package invoice

import (
	"errors"
	"fmt"
)

func Validate(doc *Document) error {
	var problems []string
	if doc.Seller.Name == "" {
		problems = append(problems, "missing vendeur nom")
	}
	if len(doc.Seller.Address) == 0 {
		problems = append(problems, "missing vendeur adresse")
	}
	if doc.Seller.Email == "" {
		problems = append(problems, "missing vendeur email")
	}
	if doc.Seller.Phone == "" {
		problems = append(problems, "missing vendeur telephone")
	}
	if doc.Buyer.Name == "" {
		problems = append(problems, "missing acheteur nom")
	}
	if len(doc.Buyer.Address) == 0 {
		problems = append(problems, "missing acheteur adresse")
	}
	if doc.Invoice.Number == "" {
		problems = append(problems, "missing facture numero")
	}
	if doc.Invoice.Subject == "" {
		problems = append(problems, "missing facture objet")
	}
	if doc.Invoice.Location == "" {
		problems = append(problems, "missing facture lieu")
	}
	if doc.Invoice.Date.IsZero() {
		problems = append(problems, "missing facture date")
	}
	if doc.Invoice.Description == "" {
		problems = append(problems, "missing facture description")
	}
	if len(doc.Items) == 0 {
		problems = append(problems, "missing prestations")
	}
	if doc.Payment.Holder == "" {
		problems = append(problems, "missing paiement titulaire")
	}
	if doc.Payment.IBAN == "" {
		problems = append(problems, "missing paiement IBAN")
	}
	if len(problems) > 0 {
		return errors.New(stringsJoin(problems, "; "))
	}
	return nil
}

func ComputeTotals(doc *Document) {
	var total Money
	for _, item := range doc.Items {
		line := LineAmount(item)
		total += line
	}
	doc.Totals.TotalExclTax = total
}

func stringsJoin(values []string, sep string) string {
	if len(values) == 0 {
		return ""
	}
	out := values[0]
	for i := 1; i < len(values); i++ {
		out += sep + values[i]
	}
	return out
}

func FormatMoney(m Money) string {
	return m.String()
}

func LineAmount(item Item) Money {
	// Quantity is stored in hundredths. Round to nearest cent.
	cents := int64(item.UnitPrice)
	qty := int64(item.Quantity)
	product := cents * qty
	if product >= 0 {
		return Money((product + 50) / 100)
	}
	return Money((product - 50) / 100)
}

func RequireNoError(err error, msg string) error {
	if err != nil {
		return fmt.Errorf("%s: %w", msg, err)
	}
	return nil
}