/*
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * Copyright 2010-2017 Danny Robson <danny@nerdcruft.net>
 */

#ifndef __DEBUG_HPP
#define __DEBUG_HPP

//#include "maths.hpp" // XXX: See notes at the end of file for maths.hpp inclusion
#include <cmath>
#include <algorithm>
#include <stdexcept>
#include <string>
#include <thread>
#include <iostream>


///////////////////////////////////////////////////////////////////////////////
// it is fractionally easier to define a constexpr variable which can be used
// in constexpr-if to enable/disable some codepaths rather than deal with
// macros in some scenarios. eg, templates are complicated enough without
// (more) macros.
#if !defined(NDEBUG)
    constexpr bool debug_enabled = true;
    constexpr bool assertions_enabled = true;
#else
    constexpr bool debug_enabled = false;
    constexpr bool assertions_enabled = false;
#endif


///----------------------------------------------------------------------------
/// enable some code only if assertions are enabled
///
/// explicitly does not use constexpr if to remove the code as some paths may
/// refer to variables which do not always exist, and current compiler
/// implementations are a little picky here.
#ifndef NDEBUG
#define DEBUG_ONLY(X) do { X; } while (0)
#else
#define DEBUG_ONLY(X) do {  ; } while (0)
#endif

//#define DEBUG_ONLY(X) do { if constexpr (debug_enabled) { X } } while (0)


///////////////////////////////////////////////////////////////////////////////
#define EXIT_XSUCCESS        0
#define EXIT_XSKIP          77
#define EXIT_XHARD_ERROR    99


///////////////////////////////////////////////////////////////////////////////
#define TRACE {                                                                     \
    DEBUG_ONLY (                                                                    \
        std::clog << "tid: " << std::this_thread::get_id () << "; " << __FILE__ << ":" << __func__ << ":" << __LINE__ << std::endl;   \
    );                                                                              \
}


#define WARN(C) do {                                                                                \
    DEBUG_ONLY (                                                                                    \
        if (C) {                                                                                    \
            std::cerr << __FILE__ << ":" << __func__ << ":" << __LINE__ << ", " << #C << std::endl; \
        }                                                                                           \
    );                                                                                              \
} while (0)


#define WARN_RETURN(CONDITION,VALUE) do {                           \
    if (const auto& __warn_return = (CONDITION); !!__warn_return) { \
        if constexpr (debug_enabled) {                              \
            std::clog << __FILE__ << ':'                            \
                      << __LINE__ << ':'                            \
                      << __PRETTY_FUNCTION__ << "; "                \
                      << #CONDITION << '\n';                        \
            breakpoint ();                                          \
        }                                                           \
                                                                    \
        return (VALUE);                                             \
    }                                                               \
} while (0)


#define RETURN_UNLESS(VALUE,CONDITION) do {                             \
    if (const auto &__return_unless = (CONDITION); !__return_unless) {  \
        if constexpr (debug_enabled) {                                  \
            std::clog << __FILE__ << ':'                                \
                      << __LINE__ << ':'                                \
                      << __PRETTY_FUNCTION__ << "; "                    \
                      << #CONDITION << '\n';                            \
            breakpoint ();                                              \
        }                                                               \
                                                                        \
        return (VALUE);                                                 \
    }                                                                   \
} while (0)


///////////////////////////////////////////////////////////////////////////////
#define _CHECK_PANIC(FMT,...) do {                          \
    panic ("%s:%s:%i:%s\n" FMT,                             \
           PACKAGE, __FILE__, __LINE__, __func__,           \
           __VA_ARGS__);                                    \
} while(0)


///////////////////////////////////////////////////////////////////////////////
#define CHECK(C) do {   \
    DEBUG_ONLY (        \
        if (!(C))       \
            panic (#C); \
    );                  \
} while (0)


///////////////////////////////////////////////////////////////////////////////
#define CHECK_SANITY(A) \
::util::debug::scoped_sanity PASTE(__scoped_sanity_checker,__LINE__) (A); \
(void)PASTE(__scoped_sanity_checker,__LINE__);


///////////////////////////////////////////////////////////////////////////////
#define CHECK_EQ(A,B) do {                                  \
    DEBUG_ONLY (                                            \
        const auto &__a = (A);                              \
        const auto &__b = (B);                              \
                                                            \
        if (!::util::almost_equal (__a, __b)) {             \
            _CHECK_PANIC("expected equality\n"              \
                         "__a: %s is %!\n"                  \
                         "__b: %s is %!\n",                 \
                         #A, __a,                           \
                         #B, __b);                          \
        }                                                   \
    );                                                      \
} while (0)


