<?php

declare(strict_types = 1);

namespace Sop\CryptoTypes\Asymmetric;

use Sop\CryptoEncoding\PEM;
use Sop\CryptoTypes\AlgorithmIdentifier\Feature\AlgorithmIdentifierType;

/**
 * Base class for private keys.
 */
abstract class PrivateKey
{
    /**
     * Get the private key algorithm identifier.
     *
     * @return AlgorithmIdentifierType
     */
    abstract public function algorithmIdentifier(): AlgorithmIdentifierType;

    /**
     * Get public key component of the asymmetric key pair.
     *
     * @return PublicKey
     */
    abstract public function publicKey(): PublicKey;

    /**
     * Get DER encoding of the private key.
     *
     * @return string
     */
    abstract public function toDER(): string;

    /**
     * Get the private key as a PEM.
     *
     * @return PEM
     */
    abstract public function toPEM(): PEM;

    /**
     * Get the private key as a PrivateKeyInfo type.
     *
     * @return PrivateKeyInfo
     */
    public function privateKeyInfo(): PrivateKeyInfo
    {
        return PrivateKeyInfo::fromPrivateKey($this);
    }

    /**
     * Initialize private key from PEM.
     *
     * @param PEM $pem
     *
     * @throws \UnexpectedValueException
     *
     * @return PrivateKey
     */
    public static function fromPEM(PEM $pem)
    {
        switch ($pem->type()) {
            case PEM::TYPE_RSA_PRIVATE_KEY:
                return RSA\RSAPrivateKey::fromDER($pem->data());
            case PEM::TYPE_EC_PRIVATE_KEY:
                return EC\ECPrivateKey::fromDER($pem->data());
            case PEM::TYPE_PRIVATE_KEY:
                return PrivateKeyInfo::fromDER($pem->data())->privateKey();
        }
        throw new \UnexpectedValueException(
            'PEM type ' . $pem->type() . ' is not a valid private key.');
    }
}