package jwt

import (

	"crypto/ecdsa"

	"crypto/x509"

	"encoding/pem"

	"errors"

)

var (

	ErrNotECPublicKey  = errors.New("Key is not a valid ECDSA public key")

	ErrNotECPrivateKey = errors.New("Key is not a valid ECDSA private key")

)

// Parse PEM encoded Elliptic Curve Private Key Structure

func ParseECPrivateKeyFromPEM(key []byte) (*ecdsa.PrivateKey, error) {

	var err error

	// Parse PEM block

	var block *pem.Block

	if block, _ = pem.Decode(key); block == nil {

		return nil, ErrKeyMustBePEMEncoded

	}

	// Parse the key

	var parsedKey interface{}

	if parsedKey, err = x509.ParseECPrivateKey(block.Bytes); err != nil {

		return nil, err

	}

	var pkey *ecdsa.PrivateKey

	var ok bool

	if pkey, ok = parsedKey.(*ecdsa.PrivateKey); !ok {

		return nil, ErrNotECPrivateKey

	}

	return pkey, nil

}

// Parse PEM encoded PKCS1 or PKCS8 public key

func ParseECPublicKeyFromPEM(key []byte) (*ecdsa.PublicKey, error) {

	var err error

	// Parse PEM block

	var block *pem.Block

	if block, _ = pem.Decode(key); block == nil {

		return nil, ErrKeyMustBePEMEncoded

	}

	// Parse the key

	var parsedKey interface{}

	if parsedKey, err = x509.ParsePKIXPublicKey(block.Bytes); err != nil {

		if cert, err := x509.ParseCertificate(block.Bytes); err == nil {

			parsedKey = cert.PublicKey

		} else {

			return nil, err

		}

	}

	var pkey *ecdsa.PublicKey

	var ok bool

	if pkey, ok = parsedKey.(*ecdsa.PublicKey); !ok {

		return nil, ErrNotECPublicKey

	}

	return pkey, nil

}