///////////////////////////////////////////////////////////////////////////////
#define CHECK_LT(A,B) do {                                  \
    DEBUG_ONLY (                                            \
        const auto &__a = (A);                              \
        const auto &__b = (B);                              \
                                                            \
        if (__a >= __b) {                                   \
            _CHECK_PANIC("expected less than\n"             \
                          "__a: %s is %!\n"                 \
                          "__b: %s is %!\n",                \
                          #A, __a,                          \
                          #B, __b);                         \
        };                                                  \
    );                                                      \
} while (0)


///////////////////////////////////////////////////////////////////////////////
#define CHECK_LE(A,B) do {                                  \
    DEBUG_ONLY (                                            \
        const auto &__a = (A);                              \
        const auto &__b = (B);                              \
                                                            \
        if (__a > __b) {                                    \
            _CHECK_PANIC("expected less than or equal\n"    \
                         "__a: %s is %!\n"                  \
                         "__b: %s is %!\n",                 \
                         #A, __a,                           \
                         #B, __b);                          \
        }                                                   \
    );                                                      \
} while (0)


///////////////////////////////////////////////////////////////////////////////
#define CHECK_GT(A,B) do {                                  \
    DEBUG_ONLY (                                            \
        const auto &__a = (A);                              \
        const auto &__b = (B);                              \
                                                            \
        if (__a <= __b) {                                   \
            _CHECK_PANIC ("expected greater than\n"         \
                          "__a: %s is %!\n"                 \
                          "__b: %s is %!\n",                \
                          #A, __a,                          \
                          #B, __b);                         \
        }                                                   \
    );                                                      \
} while (0)


///////////////////////////////////////////////////////////////////////////////
#define CHECK_GE(A,B) do {                                  \
    DEBUG_ONLY (                                            \
        const auto &__a = (A);                              \
        const auto &__b = (B);                              \
                                                            \
        if (__a < __b) {                                    \
            _CHECK_PANIC ("expected greater or equal\n"     \
                          "__a: %s is %!\n"                 \
                          "__b: %s is %!\n",                \
                          #A, __a,                          \
                          #B, __b);                         \
        };                                                  \
    );                                                      \
} while (0)


///////////////////////////////////////////////////////////////////////////////
#define CHECK_LIMIT(V,L,H) do {                             \
    DEBUG_ONLY (                                            \
        const auto &__v = (V);                              \
        const auto &__l = (L);                              \
        const auto &__h = (H);                              \
                                                            \
        if (__v < __l || __v > __h) {                       \
            _CHECK_PANIC ("expected limit\n"                \
                          "__l: %s is %!\n"                 \
                          "__h: %s is %!\n"                 \
                          "__v: %s is %!\n",                \
                          #L, __l,                          \
                          #H, __h,                          \
                          #V, __v);                         \
        };                                                  \
    );                                                      \
} while (0)

///////////////////////////////////////////////////////////////////////////////
#define CHECK_NEQ(A,B) do {                                 \
    DEBUG_ONLY(                                             \
        const auto &__a = (A);                              \
        const auto &__b = (B);                              \
                                                            \
        if (::util::almost_equal (__a, __b)) {              \
            _CHECK_PANIC ("expected inequality\n"           \
                          "__a: %s is %!\n"                 \
                          "__b: %s is %!\n",                \
                          #A, __a,                          \
                          #B, __b);                         \
        };                                                  \
    );                                                      \
} while (0)


///////////////////////////////////////////////////////////////////////////////
#define CHECK_ZERO(A) do {                                  \
    DEBUG_ONLY (                                            \
        const auto &__a = (A);                              \
                                                            \
        if (!::util::almost_zero (__a)) {                   \
            _CHECK_PANIC ("expected zero\n"                 \
                          "__a: %s is %!\n"                 \
                          #A, __a);                         \
        };                                                  \
    );                                                      \
} while (0)


///////////////////////////////////////////////////////////////////////////////
#define CHECK_NEZ(A) do {                                   \
    DEBUG_ONLY (                                            \
        const auto &__a = (A);                              \
                                                            \
        if (::util::exactly_zero (__a))                     \
            _CHECK_PANIC ("expected non-zero\n"             \
                          "__a: %s is %!",                  \
                          #A, __a);                         \
    );                                                      \
} while (0)


