<?php

defined('BASEPATH') or exit('No direct script access allowed');

/**
 * CodeIgniter Rest Controller
 * A fully RESTful server implementation for CodeIgniter using one library, one config file and one controller.
 *
 * @package         CodeIgniter
 * @subpackage      Libraries
 * @category        Libraries
 * @author          Phil Sturgeon, Chris Kacerguis
 * @license         MIT
 * @link            https://github.com/chriskacerguis/codeigniter-restserver
 * @version         3.0.0
 */
abstract class REST_Controller extends CI_Controller
{

    // Note: Only the widely used HTTP status codes are documented

    // Informational

    const HTTP_CONTINUE = 100;
    const HTTP_SWITCHING_PROTOCOLS = 101;
    const HTTP_PROCESSING = 102;            // RFC2518

    // Success

    /**
     * The request has succeeded
     */
    const HTTP_OK = 200;

    /**
     * The server successfully created a new resource
     */
    const HTTP_CREATED = 201;
    const HTTP_ACCEPTED = 202;
    const HTTP_NON_AUTHORITATIVE_INFORMATION = 203;

    /**
     * The server successfully processed the request, though no content is returned
     */
    const HTTP_NO_CONTENT = 204;
    const HTTP_RESET_CONTENT = 205;
    const HTTP_PARTIAL_CONTENT = 206;
    const HTTP_MULTI_STATUS = 207;          // RFC4918
    const HTTP_ALREADY_REPORTED = 208;      // RFC5842
    const HTTP_IM_USED = 226;               // RFC3229

    // Redirection

    const HTTP_MULTIPLE_CHOICES = 300;
    const HTTP_MOVED_PERMANENTLY = 301;
    const HTTP_FOUND = 302;
    const HTTP_SEE_OTHER = 303;

    /**
     * The resource has not been modified since the last request
     */
    const HTTP_NOT_MODIFIED = 304;
    const HTTP_USE_PROXY = 305;
    const HTTP_RESERVED = 306;
    const HTTP_TEMPORARY_REDIRECT = 307;
    const HTTP_PERMANENTLY_REDIRECT = 308;  // RFC7238

    // Client Error

    /**
     * The request cannot be fulfilled due to multiple errors
     */
    const HTTP_BAD_REQUEST = 400;

    /**
     * The user is unauthorized to access the requested resource
     */
    const HTTP_UNAUTHORIZED = 401;
    const HTTP_PAYMENT_REQUIRED = 402;

    /**
     * The requested resource is unavailable at this present time
     */
    const HTTP_FORBIDDEN = 403;

    /**
     * The requested resource could not be found
     *
     * Note: This is sometimes used to mask if there was an UNAUTHORIZED (401) or
     * FORBIDDEN (403) error, for security reasons
     */
    const HTTP_NOT_FOUND = 404;

    /**
     * The request method is not supported by the following resource
     */
    const HTTP_METHOD_NOT_ALLOWED = 405;

    /**
     * The request was not acceptable
     */
    const HTTP_NOT_ACCEPTABLE = 406;
    const HTTP_PROXY_AUTHENTICATION_REQUIRED = 407;
    const HTTP_REQUEST_TIMEOUT = 408;

    /**
     * The request could not be completed due to a conflict with the current state
     * of the resource
     */
    const HTTP_CONFLICT = 409;
    const HTTP_GONE = 410;
    const HTTP_LENGTH_REQUIRED = 411;
    const HTTP_PRECONDITION_FAILED = 412;
    const HTTP_REQUEST_ENTITY_TOO_LARGE = 413;
    const HTTP_REQUEST_URI_TOO_LONG = 414;
    const HTTP_UNSUPPORTED_MEDIA_TYPE = 415;
    const HTTP_REQUESTED_RANGE_NOT_SATISFIABLE = 416;
    const HTTP_EXPECTATION_FAILED = 417;
    const HTTP_I_AM_A_TEAPOT = 418;                                               // RFC2324
    const HTTP_UNPROCESSABLE_ENTITY = 422;                                        // RFC4918
    const HTTP_LOCKED = 423;                                                      // RFC4918
    const HTTP_FAILED_DEPENDENCY = 424;                                           // RFC4918
    const HTTP_RESERVED_FOR_WEBDAV_ADVANCED_COLLECTIONS_EXPIRED_PROPOSAL = 425;   // RFC2817
    const HTTP_UPGRADE_REQUIRED = 426;                                            // RFC2817
    const HTTP_PRECONDITION_REQUIRED = 428;                                       // RFC6585
    const HTTP_TOO_MANY_REQUESTS = 429;                                           // RFC6585
    const HTTP_REQUEST_HEADER_FIELDS_TOO_LARGE = 431;                             // RFC6585

    // Server Error

    /**
     * The server encountered an unexpected error
     *
     * Note: This is a generic error message when no specific message
     * is suitable
     */
    const HTTP_INTERNAL_SERVER_ERROR = 500;

    /**
     * The server does not recognise the request method
     */
    const HTTP_NOT_IMPLEMENTED = 501;
    const HTTP_BAD_GATEWAY = 502;
    const HTTP_SERVICE_UNAVAILABLE = 503;
    const HTTP_GATEWAY_TIMEOUT = 504;
    const HTTP_VERSION_NOT_SUPPORTED = 505;
    const HTTP_VARIANT_ALSO_NEGOTIATES_EXPERIMENTAL = 506;                        // RFC2295
    const HTTP_INSUFFICIENT_STORAGE = 507;                                        // RFC4918
    const HTTP_LOOP_DETECTED = 508;                                               // RFC5842
    const HTTP_NOT_EXTENDED = 510;                                                // RFC2774
    const HTTP_NETWORK_AUTHENTICATION_REQUIRED = 511;

    /**
     * This defines the rest format
     * Must be overridden it in a controller so that it is set
     *
     * @var string|NULL
     */
    protected $rest_format = null;

    /**
     * Defines the list of method properties such as limit, log and level
     *
     * @var array
     */
    protected $methods = [];

    /**
     * List of allowed HTTP methods
     *
     * @var array
     */
    protected $allowed_http_methods = ['get', 'delete', 'post', 'put', 'options', 'patch', 'head'];

    /**
     * Contains details about the request
     * Fields: body, format, method, ssl
     * Note: This is a dynamic object (stdClass)
     *
     * @var object
     */
    protected $request = null;

    /**
     * Contains details about the response
     * Fields: format, lang
     * Note: This is a dynamic object (stdClass)
     *
     * @var object
     */
    protected $response = null;

    /**
     * Contains details about the REST API
     * Fields: db, ignore_limits, key, level, user_id
     * Note: This is a dynamic object (stdClass)
     *
     * @var object
     */
    protected $rest = null;

    /**
     * The arguments for the GET request method
     *
     * @var array
     */
    protected $_get_args = [];

    /**
     * The arguments for the POST request method
     *
     * @var array
     */
    protected $_post_args = [];

    /**
     * The arguments for the PUT request method
     *
     * @var array
     */
    protected $_put_args = [];

    /**
     * The arguments for the DELETE request method
     *
     * @var array
     */
    protected $_delete_args = [];

    /**
     * The arguments for the PATCH request method
     *
     * @var array
     */
    protected $_patch_args = [];

    /**
     * The arguments for the HEAD request method
     *
     * @var array
     */
    protected $_head_args = [];

    /**
     * The arguments for the OPTIONS request method
     *
     * @var array
     */
    protected $_options_args = [];

    /**
     * The arguments for the query parameters
     *
     * @var array
     */
    protected $_query_args = [];

    /**
     * The arguments from GET, POST, PUT, DELETE, PATCH, HEAD and OPTIONS request methods combined
     *
     * @var array
     */
    protected $_args = [];

    /**
     * The insert_id of the log entry (if we have one)
     *
     * @var string
     */
    protected $_insert_id = '';

    /**
     * If the request is allowed based on the API key provided
     *
     * @var bool
     */
    protected $_allow = true;

