#include <AK/Assertions.h>
#include <AK/Atomic.h>
#include <AK/StdLibExtras.h>
#include <Kernel/Syscall.h>
#include <limits.h>
#include <pthread.h>
#include <stdio.h>
#include <sys/mman.h>
#include <unistd.h>

#define PTHREAD_DEBUG

namespace {
using PthreadAttrImpl = Syscall::SC_create_thread_params;
} // end anonymous namespace

constexpr size_t required_stack_alignment = 4 * MB;
constexpr size_t highest_reasonable_guard_size = 32 * PAGE_SIZE;
constexpr size_t highest_reasonable_stack_size = 8 * MB; // That's the default in Ubuntu?

extern "C" {

static int create_thread(void* (*entry)(void*), void* argument, void* stack)
{
    int rc = syscall(SC_create_thread, entry, argument, stack);
    __RETURN_WITH_ERRNO(rc, rc, -1);
}

static void exit_thread(void* code)
{
    syscall(SC_exit_thread, code);
    ASSERT_NOT_REACHED();
}

int pthread_create(pthread_t* thread, pthread_attr_t* attributes, void* (*start_routine)(void*), void* argument_to_start_routine)
{
    if (!thread)
        return -EINVAL;

    PthreadAttrImpl default_attributes {};
    PthreadAttrImpl** arg_attributes = reinterpret_cast<PthreadAttrImpl**>(attributes);

    PthreadAttrImpl* used_attributes = arg_attributes ? *arg_attributes : &default_attributes;

    if (!used_attributes->m_stack_location) {
        // adjust stack size, user might have called setstacksize, which has no restrictions on size/alignment
        if (0 != (used_attributes->m_stack_size % required_stack_alignment))
            used_attributes->m_stack_size += required_stack_alignment - (used_attributes->m_stack_size % required_stack_alignment);

        used_attributes->m_stack_location = mmap_with_name(nullptr, used_attributes->m_stack_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, 0, 0, "Thread stack");
        if (!used_attributes->m_stack_location)
            return -1;
    }

#ifdef PTHREAD_DEBUG
    printf("pthread_create: Creating thread with attributes at %p, detach state %s, priority %d, guard page size %d, stack size %d, stack location %p\n",
        used_attributes,
        (PTHREAD_CREATE_JOINABLE == used_attributes->m_detach_state) ? "joinable" : "detached",
        used_attributes->m_schedule_priority,
        used_attributes->m_guard_page_size,
        used_attributes->m_stack_size,
        used_attributes->m_stack_location);
#endif

    int rc = create_thread(start_routine, argument_to_start_routine, used_attributes);
    if (rc < 0)
        return rc;
    *thread = rc;
    return 0;
}

void pthread_exit(void* value_ptr)
{
    exit_thread(value_ptr);
}

int pthread_join(pthread_t thread, void** exit_value_ptr)
{
    int rc = syscall(SC_join_thread, thread, exit_value_ptr);
    __RETURN_WITH_ERRNO(rc, rc, -1);
}

int pthread_mutex_init(pthread_mutex_t* mutex, const pthread_mutexattr_t* attributes)
{
    // FIXME: Implement mutex attributes
    UNUSED_PARAM(attributes);
    *mutex = 0;
    return 0;
}

int pthread_mutex_lock(pthread_mutex_t* mutex)
{
    auto* atomic = reinterpret_cast<Atomic<u32>*>(mutex);
    for (;;) {
        u32 expected = false;
        if (atomic->compare_exchange_strong(expected, true, AK::memory_order_acq_rel))
            return 0;
        sched_yield();
    }
}

int pthread_mutex_unlock(pthread_mutex_t* mutex)
{
    auto* atomic = reinterpret_cast<Atomic<u32>*>(mutex);
    atomic->store(false, AK::memory_order_release);
    return 0;
}

int pthread_attr_init(pthread_attr_t* attributes)
{
    auto* impl = new PthreadAttrImpl {};
    *attributes = impl;

