// ke_queue.c - ring-buffer message queue
#include "ke_queue.h"
#include "ke_thread.h"
#include "ke_sched.h"
#include "ob_object.h"
#include <string.h>

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

KSTATUS QueueCreate(QUEUE **out) {
    if (!out) return STATUS_INVALID_PARAMETER;
    QUEUE* q = (QUEUE *)ObAllocateObject(ObjectTypeQueue, sizeof(QUEUE));
    if (!q)  return STATUS_NO_MEMORY;
    q->Header.Destroy = QueueDestroy;
    q->Lock  = (SPINLOCK)SPINLOCK_INIT;
    q->Head  = q->Tail = q->Count = 0;
    LIST_INIT(&q->SendWaiters);
    LIST_INIT(&q->RecvWaiters);
    *out = q;
    return STATUS_SUCCESS;
}

KSTATUS KeSendMessage(QUEUE* queue, const QUEUE_MESSAGE* msg, bool blocking) {
    if (!queue || !msg) return STATUS_INVALID_PARAMETER;
    THREAD* self = KeCurrentThread();

    for (;;) {
        uintptr_t flags = KeAcquireSpinlock(&queue->Lock);
        if (queue->Count < QUEUE_DEPTH) {
            queue->Ring[queue->Tail] = *msg;
            queue->Tail = (queue->Tail + 1) % QUEUE_DEPTH;
            queue->Count++;

            // Wake a receiver if one is waiting.
            if (!LIST_IS_EMPTY(&queue->RecvWaiters)) {
                LIST_ENTRY* node = ListPopHead(&queue->RecvWaiters);
                THREAD* t = CONTAINING_RECORD(node, THREAD, SchedulerLink);
                KeReleaseSpinlock(&queue->Lock, flags);
                KeUnblockThread(t);
            } else {
                KeReleaseSpinlock(&queue->Lock, flags);
            }
            return STATUS_SUCCESS;
        }
        if (!blocking) {
            KeReleaseSpinlock(&queue->Lock, flags);
            return STATUS_QUEUE_FULL;
        }
        ListInsertTail(&queue->SendWaiters, &self->SchedulerLink);
        KeReleaseSpinlock(&queue->Lock, flags);
        KeBlockThread(self, &queue->Header);
    }
}

KSTATUS KeReceiveMessage(QUEUE* queue, QUEUE_MESSAGE* msg, bool blocking) {
    if (!queue || !msg) return STATUS_INVALID_PARAMETER;
    THREAD* self = KeCurrentThread();

    for (;;) {
        uintptr_t flags = KeAcquireSpinlock(&queue->Lock);
        if (queue->Count > 0) {
            *msg = queue->Ring[queue->Head];
            queue->Head = (queue->Head + 1) % QUEUE_DEPTH;
            queue->Count--;

            // Wake a sender if one is waiting.
            if (!LIST_IS_EMPTY(&queue->SendWaiters)) {
                LIST_ENTRY* node = ListPopHead(&queue->SendWaiters);
                THREAD* t = CONTAINING_RECORD(node, THREAD, SchedulerLink);
                KeReleaseSpinlock(&queue->Lock, flags);
                KeUnblockThread(t);
            } else {
                KeReleaseSpinlock(&queue->Lock, flags);
            }
            return STATUS_SUCCESS;
        }
        if (!blocking) {
            KeReleaseSpinlock(&queue->Lock, flags);
            return STATUS_QUEUE_EMPTY;
        }
        ListInsertTail(&queue->RecvWaiters, &self->SchedulerLink);
        KeReleaseSpinlock(&queue->Lock, flags);
        KeBlockThread(self, &queue->Header);
    }
}