<?php

namespace UglyRobot\Infinite_Uploads\Aws\Crypto;

use UglyRobot\Infinite_Uploads\GuzzleHttp\Psr7;
use UglyRobot\Infinite_Uploads\GuzzleHttp\Psr7\LimitStream;
use UglyRobot\Infinite_Uploads\Psr\Http\Message\StreamInterface;
trait DecryptionTrait
{
    /**
     * Dependency to reverse lookup the openssl_* cipher name from the AESName
     * in the MetadataEnvelope.
     *
     * @param $aesName
     *
     * @return string
     *
     * @internal
     */
    protected abstract function getCipherFromAesName($aesName);
    /**
     * Dependency to generate a CipherMethod from a set of inputs for loading
     * in to an AesDecryptingStream.
     *
     * @param string $cipherName Name of the cipher to generate for decrypting.
     * @param string $iv Base Initialization Vector for the cipher.
     * @param int $keySize Size of the encryption key, in bits, that will be
     *                     used.
     *
     * @return Cipher\CipherMethod
     *
     * @internal
     */
    protected abstract function buildCipherMethod($cipherName, $iv, $keySize);
    /**
     * Builds an AesStreamInterface using cipher options loaded from the
     * MetadataEnvelope and MaterialsProvider. Can decrypt data from both the
     * legacy and V2 encryption client workflows.
     *
     * @param string $cipherText Plain-text data to be encrypted using the
     *                           materials, algorithm, and data provided.
     * @param MaterialsProviderInterface $provider A provider to supply and encrypt
     *                                             materials used in encryption.
     * @param MetadataEnvelope $envelope A storage envelope for encryption
     *                                   metadata to be read from.
     * @param array $cipherOptions Additional verification options.
     *
     * @return AesStreamInterface
     *
     * @throws \InvalidArgumentException Thrown when a value in $cipherOptions
     *                                   is not valid.
     *
     * @internal
     */
    public function decrypt($cipherText, \UglyRobot\Infinite_Uploads\Aws\Crypto\MaterialsProviderInterface $provider, \UglyRobot\Infinite_Uploads\Aws\Crypto\MetadataEnvelope $envelope, array $cipherOptions = [])
    {
        $cipherOptions['Iv'] = base64_decode($envelope[\UglyRobot\Infinite_Uploads\Aws\Crypto\MetadataEnvelope::IV_HEADER]);
        $cipherOptions['TagLength'] = $envelope[\UglyRobot\Infinite_Uploads\Aws\Crypto\MetadataEnvelope::CRYPTO_TAG_LENGTH_HEADER] / 8;
        $cek = $provider->decryptCek(base64_decode($envelope[\UglyRobot\Infinite_Uploads\Aws\Crypto\MetadataEnvelope::CONTENT_KEY_V2_HEADER]), json_decode($envelope[\UglyRobot\Infinite_Uploads\Aws\Crypto\MetadataEnvelope::MATERIALS_DESCRIPTION_HEADER], true));
        $cipherOptions['KeySize'] = strlen($cek) * 8;
        $cipherOptions['Cipher'] = $this->getCipherFromAesName($envelope[\UglyRobot\Infinite_Uploads\Aws\Crypto\MetadataEnvelope::CONTENT_CRYPTO_SCHEME_HEADER]);
        $decryptionStream = $this->getDecryptingStream($cipherText, $cek, $cipherOptions);
        unset($cek);
        return $decryptionStream;
    }
    private function getTagFromCiphertextStream(\UglyRobot\Infinite_Uploads\Psr\Http\Message\StreamInterface $cipherText, $tagLength)
    {
        $cipherTextSize = $cipherText->getSize();
        if ($cipherTextSize == null || $cipherTextSize <= 0) {
            throw new \RuntimeException('Cannot decrypt a stream of unknown' . ' size.');
        }
        return (string) new \UglyRobot\Infinite_Uploads\GuzzleHttp\Psr7\LimitStream($cipherText, $tagLength, $cipherTextSize - $tagLength);
    }
    private function getStrippedCiphertextStream(\UglyRobot\Infinite_Uploads\Psr\Http\Message\StreamInterface $cipherText, $tagLength)
    {
        $cipherTextSize = $cipherText->getSize();
        if ($cipherTextSize == null || $cipherTextSize <= 0) {
            throw new \RuntimeException('Cannot decrypt a stream of unknown' . ' size.');
        }
        return new \UglyRobot\Infinite_Uploads\GuzzleHttp\Psr7\LimitStream($cipherText, $cipherTextSize - $tagLength, 0);
    }
    /**
     * Generates a stream that wraps the cipher text with the proper cipher and
     * uses the content encryption key (CEK) to decrypt the data when read.
     *
     * @param string $cipherText Plain-text data to be encrypted using the
     *                           materials, algorithm, and data provided.
     * @param string $cek A content encryption key for use by the stream for
     *                    encrypting the plaintext data.
     * @param array $cipherOptions Options for use in determining the cipher to
     *                             be used for encrypting data.
     *
     * @return AesStreamInterface
     *
     * @internal
     */
    protected function getDecryptingStream($cipherText, $cek, $cipherOptions)
    {
        $cipherTextStream = \UglyRobot\Infinite_Uploads\GuzzleHttp\Psr7\stream_for($cipherText);
        switch ($cipherOptions['Cipher']) {
            case 'gcm':
                $cipherOptions['Tag'] = $this->getTagFromCiphertextStream($cipherTextStream, $cipherOptions['TagLength']);
                return new \UglyRobot\Infinite_Uploads\Aws\Crypto\AesGcmDecryptingStream($this->getStrippedCiphertextStream($cipherTextStream, $cipherOptions['TagLength']), $cek, $cipherOptions['Iv'], $cipherOptions['Tag'], $cipherOptions['Aad'] = isset($cipherOptions['Aad']) ? $cipherOptions['Aad'] : null, $cipherOptions['TagLength'] ?: null, $cipherOptions['KeySize']);
            default:
                $cipherMethod = $this->buildCipherMethod($cipherOptions['Cipher'], $cipherOptions['Iv'], $cipherOptions['KeySize']);
                return new \UglyRobot\Infinite_Uploads\Aws\Crypto\AesDecryptingStream($cipherTextStream, $cek, $cipherMethod);
        }
    }
}