import { TaxCatalogProvider } from "@erp/core";
import Dinero, { Currency } from "dinero.js";

export interface InvoiceItemCalcInput {
  quantity?: string; // p.ej. "3.5"
  unit_amount?: string; // p.ej. "125.75"
  discount_percentage?: string; // p.ej. "10" (=> 10%)
  tax_codes: string[]; // ["iva_21", ...]
}

export interface InvoiceItemCalcResult {
  subtotal_amount: number;
  discount_amount: number;
  taxable_amount: number;
  taxes_amount: number;
  total_amount: number;
}

/**
 * Cálculo financiero exacto por línea de factura.
 * Usa Dinero.js (base 10^2 y round half up) → resultados seguros en céntimos.
 */
export function calculateInvoiceItemAmounts(
  item: InvoiceItemCalcInput,
  currency: string,
  taxCatalog: TaxCatalogProvider
): InvoiceItemCalcResult {
  const scale = 4;
  const toDinero = (n: number) =>
    Dinero({
      amount: n === 0 ? 0 : Math.round(n * 10 ** scale),
      precision: scale,
      currency: currency as Currency,
    });

  const qty = Number.parseFloat(item.quantity || "0") || 0;
  const unit = Number.parseFloat(item.unit_amount || "0") || 0;
  const pct = Number.parseFloat(item.discount_percentage || "0") || 0;

  // Subtotal = cantidad × precio unitario
  const subtotal = toDinero(qty * unit);

  // Descuento = subtotal × (pct / 100)
  const discount = subtotal.percentage(pct);

  // Base imponible
  const taxable = subtotal.subtract(discount);

  // Impuestos acumulados
  let taxes = toDinero(0);
  for (const code of item.tax_codes ?? []) {
    const tax = taxCatalog.findByCode(code);
    tax.map((taxItem) => {
      const pctValue = Number.parseFloat(taxItem.value) / 10 ** Number.parseInt(taxItem.scale, 10);
      const taxAmount = taxable.percentage(pctValue);
      taxes = taxes.add(taxAmount);
    });
  }

  const total = taxable.add(taxes);

  // Devuelve valores desescalados (número con 2 decimales exactos)
  const toNum = (d: Dinero.Dinero) => d.toUnit();

  return {
    subtotal_amount: toNum(subtotal),
    discount_amount: toNum(discount),
    taxable_amount: toNum(taxable),
    taxes_amount: toNum(taxes),
    total_amount: toNum(total),
  };
}