import { Injectable, Logger, BadRequestException, NotFoundException } from '@nestjs/common';
import { InjectRepository } from '@nestjs/typeorm';
import { Repository } from 'typeorm';
import { ServicePlan } from './entities/service-plan.entity';
import { PricingRule } from './entities/pricing-rule.entity';
import { Wallet } from './entities/wallet.entity';
import { WalletTransaction } from './entities/wallet-transaction.entity';
import { TransactionType, BillingCycle, PricingResourceType } from '../common/enums';
import {
  CreateServicePlanDto,
  UpdateServicePlanDto,
  CalculateCostDto,
} from './dto/billing.dto';

@Injectable()
export class BillingService {
  private readonly logger = new Logger(BillingService.name);

  constructor(
    @InjectRepository(ServicePlan) private planRepo: Repository<ServicePlan>,
    @InjectRepository(PricingRule) private ruleRepo: Repository<PricingRule>,
    @InjectRepository(Wallet) private walletRepo: Repository<Wallet>,
    @InjectRepository(WalletTransaction) private txRepo: Repository<WalletTransaction>,
  ) {}

  // ─── Service Plans ────────────────────────────────────────────────

  async createPlan(dto: CreateServicePlanDto): Promise<ServicePlan> {
    const plan = this.planRepo.create({
      name: dto.name,
      runtime: dto.runtime,
      description: dto.description,
      billingCycle: dto.billingCycle,
    });
    const saved = await this.planRepo.save(plan);

    // Create pricing rules
    const rules = dto.pricingRules.map((r) =>
      this.ruleRepo.create({ ...r, planId: saved.id }),
    );
    await this.ruleRepo.save(rules);

    return this.planRepo.findOne({ where: { id: saved.id }, relations: ['pricingRules'] }) as Promise<ServicePlan>;
  }

  async updatePlan(id: string, dto: UpdateServicePlanDto): Promise<ServicePlan> {
    const plan = await this.planRepo.findOne({ where: { id }, relations: ['pricingRules'] });
    if (!plan) throw new NotFoundException('Plan not found');

    if (dto.name !== undefined) plan.name = dto.name;
    if (dto.runtime !== undefined) plan.runtime = dto.runtime;
    if (dto.description !== undefined) plan.description = dto.description;
    if (dto.billingCycle !== undefined) plan.billingCycle = dto.billingCycle;
    if (dto.isActive !== undefined) plan.isActive = dto.isActive;

    await this.planRepo.save(plan);

    // If pricing rules are provided, replace them
    if (dto.pricingRules) {
      await this.ruleRepo.delete({ planId: id });
      const rules = dto.pricingRules.map((r) =>
        this.ruleRepo.create({ ...r, planId: id }),
      );
      await this.ruleRepo.save(rules);
    }

    return this.planRepo.findOne({ where: { id }, relations: ['pricingRules'] }) as Promise<ServicePlan>;
  }

  async deletePlan(id: string): Promise<void> {
    const plan = await this.planRepo.findOne({ where: { id } });
    if (!plan) throw new NotFoundException('Plan not found');
    await this.planRepo.remove(plan);
  }

  async findAllPlans(): Promise<ServicePlan[]> {
    return this.planRepo.find({ relations: ['pricingRules'], order: { createdAt: 'DESC' } });
  }

  async findActivePlans(): Promise<ServicePlan[]> {
    return this.planRepo.find({
      where: { isActive: true },
      relations: ['pricingRules'],
      order: { createdAt: 'DESC' },
    });
  }

  async findPlan(id: string): Promise<ServicePlan> {
    const plan = await this.planRepo.findOne({ where: { id }, relations: ['pricingRules'] });
    if (!plan) throw new NotFoundException('Plan not found');
    return plan;
  }

