#include <AK/Assertions.h>
#include <AK/Atomic.h>
#include <AK/InlineLinkedList.h>
#include <AK/StdLibExtras.h>
#include <Kernel/Syscall.h>
#include <limits.h>
#include <pthread.h>
#include <signal.h>
#include <stdio.h>
#include <sys/mman.h>
#include <time.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* thread_params)
{
    return syscall(SC_create_thread, entry, argument, thread_params);
}

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

int pthread_self()
{
    return gettid();
}

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)
{
    return syscall(SC_join_thread, thread, exit_value_ptr);
}

int pthread_detach(pthread_t thread)
{
    return syscall(SC_detach_thread, thread);
}

int pthread_sigmask(int how, const sigset_t* set, sigset_t* old_set)
{
    if (sigprocmask(how, set, old_set))
        return errno;
    return 0;
}

int pthread_mutex_init(pthread_mutex_t* mutex, const pthread_mutexattr_t* attributes)
{
    mutex->lock = 0;
    mutex->owner = 0;
    mutex->level = 0;
    mutex->type = attributes ? attributes->type : PTHREAD_MUTEX_NORMAL;
    return 0;
}

int pthread_mutex_destroy(pthread_mutex_t*)
{
    return 0;
}

int pthread_mutex_lock(pthread_mutex_t* mutex)
{
    auto& atomic = reinterpret_cast<Atomic<u32>&>(mutex->lock);
    pthread_t this_thread = pthread_self();
    for (;;) {
        u32 expected = false;
        if (!atomic.compare_exchange_strong(expected, true, AK::memory_order_acq_rel)) {
            if (mutex->type == PTHREAD_MUTEX_RECURSIVE && mutex->owner == this_thread) {
                mutex->level++;
                return 0;
            }
            sched_yield();
            continue;
        }
        mutex->owner = this_thread;
        mutex->level = 0;
        return 0;
    }
}

int pthread_mutex_trylock(pthread_mutex_t* mutex)
{
    auto& atomic = reinterpret_cast<Atomic<u32>&>(mutex->lock);
    u32 expected = false;
    if (!atomic.compare_exchange_strong(expected, true, AK::memory_order_acq_rel)) {
        if (mutex->type == PTHREAD_MUTEX_RECURSIVE && mutex->owner == pthread_self()) {
            mutex->level++;
            return 0;
        }
        return EBUSY;
    }
    mutex->owner = pthread_self();
    mutex->level = 0;
    return 0;
}

int pthread_mutex_unlock(pthread_mutex_t* mutex)
{
    if (mutex->type == PTHREAD_MUTEX_RECURSIVE && mutex->level > 0) {
        mutex->level--;
        return 0;
    }
    mutex->owner = 0;
    mutex->lock = 0;
    return 0;
}

int pthread_mutexattr_init(pthread_mutexattr_t* attr)
{
    attr->type = PTHREAD_MUTEX_NORMAL;
    return 0;
}

int pthread_mutexattr_destroy(pthread_mutexattr_t*)
{
    return 0;
}

int pthread_mutexattr_settype(pthread_mutexattr_t* attr, int type)
{
    if (!attr)
        return EINVAL;
    if (type != PTHREAD_MUTEX_NORMAL && type != PTHREAD_MUTEX_RECURSIVE)
        return EINVAL;
    attr->type = type;
    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;
}

int pthread_getschedparam(pthread_t thread, int* policy, struct sched_param* param)
{
    (void)thread;
    (void)policy;
    (void)param;
    return 0;
}

int pthread_setschedparam(pthread_t thread, int policy, const struct sched_param* param)
{
    (void)thread;
    (void)policy;
    (void)param;
    return 0;
}

struct WaitNode : public InlineLinkedListNode<WaitNode> {
    volatile bool waiting { true };
    WaitNode* m_next { nullptr };
    WaitNode* m_prev { nullptr };
};

struct ConditionVariable {
    InlineLinkedList<WaitNode> waiters;
    clockid_t clock { CLOCK_MONOTONIC };
};

