    // Copyright (C) 2003  Davis E. King (davis@dlib.net)
    // License: Boost Software License   See LICENSE.txt for the full license.
    #ifndef DLIB_ERROr_
    #define DLIB_ERROr_

    #include <string>
    #include <new>          // for std::bad_alloc
    #include <iostream>
    #include <cassert>
    #include <cstdlib>
    #include <exception>

    // -------------------------------
    // ------ exception classes ------
    // -------------------------------

    namespace dlib
    {

    // ----------------------------------------------------------------------------------------

        enum error_type
        {
            EPORT_IN_USE,
            ETIMEOUT,
            ECONNECTION,
            ELISTENER,
            ERESOLVE,
            EMONITOR,
            ECREATE_THREAD,
            ECREATE_MUTEX,
            ECREATE_SIGNALER,
            EUNSPECIFIED,
            EGENERAL_TYPE1,
            EGENERAL_TYPE2,
            EGENERAL_TYPE3,
            EINVALID_OPTION,
            ETOO_FEW_ARGS,
            ETOO_MANY_ARGS,
            ESOCKET,
            ETHREAD,
            EGUI,
            EFATAL,
            EBROKEN_ASSERT,
            EIMAGE_LOAD,
            EDIR_CREATE,
            EINCOMPATIBLE_OPTIONS,
            EMISSING_REQUIRED_OPTION,
            EINVALID_OPTION_ARG,
            EMULTIPLE_OCCURANCES,
            ECONFIG_READER,
            EIMAGE_SAVE,
            ECAST_TO_STRING,
            ESTRING_CAST,
            EUTF8_TO_UTF32,
            EOPTION_PARSE
        };

    // ----------------------------------------------------------------------------------------

        // the base exception class
        class error : public std::exception
        {
            /*!
                WHAT THIS OBJECT REPRESENTS
                    This is the base exception class for the dlib library.  i.e. all
                    exceptions in this library inherit from this class.
            !*/

        public:
            error(
                error_type t,
                const std::string& a
            ): info(a), type(t) {}
            /*!
                ensures
                    - #type == t
                    - #info == a
            !*/

            error(
                error_type t
            ): type(t) {}
            /*!
                ensures
                    - #type == t
                    - #info == ""
            !*/

            error(
                const std::string& a
            ): info(a), type(EUNSPECIFIED) {}
            /*!
                ensures
                    - #type == EUNSPECIFIED
                    - #info == a
            !*/

            error(
            ): type(EUNSPECIFIED) {}
            /*!
                ensures
                    - #type == EUNSPECIFIED
                    - #info == ""
            !*/

            virtual ~error(
            ) throw() {}
            /*!
                ensures
                    - does nothing
            !*/

            const char* what(
            ) const throw()
            /*!
                ensures
                    - if (info.size() != 0) then
                        - returns info.c_str()
                    - else
                        - returns type_to_string(type)
            !*/
            {
                if (info.size() > 0)
                    return info.c_str();
                else
                    return type_to_string();
            }

