// Copyright The OpenTelemetry Authors
//
// 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 otlpconfig // import "go.opentelemetry.io/otel/exporters/otlp/otlpmetric/internal/otlpconfig"

import (
	"crypto/tls"
	"crypto/x509"
	"errors"
	"io/ioutil"
)

// ReadTLSConfigFromFile reads a PEM certificate file and creates
// a tls.Config that will use this certifate to verify a server certificate.
func ReadTLSConfigFromFile(path string) (*tls.Config, error) {
	b, err := ioutil.ReadFile(path)
	if err != nil {
		return nil, err
	}

	return CreateTLSConfig(b)
}

// CreateTLSConfig creates a tls.Config from a raw certificate bytes
// to verify a server certificate.
func CreateTLSConfig(certBytes []byte) (*tls.Config, error) {
	cp := x509.NewCertPool()
	if ok := cp.AppendCertsFromPEM(certBytes); !ok {
		return nil, errors.New("failed to append certificate to the cert pool")
	}

	return &tls.Config{
		RootCAs: cp,
	}, nil
}