import { getErrorMessage } from "../common/utils/error.util";
import { Injectable, NotFoundException, Inject } from "@nestjs/common";
import { Subscription, SubscriptionList, InvoiceList } from "@customer-portal/shared";
import { WhmcsService } from "../vendors/whmcs/whmcs.service";
import { MappingsService } from "../mappings/mappings.service";
import { Logger } from "nestjs-pino";

export interface GetSubscriptionsOptions {
  status?: string;
}

@Injectable()
export class SubscriptionsService {
  constructor(
    private readonly whmcsService: WhmcsService,
    private readonly mappingsService: MappingsService,
    @Inject(Logger) private readonly logger: Logger
  ) {}

  /**
   * Get all subscriptions for a user
   */
  async getSubscriptions(
    userId: string,
    options: GetSubscriptionsOptions = {}
  ): Promise<SubscriptionList> {
    const { status } = options;

    try {
      // Get WHMCS client ID from user mapping
      const mapping = await this.mappingsService.findByUserId(userId);
      if (!mapping?.whmcsClientId) {
        throw new NotFoundException("WHMCS client mapping not found");
      }

      // Fetch subscriptions from WHMCS
      const subscriptionList = await this.whmcsService.getSubscriptions(
        mapping.whmcsClientId,
        userId,
        { status }
      );

      this.logger.log(
        `Retrieved ${subscriptionList.subscriptions.length} subscriptions for user ${userId}`,
        {
          status,
          totalCount: subscriptionList.totalCount,
        }
      );

      return subscriptionList;
    } catch (error) {
      this.logger.error(`Failed to get subscriptions for user ${userId}`, {
        error: getErrorMessage(error),
        options,
      });

      if (error instanceof NotFoundException) {
        throw error;
      }

      throw new Error(`Failed to retrieve subscriptions: ${getErrorMessage(error)}`);
    }
  }

  /**
   * Get individual subscription by ID
   */
  async getSubscriptionById(userId: string, subscriptionId: number): Promise<Subscription> {
    try {
      // Validate subscription ID
      if (!subscriptionId || subscriptionId < 1) {
        throw new Error("Invalid subscription ID");
      }

      // Get WHMCS client ID from user mapping
      const mapping = await this.mappingsService.findByUserId(userId);
      if (!mapping?.whmcsClientId) {
        throw new NotFoundException("WHMCS client mapping not found");
      }

      // Fetch subscription from WHMCS
      const subscription = await this.whmcsService.getSubscriptionById(
        mapping.whmcsClientId,
        userId,
        subscriptionId
      );

      this.logger.log(`Retrieved subscription ${subscriptionId} for user ${userId}`, {
        productName: subscription.productName,
        status: subscription.status,
        amount: subscription.amount,
        currency: subscription.currency,
      });

      return subscription;
    } catch (error) {
      this.logger.error(`Failed to get subscription ${subscriptionId} for user ${userId}`, {
        error: getErrorMessage(error),
      });

      if (error instanceof NotFoundException) {
        throw error;
      }

      throw new Error(`Failed to retrieve subscription: ${getErrorMessage(error)}`);
    }
  }

  /**
   * Get active subscriptions for a user
   */
  async getActiveSubscriptions(userId: string): Promise<Subscription[]> {
    try {
      const subscriptionList = await this.getSubscriptions(userId, {
        status: "Active",
      });
      return subscriptionList.subscriptions;
    } catch (error) {
      this.logger.error(`Failed to get active subscriptions for user ${userId}`, {
        error: getErrorMessage(error),
      });
      throw error;
    }
  }

  /**
   * Get subscriptions by status
   */
  async getSubscriptionsByStatus(userId: string, status: string): Promise<Subscription[]> {
    try {
      // Validate status
      const validStatuses = [
        "Active",
        "Suspended",
        "Terminated",
        "Cancelled",
        "Pending",
        "Completed",
      ];
      if (!validStatuses.includes(status)) {
        throw new Error(`Invalid status. Must be one of: ${validStatuses.join(", ")}`);
      }

      const subscriptionList = await this.getSubscriptions(userId, { status });
      return subscriptionList.subscriptions;
    } catch (error) {
      this.logger.error(`Failed to get ${status} subscriptions for user ${userId}`, {
        error: getErrorMessage(error),
      });
      throw error;
    }
  }

  /**
   * Get suspended subscriptions for a user
   */
  async getSuspendedSubscriptions(userId: string): Promise<Subscription[]> {
    return this.getSubscriptionsByStatus(userId, "Suspended");
  }

  /**
   * Get cancelled subscriptions for a user
   */
  async getCancelledSubscriptions(userId: string): Promise<Subscription[]> {
    return this.getSubscriptionsByStatus(userId, "Cancelled");
  }