            const char* type_to_string (
            ) const throw()
            /*!
                ensures
                    - returns a string that names the contents of the type member.
            !*/
            {
                if ( type == EPORT_IN_USE) return "EPORT_IN_USE";
                else if ( type == ETIMEOUT) return "ETIMEOUT";
                else if ( type == ECONNECTION) return "ECONNECTION";
                else if ( type == ELISTENER) return "ELISTENER";
                else if ( type == ERESOLVE) return "ERESOLVE";
                else if ( type == EMONITOR) return "EMONITOR";
                else if ( type == ECREATE_THREAD) return "ECREATE_THREAD";
                else if ( type == ECREATE_MUTEX) return "ECREATE_MUTEX";
                else if ( type == ECREATE_SIGNALER) return "ECREATE_SIGNALER";
                else if ( type == EUNSPECIFIED) return "EUNSPECIFIED";
                else if ( type == EGENERAL_TYPE1) return "EGENERAL_TYPE1";
                else if ( type == EGENERAL_TYPE2) return "EGENERAL_TYPE2";
                else if ( type == EGENERAL_TYPE3) return "EGENERAL_TYPE3";
                else if ( type == EINVALID_OPTION) return "EINVALID_OPTION";
                else if ( type == ETOO_FEW_ARGS) return "ETOO_FEW_ARGS";
                else if ( type == ETOO_MANY_ARGS) return "ETOO_MANY_ARGS";
                else if ( type == ESOCKET) return "ESOCKET";
                else if ( type == ETHREAD) return "ETHREAD";
                else if ( type == EGUI) return "EGUI";
                else if ( type == EFATAL) return "EFATAL";
                else if ( type == EBROKEN_ASSERT) return "EBROKEN_ASSERT";
                else if ( type == EIMAGE_LOAD) return "EIMAGE_LOAD";
                else if ( type == EDIR_CREATE) return "EDIR_CREATE";
                else if ( type == EINCOMPATIBLE_OPTIONS) return "EINCOMPATIBLE_OPTIONS";
                else if ( type == EMISSING_REQUIRED_OPTION) return "EMISSING_REQUIRED_OPTION";
                else if ( type == EINVALID_OPTION_ARG) return "EINVALID_OPTION_ARG";
                else if ( type == EMULTIPLE_OCCURANCES) return "EMULTIPLE_OCCURANCES";
                else if ( type == ECONFIG_READER) return "ECONFIG_READER";
                else if ( type == EIMAGE_SAVE) return "EIMAGE_SAVE";
                else if ( type == ECAST_TO_STRING) return "ECAST_TO_STRING";
                else if ( type == ESTRING_CAST) return "ESTRING_CAST";
                else if ( type == EUTF8_TO_UTF32) return "EUTF8_TO_UTF32";
                else if ( type == EOPTION_PARSE) return "EOPTION_PARSE";
                else return "undefined error type";
            }

            const std::string info;  // info about the error
            const error_type type; // the type of the error

        private:
            const error& operator=(const error&);
        };

    // ----------------------------------------------------------------------------------------

        class fatal_error : public error
        {
            /*!
                WHAT THIS OBJECT REPRESENTS
                    As the name says, this object represents some kind of fatal error.
                    That is, it represents an unrecoverable error and any program that
                    throws this exception is, by definition, buggy and needs to be fixed.

                    Note that a fatal_error exception can only be thrown once.  The second
                    time an application attempts to construct a fatal_error it will be
                    immediately aborted and an error message will be printed to std::cerr.
                    The reason for this is because the first fatal_error was apparently ignored
                    so the second fatal_error is going to make itself impossible to ignore
                    by calling abort.  The lesson here is that you should not try to ignore
                    fatal errors.

                    This is also the exception thrown by the DLIB_ASSERT and DLIB_CASSERT macros.
            !*/

        public:
            fatal_error(
                error_type t,
                const std::string& a
            ): error(t,a) {check_for_previous_fatal_errors();}
            /*!
                ensures
                    - #type == t
                    - #info == a
            !*/

            fatal_error(
                error_type t
            ): error(t) {check_for_previous_fatal_errors();}
            /*!
                ensures
                    - #type == t
                    - #info == ""
            !*/

            fatal_error(
                const std::string& a
            ): error(EFATAL,a) {check_for_previous_fatal_errors();}
            /*!
                ensures
                    - #type == EFATAL
                    - #info == a
            !*/

            fatal_error(
            ): error(EFATAL) {check_for_previous_fatal_errors();}
            /*!
                ensures
                    - #type == EFATAL
                    - #info == ""
            !*/

        private:

            static inline char* message ()
            {
                static char buf[2000];
                buf[1999] = '\0'; // just to be extra safe
                return buf;
            }