    /**
     * The LDAP Distinguished Name of the User post authentication
     *
     * @var string
     */
    protected $_user_ldap_dn = '';

    /**
     * The start of the response time from the server
     *
     * @var string
     */
    protected $_start_rtime = '';

    /**
     * The end of the response time from the server
     *
     * @var string
     */
    protected $_end_rtime = '';

    /**
     * List all supported methods, the first will be the default format
     *
     * @var array
     */
    protected $_supported_formats = [
            'json' => 'application/json',
            'array' => 'application/json',
            'csv' => 'application/csv',
            'html' => 'text/html',
            'jsonp' => 'application/javascript',
            'php' => 'text/plain',
            'serialized' => 'application/vnd.php.serialized',
            'xml' => 'application/xml'
        ];

    /**
     * Information about the current API user
     *
     * @var object
     */
    protected $_apiuser;

    /**
     * Whether or not to perform a CORS check and apply CORS headers to the request
     *
     * @var bool
     */
    protected $check_cors = null;

    /**
     * Enable XSS flag
     * Determines whether the XSS filter is always active when
     * GET, OPTIONS, HEAD, POST, PUT, DELETE and PATCH data is encountered
     * Set automatically based on config setting
     *
     * @var bool
     */
    protected $_enable_xss = false;

    /**
     * HTTP status codes and their respective description
     * Note: Only the widely used HTTP status codes are used
     *
     * @var array
     * @link http://www.restapitutorial.com/httpstatuscodes.html
     */
    protected $http_status_codes = [
        self::HTTP_OK => 'OK',
        self::HTTP_CREATED => 'CREATED',
        self::HTTP_NO_CONTENT => 'NO CONTENT',
        self::HTTP_NOT_MODIFIED => 'NOT MODIFIED',
        self::HTTP_BAD_REQUEST => 'BAD REQUEST',
        self::HTTP_UNAUTHORIZED => 'UNAUTHORIZED',
        self::HTTP_FORBIDDEN => 'FORBIDDEN',
        self::HTTP_NOT_FOUND => 'NOT FOUND',
        self::HTTP_METHOD_NOT_ALLOWED => 'METHOD NOT ALLOWED',
        self::HTTP_NOT_ACCEPTABLE => 'NOT ACCEPTABLE',
        self::HTTP_CONFLICT => 'CONFLICT',
        self::HTTP_INTERNAL_SERVER_ERROR => 'INTERNAL SERVER ERROR',
        self::HTTP_NOT_IMPLEMENTED => 'NOT IMPLEMENTED'
    ];

    /**
     * Extend this function to apply additional checking early on in the process
     *
     * @access protected
     * @return void
     */
    protected function early_checks()
    {
    }

    /**
     * Constructor for the REST API
     *
     * @access public
     * @param string $config Configuration filename minus the file extension
     * e.g: my_rest.php is passed as 'my_rest'
     * @return void
     */
    public function __construct($config = 'rest')
    {
        parent::__construct();

        // Disable XML Entity (security vulnerability)
        libxml_disable_entity_loader(true);

        // Check to see if PHP is equal to or greater than 5.4.x
        if (is_php('5.4') === false) {
            // CodeIgniter 3 is recommended for v5.4 or above
            throw new Exception('Using PHP v' . PHP_VERSION . ', though PHP v5.4 or greater is required');
        }

        // Check to see if this is CI 3.x
        if (explode('.', CI_VERSION, 2)[0] < 3) {
            throw new Exception('REST Server requires CodeIgniter 3.x');
        }

        // Set the default value of global xss filtering. Same approach as CodeIgniter 3
        $this->_enable_xss = ($this->config->item('global_xss_filtering') === true);

        // Don't try to parse template variables like {elapsed_time} and {memory_usage}
        // when output is displayed for not damaging data accidentally
        $this->output->parse_exec_vars = false;

        // Start the timer for how long the request takes
        $this->_start_rtime = microtime(true);

        // Load the rest.php configuration file
        $this->load->config($config);

        // At present the library is bundled with REST_Controller 2.5+, but will eventually be part of CodeIgniter (no citation)
        $this->load->library('format');

        // Determine supported output formats from configuration
        $supported_formats = $this->config->item('rest_supported_formats');

        // Validate the configuration setting output formats
        if (empty($supported_formats)) {
            $supported_formats = [];
        }

        if (!is_array($supported_formats)) {
            $supported_formats = [$supported_formats];
        }

        // Add silently the default output format if it is missing
        $default_format = $this->_get_default_output_format();
        if (!in_array($default_format, $supported_formats)) {
            $supported_formats[] = $default_format;
        }

        // Now update $this->_supported_formats
        $this->_supported_formats = array_intersect_key($this->_supported_formats, array_flip($supported_formats));

        // Get the language
        $language = $this->config->item('rest_language');
        if ($language === null) {
            $language = 'english';
        }

        // Load the language file
        $this->lang->load_lines('../modules/codeigniter_restserver/language/' . $language . '/*.php');

        // Initialise the response, request and rest objects
        $this->request = new stdClass();
        $this->response = new stdClass();
        $this->rest = new stdClass();

        // Check to see if the current IP address is blacklisted
        if ($this->config->item('rest_ip_blacklist_enabled') === true) {
            $this->_check_blacklist_auth();
        }

        // Determine whether the connection is HTTPS
        $this->request->ssl = is_https();

        // How is this request being made? GET, POST, PATCH, DELETE, INSERT, PUT, HEAD or OPTIONS
        $this->request->method = $this->_detect_method();

        // Check for CORS access request
        $check_cors = $this->config->item('check_cors');
        if ($check_cors === true) {
            $this->_check_cors();
        }

        // Create an argument container if it doesn't exist e.g. _get_args
        if (isset($this->{'_' . $this->request->method . '_args'}) === false) {
            $this->{'_' . $this->request->method . '_args'} = [];
        }

        // Set up the query parameters
        $this->_parse_query();

        // Set up the GET variables
        $this->_get_args = array_merge($this->_get_args, $this->uri->ruri_to_assoc());

        // Try to find a format for the request (means we have a request body)
        $this->request->format = $this->_detect_input_format();

        // Not all methods have a body attached with them
        $this->request->body = null;

        $this->{'_parse_' . $this->request->method}();

        // Now we know all about our request, let's try and parse the body if it exists
        if ($this->request->format && $this->request->body) {
            $this->request->body = $this->format->factory($this->request->body, $this->request->format)->to_array();
            // Assign payload arguments to proper method container
            $this->{'_' . $this->request->method . '_args'} = $this->request->body;
        }

        // Merge both for one mega-args variable
        $this->_args = array_merge(
            $this->_get_args,
            $this->_options_args,
            $this->_patch_args,
            $this->_head_args,
            $this->_put_args,
            $this->_post_args,
            $this->_delete_args,
            $this->{'_' . $this->request->method . '_args'}
        );

        // Which format should the data be returned in?
        $this->response->format = $this->_detect_output_format();

        // Which language should the data be returned in?
        $this->response->lang = $this->_detect_lang();

        // Extend this function to apply additional checking early on in the process
        $this->early_checks();

        // Load DB if its enabled
        if ($this->config->item('rest_database_group') && ($this->config->item('rest_enable_keys') || $this->config->item('rest_enable_logging'))) {
            $this->rest->db = $this->load->database($this->config->item('rest_database_group'), true);
        }

        // Use whatever database is in use (isset returns FALSE)
        elseif (property_exists($this, 'db')) {
            $this->rest->db = $this->db;
        }

        // Check if there is a specific auth type for the current class/method
        // _auth_override_check could exit so we need $this->rest->db initialized before
        $this->auth_override = $this->_auth_override_check();

        // Checking for keys? GET TO WorK!
        // Skip keys test for $config['auth_override_class_method']['class'['method'] = 'none'
        if ($this->config->item('rest_enable_keys') && $this->auth_override !== true) {
            $this->_allow = $this->_detect_api_key();
        }

