/***
    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 <sys/random.h>

namespace Aurora
{
    #define read_barrier() __asm__ __volatile__("lfence" ::: "memory")

    static const auto kAioRingMagic = 0xa10a10a1u; 

    void InitLinuxAddresses()
    {
    
    }

    int pidfd_getfd(int pidfd, int targetfd,
                    unsigned int flags)
    {
        return syscall(SYS_pidfd_getfd, pidfd, targetfd, flags);
    }

    int pidfd_open(pid_t pid, unsigned int flags)
    {
        return syscall(SYS_pidfd_open, pid, flags);
    }

    long set_robust_list(struct robust_list_head *head, size_t len)
    {
        return syscall(SYS_set_robust_list, head, len);
    }

    long get_robust_list(int pid, struct robust_list_head **head_ptr, size_t *len_ptr)
    {
        return syscall(SYS_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 syscall(SYS_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 syscall(__NR_io_setup, nr, ctxp);
    }

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

    int io_submit(aio_context_t ctx, long nr, struct iocb **iocbpp)
    {
        return syscall(__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)
    {
        int i {};

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

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

            events[i++] = pRing->events[head];
            read_barrier();
            pRing->head = (head + 1) % pRing->nr;
        }

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

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

    do_syscall:
        return syscall(__NR_io_getevents,
                       ctx, min_nr - i,
                       max_nr - i,
                       &events[i], timeout) + i;
    }

    int io_cancel(aio_context_t ctx_id, struct iocb *iocb,
                         struct io_event *result)
    {
        return syscall(SYS_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 = syscall(SYS_getrandom, pBuffer, uLength, 1);
        if (ret == ENOSYS)
        {
            gShouldNotGetRand = 1;
        }
        
        return ret;
    }
}