int pthread_cond_init(pthread_cond_t* cond, const pthread_condattr_t* attr)
{
    auto& condvar = *new ConditionVariable;
    cond->storage = &condvar;
    if (attr)
        condvar.clock = attr->clockid;
    return 0;
}

int pthread_cond_destroy(pthread_cond_t* cond)
{
    delete static_cast<ConditionVariable*>(cond->storage);
    return 0;
}

int pthread_cond_wait(pthread_cond_t* cond, pthread_mutex_t* mutex)
{
    WaitNode node;
    auto& condvar = *(ConditionVariable*)cond->storage;
    condvar.waiters.append(&node);
    while (node.waiting) {
        pthread_mutex_unlock(mutex);
        sched_yield();
        pthread_mutex_lock(mutex);
    }
    return 0;
}

int pthread_condattr_init(pthread_condattr_t* attr)
{
    attr->clockid = CLOCK_MONOTONIC;
    return 0;
}

int pthread_condattr_destroy(pthread_condattr_t*)
{
    return 0;
}

int pthread_condattr_setclock(pthread_condattr_t* attr, clockid_t clock)
{
    attr->clockid = clock;
    return 0;
}

int pthread_cond_timedwait(pthread_cond_t* cond, pthread_mutex_t* mutex, const struct timespec* abstime)
{
    WaitNode node;
    auto& condvar = *(ConditionVariable*)cond->storage;
    condvar.waiters.append(&node);
    while (node.waiting) {
        struct timespec now;
        if (clock_gettime(condvar.clock, &now) < 0) {
            dbgprintf("pthread_cond_timedwait: clock_gettime() failed\n");
            return errno;
        }
        if ((abstime->tv_sec < now.tv_sec) || (abstime->tv_sec == now.tv_sec && abstime->tv_nsec <= now.tv_nsec)) {
            return ETIMEDOUT;
        }
        pthread_mutex_unlock(mutex);
        sched_yield();
        pthread_mutex_lock(mutex);
    }
    return 0;
}

int pthread_cond_signal(pthread_cond_t* cond)
{
    auto& condvar = *(ConditionVariable*)cond->storage;
    if (condvar.waiters.is_empty())
        return 0;
    auto* node = condvar.waiters.remove_head();
    node->waiting = false;
    return 0;
}

int pthread_cond_broadcast(pthread_cond_t* cond)
{
    auto& condvar = *(ConditionVariable*)cond->storage;
    while (!condvar.waiters.is_empty()) {
        auto* node = condvar.waiters.remove_head();
        node->waiting = false;
    }
    return 0;
}

static const int max_keys = 64;

typedef void (*KeyDestructor)(void*);

struct KeyTable {
    // FIXME: Invoke key destructors on thread exit!
    KeyDestructor destructors[64] { nullptr };
    int next { 0 };
    pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
};

struct SpecificTable {
    void* values[64] { nullptr };
};

static KeyTable s_keys;

__thread SpecificTable t_specifics;

int pthread_key_create(pthread_key_t* key, KeyDestructor destructor)
{
    int ret = 0;
    pthread_mutex_lock(&s_keys.mutex);
    if (s_keys.next >= max_keys) {
        ret = ENOMEM;
    } else {
        *key = s_keys.next++;
        s_keys.destructors[*key] = destructor;
        ret = 0;
    }
    pthread_mutex_unlock(&s_keys.mutex);
    return ret;
}

void* pthread_getspecific(pthread_key_t key)
{
    if (key < 0)
        return nullptr;
    if (key >= max_keys)
        return nullptr;
    return t_specifics.values[key];
}

int pthread_setspecific(pthread_key_t key, const void* value)
{
    if (key < 0)
        return EINVAL;
    if (key >= max_keys)
        return EINVAL;

    t_specifics.values[key] = const_cast<void*>(value);
    return 0;
}
int pthread_setname_np(pthread_t thread, const char* buffer, int buffer_size)
{
    return syscall(SC_set_thread_name, thread, buffer, buffer_size);
}

int pthread_getname_np(pthread_t thread, char* buffer, int buffer_size)
{
    return syscall(SC_get_thread_name, thread, buffer, buffer_size);
}

} // extern "C"
