/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

#include "qpid/dispatch/python_embedded.h"

#include "entity_cache.h"

#include "entity.h"

#include "qpid/dispatch/ctools.h"
#include "qpid/dispatch/threading.h"

#include <structmember.h>

typedef enum { REMOVE=0, ADD=1 }  action_t;

typedef struct entity_event_t {
    DEQ_LINKS(struct entity_event_t);
    action_t action;
    const char *type;
    void *object;
} entity_event_t;

DEQ_DECLARE(entity_event_t, entity_event_list_t);

static entity_event_t *entity_event(action_t action, const char *type, void *object) {
    entity_event_t *event = NEW(entity_event_t);
    DEQ_ITEM_INIT(event);
    event->action = action;
    event->type = type;
    event->object = object;
    return event;
}

static sys_mutex_t *event_lock = 0;
static entity_event_list_t  event_list;

void qd_entity_cache_initialize() {
    event_lock = sys_mutex();
    DEQ_INIT(event_list);
}

void qd_entity_cache_free_entries() {
    sys_mutex_lock(event_lock);
    entity_event_t *event = DEQ_HEAD(event_list);
    while (event) {
        DEQ_REMOVE_HEAD(event_list);
        free(event);
        event = DEQ_HEAD(event_list);
    }
    sys_mutex_unlock(event_lock);
}

static void push_event(action_t action, const char *type, void *object) {
    if (!event_lock) return;    /* Unit tests don't call qd_entity_cache_initialize */
    sys_mutex_lock(event_lock);
    entity_event_t *event = entity_event(action, type, object);
    DEQ_INSERT_TAIL(event_list, event);
    sys_mutex_unlock(event_lock);
}

void qd_entity_cache_add(const char *type, void *object) { push_event(ADD, type, object); }

void qd_entity_cache_remove(const char *type, void *object) { push_event(REMOVE, type, object); }

// Get events in the add/remove cache into a python list of (action, type, pointer)
// Locks the entity cache so entities can be updated safely (prevent entities from being deleted.)
// Do not process any entities if return error code != 0
// Must call qd_entity_refresh_end when done, regardless of error code.
QD_EXPORT qd_error_t qd_entity_refresh_begin(PyObject *list) {
    if (!event_lock) return QD_ERROR_NONE;    /* Unit tests don't call qd_entity_cache_initialize */
    qd_error_clear();
    sys_mutex_lock(event_lock);
    entity_event_t *event = DEQ_HEAD(event_list);
    while (event) {
        PyObject *tuple = Py_BuildValue("(isN)", (int)event->action, event->type, PyLong_FromVoidPtr(event->object));
        if (!tuple) { qd_error_py(); break; }
        int err = PyList_Append(list, tuple);
        Py_DECREF(tuple);
        if (err) { qd_error_py(); break; }
        DEQ_REMOVE_HEAD(event_list);
        free(event);
        event = DEQ_HEAD(event_list);
    }
    return qd_error_code();
}

QD_EXPORT void qd_entity_refresh_end() {
    sys_mutex_unlock(event_lock);
}