            static inline void dlib_fatal_error_terminate (
            )
            {
                std::cerr << "\n**************************** FATAL ERROR DETECTED ****************************";
                std::cerr << message() << std::endl;
                std::cerr << "******************************************************************************\n" << std::endl;
            }

            void check_for_previous_fatal_errors()
            {
                static bool is_first_fatal_error = true;
                if (is_first_fatal_error == false)
                {
                    std::cerr << "\n\n ************************** FATAL ERROR DETECTED ************************** " << std::endl;
                    std::cerr << " ************************** FATAL ERROR DETECTED ************************** " << std::endl;
                    std::cerr << " ************************** FATAL ERROR DETECTED ************************** \n" << std::endl;
                    std::cerr << "Two fatal errors have been detected, the first was inappropriately ignored. \n"
                              << "To prevent further fatal errors from being ignored this application will be \n"
                              << "terminated immediately and you should go fix this buggy program.\n\n"
                              << "The error message from this fatal error was:\n" << this->what() << "\n\n" << std::endl;
                    using namespace std;
                    assert(false);
                    abort();
                }
                else
                {
                    // copy the message into the fixed message buffer so that it can be recalled by dlib_fatal_error_terminate
                    // if needed.
                    char* msg = message();
                    unsigned long i;
                    for (i = 0; i < 2000-1 && i < this->info.size(); ++i)
                        msg[i] = info[i];
                    msg[i] = '\0';

                    // set this termination handler so that if the user doesn't catch this dlib::fatal_error that is being
                    // thrown then it will eventually be printed to standard error
                    std::set_terminate(&dlib_fatal_error_terminate);
                }
                is_first_fatal_error = false;
            }
        };

    // ----------------------------------------------------------------------------------------

        class gui_error : public error
        {
        public:
            gui_error(
                error_type t,
                const std::string& a
            ): error(t,a) {}
            /*!
                ensures
                    - #type == t
                    - #info == a
            !*/

            gui_error(
                error_type t
            ): error(t) {}
            /*!
                ensures
                    - #type == t
                    - #info == ""
            !*/

            gui_error(
                const std::string& a
            ): error(EGUI,a) {}
            /*!
                ensures
                    - #type == EGUI
                    - #info == a
            !*/

            gui_error(
            ): error(EGUI) {}
            /*!
                ensures
                    - #type == EGUI
                    - #info == ""
            !*/
        };

    // ----------------------------------------------------------------------------------------

        class socket_error : public error
        {
        public:
            socket_error(
                error_type t,
                const std::string& a
            ): error(t,a) {}
            /*!
                ensures
                    - #type == t
                    - #info == a
            !*/

            socket_error(
                error_type t
            ): error(t) {}
            /*!
                ensures
                    - #type == t
                    - #info == ""
            !*/

            socket_error(
                const std::string& a
            ): error(ESOCKET,a) {}
            /*!
                ensures
                    - #type == ESOCKET
                    - #info == a
            !*/

            socket_error(
            ): error(ESOCKET) {}
            /*!
                ensures
                    - #type == ESOCKET
                    - #info == ""
            !*/
        };

    // ----------------------------------------------------------------------------------------

        class thread_error : public error
        {
        public:
            thread_error(
                error_type t,
                const std::string& a
            ): error(t,a) {}
            /*!
                ensures
                    - #type == t
                    - #info == a
            !*/

            thread_error(
                error_type t
            ): error(t) {}
            /*!
                ensures
                    - #type == t
                    - #info == ""
            !*/

            thread_error(
                const std::string& a
            ): error(ETHREAD,a) {}
            /*!
                ensures
                    - #type == ETHREAD
                    - #info == a
            !*/

            thread_error(
            ): error(ETHREAD) {}
            /*!
                ensures
                    - #type == ETHREAD
                    - #info == ""
            !*/
        };

    // ----------------------------------------------------------------------------------------

    }

    #endif // DLIB_ERROr_