        // Only allow ajax requests
        if ($this->input->is_ajax_request() === false && $this->config->item('rest_ajax_only')) {
            // Display an error response
            $this->response([
                    $this->config->item('rest_status_field_name') => false,
                    $this->config->item('rest_message_field_name') => $this->lang->line('text_rest_ajax_only')
                ], self::HTTP_NOT_ACCEPTABLE);
        }

        // When there is no specific override for the current class/method, use the default auth value set in the config
        if ($this->auth_override === false && (!($this->config->item('rest_enable_keys') && $this->_allow === true) || ($this->config->item('allow_auth_and_keys') === true && $this->_allow === true))) {
            $rest_auth = strtolower($this->config->item('rest_auth'));
            switch ($rest_auth) {
                case 'basic':
                    $this->_prepare_basic_auth();
                    break;
                case 'digest':
                    $this->_prepare_digest_auth();
                    break;
                case 'session':
                    $this->_check_php_session();
                    break;
            }
            if ($this->config->item('rest_ip_whitelist_enabled') === true) {
                $this->_check_whitelist_auth();
            }
        }
    }

    /**
     * Deconstructor
     *
     * @author Chris Kacerguis
     * @access public
     * @return void
     */
    public function __destruct()
    {
        // Get the current timestamp
        $this->_end_rtime = microtime(true);

        // Log the loading time to the log table
        if ($this->config->item('rest_enable_logging') === true) {
            $this->_log_access_time();
        }
    }

    /**
     * Requests are not made to methods directly, the request will be for
     * an "object". This simply maps the object and method to the correct
     * Controller method
     *
     * @access public
     * @param  string $object_called
     * @param  array $arguments The arguments passed to the controller method
     */
    public function _remap($object_called, $arguments = [])
    {
        // Should we answer if not over SSL?
        if ($this->config->item('force_https') && $this->request->ssl === false) {
            $this->response([
                    $this->config->item('rest_status_field_name') => false,
                    $this->config->item('rest_message_field_name') => $this->lang->line('text_rest_unsupported')
                ], self::HTTP_FORBIDDEN);
        }

        // Remove the supported format from the function name e.g. index.json => index
        $object_called = preg_replace('/^(.*)\.(?:' . implode('|', array_keys($this->_supported_formats)) . ')$/', '$1', $object_called);

        $controller_method = $object_called . '_' . $this->request->method;

        // Do we want to log this method (if allowed by config)?
        $log_method = !(isset($this->methods[$controller_method]['log']) && $this->methods[$controller_method]['log'] === false);

        // Use keys for this method?
        $use_key = !(isset($this->methods[$controller_method]['key']) && $this->methods[$controller_method]['key'] === false);

        // They provided a key, but it wasn't valid, so get them out of here
        if ($this->config->item('rest_enable_keys') && $use_key && $this->_allow === false) {
            if ($this->config->item('rest_enable_logging') && $log_method) {
                $this->_log_request();
            }

            $this->response([
                    $this->config->item('rest_status_field_name') => false,
                    $this->config->item('rest_message_field_name') => sprintf($this->lang->line('text_rest_invalid_api_key'), $this->rest->key)
                ], self::HTTP_FORBIDDEN);
        }

        // Check to see if this key has access to the requested controller
        if ($this->config->item('rest_enable_keys') && $use_key && empty($this->rest->key) === false && $this->_check_access() === false) {
            if ($this->config->item('rest_enable_logging') && $log_method) {
                $this->_log_request();
            }

            $this->response([
                    $this->config->item('rest_status_field_name') => false,
                    $this->config->item('rest_message_field_name') => $this->lang->line('text_rest_api_key_unauthorized')
                ], self::HTTP_UNAUTHORIZED);
        }

        // Sure it exists, but can they do anything with it?
        if (method_exists($this, $controller_method) === false) {
            $this->response([
                    $this->config->item('rest_status_field_name') => false,
                    $this->config->item('rest_message_field_name') => $this->lang->line('text_rest_unknown_method')
                ], self::HTTP_NOT_FOUND);
        }

        // Doing key related stuff? Can only do it if they have a key right?
        if ($this->config->item('rest_enable_keys') && empty($this->rest->key) === false) {
            // Check the limit
            if ($this->config->item('rest_enable_limits') && $this->_check_limit($controller_method) === false) {
                $response = [$this->config->item('rest_status_field_name') => false, $this->config->item('rest_message_field_name') => $this->lang->line('text_rest_api_key_time_limit')];
                $this->response($response, self::HTTP_UNAUTHORIZED);
            }

            // If no level is set use 0, they probably aren't using permissions
            $level = isset($this->methods[$controller_method]['level']) ? $this->methods[$controller_method]['level'] : 0;

            // If no level is set, or it is lower than/equal to the key's level
            $authorized = $level <= $this->rest->level;
            // IM TELLIN!
            if ($this->config->item('rest_enable_logging') && $log_method) {
                $this->_log_request($authorized);
            }
            if ($authorized === false) {
                // They don't have good enough perms
                $response = [$this->config->item('rest_status_field_name') => false, $this->config->item('rest_message_field_name') => $this->lang->line('text_rest_api_key_permissions')];
                $this->response($response, self::HTTP_UNAUTHORIZED);
            }
        }

        // No key stuff, but record that stuff is happening
        elseif ($this->config->item('rest_enable_logging') && $log_method) {
            $this->_log_request($authorized = true);
        }

        // Call the controller method and passed arguments
        try {
            call_user_func_array([$this, $controller_method], $arguments);
        } catch (Exception $ex) {
            // If the method doesn't exist, then the error will be caught and an error response shown
            $this->response([
                    $this->config->item('rest_status_field_name') => false,
                    $this->config->item('rest_message_field_name') => [
                        'classname' => get_class($ex),
                        'message' => $ex->getMessage()
                    ]
                ], self::HTTP_INTERNAL_SERVER_ERROR);
        }
    }

    /**
     * Takes mixed data and optionally a status code, then creates the response
     *
     * @access public
     * @param array|NULL $data Data to output to the user
     * @param int|NULL $http_code HTTP status code
     * @param bool $continue TRUE to flush the response to the client and continue
     * running the script; otherwise, exit
     */
    public function response($data = null, $http_code = null, $continue = false)
    {
        // If the HTTP status is not NULL, then cast as an integer
        if ($http_code !== null) {
            // So as to be safe later on in the process
            $http_code = (int) $http_code;
        }

        // Set the output as NULL by default
        $output = null;

        // If data is NULL and no HTTP status code provided, then display, error and exit
        if ($data === null && $http_code === null) {
            $http_code = self::HTTP_NOT_FOUND;
        }

        // If data is not NULL and a HTTP status code provided, then continue
        elseif ($data !== null) {
            // If the format method exists, call and return the output in that format
            if (method_exists($this->format, 'to_' . $this->response->format)) {
                // Set the format header
                $this->output->set_content_type($this->_supported_formats[$this->response->format], strtolower($this->config->item('charset')));
                $output = $this->format->factory($data)->{'to_' . $this->response->format}();

                // An array must be parsed as a string, so as not to cause an array to string error
                // Json is the most appropriate form for such a datatype
                if ($this->response->format === 'array') {
                    $output = $this->format->factory($output)->{'to_json'}();
                }
            } else {
                // If an array or object, then parse as a json, so as to be a 'string'
                if (is_array($data) || is_object($data)) {
                    $data = $this->format->factory($data)->{'to_json'}();
                }

                // Format is not supported, so output the raw data as a string
                $output = $data;
            }
        }

        // If not greater than zero, then set the HTTP status code as 200 by default
        // Though perhaps 500 should be set instead, for the developer not passing a
        // correct HTTP status code
        $http_code > 0 || $http_code = self::HTTP_OK;

        $this->output->set_status_header($http_code);

        // JC: Log response code only if rest logging enabled
        if ($this->config->item('rest_enable_logging') === true) {
            $this->_log_response_code($http_code);
        }

