make ledger.Deltas.Transactions()

src/ledger/transaction.go

@@ -10,9 +10,35 @@ import (
 	"regexp"
 	"slices"
 	"strconv"
+	"strings"
 	"unicode"
 )
 
+type Transaction Deltas
+
+type Transactions []Transaction
+
+func (deltas Deltas) Transactions() Transactions {
+	m := make(map[string]Transaction)
+	for _, d := range deltas {
+		m[d.Transaction] = append(m[d.Transaction], d)
+	}
+
+	result := make(Transactions, 0, len(m))
+	for _, v := range m {
+		result = append(result, v)
+	}
+
+	slices.SortFunc(result, func(a, b Transaction) int {
+		if a[0].Date == b[0].Date {
+			return strings.Compare(a[0].Transaction, b[0].Transaction)
+		}
+		return strings.Compare(a[0].Date, b[0].Date)
+	})
+
+	return result
+}
+
 type transaction struct {
 	date        string
 	description string

src/ledger/transaction_test.go

@@ -8,6 +8,25 @@ import (
 	"testing"
 )
 
+func TestDeltasTransactions(t *testing.T) {
+	given := Deltas{
+		Delta{Date: "2", Name: "x", Transaction: "a"},
+		Delta{Date: "2", Name: "y", Transaction: "a"},
+		Delta{Date: "1", Name: "z", Transaction: "b"},
+	}
+
+	got := given.Transactions()
+	if len(got) != 2 {
+		t.Error(len(got))
+	}
+	if len(got[0]) != 1 {
+		t.Error("first xaction is not earliest date", len(got[0]))
+	}
+	if len(got[1]) != 2 {
+		t.Error("second xaction is not latest date", len(got[1]))
+	}
+}
+
 func TestReadTransaction(t *testing.T) {
 	cases := map[string]struct {
 		input string