bgpwtf/invoice/calc.go

package main

import (
	"sort"
	"time"

	pb "code.hackerspace.pl/hscloud/bgpwtf/invoice/proto"
)

// calculateInvoiceData applies all business logic to populate an Invoice's
// denormalized fields from its InvoiceData.
func calculateInvoiceData(p *pb.Invoice) {
	// Populate default unit.
	// TODO(q3k): this really should be done on invoice submit instead.
	p.Unit = p.Data.Unit
	if p.Unit == "" {
		p.Unit = "€"
	}

	// Calculate totals.
	p.TotalNet = 0
	p.Total = 0
	for _, i := range p.Data.Item {
		rowTotalNet := uint64(i.UnitPrice * i.Count)
		rowTotal := uint64(float64(rowTotalNet) * (float64(1) + float64(i.Vat)/100000))

		p.TotalNet += rowTotalNet
		p.Total += rowTotal
		i.TotalNet = rowTotalNet
		i.Total = rowTotal
	}

	// Calculate due date.
	due := int64(time.Hour*24) * p.Data.DaysDue
	p.DueDate = time.Unix(0, p.Date).Add(time.Duration(due)).UnixNano()

	// Denormalize Items' GTUCodes into the Invoice's summary GTU codes.
	codeSet := make(map[pb.GTUCode]bool)
	for _, item := range p.Data.Item {
		for _, code := range item.GtuCode {
			codeSet[code] = true
		}
	}
	var codes []pb.GTUCode
	for c, _ := range codeSet {
		codes = append(codes, c)
	}
	sort.Slice(codes, func(i, j int) bool { return codes[i] < codes[j] })
	p.GtuCode = codes
}