  /**
   * Get pending subscriptions for a user
   */
  async getPendingSubscriptions(userId: string): Promise<Subscription[]> {
    return this.getSubscriptionsByStatus(userId, "Pending");
  }

  /**
   * Get subscription statistics for a user
   */
  async getSubscriptionStats(userId: string): Promise<{
    total: number;
    active: number;
    suspended: number;
    cancelled: number;
    pending: number;
    completed: number;
    totalMonthlyRevenue: number;
    activeMonthlyRevenue: number;
    currency: string;
  }> {
    try {
      // Get WHMCS client ID from user mapping
      const mapping = await this.mappingsService.findByUserId(userId);
      if (!mapping?.whmcsClientId) {
        throw new NotFoundException("WHMCS client mapping not found");
      }

      // Get basic stats from WHMCS service
      const basicStats = await this.whmcsService.getSubscriptionStats(
        mapping.whmcsClientId,
        userId
      );

      // Get all subscriptions for financial calculations
      const subscriptionList = await this.getSubscriptions(userId);
      const subscriptions = subscriptionList.subscriptions;

      // Calculate revenue metrics
      const totalMonthlyRevenue = subscriptions
        .filter(s => s.cycle === "Monthly")
        .reduce((sum, s) => sum + s.amount, 0);

      const activeMonthlyRevenue = subscriptions
        .filter(s => s.status === "Active" && s.cycle === "Monthly")
        .reduce((sum, s) => sum + s.amount, 0);

      const stats = {
        ...basicStats,
        completed: subscriptions.filter(s => s.status === "Completed").length,
        totalMonthlyRevenue,
        activeMonthlyRevenue,
        currency: subscriptions[0]?.currency || "USD",
      };

      this.logger.log(`Generated subscription stats for user ${userId}`, {
        ...stats,
        // Don't log revenue amounts for security
        totalMonthlyRevenue: "[CALCULATED]",
        activeMonthlyRevenue: "[CALCULATED]",
      });

      return stats;
    } catch (error) {
      this.logger.error(`Failed to generate subscription stats for user ${userId}`, {
        error: getErrorMessage(error),
      });
      throw error;
    }
  }

  /**
   * Get subscriptions expiring soon (within next 30 days)
   */
  async getExpiringSoon(userId: string, days: number = 30): Promise<Subscription[]> {
    try {
      const subscriptionList = await this.getSubscriptions(userId);
      const subscriptions = subscriptionList.subscriptions;

      const cutoffDate = new Date();
      cutoffDate.setDate(cutoffDate.getDate() + days);

      const expiringSoon = subscriptions.filter(subscription => {
        if (!subscription.nextDue || subscription.status !== "Active") {
          return false;
        }

        const nextDueDate = new Date(subscription.nextDue);
        return nextDueDate <= cutoffDate;
      });

      this.logger.log(
        `Found ${expiringSoon.length} subscriptions expiring within ${days} days for user ${userId}`
      );
      return expiringSoon;
    } catch (error) {
      this.logger.error(`Failed to get expiring subscriptions for user ${userId}`, {
        error: getErrorMessage(error),
        days,
      });
      throw error;
    }
  }

  /**
   * Get recent subscription activity (newly created or status changed)
   */
  async getRecentActivity(userId: string, days: number = 30): Promise<Subscription[]> {
    try {
      const subscriptionList = await this.getSubscriptions(userId);
      const subscriptions = subscriptionList.subscriptions;

      const cutoffDate = new Date();
      cutoffDate.setDate(cutoffDate.getDate() - days);

      const recentActivity = subscriptions.filter(subscription => {
        const registrationDate = new Date(subscription.registrationDate);
        return registrationDate >= cutoffDate;
      });

      this.logger.log(
        `Found ${recentActivity.length} recent subscription activities within ${days} days for user ${userId}`
      );
      return recentActivity;
    } catch (error) {
      this.logger.error(`Failed to get recent subscription activity for user ${userId}`, {
        error: getErrorMessage(error),
        days,
      });
      throw error;
    }
  }

  /**
   * Search subscriptions by product name or domain
   */
  async searchSubscriptions(userId: string, query: string): Promise<Subscription[]> {
    try {
      if (!query || query.trim().length < 2) {
        throw new Error("Search query must be at least 2 characters long");
      }

      const subscriptionList = await this.getSubscriptions(userId);
      const subscriptions = subscriptionList.subscriptions;

      const searchTerm = query.toLowerCase().trim();
      const matches = subscriptions.filter(subscription => {
        const productName = subscription.productName.toLowerCase();
        const domain = subscription.domain?.toLowerCase() || "";

        return productName.includes(searchTerm) || domain.includes(searchTerm);
      });

      this.logger.log(
        `Found ${matches.length} subscriptions matching query "${query}" for user ${userId}`
      );
      return matches;
    } catch (error) {
      this.logger.error(`Failed to search subscriptions for user ${userId}`, {
        error: getErrorMessage(error),
        query,
      });
      throw error;
    }
  }