  // ─── Cost Calculation ─────────────────────────────────────────────

  /**
   * Calculate cost for an application config against all active plans.
   * Returns breakdown for each billing cycle (hourly, monthly, yearly).
   */
  async calculateCost(dto: CalculateCostDto): Promise<{
    hourly: number;
    monthly: number;
    yearly: number;
    breakdown: { label: string; hourly: number; monthly: number; yearly: number }[];
  }> {
    // Only use active plans that match the requested runtime
    const plans = await this.planRepo.find({
      where: { isActive: true, runtime: dto.runtime as any },
      relations: ['pricingRules'],
    });

    if (plans.length === 0) {
      return { hourly: 0, monthly: 0, yearly: 0, breakdown: [] };
    }

    // Gather all active pricing rules across all plans, grouped by cycle
    const hourlyRules: PricingRule[] = [];
    const monthlyRules: PricingRule[] = [];
    const yearlyRules: PricingRule[] = [];

    for (const plan of plans) {
      switch (plan.billingCycle) {
        case BillingCycle.HOURLY: hourlyRules.push(...plan.pricingRules); break;
        case BillingCycle.MONTHLY: monthlyRules.push(...plan.pricingRules); break;
        case BillingCycle.YEARLY: yearlyRules.push(...plan.pricingRules); break;
      }
    }

    // Use the first available set of rules, or compute cross-conversions
    const rules = hourlyRules.length > 0 ? hourlyRules : monthlyRules.length > 0 ? monthlyRules : yearlyRules;
    const baseCycle = hourlyRules.length > 0 ? 'hourly' : monthlyRules.length > 0 ? 'monthly' : 'yearly';

    // Parse resource values
    const cpuCores = this.parseCpuToCores(dto.cpuLimit);
    const memoryGb = this.parseMemoryToGb(dto.memoryLimit);
    const storageGb = dto.dbStorageSize ? parseFloat(dto.dbStorageSize.replace('Gi', '')) || 0 : 0;
    const hasDatabase = dto.databaseType !== 'none';
    const replicas = dto.replicas || 1;

    const breakdown: { label: string; hourly: number; monthly: number; yearly: number }[] = [];
    let totalBase = 0;

    for (const rule of rules) {
      let cost = 0;
      let label = '';

      switch (rule.resourceType) {
        case PricingResourceType.BASE_FEE:
          cost = Number(rule.unitPrice);
          label = 'Base fee';
          break;
        case PricingResourceType.CPU_PER_CORE:
          cost = cpuCores * replicas * Number(rule.unitPrice);
          label = `CPU (${(cpuCores * replicas).toFixed(2)} core)`;
          break;
        case PricingResourceType.MEMORY_PER_GB:
          cost = memoryGb * replicas * Number(rule.unitPrice);
          label = `Memory (${(memoryGb * replicas).toFixed(2)} GB)`;
          break;
        case PricingResourceType.STORAGE_PER_GB:
          cost = storageGb * Number(rule.unitPrice);
          label = `Storage (${storageGb} GB)`;
          break;
        case PricingResourceType.DATABASE_ADDON:
          cost = hasDatabase ? Number(rule.unitPrice) : 0;
          label = 'Database addon';
          break;
      }

      if (cost > 0) {
        const hourly = baseCycle === 'hourly' ? cost : baseCycle === 'monthly' ? cost / 720 : cost / 8640;
        const monthly = baseCycle === 'monthly' ? cost : baseCycle === 'hourly' ? cost * 720 : cost / 12;
        const yearly = baseCycle === 'yearly' ? cost : baseCycle === 'monthly' ? cost * 12 : cost * 8640;

        breakdown.push({ label, hourly: Math.round(hourly), monthly: Math.round(monthly), yearly: Math.round(yearly) });
        totalBase += cost;
      }
    }

    const hourlyTotal = baseCycle === 'hourly' ? totalBase : baseCycle === 'monthly' ? totalBase / 720 : totalBase / 8640;
    const monthlyTotal = baseCycle === 'monthly' ? totalBase : baseCycle === 'hourly' ? totalBase * 720 : totalBase / 12;
    const yearlyTotal = baseCycle === 'yearly' ? totalBase : baseCycle === 'monthly' ? totalBase * 12 : totalBase * 8640;