///////////////////////////////////////////////////////////////////////////////
#define CHECK_MOD(V,M) do {                                         \
    DEBUG_ONLY (                                                    \
        const auto &__check_mod_v = (V);                            \
        const auto &__check_mod_m = (M);                            \
                                                                    \
        if (!::util::exactly_zero (__check_mod_v % __check_mod_m))  \
            _CHECK_PANIC ("expected zero modulus\n"                 \
                          "__v: %s is %!\n"                         \
                          "__m: %s is %!",                          \
                          #V, __check_mod_v,                        \
                          #M, __check_mod_m);                       \
    );                                                              \
} while (0)


///////////////////////////////////////////////////////////////////////////////
#if defined(ENABLE_DEBUGGING)
#define CHECK_ENUM(C, ...) do {                         \
    const auto &__c = (C);                              \
    const auto &__e = { __VA_ARGS__ };                  \
                                                        \
    if (std::find (std::cbegin (__e),                   \
                   std::cend   (__e),                   \
                  __c) == std::end (__e)) {             \
        _CHECK_PANIC("expect enum\n"                    \
                     "__c: %s is %!",                   \
                     #C, __c);                          \
    }                                                   \
} while (0)
#else
#define CHECK_ENUM(C,...)
#endif


#if !defined(NDEBUG)
    #define CHECK_FINITE(V) do {                    \
        const auto &__v = (V);                      \
        if (!std::isfinite (__v)) {                 \
            _CHECK_PANIC ("expected finite value\n" \
                          "__v: %! is %!",          \
                          #V, __v);                 \
        }                                           \
    } while (0)
#else
#define CHECK_FINITE(V,...)
#endif




///////////////////////////////////////////////////////////////////////////////
#define CHECK_THROWS(E,C) do {                              \
    DEBUG_ONLY (                                            \
        bool caught = false;                                \
                                                            \
        try                                                 \
            { C; }                                          \
        catch (E)                                           \
            { caught = true; }                              \
                                                            \
        if (!caught)                                        \
            _CHECK_PANIC ("expected exception: %s", #E);    \
    );                                                      \
} while (0)


///////////////////////////////////////////////////////////////////////////////
#define CHECK_NOTHROW(C) do {                               \
    DEBUG_ONLY (                                            \
        try {                                               \
            C;                                              \
        } catch (const std::exception &e) {                 \
            _CHECK_PANIC ("unexpected exception: %s",       \
                          e.what ());                       \
        } catch (...) {                                     \
            _CHECK_PANIC ("unexpected exception: %s",       \
                          "unknown");                       \
        }                                                   \
    );                                                      \
} while (0)


///////////////////////////////////////////////////////////////////////////////
/// make the compiler think a particular variable may now be aliased somewhere.
///
/// useful for preventing optimisations eliding a variable.
///
/// stolen from Chandler Carruth's 2015 talk: "Tuning C++".
namespace util::debug {
    template <class T>
    inline T*
    escape (T *t)
    {
        asm volatile ("": : "g"(t): "memory");
        return t;
    }


    template <class T>
    inline const T*
    escape (const T *t)
    {
        asm volatile ("": : "g"(t): "memory");
        return t;
    }


    template <class T>
    inline const T&
    escape (const T &t)
    {
        return *escape (&t);
    }


    template <class T>
    inline T&
    escape (T &t)
    {
        return *escape (&t);
    }


    template <typename T, typename ...Args>
    inline void
    escape (T t, Args ...args)
    {
        escape (t);
        escape (args...);
    }
}


///////////////////////////////////////////////////////////////////////////////
/// force the compiler to conceptually dirty the global memory space.
///
/// stolen from Chandler Carruth's 2015 talk: "Tuning C++".
namespace util::debug {
    inline void
    clobber (void)
    {
        asm volatile ("": : : "memory");
    }
}


void breakpoint (void);


///////////////////////////////////////////////////////////////////////////////
#include "log.hpp"
#include "backtrace.hpp"


namespace util::debug::detail {
    void panic [[noreturn]] (const char *msg);

    template <typename ...Args, size_t N>
    void panic [[noreturn]] (const char (&fmt)[N], const Args& ...args)
    {
        LOG_EMERGENCY (fmt, args...);
        LOG_EMERGENCY ("%!", ::debug::backtrace ());
        breakpoint ();
        abort ();
    }

    void not_implemented [[noreturn]] (const char *msg);
    void unreachable [[noreturn]] (const char *msg);
}



constexpr void
panic [[noreturn]] (const char *msg)
{
    ! msg
    ? panic (msg)
    : util::debug::detail::panic (msg);
}


template <typename ...Args, size_t N>
constexpr void
panic [[noreturn]] (const char (&fmt)[N], const Args&... args)
{
    util::debug::detail::panic (fmt, args...);
}


///////////////////////////////////////////////////////////////////////////////
// not_implemented/unreachable/panic must be callable from constexpr contexts.
// but they rely on functions that aren't constexpr to perform the controlled
// abort.
//
// we can work around this in the same way assert does by using a conditional
// that hides an extern function that actually does the work. as we can't
// utilise external state this has to be the message variable which will
// assume isn't ever null.
//
// to avoid warnings about a return from a noreturn function we recurse into
// ourself in the alternate case. this branch shouldn't ever be taken, but if
// it is we were planning on crashing anyway...