  /**
   * Get invoices related to a specific subscription
   */
  async getSubscriptionInvoices(
    userId: string,
    subscriptionId: number,
    options: { page?: number; limit?: number } = {}
  ): Promise<InvoiceList> {
    const { page = 1, limit = 10 } = options;

    try {
      // Validate subscription exists and belongs to user
      await this.getSubscriptionById(userId, subscriptionId);

      // Get WHMCS client ID from user mapping
      const mapping = await this.mappingsService.findByUserId(userId);
      if (!mapping?.whmcsClientId) {
        throw new NotFoundException("WHMCS client mapping not found");
      }

      // Get all invoices for the user WITH ITEMS (needed for subscription linking)
      // TODO: Consider implementing server-side filtering in WHMCS service to improve performance
      const allInvoices = await this.whmcsService.getInvoicesWithItems(
        mapping.whmcsClientId,
        userId,
        { page: 1, limit: 1000 } // Get more to filter locally
      );

      // Filter invoices that have items related to this subscription
      // Note: subscriptionId is the same as serviceId in our current WHMCS mapping
      this.logger.debug(
        `Filtering ${allInvoices.invoices.length} invoices for subscription ${subscriptionId}`,
        {
          totalInvoices: allInvoices.invoices.length,
          invoicesWithItems: allInvoices.invoices.filter(inv => inv.items && inv.items.length > 0)
            .length,
          subscriptionId,
        }
      );

      const relatedInvoices = allInvoices.invoices.filter(invoice => {
        const hasItems = invoice.items && invoice.items.length > 0;
        if (!hasItems) {
          this.logger.debug(`Invoice ${invoice.id} has no items`);
          return false;
        }

        const hasMatchingService = invoice.items?.some(item => {
          this.logger.debug(
            `Checking item: serviceId=${item.serviceId}, subscriptionId=${subscriptionId}`,
            {
              itemServiceId: item.serviceId,
              subscriptionId,
              matches: item.serviceId === subscriptionId,
            }
          );
          return item.serviceId === subscriptionId;
        });

        return hasMatchingService;
      });

      // Apply pagination to filtered results
      const startIndex = (page - 1) * limit;
      const endIndex = startIndex + limit;
      const paginatedInvoices = relatedInvoices.slice(startIndex, endIndex);

      const result: InvoiceList = {
        invoices: paginatedInvoices,
        pagination: {
          page,
          totalPages: Math.ceil(relatedInvoices.length / limit),
          totalItems: relatedInvoices.length,
        },
      };

      this.logger.log(
        `Retrieved ${paginatedInvoices.length} invoices for subscription ${subscriptionId}`,
        {
          userId,
          subscriptionId,
          totalRelated: relatedInvoices.length,
          page,
          limit,
        }
      );

      return result;
    } catch (error) {
      this.logger.error(`Failed to get invoices for subscription ${subscriptionId}`, {
        error: getErrorMessage(error),
        userId,
        subscriptionId,
        options,
      });

      if (error instanceof NotFoundException) {
        throw error;
      }

      throw new Error(`Failed to retrieve subscription invoices: ${getErrorMessage(error)}`);
    }
  }

  /**
   * Invalidate subscription cache for a user
   */
  async invalidateCache(userId: string, subscriptionId?: number): Promise<void> {
    try {
      if (subscriptionId) {
        await this.whmcsService.invalidateSubscriptionCache(userId, subscriptionId);
      } else {
        await this.whmcsService.invalidateUserCache(userId);
      }

      this.logger.log(
        `Invalidated subscription cache for user ${userId}${subscriptionId ? `, subscription ${subscriptionId}` : ""}`
      );
    } catch (error) {
      this.logger.error(`Failed to invalidate subscription cache for user ${userId}`, {
        error: getErrorMessage(error),
        subscriptionId,
      });
    }
  }

  /**
   * Health check for subscription service
   */
  async healthCheck(): Promise<{ status: string; details: any }> {
    try {
      const whmcsHealthy = await this.whmcsService.healthCheck();

      return {
        status: whmcsHealthy ? "healthy" : "unhealthy",
        details: {
          whmcsApi: whmcsHealthy ? "connected" : "disconnected",
          timestamp: new Date().toISOString(),
        },
      };
    } catch (error) {
      this.logger.error("Subscription service health check failed", {
        error: getErrorMessage(error),
      });
      return {
        status: "unhealthy",
        details: {
          error: getErrorMessage(error),
          timestamp: new Date().toISOString(),
        },
      };
    }
  }
}