import Stripe from 'stripe';
import { loadBillingConfig, SubscriptionTier } from '../config/billing.config';
import type { Subscription, SubscriptionCreateSchema, SubscriptionUpdateSchema } from '../models/subscription.model';

const config = loadBillingConfig();
const stripe = new Stripe(config.stripe.apiKey, { apiVersion: '2024-04-10' });

export class BillingService {
  private static instance: BillingService;

  private constructor() {}

  static getInstance(): BillingService {
    if (!BillingService.instance) {
      BillingService.instance = new BillingService();
    }
    return BillingService.instance;
  }

  async createCustomer(email: string, userId: string): Promise<Stripe.Customer> {
    const customer = await stripe.customers.create({
      email,
      metadata: { userId },
    });
    return customer;
  }

  async getCustomer(customerId: string): Promise<Stripe.Customer | null> {
    try {
      const customer = await stripe.customers.retrieve(customerId);
      return customer as Stripe.Customer;
    } catch {
      return null;
    }
  }

  async createSubscription(
    userId: string,
    tier: SubscriptionTier,
    customerId: string
  ): Promise<{ subscription: Stripe.Subscription; customer: Stripe.Customer }> {
    const tierConfig = config.tiers[tier];

    const subscription = await stripe.subscriptions.create({
      customer: customerId,
      items: [{ price: tierConfig.priceId }],
      metadata: { userId, tier },
    });

    const customer = await this.getCustomer(customerId);

    return { subscription, customer: customer! };
  }

  async cancelSubscription(
    subscriptionId: string,
    cancelAtPeriodEnd: boolean = false
  ): Promise<Stripe.Subscription> {
    if (cancelAtPeriodEnd) {
      return await stripe.subscriptions.update(subscriptionId, {
        cancel_at_period_end: true,
      });
    }
    return await stripe.subscriptions.cancel(subscriptionId);
  }

  async updateSubscription(
    subscriptionId: string,
    newTier: SubscriptionTier
  ): Promise<Stripe.Subscription> {
    const newTierConfig = config.tiers[newTier];
    
    const subscription = await stripe.subscriptions.retrieve(subscriptionId);
    
    const updated = await stripe.subscriptions.update(subscriptionId, {
      proration_behavior: 'create_prorations',
      items: [
        {
          id: subscription.items.data[0]?.id,
          price: newTierConfig.priceId,
        },
      ],
    });

    return updated;
  }

  async createCustomerPortalSession(
    customerId: string,
    returnUrl: string
  ): Promise<Stripe.BillingPortal.Session> {
    return await stripe.billingPortal.sessions.create({
      customer: customerId,
      return_url: returnUrl,
    });
  }

  async getSubscription(subscriptionId: string): Promise<Stripe.Subscription | null> {
    try {
      const subscription = await stripe.subscriptions.retrieve(subscriptionId);
      return subscription;
    } catch {
      return null;
    }
  }

  async getTierLimits(tier: SubscriptionTier) {
    return config.tiers[tier];
  }

  async checkUsageAgainstLimit(
    userId: string,
    tier: SubscriptionTier,
    currentUsage: number
  ): Promise<{ withinLimit: boolean; remaining: number; limit: number }> {
    const tierConfig = config.tiers[tier];
    const limit = tierConfig.callMinutesLimit;
    const remaining = Math.max(0, limit - currentUsage);

    return {
      withinLimit: currentUsage <= limit,
      remaining,
      limit,
    };
  }

  async createInvoice(
    customerId: string,
    amount: number,
    description: string,
    metadata?: Record<string, string>
  ): Promise<Stripe.Invoice> {
    return await stripe.invoices.create({
      customer: customerId,
      metadata: { ...metadata, description },
    });
  }

  async handleWebhook(
    sig: string,
    body: Buffer
  ): Promise<Stripe.Event> {
    return stripe.webhooks.constructEvent(body, sig, config.stripe.webhookSecret);
  }

  async getInvoiceHistory(customerId: string): Promise<Stripe.ApiList<Stripe.Invoice>> {
    return await stripe.invoices.list({
      customer: customerId,
      limit: 100,
    });
  }
}