        // Output the data
        $this->output->set_output($output);

        if ($continue === false) {
            // Display the data and exit execution
            $this->output->_display();
            exit;
        }

        // Otherwise dump the output automatically
    }

    /**
     * Takes mixed data and optionally a status code, then creates the response
     * within the buffers of the Output class. The response is sent to the client
     * lately by the framework, after the current controller's method termination.
     * All the hooks after the controller's method termination are executable
     *
     * @access public
     * @param array|NULL $data Data to output to the user
     * @param int|NULL $http_code HTTP status code
     */
    public function set_response($data = null, $http_code = null)
    {
        $this->response($data, $http_code, true);
    }

    /**
     * Get the input format e.g. json or xml
     *
     * @access protected
     * @return string|NULL Supported input format; otherwise, NULL
     */
    protected function _detect_input_format()
    {
        // Get the CONTENT-TYPE value from the SERVER variable
        $content_type = $this->input->server('CONTENT_TYPE');

        if (empty($content_type) === false) {
            // Check all formats against the HTTP_ACCEPT header
            foreach ($this->_supported_formats as $key => $value) {
                // $key = format e.g. csv
                // $value = mime type e.g. application/csv

                // If a semi-colon exists in the string, then explode by ; and get the value of where
                // the current array pointer resides. This will generally be the first element of the array
                $content_type = (strpos($content_type, ';') !== false ? current(explode(';', $content_type)) : $content_type);

                // If both the mime types match, then return the format
                if ($content_type === $value) {
                    return $key;
                }
            }
        }

        return null;
    }

    /**
     * Gets the default format from the configuration. Fallbacks to 'json'
     * if the corresponding configuration option $config['rest_default_format']
     * is missing or is empty
     *
     * @access protected
     * @return string The default supported input format
     */
    protected function _get_default_output_format()
    {
        $default_format = (string) $this->config->item('rest_default_format');
        return $default_format === '' ? 'json' : $default_format;
    }

    /**
     * Detect which format should be used to output the data
     *
     * @access protected
     * @return mixed|NULL|string Output format
     */
    protected function _detect_output_format()
    {
        // Concatenate formats to a regex pattern e.g. \.(csv|json|xml)
        $pattern = '/\.(' . implode('|', array_keys($this->_supported_formats)) . ')($|\/)/';
        $matches = [];

        // Check if a file extension is used e.g. http://example.com/api/index.json?param1=param2
        if (preg_match($pattern, $this->uri->uri_string(), $matches)) {
            return $matches[1];
        }

        // Get the format parameter named as 'format'
        if (isset($this->_get_args['format'])) {
            $format = strtolower($this->_get_args['format']);

            if (isset($this->_supported_formats[$format]) === true) {
                return $format;
            }
        }

        // Get the HTTP_ACCEPT server variable
        $http_accept = $this->input->server('HTTP_ACCEPT');

        // Otherwise, check the HTTP_ACCEPT server variable
        if ($this->config->item('rest_ignore_http_accept') === false && $http_accept !== null) {
            // Check all formats against the HTTP_ACCEPT header
            foreach (array_keys($this->_supported_formats) as $format) {
                // Has this format been requested?
                if (strpos($http_accept, $format) !== false) {
                    if ($format !== 'html' && $format !== 'xml') {
                        // If not HTML or XML assume it's correct
                        return $format;
                    } elseif ($format === 'html' && strpos($http_accept, 'xml') === false) {
                        // HTML or XML have shown up as a match
                        // If it is truly HTML, it wont want any XML
                        return $format;
                    } elseif ($format === 'xml' && strpos($http_accept, 'html') === false) {
                        // If it is truly XML, it wont want any HTML
                        return $format;
                    }
                }
            }
        }

        // Check if the controller has a default format
        if (empty($this->rest_format) === false) {
            return $this->rest_format;
        }

        // Obtain the default format from the configuration
        return $this->_get_default_output_format();
    }

    /**
     * Get the HTTP request string e.g. get or post
     *
     * @access protected
     * @return string|NULL Supported request method as a lowercase string; otherwise, NULL if not supported
     */
    protected function _detect_method()
    {
        // Declare a variable to store the method
        $method = null;

        // Determine whether the 'enable_emulate_request' setting is enabled
        if ($this->config->item('enable_emulate_request') === true) {
            $method = $this->input->post('_method');
            if ($method === null) {
                $method = $this->input->server('HTTP_X_HTTP_METHOD_OVERRIDE');
            }

            $method = strtolower($method);
        }

        if (empty($method)) {
            // Get the request method as a lowercase string
            $method = $this->input->method();
        }

        return in_array($method, $this->allowed_http_methods) && method_exists($this, '_parse_' . $method) ? $method : 'get';
    }

    /**
     * See if the user has provided an API key
     *
     * @access protected
     * @return bool
     */
    protected function _detect_api_key()
    {
        // Get the api key name variable set in the rest config file
        $api_key_variable = $this->config->item('rest_key_name');

        // Work out the name of the SERVER entry based on config
        $key_name = 'HTTP_' . strtoupper(str_replace('-', '_', $api_key_variable));

        $this->rest->key = null;
        $this->rest->level = null;
        $this->rest->user_id = null;
        $this->rest->ignore_limits = false;

        // Find the key from server or arguments
        if (($key = isset($this->_args[$api_key_variable]) ? $this->_args[$api_key_variable] : $this->input->server($key_name))) {
            if (!($row = $this->rest->db->where($this->config->item('rest_key_column'), $key)->get($this->config->item('rest_keys_table'))->row())) {
                return false;
            }

            $this->rest->key = $row->{$this->config->item('rest_key_column')};

            isset($row->user_id) && $this->rest->user_id = $row->user_id;
            isset($row->level) && $this->rest->level = $row->level;
            isset($row->ignore_limits) && $this->rest->ignore_limits = $row->ignore_limits;

            $this->_apiuser = $row;

            /*
             * If "is private key" is enabled, compare the ip address with the list
             * of valid ip addresses stored in the database
             */
            if (empty($row->is_private_key) === false) {
                // Check for a list of valid ip addresses
                if (isset($row->ip_addresses)) {
                    // multiple ip addresses must be separated using a comma, explode and loop
                    $list_ip_addresses = explode(',', $row->ip_addresses);
                    $found_address = false;

                    foreach ($list_ip_addresses as $ip_address) {
                        if ($this->input->ip_address() === trim($ip_address)) {
                            // there is a match, set the the value to TRUE and break out of the loop
                            $found_address = true;
                            break;
                        }
                    }

                    return $found_address;
                } else {
                    // There should be at least one IP address for this private key
                    return false;
                }
            }

            return true;
        }

        // No key has been sent
        return false;
    }

    /**
     * Preferred return language
     *
     * @access protected
     * @return string|NULL The language code
     */
    protected function _detect_lang()
    {
        $lang = $this->input->server('HTTP_ACCEPT_LANGUAGE');
        if ($lang === null) {
            return null;
        }

        // It appears more than one language has been sent using a comma delimiter
        if (strpos($lang, ',') !== false) {
            $langs = explode(',', $lang);

            $return_langs = [];
            foreach ($langs as $lang) {
                // Remove weight and trim leading and trailing whitespace
                list($lang) = explode(';', $lang);
                $return_langs[] = trim($lang);
            }

            return $return_langs;
        }

        // Otherwise simply return as a string
        return $lang;
    }

    /**
     * Add the request to the log table
     *
     * @access protected
     * @param bool $authorized TRUE the user is authorized; otherwise, FALSE
     * @return bool TRUE the data was inserted; otherwise, FALSE
     */
    protected function _log_request($authorized = false)
    {
        // Insert the request into the log table
        $is_inserted = $this->rest->db
            ->insert(
                $this->config->item('rest_logs_table'), [
                'uri' => $this->uri->uri_string(),
                'method' => $this->request->method,
                'params' => $this->_args ? ($this->config->item('rest_logs_json_params') === true ? json_encode($this->_args) : serialize($this->_args)) : null,
                'api_key' => isset($this->rest->key) ? $this->rest->key : '',
                'ip_address' => $this->input->ip_address(),
                'time' => time(),
                'authorized' => $authorized
            ]);