#ifdef PTHREAD_DEBUG
    printf("pthread_attr_init: New thread attributes at %p, detach state %s, priority %d, guard page size %d, stack size %d, stack location %p\n",
        impl,
        (PTHREAD_CREATE_JOINABLE == impl->m_detach_state) ? "joinable" : "detached",
        impl->m_schedule_priority,
        impl->m_guard_page_size,
        impl->m_stack_size,
        impl->m_stack_location);
#endif

    return 0;
}

int pthread_attr_destroy(pthread_attr_t* attributes)
{
    auto* attributes_impl = *(reinterpret_cast<PthreadAttrImpl**>(attributes));
    delete attributes_impl;
    return 0;
}

int pthread_attr_getdetachstate(const pthread_attr_t* attributes, int* p_detach_state)
{
    auto* attributes_impl = *(reinterpret_cast<const PthreadAttrImpl* const*>(attributes));

    if (!attributes_impl || !p_detach_state)
        return EINVAL;

    *p_detach_state = attributes_impl->m_detach_state;
    return 0;
}

int pthread_attr_setdetachstate(pthread_attr_t* attributes, int detach_state)
{
    auto* attributes_impl = *(reinterpret_cast<PthreadAttrImpl**>(attributes));

    if (!attributes_impl)
        return EINVAL;

    if ((PTHREAD_CREATE_JOINABLE != detach_state) || PTHREAD_CREATE_DETACHED != detach_state)
        return EINVAL;

    attributes_impl->m_detach_state = detach_state;

#ifdef PTHREAD_DEBUG
    printf("pthread_attr_setdetachstate: Thread attributes at %p, detach state %s, priority %d, guard page size %d, stack size %d, stack location %p\n",
        attributes_impl,
        (PTHREAD_CREATE_JOINABLE == attributes_impl->m_detach_state) ? "joinable" : "detached",
        attributes_impl->m_schedule_priority,
        attributes_impl->m_guard_page_size,
        attributes_impl->m_stack_size,
        attributes_impl->m_stack_location);
#endif

    return 0;
}

int pthread_attr_getguardsize(const pthread_attr_t* attributes, size_t* p_guard_size)
{
    auto* attributes_impl = *(reinterpret_cast<const PthreadAttrImpl* const*>(attributes));

    if (!attributes_impl || !p_guard_size)
        return EINVAL;

    *p_guard_size = attributes_impl->m_reported_guard_page_size;
    return 0;
}

int pthread_attr_setguardsize(pthread_attr_t* attributes, size_t guard_size)
{
    auto* attributes_impl = *(reinterpret_cast<PthreadAttrImpl**>(attributes));

    if (!attributes_impl)
        return EINVAL;

    size_t actual_guard_size = guard_size;
    // round up
    if (0 != (guard_size % PAGE_SIZE))
        actual_guard_size += PAGE_SIZE - (guard_size % PAGE_SIZE);

    // what is the user even doing?
    if (actual_guard_size > highest_reasonable_guard_size) {
        return EINVAL;
    }

    attributes_impl->m_guard_page_size = actual_guard_size;
    attributes_impl->m_reported_guard_page_size = guard_size; // POSIX, why?

#ifdef PTHREAD_DEBUG
    printf("pthread_attr_setguardsize: Thread attributes at %p, detach state %s, priority %d, guard page size %d, stack size %d, stack location %p\n",
        attributes_impl,
        (PTHREAD_CREATE_JOINABLE == attributes_impl->m_detach_state) ? "joinable" : "detached",
        attributes_impl->m_schedule_priority,
        attributes_impl->m_guard_page_size,
        attributes_impl->m_stack_size,
        attributes_impl->m_stack_location);
#endif

    return 0;
}

int pthread_attr_getschedparam(const pthread_attr_t* attributes, struct sched_param* p_sched_param)
{
    auto* attributes_impl = *(reinterpret_cast<const PthreadAttrImpl* const*>(attributes));

    if (!attributes_impl || !p_sched_param)
        return EINVAL;

    p_sched_param->sched_priority = attributes_impl->m_schedule_priority;
    return 0;
}

int pthread_attr_setschedparam(pthread_attr_t* attributes, const struct sched_param* p_sched_param)
{
    auto* attributes_impl = *(reinterpret_cast<PthreadAttrImpl**>(attributes));
    if (!attributes_impl || !p_sched_param)
        return EINVAL;

