// Copyright 2019, 2020 OCI Contributors
// Copyright 2017 Docker, 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
//
//     https://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 digest

import (
	"hash"
	"io"
)

// Verifier presents a general verification interface to be used with message
// digests and other byte stream verifications. Users instantiate a Verifier
// from one of the various methods, write the data under test to it then check
// the result with the Verified method.
type Verifier interface {
	io.Writer

	// Verified will return true if the content written to Verifier matches
	// the digest.
	Verified() bool
}

type hashVerifier struct {
	digest Digest
	hash   hash.Hash
}

func (hv hashVerifier) Write(p []byte) (n int, err error) {
	return hv.hash.Write(p)
}

func (hv hashVerifier) Verified() bool {
	return hv.digest == NewDigest(hv.digest.Algorithm(), hv.hash)
}