/***
    Copyright (C) 2023 J Reece Wilson (a/k/a "Reece"). All rights reserved.

    File: AuProcAddresses.Linux.cpp
    Date: 2023-8-11
    Author: Reece
***/
#include <RuntimeInternal.hpp>
#include <sys/syscall.h>
#include <linux/futex.h>
#include <Time/Time.hpp>
#include <dlfcn.h>

#define AURORA_IS_GLIBC

#if !defined(__NR_close_range)
    #define __NR_close_range 436
#endif

namespace Aurora
{
    static const auto kAioRingMagic = 0xa10a10a1u; 

    void InitLinuxAddresses()
    {
        pgetsockname = getsockname;

    #if defined(RTLD_NEXT)
        p__cxa_throw            = (decltype(p__cxa_throw))dlsym(RTLD_NEXT, "__cxa_throw");
        p_Unwind_RaiseException = (decltype(p_Unwind_RaiseException))dlsym(RTLD_NEXT, "_Unwind_RaiseException");
    #endif

    #if defined(RTLD_DEFAULT)
        if (!p_Unwind_RaiseException)
        {
            p_Unwind_RaiseException = (decltype(p_Unwind_RaiseException))dlsym(RTLD_DEFAULT, "_Unwind_RaiseException");
        }

        if (!p__cxa_throw)
        {
            p__cxa_throw = (decltype(p__cxa_throw))dlsym(RTLD_DEFAULT, "__cxa_throw");
        }

        pgai_error     = (decltype(pgai_error))dlsym(RTLD_DEFAULT, "gai_error");
        pgai_cancel    = (decltype(pgai_cancel))dlsym(RTLD_DEFAULT, "gai_cancel");
        pgetaddrinfo_a = (decltype(pgetaddrinfo_a))dlsym(RTLD_DEFAULT, "getaddrinfo_a");
    #endif
    }

    template <typename... T>
    long syscallFuckYou(T &&... args)
    {
        // sysdeps/unix/sysv/linux/x86_64/syscall.S
        // Fuck Freetards
        long iFuckResult = syscall(AuForward<T &&>(args)...);
    #if defined(AURORA_IS_GLIBC)
        if (iFuckResult == -1 && 
            errno > 0)
        {
            return (0 - errno);
        }
    #else
        // TODO: if defined UNIX has a libc wrapper. why would we assume there's a CRT to begin with?
        errno = (0 - iFuckResult);
    #endif
        return iFuckResult;
        // Imagine going out of your way to define a varadic syscall wrapper that works without any special formatting parameters, 
        // works across all abis, just to fuck it into uselessness by returning -ENOSYS and -1 spuriously.
        // Nooo we cant just have all the != 0 and if (n >= 0) checks pass, we must enforce `error == -1` is true everywhere as a convention!!!
        // People trying to interface with the kernel directly must never know what the kernel actually said!!!
        // Look through all their (GNU) garbage hand written assembly *and* C macros, you'll see its litered with SYSCALL_ERROR_LABEL,
        // because i swear to god it looks like cmpq and jae are the only instructions they know how to use. 
        // Worse, its rationalized as and I quote, 
        //     "Linus said he will make sure the no syscall returns a value in -1 .. -4095 as a valid result so we can safely test with -4095"
        // So these copy/pasted instructions are hard-coding a "linus said so once"-based test, and now Linux-like OSes are forever limited to 4k errors?
        // I guess it's like the other FUTEX issue where every single thead and every single process under Linux is bound to one ABI defined by glib,
        // and the kernels stance on the matter is, I quote "must only be changed if the change is first communicated with the glibc folks."
        // That meaning, it doesn't matter because they're just going to half-ass things together holding hands.
        // Daily reminder, Lin-shit is half-assed HW abstraction layer held together with forced driver source sharing and glibc+freeedesktop hopes and dreams.
        // Fucking retards, I swear
    }

    int pidfd_getfd(int pidfd, int targetfd,
                    unsigned int flags)
    {
        return syscallFuckYou(__NR_pidfd_getfd, pidfd, targetfd, flags);
    }

    int pidfd_open(pid_t pid, unsigned int flags)
    {
        return syscallFuckYou(__NR_pidfd_open, pid, flags);
    }

    long set_robust_list(struct robust_list_head *head, size_t len)
    {
        return syscallFuckYou(__NR_set_robust_list, head, len);
    }

    long get_robust_list(int pid, struct robust_list_head **head_ptr, size_t *len_ptr)
    {
        return syscallFuckYou(__NR_get_robust_list, pid, head_ptr, len_ptr);
    }

