money/internal/report/report_test.go

package report

import (
	"testing"

	"git.petrovv.com/nikola/money/internal/model"
)

func leg(id int64, amount int64, transferID *int64) model.Transaction {
	return model.Transaction{
		ID:          id,
		AccountSlug: "nlb",
		Currency:    "EUR",
		MinorDigits: 2,
		Date:        "2026-03-06",
		AmountMinor: amount,
		RuleTag:     "moving",
		TransferID:  transferID,
	}
}

// A matched transfer is money moved, not money spent, so neither leg reaches
// the report at all.
func TestByTagLeavesTransferLegsOut(t *testing.T) {
	id := int64(1)
	rows := ByTag([]model.Transaction{
		leg(1, -50000, &id),
		leg(2, 50000, &id),
		{Currency: "EUR", MinorDigits: 2, AmountMinor: -2000, RuleTag: "groceries"},
	})

	if len(rows) != 1 || rows[0].Tag != "groceries" {
		t.Fatalf("rows = %+v, want only the groceries row", rows)
	}
	if rows[0].Out != 2000 {
		t.Errorf("out = %d, want only the shopping", rows[0].Out)
	}
}

// An unpaired leg is not a transfer, so it still counts. Money that left an
// account and cannot be shown to have arrived must not quietly vanish from the
// report.
func TestByTagKeepsUnpairedLegs(t *testing.T) {
	rows := ByTag([]model.Transaction{leg(1, -50000, nil)})
	if len(rows) != 1 || rows[0].Out != 50000 {
		t.Fatalf("rows = %+v, want the unpaired leg counted", rows)
	}
}

// A report scoped to one account or month usually holds one side of a
// movement, so the summary counts legs rather than claiming whole transfers.
func TestExcludedCountsLegsInView(t *testing.T) {
	id := int64(1)
	got := Excluded([]model.Transaction{
		leg(1, -50000, &id),
		{Currency: "EUR", MinorDigits: 2, AmountMinor: -2000, RuleTag: "groceries"},
	})
	if len(got) != 1 {
		t.Fatalf("excluded = %+v, want one currency", got)
	}
	if got[0].Legs != 1 || got[0].Out != 50000 || got[0].In != 0 || got[0].Currency != "EUR" {
		t.Errorf("excluded = %+v, want 1 leg and 50000 out in EUR", got[0])
	}
}

// An exchange has its legs in two currencies, so each side reports only what it
// saw. Summing the two would be meaningless: there are no rates here.
func TestExcludedSplitsAnExchangeByCurrency(t *testing.T) {
	id := int64(1)
	arriving := leg(2, 97790, &id)
	arriving.Currency = "BGN"

	got := Excluded([]model.Transaction{leg(1, -50000, &id), arriving})
	if len(got) != 2 {
		t.Fatalf("excluded = %+v, want a row per currency", got)
	}
	bgn, eur := got[0], got[1]
	if bgn.Currency != "BGN" || bgn.In != 97790 || bgn.Out != 0 {
		t.Errorf("BGN row = %+v, want only the arriving leg", bgn)
	}
	if eur.Currency != "EUR" || eur.Out != 50000 || eur.In != 0 {
		t.Errorf("EUR row = %+v, want only the leaving leg", eur)
	}
}

// A definition with a tolerance pairs legs that disagree, and the pair leaves
// the report with the difference inside it. That difference is real money, so
// the summary has to name it or it is simply lost.
func TestExcludedReportsTheFee(t *testing.T) {
	id := int64(1)
	got := Excluded([]model.Transaction{leg(1, -50000, &id), leg(2, 49500, &id)})
	if len(got) != 1 {
		t.Fatalf("excluded = %+v, want one currency", got)
	}
	if got[0].Fee != 500 || got[0].Pairs != 1 || got[0].Legs != 2 {
		t.Errorf("excluded = %+v, want a 5.00 fee over 1 pair and 2 legs", got[0])
	}
}

// Half a pair cannot say what the other half received, so a report scoped to
// one account or month reports the leg it saw and claims no fee at all.
func TestExcludedClaimsNoFeeFromHalfAPair(t *testing.T) {
	id := int64(1)
	got := Excluded([]model.Transaction{leg(1, -50000, &id)})
	if len(got) != 1 {
		t.Fatalf("excluded = %+v, want one currency", got)
	}
	if got[0].Fee != 0 || got[0].Pairs != 0 || got[0].Legs != 1 {
		t.Errorf("excluded = %+v, want no fee and no complete pair", got[0])
	}
}

// Without a tolerance the two legs are exact opposites, so there is nothing to
// report and the line stays as it was.
func TestExcludedReportsNoFeeForAnExactPair(t *testing.T) {
	id := int64(1)
	got := Excluded([]model.Transaction{leg(1, -50000, &id), leg(2, 50000, &id)})
	if len(got) != 1 || got[0].Fee != 0 || got[0].Pairs != 1 {
		t.Errorf("excluded = %+v, want one pair and no fee", got)
	}
}

// The legs of an exchange are in different units, so subtracting one from the
// other would produce a number meaning nothing.
func TestExcludedClaimsNoFeeAcrossCurrencies(t *testing.T) {
	id := int64(1)
	arriving := leg(2, 97790, &id)
	arriving.Currency = "BGN"

	for _, row := range Excluded([]model.Transaction{leg(1, -50000, &id), arriving}) {
		if row.Fee != 0 || row.Pairs != 0 {
			t.Errorf("%s row = %+v, want no fee across currencies", row.Currency, row)
		}
	}
}