    // NOTE: This must track sched_get_priority_[min,max] and ThreadPriority enum in Thread.h
    if (p_sched_param->sched_priority < 0 || p_sched_param->sched_priority > 3)
        return ENOTSUP;

    attributes_impl->m_schedule_priority = p_sched_param->sched_priority;

#ifdef PTHREAD_DEBUG
    printf("pthread_attr_setschedparam: Thread attributes at %p, detach state %s, priority %d, guard page size %d, stack size %d, stack location %p\n",
        attributes_impl,
        (PTHREAD_CREATE_JOINABLE == attributes_impl->m_detach_state) ? "joinable" : "detached",
        attributes_impl->m_schedule_priority,
        attributes_impl->m_guard_page_size,
        attributes_impl->m_stack_size,
        attributes_impl->m_stack_location);
#endif

    return 0;
}

int pthread_attr_getstack(const pthread_attr_t* attributes, void** p_stack_ptr, size_t* p_stack_size)
{
    auto* attributes_impl = *(reinterpret_cast<const PthreadAttrImpl* const*>(attributes));

    if (!attributes_impl || !p_stack_ptr || !p_stack_size)
        return EINVAL;

    *p_stack_ptr = attributes_impl->m_stack_location;
    *p_stack_size = attributes_impl->m_stack_size;

    return 0;
}

int pthread_attr_setstack(pthread_attr_t* attributes, void* p_stack, size_t stack_size)
{
    auto* attributes_impl = *(reinterpret_cast<PthreadAttrImpl**>(attributes));

    if (!attributes_impl || !p_stack)
        return EINVAL;

    // Check for required alignment on size
    if (0 != (stack_size % required_stack_alignment))
        return EINVAL;

    // FIXME: Check for required alignment on pointer?

    // FIXME: "[EACCES] The stack page(s) described by stackaddr and stacksize are not both readable and writable by the thread."
    // Have to check that the whole range is mapped to this process/thread? Can we defer this to create_thread?

    attributes_impl->m_stack_size = stack_size;
    attributes_impl->m_stack_location = p_stack;

#ifdef PTHREAD_DEBUG
    printf("pthread_attr_setstack: Thread attributes at %p, detach state %s, priority %d, guard page size %d, stack size %d, stack location %p\n",
        attributes_impl,
        (PTHREAD_CREATE_JOINABLE == attributes_impl->m_detach_state) ? "joinable" : "detached",
        attributes_impl->m_schedule_priority,
        attributes_impl->m_guard_page_size,
        attributes_impl->m_stack_size,
        attributes_impl->m_stack_location);
#endif

    return 0;
}

int pthread_attr_getstacksize(const pthread_attr_t* attributes, size_t* p_stack_size)
{
    auto* attributes_impl = *(reinterpret_cast<const PthreadAttrImpl* const*>(attributes));

    if (!attributes_impl || !p_stack_size)
        return EINVAL;

    *p_stack_size = attributes_impl->m_stack_size;
    return 0;
}

int pthread_attr_setstacksize(pthread_attr_t* attributes, size_t stack_size)
{
    auto* attributes_impl = *(reinterpret_cast<PthreadAttrImpl**>(attributes));

    if (!attributes_impl)
        return EINVAL;

    if ((stack_size < PTHREAD_STACK_MIN) || stack_size > highest_reasonable_stack_size)
        return EINVAL;

    attributes_impl->m_stack_size = stack_size;

#ifdef PTHREAD_DEBUG
    printf("pthread_attr_setstacksize: Thread attributes at %p, detach state %s, priority %d, guard page size %d, stack size %d, stack location %p\n",
        attributes_impl,
        (PTHREAD_CREATE_JOINABLE == attributes_impl->m_detach_state) ? "joinable" : "detached",
        attributes_impl->m_schedule_priority,
        attributes_impl->m_guard_page_size,
        attributes_impl->m_stack_size,
        attributes_impl->m_stack_location);
#endif

    return 0;
}
}