan = 0,
      requestId = null,
      source = 'manual',
   }) => {
      if (!userId || !docId) return null;

      // 生成事件统一沉淀 token 与金额快照，后续审计不受配置变更影响。
      const inputTokens = Number(usage.inputTokens || 0);
      const outputTokens = Number(usage.outputTokens || 0);
      const embeddingTokens = Number(usage.embeddingTokens || 0);
      const totalTokens = Number(usage.totalTokens || 0);

      const result = await orm.query(
         `INSERT INTO quota_event (
            user_id, doc_id, doc_kind, chapter_key, event_type, source,
            input_tokens, output_tokens, embedding_tokens, total_tokens,
            token_per_yuan, amount_yuan, billing_status, request_id, created_at
          ) VALUES (
            :userId, :docId, :docKind, :chapterKey, 'generate', :source,
            :inputTokens, :outputTokens, :embeddingTokens, :totalTokens,
            :tokenPerYuanSnapshot, :amountYuan, :billingStatus, :requestId, now()
          ) RETURNING id;`,
         {
            replacements: {
               userId,
               docId,
               docKind: docKind || null,
               chapterKey,
               source,
               inputTokens,
               outputTokens,
               embeddingTokens,
               totalTokens,
               tokenPerYuanSnapshot,
               amountYuan,
               billingStatus,
               requestId,
            },
         }
      );

      return extractFirstRow(result)?.id || null;
   };

   const updateGenerateBillingStatus = async ({ eventId, billingStatus }) => {
      if (!eventId) return;
      await orm.query(
         `UPDATE quota_event
          SET billing_status = :billingStatus
          WHERE id = :eventId;`,
         {
            replacements: { eventId, billingStatus },
            type: QueryTypes.UPDATE,
         }
      );
   };

   const createRequestId = ({ userId, docKind, docId, chapterKey = '' }) => {
      return [
         'gen',
         userId,
         docKind || 'unknown',
         docId,
         chapterKey || 'none',
         Date.now(),
         crypto.randomBytes(4).toString('hex'),
      ].join('_');
   };

   const createCreateChargeRequestId = ({ userId, docKind, docId }) => {
      return [
         'create',
         userId,
         docKind || 'unknown',
         docId || 'none',
         Date.now(),
         crypto.randomBytes(4).toString('hex'),
      ].join('_');
   };

   const resolveChargeUserId = async ({ transaction, userId, externalUserId = '' }) => {
      return resolveAideductUserId({
         transaction,
         userId,
         externalUserId,
      });
   };

   const settleGenerateBilling = async ({
      eventId,
      aideductUserId,
      amountYuan,
      requestId,
      logger,
   }) => {
      const service = app.fs.aideductService;
      if (!service?.preDeduct || !service?.confirmDeduct || !service?.rollbackDeduct) {
         // 没有外部钱包服务时，保留 usage 流水但标记为 skip。
         await updateGenerateBillingStatus({ eventId, billingStatus: BILLING_STATUS.SKIP });
         return BILLING_STATUS.SKIP;
      }

      try {
         // 两阶段扣费：先预扣再确认，确保外部账务一致性。
         await service.preDeduct({ userId: aideductUserId, amount: amountYuan, requestId });
         await service.confirmDeduct({ userId: aideductUserId, amount: amountYuan, requestId });
         await updateGenerateBillingStatus({ eventId, billingStatus: BILLING_STATUS.CONFIRMED });
         return BILLING_STATUS.CONFIRMED;
      } catch (error) {
         try {
            // 任何失败都尝试回退预扣，避免冻结金额悬挂。
            await service.rollbackDeduct({ userId: aideductUserId, amount: amountYuan, requestId });
         } catch (rollbackError) {
            logger?.log?.(rollbackError);
         }
         await updateGenerateBillingStatus({ eventId, billingStatus: BILLING_STATUS.ROLLED_BACK });
         logger?.log?.(error);
         return BILLING_STATUS.ROLLED_BACK;
      }
   };

   return {
      DOC_KIND,
      EVENT_TYPE,
      BILLING_STATUS,
      QUOTA_ERROR_CODE,
      tokenPerYuan,
      createChargeYuan,
      normalizeUserId,
      toUsageFromResponse,
      calculateAmountYuan,
      getUserQuotaSnapshot,
      checkCreateQuota,
      recordCreateEvent,
      checkAndRecordRewrite,
      markChapterFirstFree,
      isDocGenerateBillingExemptByCreate,
      recordGenerateEvent,
      updateGenerateBillingStatus,
      createRequestId,
      createCreateChargeRequestId,
      resolveChargeUserId,
      settleGenerateBilling,
   };
};

module.exports = async (app) => {
   app.fs = app.fs || {};
   app.fs.quotaBillingService = buildService(app);
};