import { Injectable, NotFoundException, BadRequestException } from '@nestjs/common';
import { TenantService } from '../../database/tenant.service';

@Injectable()
export class PaymentsService {
  constructor(private tenant: TenantService) {}

  async findAll() {
    return this.tenant.query(`
      SELECT p.*, u.unit_number, i.invoice_number
      FROM payments p
      JOIN units u ON u.id = p.unit_id
      LEFT JOIN invoices i ON i.id = p.invoice_id
      ORDER BY p.payment_date DESC, p.created_at DESC
    `);
  }

  async findOne(id: string) {
    const rows = await this.tenant.query(`
      SELECT p.*, u.unit_number, i.invoice_number FROM payments p
      JOIN units u ON u.id = p.unit_id
      LEFT JOIN invoices i ON i.id = p.invoice_id
      WHERE p.id = $1`, [id]);
    if (!rows.length) throw new NotFoundException('Payment not found');
    return rows[0];
  }

  async create(dto: any, userId: string) {
    // Validate invoice exists and get details
    let invoice: any = null;
    if (dto.invoice_id) {
      const rows = await this.tenant.query('SELECT * FROM invoices WHERE id = $1', [dto.invoice_id]);
      if (!rows.length) throw new NotFoundException('Invoice not found');
      invoice = rows[0];
      if (invoice.status === 'paid') throw new BadRequestException('Invoice is already paid');
      if (invoice.status === 'void') throw new BadRequestException('Cannot pay void invoice');
    }

    // Get fiscal period
    const payDate = new Date(dto.payment_date);
    let fp = await this.tenant.query(
      'SELECT id FROM fiscal_periods WHERE year = $1 AND month = $2',
      [payDate.getFullYear(), payDate.getMonth() + 1],
    );
    if (!fp.length) {
      fp = await this.tenant.query(
        `INSERT INTO fiscal_periods (year, month, status) VALUES ($1, $2, 'open') RETURNING id`,
        [payDate.getFullYear(), payDate.getMonth() + 1],
      );
    }

    // Create payment record
    const payment = await this.tenant.query(
      `INSERT INTO payments (unit_id, invoice_id, payment_date, amount, payment_method, reference_number, notes, received_by)
       VALUES ($1, $2, $3, $4, $5, $6, $7, $8) RETURNING *`,
      [dto.unit_id, dto.invoice_id || null, dto.payment_date, dto.amount, dto.payment_method || 'check',
       dto.reference_number || null, dto.notes || null, userId],
    );

    // Create journal entry: DR Cash, CR Accounts Receivable
    const cashAccount = await this.tenant.query(`SELECT id FROM accounts WHERE account_number = '1000'`);
    const arAccount = await this.tenant.query(`SELECT id FROM accounts WHERE account_number = '1200'`);

    if (cashAccount.length && arAccount.length) {
      const je = await this.tenant.query(
        `INSERT INTO journal_entries (entry_date, description, entry_type, fiscal_period_id, source_type, source_id, is_posted, posted_at, created_by)
         VALUES ($1, $2, 'payment', $3, 'payment', $4, true, NOW(), $5) RETURNING id`,
        [dto.payment_date, `Payment received - ${dto.reference_number || 'N/A'}`, fp[0].id, payment[0].id, userId],
      );
      await this.tenant.query(
        `INSERT INTO journal_entry_lines (journal_entry_id, account_id, debit, credit) VALUES ($1, $2, $3, 0), ($1, $4, 0, $3)`,
        [je[0].id, cashAccount[0].id, dto.amount, arAccount[0].id],
      );
      await this.tenant.query(`UPDATE payments SET journal_entry_id = $1 WHERE id = $2`, [je[0].id, payment[0].id]);
    }

    // Update invoice if linked
    if (invoice) {
      const newPaid = parseFloat(invoice.amount_paid) + parseFloat(dto.amount);
      const invoiceAmt = parseFloat(invoice.amount);
      const newStatus = newPaid >= invoiceAmt ? 'paid' : 'partial';
      await this.tenant.query(
        `UPDATE invoices SET amount_paid = $1, status = $2, paid_at = CASE WHEN $2 = 'paid' THEN NOW() ELSE paid_at END, updated_at = NOW() WHERE id = $3`,
        [newPaid, newStatus, invoice.id],
      );
    }

    return payment[0];
  }
}