    static int futex(uint32_t *uaddr, int futex_op, uint32_t val,
                     const struct timespec *timeout, 
                     uint32_t *uaddr2, uint32_t val3)
    {
        return syscallFuckYou(__NR_futex, uaddr, futex_op, val, timeout, uaddr2, val3);
    }

    int futex_wait(uint32_t *addr, uint32_t expected)
    {
        return futex(addr, FUTEX_WAIT | FUTEX_PRIVATE_FLAG, expected, 0, 0, 0);
    }

    int futex_wait(uint32_t *addr, uint32_t expected, const struct timespec *timeout)
    {
        if (timeout)
        {
            return futex(addr, FUTEX_WAIT_BITSET | FUTEX_PRIVATE_FLAG, expected, timeout, 0, FUTEX_BITSET_MATCH_ANY);
        }
        else
        {
            return futex(addr, FUTEX_WAIT | FUTEX_PRIVATE_FLAG, expected, timeout, 0, 0);
        }
    }

    int futex_wait_shared(uint32_t *addr, uint32_t expected, const struct timespec *timeout)
    {
        if (timeout)
        {
            return futex(addr, FUTEX_WAIT_BITSET, expected, timeout, 0, FUTEX_BITSET_MATCH_ANY);
        }
        else
        {
            return futex(addr, FUTEX_WAIT, expected, timeout, 0, 0);
        }
    }

    int futex_wake(uint32_t *addr, uint32_t nthreads)
    {
        return futex(addr, FUTEX_WAKE | FUTEX_PRIVATE_FLAG, nthreads, 0, 0, 0);
    }

    int futex_wake_shared(uint32_t *addr, uint32_t nthreads)
    {
        return futex(addr, FUTEX_WAKE, nthreads, 0, 0, 0);
    }

    int futex_wait(volatile uint32_t *addr, uint32_t expected)
    {
        return futex((uint32_t *)addr, FUTEX_WAIT | FUTEX_PRIVATE_FLAG, expected, 0, 0, 0);
    }

    int futex_wait(volatile uint32_t *addr, uint32_t expected, const struct timespec *timeout)
    {
        if (timeout)
        {
            return futex((uint32_t *)addr, FUTEX_WAIT_BITSET | FUTEX_PRIVATE_FLAG, expected, timeout, 0, FUTEX_BITSET_MATCH_ANY);
        }
        else
        {
            return futex((uint32_t *)addr, FUTEX_WAIT | FUTEX_PRIVATE_FLAG, expected, timeout, 0, 0);
        }
    }

    int futex_wake(volatile uint32_t *addr, uint32_t nthreads)
    {
        return futex((uint32_t *)addr, FUTEX_WAKE | FUTEX_PRIVATE_FLAG, nthreads, 0, 0, 0);
    }

    int io_setup(unsigned nr, aio_context_t *ctxp)
    {
        return syscallFuckYou(__NR_io_setup, nr, ctxp);
    }

    int io_destroy(aio_context_t ctx)
    {
        return syscallFuckYou(__NR_io_destroy, ctx);
    }

    int io_submit(aio_context_t ctx, long nr, struct iocb **iocbpp)
    {
        return syscallFuckYou(__NR_io_submit, ctx, nr, iocbpp);
    }

    #if 0
    int io_getevents(aio_context_t ctx, long min_nr, long max_nr,
                     struct io_event *events,
                     struct timespec *timeout)
    {
        return syscall(__NR_io_getevents, ctx, min_nr, max_nr, events, timeout);
    }
    #endif

    struct aio_ring
    {
        unsigned id;
        unsigned nr;
        unsigned head;
        unsigned tail;

        unsigned magic;
        unsigned compat_features;
        unsigned incompat_features;
        unsigned header_length;

        struct io_event events[0];
    };

    int io_getevents(aio_context_t ctx,
                     long min_nr, long max_nr,
                     struct io_event *events,
                     struct timespec *timeout,
                     bool bStrictUserspaceOnly)
    {
        int i {};

        auto pRing = (struct aio_ring *)ctx;
        
        if (!pRing ||
            pRing->magic != kAioRingMagic)
        {
            goto do_syscall;
        }

        while (i < max_nr)
        {
            auto head = AuAtomicLoad(&pRing->head);
            if (head == pRing->tail) 
            {
                break;
            }

            events[i++] = pRing->events[head];

            auto nextHead = (head + 1) % pRing->nr;
            if (AuAtomicCompareExchange(&pRing->head,
                                        nextHead,
                                        head) != head)
            {
                i--;
            }
        }

        if (!i &&
            timeout &&
            !timeout->tv_sec &&
            !timeout->tv_nsec)
        {
            return 0;
        }

