/*
Copyright 2014 The Kubernetes 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 cert

import (
	"crypto"
	"crypto/ecdsa"
	"crypto/rsa"
	"crypto/x509"
	"encoding/pem"
	"fmt"
	"io/ioutil"
	"os"
	"path/filepath"
)

// CanReadCertAndKey returns true if the certificate and key files already exists,
// otherwise returns false. If lost one of cert and key, returns error.
func CanReadCertAndKey(certPath, keyPath string) (bool, error) {
	certReadable := canReadFile(certPath)
	keyReadable := canReadFile(keyPath)

	if certReadable == false && keyReadable == false {
		return false, nil
	}

	if certReadable == false {
		return false, fmt.Errorf("error reading %s, certificate and key must be supplied as a pair", certPath)
	}

	if keyReadable == false {
		return false, fmt.Errorf("error reading %s, certificate and key must be supplied as a pair", keyPath)
	}

	return true, nil
}

// If the file represented by path exists and
// readable, returns true otherwise returns false.
func canReadFile(path string) bool {
	f, err := os.Open(path)
	if err != nil {
		return false
	}

	defer f.Close()

	return true
}

// WriteCert writes the pem-encoded certificate data to certPath.
// The certificate file will be created with file mode 0644.
// If the certificate file already exists, it will be overwritten.
// The parent directory of the certPath will be created as needed with file mode 0755.
func WriteCert(certPath string, data []byte) error {
	if err := os.MkdirAll(filepath.Dir(certPath), os.FileMode(0755)); err != nil {
		return err
	}
	return ioutil.WriteFile(certPath, data, os.FileMode(0644))
}

// WriteKey writes the pem-encoded key data to keyPath.
// The key file will be created with file mode 0600.
// If the key file already exists, it will be overwritten.
// The parent directory of the keyPath will be created as needed with file mode 0755.
func WriteKey(keyPath string, data []byte) error {
	if err := os.MkdirAll(filepath.Dir(keyPath), os.FileMode(0755)); err != nil {
		return err
	}
	return ioutil.WriteFile(keyPath, data, os.FileMode(0600))
}

// LoadOrGenerateKeyFile looks for a key in the file at the given path. If it
// can't find one, it will generate a new key and store it there.
func LoadOrGenerateKeyFile(keyPath string) (data []byte, wasGenerated bool, err error) {
	loadedData, err := ioutil.ReadFile(keyPath)
	// Call verifyKeyData to ensure the file wasn't empty/corrupt.
	if err == nil && verifyKeyData(loadedData) {
		return loadedData, false, err
	}
	if !os.IsNotExist(err) {
		return nil, false, fmt.Errorf("error loading key from %s: %v", keyPath, err)
	}

	generatedData, err := MakeEllipticPrivateKeyPEM()
	if err != nil {
		return nil, false, fmt.Errorf("error generating key: %v", err)
	}
	if err := WriteKey(keyPath, generatedData); err != nil {
		return nil, false, fmt.Errorf("error writing key to %s: %v", keyPath, err)
	}
	return generatedData, true, nil
}

// MarshalPrivateKeyToPEM converts a known private key type of RSA or ECDSA to
// a PEM encoded block or returns an error.
func MarshalPrivateKeyToPEM(privateKey crypto.PrivateKey) ([]byte, error) {
	switch t := privateKey.(type) {
	case *ecdsa.PrivateKey:
		derBytes, err := x509.MarshalECPrivateKey(t)
		if err != nil {
			return nil, err
		}
		privateKeyPemBlock := &pem.Block{
			Type:  ECPrivateKeyBlockType,
			Bytes: derBytes,
		}
		return pem.EncodeToMemory(privateKeyPemBlock), nil
	case *rsa.PrivateKey:
		return EncodePrivateKeyPEM(t), nil
	default:
		return nil, fmt.Errorf("private key is not a recognized type: %T", privateKey)
	}
}

// NewPool returns an x509.CertPool containing the certificates in the given PEM-encoded file.
// Returns an error if the file could not be read, a certificate could not be parsed, or if the file does not contain any certificates
func NewPool(filename string) (*x509.CertPool, error) {
	certs, err := CertsFromFile(filename)
	if err != nil {
		return nil, err
	}
	pool := x509.NewCertPool()
	for _, cert := range certs {
		pool.AddCert(cert)
	}
	return pool, nil
}

// CertsFromFile returns the x509.Certificates contained in the given PEM-encoded file.
// Returns an error if the file could not be read, a certificate could not be parsed, or if the file does not contain any certificates
func CertsFromFile(file string) ([]*x509.Certificate, error) {
	pemBlock, err := ioutil.ReadFile(file)
	if err != nil {
		return nil, err
	}
	certs, err := ParseCertsPEM(pemBlock)
	if err != nil {
		return nil, fmt.Errorf("error reading %s: %s", file, err)
	}
	return certs, nil
}

// PrivateKeyFromFile returns the private key in rsa.PrivateKey or ecdsa.PrivateKey format from a given PEM-encoded file.
// Returns an error if the file could not be read or if the private key could not be parsed.
func PrivateKeyFromFile(file string) (interface{}, error) {
	data, err := ioutil.ReadFile(file)
	if err != nil {
		return nil, err
	}
	key, err := ParsePrivateKeyPEM(data)
	if err != nil {
		return nil, fmt.Errorf("error reading private key file %s: %v", file, err)
	}
	return key, nil
}

// PublicKeysFromFile returns the public keys in rsa.PublicKey or ecdsa.PublicKey format from a given PEM-encoded file.
// Reads public keys from both public and private key files.
func PublicKeysFromFile(file string) ([]interface{}, error) {
	data, err := ioutil.ReadFile(file)
	if err != nil {
		return nil, err
	}
	keys, err := ParsePublicKeysPEM(data)
	if err != nil {
		return nil, fmt.Errorf("error reading public key file %s: %v", file, err)
	}
	return keys, nil
}

// verifyKeyData returns true if the provided data appears to be a valid private key.
func verifyKeyData(data []byte) bool {
	if len(data) == 0 {
		return false
	}
	_, err := ParsePrivateKeyPEM(data)
	return err == nil
}