// This source code is dual-licensed under the Mozilla Public License ("MPL"),
// version 1.1 and the Apache License ("ASL"), version 2.0.
//
// The ASL v2.0:
//
// ---------------------------------------------------------------------------
// Copyright 2016 Pivotal Software, Inc.
//
// Licensed 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.
// ---------------------------------------------------------------------------
//
// The MPL v1.1:
//
// ---------------------------------------------------------------------------
// The contents of this file are subject to the Mozilla Public License
// Version 1.1 (the "License"); you may not use this file except in
// compliance with the License. You may obtain a copy of the License at
// https://www.mozilla.org/MPL/
//
// Software distributed under the License is distributed on an "AS IS"
// basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the
// License for the specific language governing rights and limitations
// under the License.
//
// The Original Code is RabbitMQ
//
// The Initial Developer of the Original Code is Pivotal Software, Inc.
// All Rights Reserved.
//
// Alternatively, the contents of this file may be used under the terms
// of the Apache Standard license (the "ASL License"), in which case the
// provisions of the ASL License are applicable instead of those
// above. If you wish to allow use of your version of this file only
// under the terms of the ASL License and not to allow others to use
// your version of this file under the MPL, indicate your decision by
// deleting the provisions above and replace them with the notice and
// other provisions required by the ASL License. If you do not delete
// the provisions above, a recipient may use your version of this file
// under either the MPL or the ASL License.
// ---------------------------------------------------------------------------

#import "RMQGCDSerialQueue.h"
#import <libkern/OSAtomic.h>

typedef NS_ENUM(int32_t, RMQGCDSerialQueueStatus) {
    RMQGCDSerialQueueStatusNormal = 1,
    RMQGCDSerialQueueStatusSuspended,
};

@interface RMQGCDSerialQueue ()
@property (nonatomic, readwrite) NSString *name;
@property (nonatomic, readwrite) dispatch_queue_t dispatchQueue;
@property (atomic, readwrite) volatile int32_t status;
@end

@implementation RMQGCDSerialQueue

- (instancetype)initWithName:(NSString *)name {
    self = [super init];
    if (self) {
        self.name = name;
        self.status = RMQGCDSerialQueueStatusNormal;
        NSString *qName = [NSString stringWithFormat:@"RMQGCDSerialQueue (%@)", name];
        self.dispatchQueue = dispatch_queue_create([qName cStringUsingEncoding:NSUTF8StringEncoding], NULL);
    }
    return self;
}

- (instancetype)init {
    [self doesNotRecognizeSelector:_cmd];
    return nil;
}

- (void)dealloc {
    [self resume];
}

- (void)enqueue:(RMQOperation)operation {
    dispatch_async(self.dispatchQueue, operation);
}

- (void)blockingEnqueue:(RMQOperation)operation {
    dispatch_sync(self.dispatchQueue, operation);
}

- (void)delayedBy:(NSNumber *)delay
          enqueue:(RMQOperation)operation {
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delay.doubleValue * NSEC_PER_SEC)),
                   self.dispatchQueue,
                   operation);
}

- (void)suspend {
    if (self.status == RMQGCDSerialQueueStatusSuspended) {
        return;
    }
    while (true) {
        if (OSAtomicCompareAndSwap32(self.status,
                                     RMQGCDSerialQueueStatusSuspended,
                                     &_status)) {
            dispatch_suspend(self.dispatchQueue);
            return;
        }
    }
}

- (void)resume {
    if (self.status == RMQGCDSerialQueueStatusNormal) {
        return;
    }
    while (true) {
        if (OSAtomicCompareAndSwap32(self.status,
                                     RMQGCDSerialQueueStatusNormal,
                                     &_status)) {
            dispatch_resume(self.dispatchQueue);
            return;
        }
    }
}

@end