        // Get the last insert id to update at a later stage of the request
        $this->_insert_id = $this->rest->db->insert_id();

        return $is_inserted;
    }

    /**
     * Check if the requests to a controller method exceed a limit
     *
     * @access protected
     * @param  string $controller_method The method being called
     * @return bool TRUE the call limit is below the threshold; otherwise, FALSE
     */
    protected function _check_limit($controller_method)
    {
        // They are special, or it might not even have a limit
        if (empty($this->rest->ignore_limits) === false) {
            // Everything is fine
            return true;
        }

        switch ($this->config->item('rest_limits_method')) {
          case 'API_KEY':
            $limited_uri = 'api-key:' . (isset($this->rest->key) ? $this->rest->key : '');
            $limited_method_name = isset($this->rest->key) ? $this->rest->key : '';
            break;

          case 'METHOD_NAME':
            $limited_uri = 'method-name:' . $controller_method;
            $limited_method_name =  $controller_method;
            break;

          case 'ROUTED_URL':
          default:
            $limited_uri = $this->uri->ruri_string();
            if (strpos(strrev($limited_uri), strrev($this->response->format)) === 0) {
                $limited_uri = substr($limited_uri, 0, -strlen($this->response->format) - 1);
            }
            $limited_uri = 'uri:' . $limited_uri . ':' . $this->request->method; // It's good to differentiate GET from PUT
            $limited_method_name = $controller_method;
            break;
        }

        if (isset($this->methods[$limited_method_name]['limit']) === false) {
            // Everything is fine
            return true;
        }

        // How many times can you get to this method in a defined time_limit (default: 1 hour)?
        $limit = $this->methods[$limited_method_name]['limit'];

        $time_limit = (isset($this->methods[$limited_method_name]['time']) ? $this->methods[$limited_method_name]['time'] : 3600); // 3600 = 60 * 60

        // Get data about a keys' usage and limit to one row
        $result = $this->rest->db
            ->where('uri', $limited_uri)
            ->where('api_key', $this->rest->key)
            ->get($this->config->item('rest_limits_table'))
            ->row();

        // No calls have been made for this key
        if ($result === null) {
            // Create a new row for the following key
            $this->rest->db->insert($this->config->item('rest_limits_table'), [
                'uri' => $limited_uri,
                'api_key' => isset($this->rest->key) ? $this->rest->key : '',
                'count' => 1,
                'hour_started' => time()
            ]);
        }

        // Been a time limit (or by default an hour) since they called
        elseif ($result->hour_started < (time() - $time_limit)) {
            // Reset the started period and count
            $this->rest->db
                ->where('uri', $limited_uri)
                ->where('api_key', isset($this->rest->key) ? $this->rest->key : '')
                ->set('hour_started', time())
                ->set('count', 1)
                ->update($this->config->item('rest_limits_table'));
        }

        // They have called within the hour, so lets update
        else {
            // The limit has been exceeded
            if ($result->count >= $limit) {
                return false;
            }

            // Increase the count by one
            $this->rest->db
                ->where('uri', $limited_uri)
                ->where('api_key', $this->rest->key)
                ->set('count', 'count + 1', false)
                ->update($this->config->item('rest_limits_table'));
        }

        return true;
    }

    /**
     * Check if there is a specific auth type set for the current class/method/HTTP-method being called
     *
     * @access protected
     * @return bool
     */
    protected function _auth_override_check()
    {
        // Assign the class/method auth type override array from the config
        $auth_override_class_method = $this->config->item('auth_override_class_method');

        // Check to see if the override array is even populated
        if (!empty($auth_override_class_method)) {
            // check for wildcard flag for rules for classes
            if (!empty($auth_override_class_method[$this->router->class]['*'])) {
                // Check for class overrides

                // None auth override found, prepare nothing but send back a TRUE override flag
                if ($auth_override_class_method[$this->router->class]['*'] === 'none') {
                    return true;
                }

                // Basic auth override found, prepare basic
                if ($auth_override_class_method[$this->router->class]['*'] === 'basic') {
                    $this->_prepare_basic_auth();

                    return true;
                }

                // Digest auth override found, prepare digest
                if ($auth_override_class_method[$this->router->class]['*'] === 'digest') {
                    $this->_prepare_digest_auth();

                    return true;
                }

                // Session auth override found, check session
                if ($auth_override_class_method[$this->router->class]['*'] === 'session') {
                    $this->_check_php_session();

                    return true;
                }

                // Whitelist auth override found, check client's ip against config whitelist
                if ($auth_override_class_method[$this->router->class]['*'] === 'whitelist') {
                    $this->_check_whitelist_auth();

                    return true;
                }
            }

            // Check to see if there's an override value set for the current class/method being called
            if (!empty($auth_override_class_method[$this->router->class][$this->router->method])) {
                // None auth override found, prepare nothing but send back a TRUE override flag
                if ($auth_override_class_method[$this->router->class][$this->router->method] === 'none') {
                    return true;
                }

                // Basic auth override found, prepare basic
                if ($auth_override_class_method[$this->router->class][$this->router->method] === 'basic') {
                    $this->_prepare_basic_auth();

                    return true;
                }

                // Digest auth override found, prepare digest
                if ($auth_override_class_method[$this->router->class][$this->router->method] === 'digest') {
                    $this->_prepare_digest_auth();

                    return true;
                }

                // Session auth override found, check session
                if ($auth_override_class_method[$this->router->class][$this->router->method] === 'session') {
                    $this->_check_php_session();

                    return true;
                }

                // Whitelist auth override found, check client's ip against config whitelist
                if ($auth_override_class_method[$this->router->class][$this->router->method] === 'whitelist') {
                    $this->_check_whitelist_auth();

                    return true;
                }
            }
        }

        // Assign the class/method/HTTP-method auth type override array from the config
        $auth_override_class_method_http = $this->config->item('auth_override_class_method_http');

        // Check to see if the override array is even populated
        if (!empty($auth_override_class_method_http)) {
            // check for wildcard flag for rules for classes
            if (!empty($auth_override_class_method_http[$this->router->class]['*'][$this->request->method])) {
                // None auth override found, prepare nothing but send back a TRUE override flag
                if ($auth_override_class_method_http[$this->router->class]['*'][$this->request->method] === 'none') {
                    return true;
                }

                // Basic auth override found, prepare basic
                if ($auth_override_class_method_http[$this->router->class]['*'][$this->request->method] === 'basic') {
                    $this->_prepare_basic_auth();

                    return true;
                }

                // Digest auth override found, prepare digest
                if ($auth_override_class_method_http[$this->router->class]['*'][$this->request->method] === 'digest') {
                    $this->_prepare_digest_auth();

                    return true;
                }

                // Session auth override found, check session
                if ($auth_override_class_method_http[$this->router->class]['*'][$this->request->method] === 'session') {
                    $this->_check_php_session();

                    return true;
                }

                // Whitelist auth override found, check client's ip against config whitelist
                if ($auth_override_class_method_http[$this->router->class]['*'][$this->request->method] === 'whitelist') {
                    $this->_check_whitelist_auth();

                    return true;
                }
            }

            // Check to see if there's an override value set for the current class/method/HTTP-method being called
            if (!empty($auth_override_class_method_http[$this->router->class][$this->router->method][$this->request->method])) {
                // None auth override found, prepare nothing but send back a TRUE override flag
                if ($auth_override_class_method_http[$this->router->class][$this->router->method][$this->request->method] === 'none') {
                    return true;
                }

