<?php

/**
 * @author Kato Twofold
 * @copyright MIT
 * 
 * The class has full support for encryption of strings, provides validation for those
 * and makes sure they can be decrypted on the other end, the key is extremely important
 * and you MUST keep track of it and not lose it as there is no way of getting it back.
 * 
 */
class kpcrypt {

    // The key to use in the encryption process
    private $key = null;

    /**
     *  
     * Define the number of blocks that should be read from the source file for each chunk.
     * For 'AES-128-CBC' each block consist of 16 bytes.
     * So if we read 10,000 blocks we load 160kb into memory. You may adjust this value
     * to read/write shorter or longer chunks.
     * 
     * The higher this size is, the faster the file will be 
     * processed but the more memory will in turn be also used
     * 
    */
    private $blocks = 10000;

    /**
     * A log of all of the errors, rather nice for debugging
     * Please don't write to this, only read from it since
     * it should only store errors about this class.
     */
    private $errorLog = [];

    // The encryption cipher to use
    private $cipherMethod = "AES-256-CBC";

    /**
     * @param string $key [Optional] The key to use for encryption, if none is mentioned a random one will be generated
     */
    public function __construct( string $key = null, string $cipherMethod = "AES-256-CBC" ) {
        // If no key is mentioned, generate one
        if ( empty($key) ) {
            $key = bin2hex(openssl_random_pseudo_bytes("64"));
        }
        
        // Lowercase the cipher
        $this->cipherMethod = strtolower($cipherMethod);

        // Check if the encryption method is valid
        if (!in_array($this->cipherMethod, openssl_get_cipher_methods())) {
            // Cypher was not in the available ciphers list.
            $this->errorLog[] = "[" . __LINE__ . "]" . $this->cipherMethod . " isn't a valid cipherMethod.";
            return FALSE;
        }

        $this->key = $key;
    }

    /**
     * Get the key that the instance is currently using, really useful for when you randomly generate it!
     * @return string The key of the instance
     */
    public function getKey() {
        return $this->key;
    }

    /**
     * Get the encryption blocks for files
     */
    public function getEncryptionBlocks() {
        return $this->blocks;
    }

    /**
     * Redefine the encryption blocks size
     */
    public function setEncryptionBlocks(int $size = 10000) {
        // Make sure the size has a minimum of blocks read.
        if ( $size < 1 ) $size = 1;

        // Set the local blocks
        $this->blocks = $size;
    }

    public function getErrors() {
        return $this->errorLog;
    }

    // #region String Encryption

        /**
         * @param string $data The data to be encrypted, this can only encrypt strings.
         * @param bool $integrity_check Check if the encrypted data can also be decypted, this will take 2x more time to process the data, but will make 100% sure that the data is safe and can be decrypted.
         */
        function encryptData(string $data, bool $integrity_check = TRUE) {
            // Grab the key from self-reference
            $key = $this->key;

            // To encrypt a string   
            $iv = openssl_random_pseudo_bytes(openssl_cipher_iv_length($this->cipherMethod));

            // Encrypt the data
            $encryptedData = openssl_encrypt($data, $this->cipherMethod, $key, OPENSSL_RAW_DATA, $iv);

            // Append the iv to the encrypted data
            $encryptedData = $iv . $encryptedData;

            // base64 encrypt to make sure we don't lose bytes
            $encryptedData = base64_encode($encryptedData);

            // Check if we should verify the integrity of the encryption
            if ($integrity_check === TRUE) {
                // Test for decryption validity
                if (md5($this->decryptData($encryptedData)) === md5($data)) {
                    // Put the output in the result
                    return $encryptedData;
                } else {
                    // Assign the output to the result
                    $this->errorLog[] = "[" . __LINE__ . "]" . "Failed integrity check";
                    return FALSE;
                }
            } else {
                // Simply return the results
                return $encryptedData;
            }
        }

        /**
         * @param string $data The data to be encrypted, this can only encrypt strings.
         */
        function decryptData(string $data) {
            // Grab the key from self-reference
            $key = $this->key;

            // base64 decode the data.
            $data = base64_decode($data);

            // Get the length of the IV
            $iv_length = openssl_cipher_iv_length($this->cipherMethod);
            // Get the IV from the decoded data
            $iv = substr($data, 0, $iv_length);

            // Get the encrypted string from the data
            $data = substr($data, $iv_length);

            // Decrypt the data
            $data = openssl_decrypt($data, $this->cipherMethod, $key, OPENSSL_RAW_DATA, $iv);
            

            // Return the data
            return $data;
        }

    // #endregion


    /**
     * File encryption should only be used on larger files ( 512kb+ )
     * Since the string encryption will work better on the smaller files, since it's all
     * in the memory, this simlpy pipes the file through itself, for every 1Mb file it only uses ~0.1Mb of memory with the default block size
     */
    // #region File Encryption

        public function encryptFile(string $fileInput, string $fileOutput, bool $integrity_check = TRUE) {

            // To encrypt a string   
            $iv = openssl_random_pseudo_bytes(openssl_cipher_iv_length($this->cipherMethod));

            // Try and open the destionation
            if ( $fout = fopen($fileOutput, 'w') ) {
                // Try and open the input file
                if ($fin = fopen($fileInput, 'rb') ) {
                    // Place the IV at the beginning of the file for later decryption
                    fwrite($fout, $iv);

                    // Start reading from the input file
                    while ( !feof($fin) ) {
                        // Read in blocks of 16
                        $plaintext = fread($fin, 16 * $this->blocks);
                        $ciphertext = openssl_encrypt($plaintext, $this->cipherMethod, $this->key, OPENSSL_RAW_DATA, $iv);
                        // Use the first 16 bytes of the ciphertext as the next initialization vector
                        $iv = substr($ciphertext, 0, 16);
                        fwrite($fout, $ciphertext);
                    }

                    // Close the input file
                    fclose($fin);

                } else {
                    $this->errorLog[] = "[" . __LINE__ . "]" . "Could not open input file for reading.";
                    // Close the output file
                    fclose($fout);
                    return false;
                }

            } else {
                $this->errorLog[] = "[" . __LINE__ . "]" . "Could not open file output path for writing.";
                return false;
            }


            // Close the output file
            fclose($fout);
            return 1;
        }

        /**
         * @param string $fileInput The path to the encrypted file we want to decrypt
         * @param string $fileOutput The path to where to place the decrypted content
         */
        public function decryptFile(string $fileInput, string $fileOutput) {


            // Try and open the destionation
            if ( $fout = fopen($fileOutput, 'w') ) {
                // Try and open the input file
                if ($fin = fopen($fileInput, 'rb') ) {
                    // Get the IV from the beginning of the file
                    $iv = fread($fin, openssl_cipher_iv_length($this->cipherMethod));

                    while (!feof($fin)) {
                        // we have to read one block more for decrypting than for encrypting
                        $ciphertext = fread($fin, 16 * ($this->blocks + 1));
                        $plaintext = openssl_decrypt($ciphertext, $this->cipherMethod, $this->key, OPENSSL_RAW_DATA, $iv);
                        // Use the first 16 bytes of the ciphertext as the next initialization vector
                        $iv = substr($ciphertext, 0, 16);
                        fwrite($fout, $plaintext);
                    }

                    // Close the input file
                    fclose($fin);
                } else {
                    $this->errorLog[] = "[" . __LINE__ . "]" . "Could not open file input path for writing.";
                    return false;
                }
                // Close the output file
                fclose($fout);
                return 1;
            } else {
                $this->errorLog[] = "[" . __LINE__ . "]" . "Could not open file output path for writing.";
                return false;
            }

        }

    // #endregion

}