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 — use explicit cast to avoid PostgreSQL type inference error
    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::VARCHAR, paid_at = CASE WHEN $3::VARCHAR = 'paid' THEN NOW() ELSE paid_at END, updated_at = NOW() WHERE id = $4`,
        [newPaid, newStatus, newStatus, invoice.id],
      );
    }

    return payment[0];
  }

  async update(id: string, dto: any, userId: string) {
    const existing = await this.findOne(id);

    const sets: string[] = [];
    const params: any[] = [];
    let idx = 1;

    if (dto.payment_date !== undefined) { sets.push(`payment_date = $${idx++}`); params.push(dto.payment_date); }
    if (dto.amount !== undefined) { sets.push(`amount = $${idx++}`); params.push(dto.amount); }
    if (dto.payment_method !== undefined) { sets.push(`payment_method = $${idx++}`); params.push(dto.payment_method); }
    if (dto.reference_number !== undefined) { sets.push(`reference_number = $${idx++}`); params.push(dto.reference_number); }
    if (dto.notes !== undefined) { sets.push(`notes = $${idx++}`); params.push(dto.notes); }

    if (!sets.length) return this.findOne(id);

    params.push(id);
    await this.tenant.query(
      `UPDATE payments SET ${sets.join(', ')} WHERE id = $${idx} RETURNING *`,
      params,
    );

    // If amount changed and payment is linked to an invoice, recalculate invoice totals
    if (dto.amount !== undefined && existing.invoice_id) {
      await this.recalculateInvoice(existing.invoice_id);
    }

    return this.findOne(id);
  }

  async delete(id: string) {
    const payment = await this.findOne(id);
    const invoiceId = payment.invoice_id;

    // Delete associated journal entry lines and journal entry
    if (payment.journal_entry_id) {
      await this.tenant.query('DELETE FROM journal_entry_lines WHERE journal_entry_id = $1', [payment.journal_entry_id]);
      await this.tenant.query('DELETE FROM journal_entries WHERE id = $1', [payment.journal_entry_id]);
    }

    // Delete the payment
    await this.tenant.query('DELETE FROM payments WHERE id = $1', [id]);

    // Recalculate invoice totals if payment was linked
    if (invoiceId) {
      await this.recalculateInvoice(invoiceId);
    }

    return { success: true };
  }

  private async recalculateInvoice(invoiceId: string) {
    // Sum all remaining payments for this invoice
    const result = await this.tenant.query(
      'SELECT COALESCE(SUM(amount), 0) as total_paid FROM payments WHERE invoice_id = $1',
      [invoiceId],
    );
    const totalPaid = parseFloat(result[0].total_paid);

    // Get the invoice amount
    const inv = await this.tenant.query('SELECT amount FROM invoices WHERE id = $1', [invoiceId]);
    if (!inv.length) return;

    const invoiceAmt = parseFloat(inv[0].amount);
    let newStatus: string;
    if (totalPaid >= invoiceAmt) {
      newStatus = 'paid';
    } else if (totalPaid > 0) {
      newStatus = 'partial';
    } else {
      newStatus = 'pending';
    }

    await this.tenant.query(
      `UPDATE invoices SET amount_paid = $1, status = $2::VARCHAR, paid_at = CASE WHEN $3::VARCHAR = 'paid' THEN NOW() ELSE NULL END, updated_at = NOW() WHERE id = $4`,
      [totalPaid, newStatus, newStatus, invoiceId],
    );
  }
}