    return {
      hourly: Math.round(hourlyTotal),
      monthly: Math.round(monthlyTotal),
      yearly: Math.round(yearlyTotal),
      breakdown,
    };
  }

  private parseCpuToCores(cpu: string): number {
    if (!cpu) return 0;
    if (cpu.endsWith('m')) return parseFloat(cpu) / 1000;
    return parseFloat(cpu) || 0;
  }

  private parseMemoryToGb(memory: string): number {
    if (!memory) return 0;
    if (memory.endsWith('Gi')) return parseFloat(memory);
    if (memory.endsWith('Mi')) return parseFloat(memory) / 1024;
    if (memory.endsWith('Ki')) return parseFloat(memory) / (1024 * 1024);
    return parseFloat(memory) / (1024 * 1024 * 1024);
  }

  // ─── Wallet ───────────────────────────────────────────────────────

  async getOrCreateWallet(userId: string): Promise<Wallet> {
    let wallet = await this.walletRepo.findOne({ where: { userId } });
    if (!wallet) {
      wallet = this.walletRepo.create({ userId, balance: 0 });
      wallet = await this.walletRepo.save(wallet);
      this.logger.log(`Created wallet for user ${userId}`);
    }
    return wallet;
  }

  async getBalance(userId: string): Promise<{ balance: number }> {
    const wallet = await this.getOrCreateWallet(userId);
    return { balance: Number(wallet.balance) };
  }

  async chargeWallet(userId: string, amount: number, description?: string): Promise<WalletTransaction> {
    if (amount <= 0) throw new BadRequestException('Amount must be positive');

    const wallet = await this.getOrCreateWallet(userId);
    wallet.balance = Number(wallet.balance) + amount;
    await this.walletRepo.save(wallet);

    const tx = this.txRepo.create({
      walletId: wallet.id,
      type: TransactionType.CHARGE,
      amount,
      balanceAfter: wallet.balance,
      description: description || 'Wallet charge',
    });
    const saved = await this.txRepo.save(tx);

    this.logger.log(`Charged wallet of user ${userId}: +${amount} Toman → balance: ${wallet.balance}`);
    return saved;
  }

  async deductWallet(
    userId: string,
    amount: number,
    description?: string,
    applicationId?: string,
  ): Promise<WalletTransaction> {
    if (amount <= 0) throw new BadRequestException('Amount must be positive');

    const wallet = await this.getOrCreateWallet(userId);
    if (Number(wallet.balance) < amount) {
      throw new BadRequestException('Insufficient wallet balance');
    }

    wallet.balance = Number(wallet.balance) - amount;
    await this.walletRepo.save(wallet);

    const tx = this.txRepo.create({
      walletId: wallet.id,
      type: TransactionType.DEDUCTION,
      amount,
      balanceAfter: wallet.balance,
      description: description || 'Service payment',
      applicationId,
    });
    const saved = await this.txRepo.save(tx);

    this.logger.log(`Deducted from wallet of user ${userId}: -${amount} Toman → balance: ${wallet.balance}`);
    return saved;
  }

  async getTransactions(userId: string, limit = 50): Promise<WalletTransaction[]> {
    const wallet = await this.getOrCreateWallet(userId);
    return this.txRepo.find({
      where: { walletId: wallet.id },
      order: { createdAt: 'DESC' },
      take: limit,
    });
  }

  // Admin: charge any user's wallet
  async adminChargeWallet(userId: string, amount: number, description?: string): Promise<WalletTransaction> {
    return this.chargeWallet(userId, amount, description || 'Admin charge');
  }

  // Admin: get all wallets
  async getAllWallets(): Promise<Wallet[]> {
    return this.walletRepo.find({ relations: ['user'], order: { balance: 'DESC' } });
  }
}