// ke_semaphore.c - counting semaphore
#include <stdbool.h>
#include <ke_semaphore.h>
#include <ke_thread.h>
#include <ke_sched.h>
#include <ob_object.h>

static void SemDestroy(OBJECT* obj) { (void)obj; }

KSTATUS SemaphoreCreate(int32_t initial, int32_t max, SEMAPHORE **out) {
    if (!out || initial < 0 || max < 1 || initial > max)
        return STATUS_INVALID_PARAMETER;
    SEMAPHORE* s = (SEMAPHORE *)ObAllocateObject(ObjectTypeSemaphore, sizeof(SEMAPHORE));
    if (!s) return STATUS_NO_MEMORY;
    s->Header.Destroy = SemDestroy;
    s->Lock     = (SPINLOCK)SPINLOCK_INIT;
    s->Count    = initial;
    s->MaxCount = max;
    LIST_INIT(&s->WaitList);
    *out = s;
    return STATUS_SUCCESS;
}

KSTATUS KeWaitSemaphore(SEMAPHORE* sem) {
    if (!sem) return STATUS_INVALID_PARAMETER;
    THREAD* self = KeCurrentThread();

    while (true) {
        uintptr_t flags = KeAcquireSpinlock(&sem->Lock);
        if (sem->Count > 0) {
            sem->Count--;
            KeReleaseSpinlock(&sem->Lock, flags);
            return STATUS_SUCCESS;
        }
        ListInsertTail(&sem->WaitList, &self->SchedulerLink);
        KeReleaseSpinlock(&sem->Lock, flags);
        KeBlockThread(self, &sem->Header);
    }
}

KSTATUS KeTrySemaphore(SEMAPHORE* sem) {
    if (!sem) return STATUS_INVALID_PARAMETER;
    uintptr_t flags = KeAcquireSpinlock(&sem->Lock);
    if (sem->Count > 0) {
        sem->Count--;
        KeReleaseSpinlock(&sem->Lock, flags);
        return STATUS_SUCCESS;
    }
    KeReleaseSpinlock(&sem->Lock, flags);
    return STATUS_FAILURE;
}

void KeSignalSemaphore(SEMAPHORE* sem) {
    if (!sem) return;
    uintptr_t flags = KeAcquireSpinlock(&sem->Lock);
    if (!LIST_IS_EMPTY(&sem->WaitList)) {
        LIST_ENTRY* node = ListPopHead(&sem->WaitList);
        THREAD* waiter   = CONTAINING_RECORD(node, THREAD, SchedulerLink);
        KeReleaseSpinlock(&sem->Lock, flags);
        KeUnblockThread(waiter);
        return;
    }
    if (sem->Count < sem->MaxCount) sem->Count++;
    KeReleaseSpinlock(&sem->Lock, flags);
}