                // Basic auth override found, prepare basic
                if ($auth_override_class_method_http[$this->router->class][$this->router->method][$this->request->method] === 'basic') {
                    $this->_prepare_basic_auth();

                    return true;
                }

                // Digest auth override found, prepare digest
                if ($auth_override_class_method_http[$this->router->class][$this->router->method][$this->request->method] === 'digest') {
                    $this->_prepare_digest_auth();

                    return true;
                }

                // Session auth override found, check session
                if ($auth_override_class_method_http[$this->router->class][$this->router->method][$this->request->method] === 'session') {
                    $this->_check_php_session();

                    return true;
                }

                // Whitelist auth override found, check client's ip against config whitelist
                if ($auth_override_class_method_http[$this->router->class][$this->router->method][$this->request->method] === 'whitelist') {
                    $this->_check_whitelist_auth();

                    return true;
                }
            }
        }
        return false;
    }

    /**
     * Parse the GET request arguments
     *
     * @access protected
     * @return void
     */
    protected function _parse_get()
    {
        // Merge both the URI segments and query parameters
        $this->_get_args = array_merge($this->_get_args, $this->_query_args);
    }

    /**
     * Parse the POST request arguments
     *
     * @access protected
     * @return void
     */
    protected function _parse_post()
    {
        $this->_post_args = $_POST;

        if ($this->request->format) {
            $this->request->body = $this->input->raw_input_stream;
        }
    }

    /**
     * Parse the PUT request arguments
     *
     * @access protected
     * @return void
     */
    protected function _parse_put()
    {
        if ($this->request->format) {
            $this->request->body = $this->input->raw_input_stream;
        } elseif ($this->input->method() === 'put') {
            // If no filetype is provided, then there are probably just arguments
           $this->_put_args = $this->input->input_stream();
        }
    }

    /**
     * Parse the HEAD request arguments
     *
     * @access protected
     * @return void
     */
    protected function _parse_head()
    {
        // Parse the HEAD variables
        parse_str(parse_url($this->input->server('REQUEST_URI'), PHP_URL_QUERY), $head);

        // Merge both the URI segments and HEAD params
        $this->_head_args = array_merge($this->_head_args, $head);
    }

    /**
     * Parse the OPTIONS request arguments
     *
     * @access protected
     * @return void
     */
    protected function _parse_options()
    {
        // Parse the OPTIONS variables
        parse_str(parse_url($this->input->server('REQUEST_URI'), PHP_URL_QUERY), $options);

        // Merge both the URI segments and OPTIONS params
        $this->_options_args = array_merge($this->_options_args, $options);
    }

    /**
     * Parse the PATCH request arguments
     *
     * @access protected
     * @return void
     */
    protected function _parse_patch()
    {
        // It might be a HTTP body
        if ($this->request->format) {
            $this->request->body = $this->input->raw_input_stream;
        } elseif ($this->input->method() === 'patch') {
            // If no filetype is provided, then there are probably just arguments
            $this->_patch_args = $this->input->input_stream();
        }
    }

    /**
     * Parse the DELETE request arguments
     *
     * @access protected
     * @return void
     */
    protected function _parse_delete()
    {
        // These should exist if a DELETE request
        if ($this->input->method() === 'delete') {
            $this->_delete_args = $this->input->input_stream();
        }
    }

    /**
     * Parse the query parameters
     *
     * @access protected
     * @return void
     */
    protected function _parse_query()
    {
        $this->_query_args = $this->input->get();
    }

    // INPUT FUNCTION --------------------------------------------------------------

    /**
     * Retrieve a value from a GET request
     *
     * @access public
     * @param NULL $key Key to retrieve from the GET request
     * If NULL an array of arguments is returned
     * @param NULL $xss_clean Whether to apply XSS filtering
     * @return array|string|NULL Value from the GET request; otherwise, NULL
     */
    public function get($key = null, $xss_clean = null)
    {
        if ($key === null) {
            return $this->_get_args;
        }

        return isset($this->_get_args[$key]) ? $this->_xss_clean($this->_get_args[$key], $xss_clean) : null;
    }

    /**
     * Retrieve a value from a OPTIONS request
     *
     * @access public
     * @param NULL $key Key to retrieve from the OPTIONS request.
     * If NULL an array of arguments is returned
     * @param NULL $xss_clean Whether to apply XSS filtering
     * @return array|string|NULL Value from the OPTIONS request; otherwise, NULL
     */
    public function options($key = null, $xss_clean = null)
    {
        if ($key === null) {
            return $this->_options_args;
        }

        return isset($this->_options_args[$key]) ? $this->_xss_clean($this->_options_args[$key], $xss_clean) : null;
    }

    /**
     * Retrieve a value from a HEAD request
     *
     * @access public
     * @param NULL $key Key to retrieve from the HEAD request
     * If NULL an array of arguments is returned
     * @param NULL $xss_clean Whether to apply XSS filtering
     * @return array|string|NULL Value from the HEAD request; otherwise, NULL
     */
    public function head($key = null, $xss_clean = null)
    {
        if ($key === null) {
            return $this->_head_args;
        }

        return isset($this->_head_args[$key]) ? $this->_xss_clean($this->_head_args[$key], $xss_clean) : null;
    }

    /**
     * Retrieve a value from a POST request
     *
     * @access public
     * @param NULL $key Key to retrieve from the POST request
     * If NULL an array of arguments is returned
     * @param NULL $xss_clean Whether to apply XSS filtering
     * @return array|string|NULL Value from the POST request; otherwise, NULL
     */
    public function post($key = null, $xss_clean = null)
    {
        if ($key === null) {
            return $this->_post_args;
        }

        return isset($this->_post_args[$key]) ? $this->_xss_clean($this->_post_args[$key], $xss_clean) : null;
    }

    /**
     * Retrieve a value from a PUT request
     *
     * @access public
     * @param NULL $key Key to retrieve from the PUT request
     * If NULL an array of arguments is returned
     * @param NULL $xss_clean Whether to apply XSS filtering
     * @return array|string|NULL Value from the PUT request; otherwise, NULL
     */
    public function put($key = null, $xss_clean = null)
    {
        if ($key === null) {
            return $this->_put_args;
        }

        return isset($this->_put_args[$key]) ? $this->_xss_clean($this->_put_args[$key], $xss_clean) : null;
    }

    /**
     * Retrieve a value from a DELETE request
     *
     * @access public
     * @param NULL $key Key to retrieve from the DELETE request
     * If NULL an array of arguments is returned
     * @param NULL $xss_clean Whether to apply XSS filtering
     * @return array|string|NULL Value from the DELETE request; otherwise, NULL
     */
    public function delete($key = null, $xss_clean = null)
    {
        if ($key === null) {
            return $this->_delete_args;
        }

        return isset($this->_delete_args[$key]) ? $this->_xss_clean($this->_delete_args[$key], $xss_clean) : null;
    }

    /**
     * Retrieve a value from a PATCH request
     *
     * @access public
     * @param NULL $key Key to retrieve from the PATCH request
     * If NULL an array of arguments is returned
     * @param NULL $xss_clean Whether to apply XSS filtering
     * @return array|string|NULL Value from the PATCH request; otherwise, NULL
     */
    public function patch($key = null, $xss_clean = null)
    {
        if ($key === null) {
            return $this->_patch_args;
        }

        return isset($this->_patch_args[$key]) ? $this->_xss_clean($this->_patch_args[$key], $xss_clean) : null;
    }

    /**
     * Retrieve a value from the query parameters
     *
     * @access public
     * @param NULL $key Key to retrieve from the query parameters
     * If NULL an array of arguments is returned
     * @param NULL $xss_clean Whether to apply XSS filtering
     * @return array|string|NULL Value from the query parameters; otherwise, NULL
     */
    public function query($key = null, $xss_clean = null)
    {
        if ($key === null) {
            return $this->_query_args;
        }

        return isset($this->_query_args[$key]) ? $this->_xss_clean($this->_query_args[$key], $xss_clean) : null;
    }

