/*
Copyright IBM Corp. 2016 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 ecdsa

import (
	"crypto/sha256"
	"crypto/sha512"
	"fmt"
	"hash"

	"golang.org/x/crypto/sha3"

	"github.com/hyperledger/fabric/core/crypto/primitives"
)

func getHashSHA2(bitsize int) (hash.Hash, error) {
	switch bitsize {
	case 224:
		return sha256.New224(), nil
	case 256:
		return sha256.New(), nil
	case 384:
		return sha512.New384(), nil
	case 512:
		return sha512.New(), nil
	case 521:
		return sha512.New(), nil
	default:
		return nil, fmt.Errorf("Invalid bitsize. It was [%d]. Expected [224, 256, 384, 512, 521]", bitsize)
	}
}

func getHashSHA3(bitsize int) (hash.Hash, error) {
	switch bitsize {
	case 224:
		return sha3.New224(), nil
	case 256:
		return sha3.New256(), nil
	case 384:
		return sha3.New384(), nil
	case 512:
		return sha3.New512(), nil
	case 521:
		return sha3.New512(), nil
	default:
		return nil, fmt.Errorf("Invalid bitsize. It was [%d]. Expected [224, 256, 384, 512, 521]", bitsize)
	}
}

func computeHash(msg []byte, bitsize int) ([]byte, error) {
	var hash hash.Hash
	var err error
	switch primitives.GetHashAlgorithm() {
	case "SHA2":
		hash, err = getHashSHA2(bitsize)
	case "SHA3":
		hash, err = getHashSHA3(bitsize)
	default:
		return nil, fmt.Errorf("Invalid hash algorithm " + primitives.GetHashAlgorithm())
	}

	if err != nil {
		return nil, err
	}

	hash.Write(msg)
	return hash.Sum(nil), nil
}