feat(schema): add methods for proto <> schema conversions (#72)

* add toproto and fromproto

* refactor

* add tests

* go mod tidy

* add error

* add clarifying comment

* fix comment

* undo

* undo

proto/schema/v1/schema.proto

@@ -2,6 +2,8 @@ syntax = "proto3";
 
 package schema.v1;
 
+option go_package = "github.com/conduitio/conduit-commons/proto/schema/v1";
+
 // Schema is a representation of a schema in the schema registry.
 message Schema {
   enum Type {

schema/errors.go

@@ -0,0 +1,20 @@
+// Copyright © 2024 Meroxa, Inc.
+//
+// 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 schema
+
+import "errors"
+
+// errInvalidProtoIsNil is returned when trying to convert a schema object to a proto schema, and the proto is nil.
+var errInvalidProtoIsNil = errors.New("invalid proto: nil")

schema/proto.go

@@ -0,0 +1,63 @@
+// Copyright © 2024 Meroxa, Inc.
+//
+// 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 schema
+
+import (
+	schemav1 "github.com/conduitio/conduit-commons/proto/schema/v1"
+)
+
+func _() {
+	// An "invalid array index" compiler error signifies that the constant values have changed.
+	var cTypes [1]struct{}
+	// Compatibility between the schema type in conduit-commons and the Protobuf schema type
+	_ = cTypes[int(TypeAvro)-int(schemav1.Schema_TYPE_AVRO)]
+}
+
+// -- From Proto To Schema ----------------------------------------------------
+
+// FromProto takes data from the supplied proto object and populates the
+// receiver. If the proto object is nil, the receiver is set to its zero value.
+// If the function returns an error, the receiver could be partially populated.
+func (s *Schema) FromProto(proto *schemav1.Schema) error {
+	if proto == nil {
+		*s = Schema{}
+		return nil
+	}
+
+	s.Subject = proto.Subject
+	s.Version = int(proto.Version)
+	s.Type = Type(proto.Type)
+	s.Bytes = proto.Bytes
+
+	return nil
+}
+
+// -- From Schema To Proto ----------------------------------------------------
+
+// ToProto takes data from the receiver and populates the supplied proto object.
+// If the function returns an error, the proto object could be partially
+// populated.
+func (s *Schema) ToProto(proto *schemav1.Schema) error {
+	if proto == nil {
+		return errInvalidProtoIsNil
+	}
+
+	proto.Subject = s.Subject
+	proto.Version = int32(s.Version)
+	proto.Type = schemav1.Schema_Type(s.Type)
+	proto.Bytes = s.Bytes
+
+	return nil
+}

schema/proto_test.go

@@ -0,0 +1,95 @@
+// Copyright © 2024 Meroxa, Inc.
+//
+// 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 schema
+
+import (
+	"testing"
+
+	schemav1 "github.com/conduitio/conduit-commons/proto/schema/v1"
+	"github.com/matryer/is"
+)
+
+func TestSchema_FromProto(t *testing.T) {
+	is := is.New(t)
+
+	s1 := &schemav1.Schema{
+		Subject: "subject",
+		Version: 1,
+		Type:    schemav1.Schema_TYPE_AVRO,
+		Bytes:   []byte("bytes"),
+	}
+
+	want := Schema{
+		Subject: "subject",
+		Version: 1,
+		Type:    TypeAvro,
+		Bytes:   []byte("bytes"),
+	}
+
+	var got Schema
+	err := got.FromProto(s1)
+	is.NoErr(err)
+	is.Equal(got, want)
+}
+
+func TestSchema_ToProto(t *testing.T) {
+	is := is.New(t)
+
+	testCases := []struct {
+		name    string
+		in      *schemav1.Schema
+		want    *schemav1.Schema
+		wantErr error
+	}{
+		{
+			name:    "when proto object is nil",
+			in:      nil,
+			want:    nil,
+			wantErr: errInvalidProtoIsNil,
+		},
+		{
+			name: "when proto object is not nil",
+			in:   &schemav1.Schema{},
+			want: &schemav1.Schema{
+				Subject: "subject",
+				Version: 1,
+				Type:    schemav1.Schema_TYPE_AVRO,
+				Bytes:   []byte("bytes"),
+			},
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			is := is.New(t)
+
+			s1 := Schema{
+				Subject: "subject",
+				Version: 1,
+				Type:    TypeAvro,
+				Bytes:   []byte("bytes"),
+			}
+
+			err := s1.ToProto(tc.in)
+
+			if tc.wantErr == nil {
+				is.NoErr(err)
+				is.Equal(tc.in, tc.want)
+			} else {
+				is.Equal(err.Error(), tc.wantErr.Error())
+			}
+		})
+	}
+}