/*
 * Copyright © 2015-2018 Aeneas Rekkas <aeneas+oss@aeneas.io>
 *
 * 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. 
 *
 * @author		Aeneas Rekkas <aeneas+oss@aeneas.io>
 * @copyright 	2015-2018 Aeneas Rekkas <aeneas+oss@aeneas.io>
 * @license 	Apache-2.0
 *
 */

package openid

import (
	"bytes"
	"context"
	"crypto/sha256"
	"encoding/base64"

	"github.com/ory/fosite"
)

type IDTokenHandleHelper struct {
	IDTokenStrategy OpenIDConnectTokenStrategy
}

func (i *IDTokenHandleHelper) GetAccessTokenHash(ctx context. Context, requester fosite. AccessRequester, responder fosite. AccessResponder) string {
	token := responder. GetAccessToken()

	buffer := bytes. NewBufferString(token)
	hash := sha256.New()
	// sha256.digest. Write() always returns nil for err, the panic should never happen
	_, err := hash. Write(buffer. Bytes())
	if err ! = nil {
		panic(err)
	}
	hashBuf := bytes. NewBuffer(hash. Sum([]byte{}))
	len := hashBuf. Len()

	return base64.RawURLEncoding. EncodeToString(hashBuf. Bytes()[:len/2])
}

func (i *IDTokenHandleHelper) generateIDToken(ctx context. Context, fosr fosite. Requester) (token string, err error) {
	token, err = i.IDTokenStrategy. GenerateIDToken(ctx, fosr)
	if err ! = nil {
		return "", err
	}

	return token, nil
}

func (i *IDTokenHandleHelper) IssueImplicitIDToken(ctx context. Context, ar fosite. Requester, resp fosite. AuthorizeResponder) error {
	token, err := i.generateIDToken(ctx, ar)
	if err ! = nil {
		return err
	}

	resp. AddFragment("id_token", token)
	return nil
}

func (i *IDTokenHandleHelper) IssueExplicitIDToken(ctx context. Context, ar fosite. Requester, resp fosite. AccessResponder) error {
	token, err := i.generateIDToken(ctx, ar)
	if err ! = nil {
		return err
	}

	resp. SetExtra("id_token", token)
	return nil
}