        if (i &&
            i >= min_nr)
        {
            return i;
        }

        if (bStrictUserspaceOnly)
        {
            return i;
        }

    do_syscall:
        int iKernelCount {};
        if ((iKernelCount = syscallFuckYou(__NR_io_getevents,
                                           ctx, min_nr - i,
                                           max_nr - i,
                                           &events[i], timeout)) > 0)
        {
            return i + iKernelCount;
        }
        else if (i)
        {
            return i;
        }
        else
        {
            return iKernelCount;
        }
    }

    int io_cancel(aio_context_t ctx_id, struct iocb *iocb,
                  struct io_event *result)
    {
        return syscallFuckYou(__NR_io_cancel, ctx_id, iocb, result);
    }

    ssize_t sys_getrandom(void *pBuffer, size_t uLength)
    {
        static AuUInt32 gShouldNotGetRand {};
        ssize_t ret {};

        if (gShouldNotGetRand)
        {
            return -ENOSYS;
        }

        ret = syscallFuckYou(__NR_getrandom, pBuffer, uLength, 1);
        if (ret == -ENOSYS)
        {
            gShouldNotGetRand = 1;
        }
        
        return ret;
    }

    int close_range(unsigned int first, unsigned int last,
                    unsigned int flags)
    {
        
        auto &platform = AuSwInfo::GetPlatformInfo();
        if (platform.uKernelMajor > 5 ||
            (platform.uKernelMajor == 5 && platform.uKernelMajor >= 9))
        {
            return syscallFuckYou(__NR_close_range, first, last, flags);
        }
        else
        {
            return -ENOSYS;
        }        
    }
    
    bool SysNativeWaitOnAddressFutexSupported()
    {
        return true;
    }

    bool SysWaitOnAddressNoTimed(const void *pTargetAddress,
                                 const void *pCompareAddress,
                                 AuUInt8 uWordSize)
    {
        int ret {};

    #if defined(AU_CPU_ENDIAN_BIG)
        if (uWordSize == 8)
        {
            pTargetAddress = AuReinterpretCast<const char *>(pTargetAddress) + 4;
            pCompareAddress = AuReinterpretCast<const char *>(pCompareAddress) + 4;
        }
    #endif

        auto uCurrent = *(AuUInt32 *)pCompareAddress;

        do
        {
            ret = futex_wait((AuUInt32 *)pTargetAddress, uCurrent, nullptr);

            if (ret == 0)
            {
                continue;
            }

            if (ret == -EAGAIN)
            {
                continue;
            }

            if (ret == -ETIMEDOUT)
            {
                return false;
            }
        }
        while (ret == -EINTR);

        return AuMemcmp(pCompareAddress, pTargetAddress, uWordSize) != 0;
    }

    bool SysWaitOnAddressTimed(const void *pTargetAddress,
                               const void *pCompareAddress,
                               AuUInt8 uWordSize,
                               AuUInt64 uAbsTimeSteadyClock,
                               AuUInt64 uRelativeNanoseconds,
                               AuOptional<AuUInt64> uAbsTimeAltClock,
                               bool bSpun)
    {
        int ret {};

    #if defined(AU_CPU_ENDIAN_BIG)
        if (uWordSize == 8)
        {
            pTargetAddress = AuReinterpretCast<const char *>(pTargetAddress) + 4;
            pCompareAddress = AuReinterpretCast<const char *>(pCompareAddress) + 4;
        }
    #endif

        auto uCurrent = *(AuUInt32 *)pCompareAddress;

        struct timespec tspec;
        Time::monoabsns2ts(&tspec, uAbsTimeAltClock ? uAbsTimeAltClock.value() : uAbsTimeSteadyClock);

        do
        {
            ret = futex_wait((AuUInt32 *)pTargetAddress, uCurrent, &tspec);

            if (ret == 0)
            {
                continue;
            }

            if (ret == -EAGAIN)
            {
                continue;
            }

            if (ret == -ETIMEDOUT)
            {
                return false;
            }
        }
        while (ret == -EINTR);

        return AuMemcmp(pCompareAddress, pTargetAddress, uWordSize) != 0;
    }

    void SysWakeNOnAddress(const void *pAddress,
                           AuUInt32 dwCount)
    {
        futex_wake((AuUInt32 *)pAddress, dwCount);
    }

    void SysWakeAllOnAddress(const void *pAddress)
    {
        futex_wake((AuUInt32 *)pAddress, INT_MAX);
    }

    void SysWakeOneOnAddress(const void *pAddress)
    {
        futex_wake((AuUInt32 *)pAddress, 1);
    }
}