// ke_mutex.c - binary ownership mutex
#include "ke_mutex.h"
#include "ke_thread.h"
#include "ke_sched.h"
#include "mm_virt.h"
#include "ob_object.h"

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

KSTATUS MutexCreate(MUTEX **out) {
    if (!out) return STATUS_INVALID_PARAMETER;
    MUTEX* m = (MUTEX *)ObAllocateObject(ObjectTypeMutex, sizeof(MUTEX));
    if (!m)  return STATUS_NO_MEMORY;
    m->Header.Destroy = MutexDestroy;
    m->Lock  = (SPINLOCK)SPINLOCK_INIT;
    m->Owner = (struct THREAD *)0;
    LIST_INIT(&m->WaitList);
    *out = m;
    return STATUS_SUCCESS;
}

KSTATUS KeAcquireMutex(MUTEX* mutex) {
    if (!mutex) return STATUS_INVALID_PARAMETER;
    THREAD* self = KeCurrentThread();

    for (;;) {
        KeAcquireSpinlock(&mutex->Lock);
        if (!mutex->Owner) {
            mutex->Owner = self;
            KeReleaseSpinlock(&mutex->Lock);
            return STATUS_SUCCESS;
        }
        // Already owned - add self to wait list and block.
        ListInsertTail(&mutex->WaitList, &self->SchedulerLink);
        KeReleaseSpinlock(&mutex->Lock);
        KeBlockThread(self, &mutex->Header);
        // KeBlockThread calls KeYield; when we return here we've been
        // unblocked by KeReleaseMutex - loop back and try to own it.
    }
}

KSTATUS KeTryAcquireMutex(MUTEX* mutex) {
    if (!mutex) return STATUS_INVALID_PARAMETER;
    THREAD* self = KeCurrentThread();
    KeAcquireSpinlock(&mutex->Lock);
    if (!mutex->Owner) {
        mutex->Owner = self;
        KeReleaseSpinlock(&mutex->Lock);
        return STATUS_SUCCESS;
    }
    KeReleaseSpinlock(&mutex->Lock);
    return STATUS_FAILURE;
}

void KeReleaseMutex(MUTEX* mutex) {
    if (!mutex) return;
    KeAcquireSpinlock(&mutex->Lock);
    mutex->Owner = (struct THREAD *)0;

    // Wake the first waiter, if any.
    if (!LIST_IS_EMPTY(&mutex->WaitList)) {
        LIST_ENTRY* node = ListPopHead(&mutex->WaitList);
        THREAD* waiter   = CONTAINING_RECORD(node, THREAD, SchedulerLink);
        KeReleaseSpinlock(&mutex->Lock);
        KeUnblockThread(waiter);
        return;
    }
    KeReleaseSpinlock(&mutex->Lock);
}