    /**
     * Sanitizes data so that Cross Site Scripting Hacks can be
     * prevented
     *
     * @access protected
     * @param  string $value Input data
     * @param  bool $xss_clean Whether to apply XSS filtering
     * @return string
     */
    protected function _xss_clean($value, $xss_clean)
    {
        is_bool($xss_clean) || $xss_clean = $this->_enable_xss;

        return $xss_clean === true ? $this->security->xss_clean($value) : $value;
    }

    /**
     * Retrieve the validation errors
     *
     * @access public
     * @return array
     */
    public function validation_errors()
    {
        $string = strip_tags($this->form_validation->error_string());

        return explode(PHP_EOL, trim($string, PHP_EOL));
    }

    // SECURITY FUNCTIONS ---------------------------------------------------------

    /**
     * Perform LDAP Authentication
     *
     * @access protected
     * @param  string $username The username to validate
     * @param  string $password The password to validate
     * @return bool
     */
    protected function _perform_ldap_auth($username = '', $password = null)
    {
        if (empty($username)) {
            log_message('debug', 'LDAP Auth: failure, empty username');
            return false;
        }

        log_message('debug', 'LDAP Auth: Loading configuration');

        $this->config->load('ldap.php', true);

        $ldap = [
            'timeout' => $this->config->item('timeout', 'ldap'),
            'host' => $this->config->item('server', 'ldap'),
            'port' => $this->config->item('port', 'ldap'),
            'rdn' => $this->config->item('binduser', 'ldap'),
            'pass' => $this->config->item('bindpw', 'ldap'),
            'basedn' => $this->config->item('basedn', 'ldap'),
        ];

        log_message('debug', 'LDAP Auth: Connect to ' . (isset($ldaphost) ? $ldaphost : '[ldap not configured]'));

        // Connect to the ldap server
        $ldapconn = ldap_connect($ldap['host'], $ldap['port']);
        if ($ldapconn) {
            log_message('debug', 'Setting timeout to ' . $ldap['timeout'] . ' seconds');

            ldap_set_option($ldapconn, LDAP_OPT_NETWORK_TIMEOUT, $ldap['timeout']);

            log_message('debug', 'LDAP Auth: Binding to ' . $ldap['host'] . ' with dn ' . $ldap['rdn']);

            // Binding to the ldap server
            $ldapbind = ldap_bind($ldapconn, $ldap['rdn'], $ldap['pass']);

            // Verify the binding
            if ($ldapbind === false) {
                log_message('error', 'LDAP Auth: bind was unsuccessful');
                return false;
            }

            log_message('debug', 'LDAP Auth: bind successful');
        }

        // Search for user
        if (($res_id = ldap_search($ldapconn, $ldap['basedn'], "uid=$username")) === false) {
            log_message('error', 'LDAP Auth: User ' . $username . ' not found in search');
            return false;
        }

        if (ldap_count_entries($ldapconn, $res_id) !== 1) {
            log_message('error', 'LDAP Auth: Failure, username ' . $username . 'found more than once');
            return false;
        }

        if (($entry_id = ldap_first_entry($ldapconn, $res_id)) === false) {
            log_message('error', 'LDAP Auth: Failure, entry of search result could not be fetched');
            return false;
        }

        if (($user_dn = ldap_get_dn($ldapconn, $entry_id)) === false) {
            log_message('error', 'LDAP Auth: Failure, user-dn could not be fetched');
            return false;
        }

        // User found, could not authenticate as user
        if (($link_id = ldap_bind($ldapconn, $user_dn, $password)) === false) {
            log_message('error', 'LDAP Auth: Failure, username/password did not match: ' . $user_dn);
            return false;
        }

        log_message('debug', 'LDAP Auth: Success ' . $user_dn . ' authenticated successfully');

        $this->_user_ldap_dn = $user_dn;

        ldap_close($ldapconn);

        return true;
    }

    /**
     * Perform Library Authentication - Override this function to change the way the library is called
     *
     * @access protected
     * @param  string $username The username to validate
     * @param  string $password The password to validate
     * @return bool
     */
    protected function _perform_library_auth($username = '', $password = null)
    {
        if (empty($username)) {
            log_message('error', 'Library Auth: Failure, empty username');
            return false;
        }

        $auth_library_class = strtolower($this->config->item('auth_library_class'));
        $auth_library_function = strtolower($this->config->item('auth_library_function'));

        if (empty($auth_library_class)) {
            log_message('debug', 'Library Auth: Failure, empty auth_library_class');
            return false;
        }

        if (empty($auth_library_function)) {
            log_message('debug', 'Library Auth: Failure, empty auth_library_function');
            return false;
        }

        if (is_callable([$auth_library_class, $auth_library_function]) === false) {
            $this->load->library($auth_library_class);
        }

        return $this->{$auth_library_class}->$auth_library_function($username, $password);
    }

    /**
     * Check if the user is logged in
     *
     * @access protected
     * @param  string $username The user's name
     * @param  bool|string $password The user's password
     * @return bool
     */
    protected function _check_login($username = null, $password = false)
    {
        if (empty($username)) {
            return false;
        }

        $auth_source = strtolower($this->config->item('auth_source'));
        $rest_auth = strtolower($this->config->item('rest_auth'));
        $valid_logins = $this->config->item('rest_valid_logins');

        if (!$this->config->item('auth_source') && $rest_auth === 'digest') {
            // For digest we do not have a password passed as argument
            return md5($username . ':' . $this->config->item('rest_realm') . ':' . (isset($valid_logins[$username]) ? $valid_logins[$username] : ''));
        }

        if ($password === false) {
            return false;
        }

        if ($auth_source === 'ldap') {
            log_message('debug', "Performing LDAP authentication for $username");

            return $this->_perform_ldap_auth($username, $password);
        }

        if ($auth_source === 'library') {
            log_message('debug', "Performing Library authentication for $username");

            return $this->_perform_library_auth($username, $password);
        }

        if (array_key_exists($username, $valid_logins) === false) {
            return false;
        }

        if ($valid_logins[$username] !== $password) {
            return false;
        }

        return true;
    }

    /**
     * Check to see if the user is logged in with a PHP session key
     *
     * @access protected
     * @return void
     */
    protected function _check_php_session()
    {
        // Get the auth_source config item
        $key = $this->config->item('auth_source');

        // If falsy, then the user isn't logged in
        if (!$this->session->userdata($key)) {
            // Display an error response
            $this->response([
                    $this->config->item('rest_status_field_name') => false,
                    $this->config->item('rest_message_field_name') => $this->lang->line('text_rest_unauthorized')
                ], self::HTTP_UNAUTHORIZED);
        }
    }

    /**
     * Prepares for basic authentication
     *
     * @access protected
     * @return void
     */
    protected function _prepare_basic_auth()
    {
        // If whitelist is enabled it has the first chance to kick them out
        if ($this->config->item('rest_ip_whitelist_enabled')) {
            $this->_check_whitelist_auth();
        }

        // Returns NULL if the SERVER variables PHP_AUTH_USER and HTTP_AUTHENTICATION don't exist
        $username = $this->input->server('PHP_AUTH_USER');
        $http_auth = $this->input->server('HTTP_AUTHENTICATION');

        $password = null;
        if ($username !== null) {
            $password = $this->input->server('PHP_AUTH_PW');
        } elseif ($http_auth !== null) {
            // If the authentication header is set as basic, then extract the username and password from
            // HTTP_AUTHORIZATION e.g. my_username:my_password. This is passed in the .htaccess file
            if (strpos(strtolower($http_auth), 'basic') === 0) {
                // Search online for HTTP_AUTHORIZATION workaround to explain what this is doing
                list($username, $password) = explode(':', base64_decode(substr($this->input->server('HTTP_AUTHORIZATION'), 6)));
            }
        }

        // Check if the user is logged into the system
        if ($this->_check_login($username, $password) === false) {
            $this->_force_login();
        }
    }

