// 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 hybrid

import (
	"github.com/golang/protobuf/proto"
	"github.com/google/tink/go/aead"
	commonpb "github.com/google/tink/proto/common_go_proto"
	eciespb "github.com/google/tink/proto/ecies_aead_hkdf_go_proto"
	tinkpb "github.com/google/tink/proto/tink_go_proto"
)

// This file contains pre-generated KeyTemplates for HybridEncrypt keys. One can use these templates
// to generate new Keysets.

// ECIESHKDFAES128GCMKeyTemplate is a KeyTemplate that generates an ECDH P-256 and decapsulation key AES128-GCM key with the following parameters:
//  - KEM: ECDH over NIST P-256
//  - DEM: AES128-GCM
//  - KDF: HKDF-HMAC-SHA256 with an empty salt
func ECIESHKDFAES128GCMKeyTemplate() *tinkpb.KeyTemplate {
	empty := []byte{}
	return createECIESAEADHKDFKeyTemplate(commonpb.EllipticCurveType_NIST_P256, commonpb.HashType_SHA256, commonpb.EcPointFormat_UNCOMPRESSED, aead.AES128GCMKeyTemplate(), empty)
}

// ECIESHKDFAES128CTRHMACSHA256KeyTemplate is a KeyTemplate that generates an ECDH P-256 and decapsulation key AES128-CTR-HMAC-SHA256 with the following parameters:
//  - KEM: ECDH over NIST P-256
//  - DEM: AES128-CTR-HMAC-SHA256 with the following parameters
//      - AES key size: 16 bytes
//      - AES CTR IV size: 16 bytes
//      - HMAC key size: 32 bytes
//      - HMAC tag size: 16 bytes
//  - KDF: HKDF-HMAC-SHA256 with an empty salt
func ECIESHKDFAES128CTRHMACSHA256KeyTemplate() *tinkpb.KeyTemplate {
	empty := []byte{}
	return createECIESAEADHKDFKeyTemplate(commonpb.EllipticCurveType_NIST_P256, commonpb.HashType_SHA256, commonpb.EcPointFormat_UNCOMPRESSED, aead.AES128CTRHMACSHA256KeyTemplate(), empty)
}

// createEciesAEADHKDFKeyTemplate creates a new ECIES-AEAD-HKDF key template with the given key
// size in bytes.
func createECIESAEADHKDFKeyTemplate(c commonpb.EllipticCurveType, ht commonpb.HashType, ptfmt commonpb.EcPointFormat, dekT *tinkpb.KeyTemplate, salt []byte) *tinkpb.KeyTemplate {
	format := &eciespb.EciesAeadHkdfKeyFormat{
		Params: &eciespb.EciesAeadHkdfParams{
			KemParams: &eciespb.EciesHkdfKemParams{
				CurveType:    c,
				HkdfHashType: ht,
				HkdfSalt:     salt,
			},
			DemParams: &eciespb.EciesAeadDemParams{
				AeadDem: dekT,
			},
			EcPointFormat: ptfmt,
		},
	}
	serializedFormat, _ := proto.Marshal(format)
	return &tinkpb.KeyTemplate{
		TypeUrl:          eciesAEADHKDFPrivateKeyTypeURL,
		Value:            serializedFormat,
		OutputPrefixType: tinkpb.OutputPrefixType_TINK,
	}
}