personal-finance/backend-api/src/services/ClientService.ts

import {Client} from '@prisma/client';
import {ClientRepository, ClientWithStats} from '../repositories/ClientRepository';
import {NotFoundError, ValidationError, ForbiddenError, ConflictError} from '../utils/errors';

export interface CreateClientDTO {
  name: string;
  email: string;
  phone?: string;
  address?: string;
  notes?: string;
}

export interface UpdateClientDTO {
  name?: string;
  email?: string;
  phone?: string;
  address?: string;
  notes?: string;
}

/**
 * Service for Client business logic
 * Implements Single Responsibility Principle - handles only business logic
 * Implements Dependency Inversion - depends on repository abstraction
 */
export class ClientService {
  constructor(private clientRepository: ClientRepository) {}

  /**
   * Create a new client
   */
  async create(userId: string, data: CreateClientDTO): Promise<Client> {
    this.validateClientData(data);

    // Check for duplicate email
    const existing = await this.clientRepository.findByEmail(userId, data.email);
    if (existing) {
      throw new ConflictError('A client with this email already exists');
    }

    return this.clientRepository.create({
      name: data.name,
      email: data.email,
      phone: data.phone,
      address: data.address,
      notes: data.notes,
      user: {
        connect: {id: userId}
      }
    });
  }

  /**
   * Get all clients for a user
   */
  async getAllByUser(userId: string): Promise<Client[]> {
    return this.clientRepository.findAllByUser(userId);
  }

  /**
   * Get clients with statistics
   */
  async getWithStats(userId: string): Promise<ClientWithStats[]> {
    return this.clientRepository.getWithStats(userId);
  }

  /**
   * Get a single client by ID
   */
  async getById(id: string, userId: string): Promise<Client> {
    const client = await this.clientRepository.findById(id);

    if (!client) {
      throw new NotFoundError('Client not found');
    }

    // Ensure user owns this client
    if (client.userId !== userId) {
      throw new ForbiddenError('Access denied');
    }

    return client;
  }

  /**
   * Update a client
   */
  async update(id: string, userId: string, data: UpdateClientDTO): Promise<Client> {
    // Verify ownership
    await this.getById(id, userId);

    if (data.email) {
      this.validateClientData(data as CreateClientDTO);

      // Check for duplicate email (excluding current client)
      const existing = await this.clientRepository.findByEmail(userId, data.email);
      if (existing && existing.id !== id) {
        throw new ConflictError('A client with this email already exists');
      }
    }

    return this.clientRepository.update(id, data);
  }

  /**
   * Delete a client
   */
  async delete(id: string, userId: string): Promise<void> {
    // Verify ownership
    await this.getById(id, userId);

    // Check if client has invoices - we still allow deletion due to cascade
    // but you might want to prevent deletion if there are invoices
    // Uncomment below to prevent deletion:
    // if (client.invoices && client.invoices.length > 0) {
    //   throw new ValidationError('Cannot delete client with existing invoices');
    // }

    await this.clientRepository.delete(id);
  }

  /**
   * Get total revenue from all clients
   */
  async getTotalRevenue(userId: string): Promise<number> {
    return this.clientRepository.getTotalRevenue(userId);
  }

  /**
   * Validate client data
   */
  private validateClientData(data: CreateClientDTO | UpdateClientDTO): void {
    if (data.email) {
      const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
      if (!emailRegex.test(data.email)) {
        throw new ValidationError('Invalid email format');
      }
    }

    if (data.phone) {
      // Basic phone validation - at least 10 digits
      const phoneDigits = data.phone.replace(/\D/g, '');
      if (phoneDigits.length < 10) {
        throw new ValidationError('Phone number must contain at least 10 digits');
      }
    }
  }
}