    /**
     * Prepares for digest authentication
     *
     * @access protected
     * @return void
     */
    protected function _prepare_digest_auth()
    {
        // If whitelist is enabled it has the first chance to kick them out
        if ($this->config->item('rest_ip_whitelist_enabled')) {
            $this->_check_whitelist_auth();
        }

        // We need to test which server authentication variable to use,
        // because the PHP ISAPI module in IIS acts different from CGI
        $digest_string = $this->input->server('PHP_AUTH_DIGEST');
        if ($digest_string === null) {
            $digest_string = $this->input->server('HTTP_AUTHORIZATION');
        }

        $unique_id = uniqid();

        // The $_SESSION['error_prompted'] variable is used to ask the password
        // again if none given or if the user enters wrong auth information
        if (empty($digest_string)) {
            $this->_force_login($unique_id);
        }

        // We need to retrieve authentication data from the $digest_string variable
        $matches = [];
        preg_match_all('@(username|nonce|uri|nc|cnonce|qop|response)=[\'"]?([^\'",]+)@', $digest_string, $matches);
        $digest = (empty($matches[1]) || empty($matches[2])) ? [] : array_combine($matches[1], $matches[2]);

        // For digest authentication the library function should return already stored md5(username:restrealm:password) for that username @see rest.php::auth_library_function config
        $username = $this->_check_login($digest['username'], true);
        if (array_key_exists('username', $digest) === false || $username === false) {
            $this->_force_login($unique_id);
        }

        $md5 = md5(strtoupper($this->request->method) . ':' . $digest['uri']);
        $valid_response = md5($username . ':' . $digest['nonce'] . ':' . $digest['nc'] . ':' . $digest['cnonce'] . ':' . $digest['qop'] . ':' . $md5);

        // Check if the string don't compare (case-insensitive)
        if (strcasecmp($digest['response'], $valid_response) !== 0) {
            // Display an error response
            $this->response([
                    $this->config->item('rest_status_field_name') => false,
                    $this->config->item('rest_message_field_name') => $this->lang->line('text_rest_invalid_credentials')
                ], self::HTTP_UNAUTHORIZED);
        }
    }

    /**
     * Checks if the client's ip is in the 'rest_ip_blacklist' config and generates a 401 response
     *
     * @access protected
     * @return void
     */
    protected function _check_blacklist_auth()
    {
        // Match an ip address in a blacklist e.g. 127.0.0.0, 0.0.0.0
        $pattern = sprintf('/(?:,\s*|^)\Q%s\E(?=,\s*|$)/m', $this->input->ip_address());

        // Returns 1, 0 or FALSE (on error only). Therefore implicitly convert 1 to TRUE
        if (preg_match($pattern, $this->config->item('rest_ip_blacklist'))) {
            // Display an error response
            $this->response([
                    $this->config->item('rest_status_field_name') => false,
                    $this->config->item('rest_message_field_name') => $this->lang->line('text_rest_ip_denied')
                ], self::HTTP_UNAUTHORIZED);
        }
    }

    /**
     * Check if the client's ip is in the 'rest_ip_whitelist' config and generates a 401 response
     *
     * @access protected
     * @return void
     */
    protected function _check_whitelist_auth()
    {
        $whitelist = explode(',', $this->config->item('rest_ip_whitelist'));

        array_push($whitelist, '127.0.0.1', '0.0.0.0');

        foreach ($whitelist as &$ip) {
            // As $ip is a reference, trim leading and trailing whitespace, then store the new value
            // using the reference
            $ip = trim($ip);
        }

        if (in_array($this->input->ip_address(), $whitelist) === false) {
            $this->response([
                    $this->config->item('rest_status_field_name') => false,
                    $this->config->item('rest_message_field_name') => $this->lang->line('text_rest_ip_unauthorized')
                ], self::HTTP_UNAUTHORIZED);
        }
    }

    /**
     * Force logging in by setting the WWW-Authenticate header
     *
     * @access protected
     * @param string $nonce A server-specified data string which should be uniquely generated
     * each time
     * @return void
     */
    protected function _force_login($nonce = '')
    {
        $rest_auth = $this->config->item('rest_auth');
        $rest_realm = $this->config->item('rest_realm');
        if (strtolower($rest_auth) === 'basic') {
            // See http://tools.ietf.org/html/rfc2617#page-5
            header('WWW-Authenticate: Basic realm="' . $rest_realm . '"');
        } elseif (strtolower($rest_auth) === 'digest') {
            // See http://tools.ietf.org/html/rfc2617#page-18
            header(
                'WWW-Authenticate: Digest realm="' . $rest_realm
                . '", qop="auth", nonce="' . $nonce
                . '", opaque="' . md5($rest_realm) . '"');
        }

        // Display an error response
        $this->response([
                $this->config->item('rest_status_field_name') => false,
                $this->config->item('rest_message_field_name') => $this->lang->line('text_rest_unauthorized')
            ], self::HTTP_UNAUTHORIZED);
    }

    /**
     * Updates the log table with the total access time
     *
     * @access protected
     * @author Chris Kacerguis
     * @return bool TRUE log table updated; otherwise, FALSE
     */
    protected function _log_access_time()
    {
        $payload['rtime'] = $this->_end_rtime - $this->_start_rtime;

        return $this->rest->db->update(
                $this->config->item('rest_logs_table'), $payload, [
                'id' => $this->_insert_id
            ]);
    }

    /**
     * Updates the log table with HTTP response code
     *
     * @access protected
     * @author Justin Chen
     * @param $http_code int HTTP status code
     * @return bool TRUE log table updated; otherwise, FALSE
     */
    protected function _log_response_code($http_code)
    {
        $payload['response_code'] = $http_code;

        return $this->rest->db->update(
            $this->config->item('rest_logs_table'), $payload, [
            'id' => $this->_insert_id
        ]);
    }

    /**
     * Check to see if the API key has access to the controller and methods
     *
     * @access protected
     * @return bool TRUE the API key has access; otherwise, FALSE
     */
    protected function _check_access()
    {
        // If we don't want to check access, just return TRUE
        if ($this->config->item('rest_enable_access') === false) {
            return true;
        }

        // Fetch controller based on path and controller name
        $controller = implode(
            '/', [
            $this->router->directory,
            $this->router->class
        ]);

        // Remove any double slashes for safety
        $controller = str_replace('//', '/', $controller);

        // Query the access table and get the number of results
        return $this->rest->db
            ->where('key', $this->rest->key)
            ->where('controller', $controller)
            ->get($this->config->item('rest_access_table'))
            ->num_rows() > 0;
    }

    /**
     * Checks allowed domains, and adds appropriate headers for HTTP access control (CORS)
     *
     * @access protected
     * @return void
     */
    protected function _check_cors()
    {
        // Convert the config items into strings
        $allowed_headers = implode(' ,', $this->config->item('allowed_cors_headers'));
        $allowed_methods = implode(' ,', $this->config->item('allowed_cors_methods'));

        // If we want to allow any domain to access the API
        if ($this->config->item('allow_any_cors_domain') === true) {
            header('Access-Control-Allow-Origin: *');
            header('Access-Control-Allow-Headers: ' . $allowed_headers);
            header('Access-Control-Allow-Methods: ' . $allowed_methods);
        }
        // We're going to allow only certain domains access
        else {
            // Store the HTTP Origin header
            $origin = (isset($_SERVER['HTTP_ORIGIN']) ? $_SERVER['HTTP_ORIGIN'] : '');

            // If the origin domain is in the allowed_cors_origins list, then add the Access Control headers
            if (in_array($origin, $this->config->item('allowed_cors_origins'))) {
                header('Access-Control-Allow-Origin: ' . $origin);
                header('Access-Control-Allow-Headers: ' . $allowed_headers);
                header('Access-Control-Allow-Methods: ' . $allowed_methods);
            }
        }

        // If the request HTTP method is 'OPTIONS', kill the response and send it to the client
        $method = $_SERVER['REQUEST_METHOD'];

        if ($method === 'OPTIONS') {
            die();
        }
    }
}
