fix: add optics and consistent copyright

Signed-off-by: Dr. Carsten Leue <carsten.leue@de.ibm.com>

optics/lens/record/generic/record.go

@@ -0,0 +1,49 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package generic
+
+import (
+	F "github.com/IBM/fp-go/function"
+	I "github.com/IBM/fp-go/identity"
+	L "github.com/IBM/fp-go/optics/lens"
+	O "github.com/IBM/fp-go/option"
+	RR "github.com/IBM/fp-go/record/generic"
+)
+
+// AtRecord returns a lens that focusses on a value in a record
+func AtRecord[M ~map[K]V, K comparable, V any](key K) L.Lens[M, O.Option[V]] {
+	addKey := F.Bind1of2(RR.UpsertAt[M, K, V])(key)
+	delKey := F.Bind1of1(RR.DeleteAt[M, K, V])(key)
+	fold := O.Fold(
+		delKey,
+		addKey,
+	)
+	return L.MakeLens(
+		RR.Lookup[M](key),
+		func(m M, v O.Option[V]) M {
+			return F.Pipe2(
+				v,
+				fold,
+				I.Ap[M, M](m),
+			)
+		},
+	)
+}
+
+// AtKey returns a `Lens` focused on a required key of a `ReadonlyRecord`
+func AtKey[M ~map[K]V, S any, K comparable, V any](key K) func(sa L.Lens[S, M]) L.Lens[S, O.Option[V]] {
+	return L.Compose[S](AtRecord[M](key))
+}

optics/lens/record/record.go

@@ -0,0 +1,32 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package record
+
+import (
+	L "github.com/IBM/fp-go/optics/lens"
+	G "github.com/IBM/fp-go/optics/lens/record/generic"
+	O "github.com/IBM/fp-go/option"
+)
+
+// AtRecord returns a lens that focusses on a value in a record
+func AtRecord[K comparable, V any](key K) L.Lens[map[K]V, O.Option[V]] {
+	return G.AtRecord[map[K]V](key)
+}
+
+// AtKey returns a `Lens` focused on a required key of a `ReadonlyRecord`
+func AtKey[S any, K comparable, V any](key K) func(sa L.Lens[S, map[K]V]) L.Lens[S, O.Option[V]] {
+	return G.AtKey[map[K]V, S](key)
+}

optics/lens/record/record_test.go

@@ -0,0 +1,41 @@
+// Copyright (c) 2023 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package record
+
+import (
+	"testing"
+
+	F "github.com/IBM/fp-go/function"
+	L "github.com/IBM/fp-go/optics/lens"
+	O "github.com/IBM/fp-go/option"
+	"github.com/stretchr/testify/assert"
+)
+
+type (
+	S = map[string]int
+)
+
+func TestAtKey(t *testing.T) {
+	sa := F.Pipe1(
+		L.Id[S](),
+		AtKey[S, string, int]("a"),
+	)
+
+	assert.Equal(t, O.Some(1), sa.Get(S{"a": 1}))
+	assert.Equal(t, S{"a": 2, "b": 2}, sa.Set(O.Some(2))(S{"a": 1, "b": 2}))
+	assert.Equal(t, S{"a": 1, "b": 2}, sa.Set(O.Some(1))(S{"b": 2}))
+	assert.Equal(t, S{"b": 2}, sa.Set(O.None[int]())(S{"a": 1, "b": 2}))
+}