Deltas does Balances and Like

ledger/deltas.go

@@ -0,0 +1,28 @@
+package ledger
+
+type Deltas []Delta
+
+func (deltas Deltas) Like(like ...Like) Deltas {
+	result := make(Deltas, 0, len(deltas))
+	for i := range deltas {
+		if likes(like).all(deltas[i]) {
+			result = append(result, deltas[i])
+		}
+	}
+	return result
+}
+
+func (deltas Deltas) Balances() (map[string]map[Currency]float64, error) {
+	result := make(map[string]map[Currency]float64)
+	for _, delta := range deltas {
+		if _, ok := result[delta.Account]; !ok {
+			result[delta.Account] = make(map[Currency]float64)
+		}
+		if _, ok := result[delta.Account][delta.Currency]; !ok {
+			result[delta.Account][delta.Currency] = 0
+		}
+		result[delta.Account][delta.Currency] += delta.Value
+	}
+
+	return result, nil
+}