///////////////////////////////////////////////////////////////////////////////
constexpr void
not_implemented [[noreturn]] (const char *msg)
{
    ! msg
    ? not_implemented (msg)
    : util::debug::detail::not_implemented (msg);
}


constexpr void
not_implemented [[noreturn]] (void)
{
    not_implemented ("operation not implemented");
}


constexpr void unimplemented [[noreturn]] (void) { not_implemented (); }


constexpr void unimplemented [[noreturn]] (const char *msg) { not_implemented (msg); }


///////////////////////////////////////////////////////////////////////////////
constexpr void
unreachable [[noreturn]] (const char *msg)
{
    ! msg
    ? unreachable (msg)
    : util::debug::detail::unreachable (msg);
}


constexpr void
unreachable [[noreturn]] (void)
{
    unreachable ("unreachable code executed");
}


///////////////////////////////////////////////////////////////////////////////
/// report a fatal error induced by an unhandled value, especially in switch
/// statements. will almost invariably abort the application.
template <typename T>
constexpr void
unhandled [[noreturn]] (T &&t) noexcept
{
    panic ("unhandled value %!", std::forward<T> (t));
}


///////////////////////////////////////////////////////////////////////////////
void warn (void);
void warn (const std::string&);
void warn (const char *);


///////////////////////////////////////////////////////////////////////////////
void await_debugger (void);
void prepare_debugger (void);

void force_console (void);

///////////////////////////////////////////////////////////////////////////////
void enable_fpe (void);
void disable_fpe (void);


///////////////////////////////////////////////////////////////////////////////
namespace util::debug {
    void init (void);


    ///////////////////////////////////////////////////////////////////////////
    // returns true if an instance of type `T' appears to be in a valid state.
    //
    // written as a struct rather than a function so that behaviour may be
    // arbitrarily specialised. all users are free to specialise this struct
    // with an user types.
    //
    // all specialisations must be safe to call on arbitrary data without
    // exceptions or faults as this mechanism is used to control some
    // debugging paths which themselves are the configuration points for
    // throwing/logging/etc behaviour.
    template <typename T>
    struct validator {
        static bool is_valid (const T&) noexcept;
    };


    //-------------------------------------------------------------------------
    template <typename T>
    bool is_valid (const T &t) noexcept
    {
        return validator<T>::is_valid (t);
    }


    //-------------------------------------------------------------------------
    // forwarding validator from a pointer type to a reference type.
    //
    // null pointers are assumed to be invalid
    template <typename T>
    struct validator<T*> {
        static bool is_valid (const T *val) noexcept
        {
            return val && ::util::debug::is_valid (*val);
        }
    };


    ///////////////////////////////////////////////////////////////////////////
    // asserts that an instance of type `T' is in a valid state.
    //
    // behaviour will be controlled by NDEBUG and other assertion machinery and
    // so may be optimised out entirely in optimised builds.
    template <typename T>
    void sanity (const T &t)
    {
        (void)t;
        CHECK (is_valid (t));
    }


    //-------------------------------------------------------------------------
    template <
        template<typename...> class T,
        typename ...Args
    >
    void sanity (const T<Args...> &t)
    {
        (void)t;
        CHECK (is_valid (t));
    }


    template <typename ValueT>
    class scoped_sanity {
    public:
        scoped_sanity (ValueT &_value):
            m_value (_value)
        {
            sanity (m_value);
        }

        ~scoped_sanity ()
        {
            sanity (m_value);
        }

    private:
        const ValueT& m_value;
    };
};


///////////////////////////////////////////////////////////////////////////////
// XXX: maths needs to be included so that CHECK_EQ/NEQ can call almost_equal,
// but maths.hpp might be using CHECK_ macros so we must include maths.hpp
// after we define the CHECK_ macros so the preprocessor can resolve them.
#include "maths.hpp"


#endif // __DEBUG_HPP