/*
 * Copyright 2017 Google
 *
 * 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.
 */

#import <OCMock/OCMock.h>
#import <XCTest/XCTest.h>

#import "FIRMessagingDefines.h"
#import "FIRMessagingPendingTopicsList.h"
#import "FIRMessagingTopicsCommon.h"

typedef void (^MockDelegateSubscriptionHandler)(NSString *topic,
                                                FIRMessagingTopicAction action,
                                                FIRMessagingTopicOperationCompletion completion);

/**
 * This object lets us provide a stub delegate where we can customize the behavior by providing
 * blocks. We need to use this instead of stubbing a OCMockProtocol because our delegate methods
 * take primitive values (e.g. action), which is not easy to use from OCMock
 * @see http://stackoverflow.com/a/6332023
 */
@interface MockPendingTopicsListDelegate: NSObject <FIRMessagingPendingTopicsListDelegate>

@property(nonatomic, assign) BOOL isReady;
@property(nonatomic, copy) MockDelegateSubscriptionHandler subscriptionHandler;
@property(nonatomic, copy) void(^updateHandler)();

@end

@implementation MockPendingTopicsListDelegate

- (BOOL)pendingTopicsListCanRequestTopicUpdates:(FIRMessagingPendingTopicsList *)list {
  return self.isReady;
}

- (void)pendingTopicsList:(FIRMessagingPendingTopicsList *)list
  requestedUpdateForTopic:(NSString *)topic
                   action:(FIRMessagingTopicAction)action
               completion:(FIRMessagingTopicOperationCompletion)completion {
  if (self.subscriptionHandler) {
    self.subscriptionHandler(topic, action, completion);
  }
}

- (void)pendingTopicsListDidUpdate:(FIRMessagingPendingTopicsList *)list {
  if (self.updateHandler) {
    self.updateHandler();
  }
}

@end

@interface FIRMessagingPendingTopicsListTest : XCTestCase

/// Using this delegate lets us prevent any topic operations from start, making it easy to measure
/// our batches
@property(nonatomic, strong) MockPendingTopicsListDelegate *notReadyDelegate;
/// Using this delegate will always begin topic operations (which will never return by default).
/// Useful for overriding with block-methods to handle update requests
@property(nonatomic, strong) MockPendingTopicsListDelegate *alwaysReadyDelegate;

@end

@implementation FIRMessagingPendingTopicsListTest

- (void)setUp {
  [super setUp];
  self.notReadyDelegate = [[MockPendingTopicsListDelegate alloc] init];
  self.notReadyDelegate.isReady = NO;

  self.alwaysReadyDelegate = [[MockPendingTopicsListDelegate alloc] init];
  self.alwaysReadyDelegate.isReady = YES;
}

- (void)tearDown {
  self.notReadyDelegate = nil;
  self.alwaysReadyDelegate = nil;
  [super tearDown];
}

- (void)testAddSingleTopic {
  FIRMessagingPendingTopicsList *pendingTopics = [[FIRMessagingPendingTopicsList alloc] init];
  pendingTopics.delegate = self.notReadyDelegate;

  [pendingTopics addOperationForTopic:@"/topics/0"
                           withAction:FIRMessagingTopicActionSubscribe
                           completion:nil];
  XCTAssertEqual(pendingTopics.numberOfBatches, 1);
}

- (void)testAddSameTopicAndActionMultipleTimes {
  FIRMessagingPendingTopicsList *pendingTopics = [[FIRMessagingPendingTopicsList alloc] init];
  pendingTopics.delegate = self.notReadyDelegate;

  [pendingTopics addOperationForTopic:@"/topics/0"
                           withAction:FIRMessagingTopicActionSubscribe
                           completion:nil];
  [pendingTopics addOperationForTopic:@"/topics/0"
                           withAction:FIRMessagingTopicActionSubscribe
                           completion:nil];
  [pendingTopics addOperationForTopic:@"/topics/0"
                           withAction:FIRMessagingTopicActionSubscribe
                           completion:nil];
  XCTAssertEqual(pendingTopics.numberOfBatches, 1);
}

- (void)testAddMultiplePendingTopicsWithSameAction {
  FIRMessagingPendingTopicsList *pendingTopics = [[FIRMessagingPendingTopicsList alloc] init];
  pendingTopics.delegate = self.notReadyDelegate;

  for (NSInteger i = 0; i < 10; i++) {
    NSString *topic = [NSString stringWithFormat:@"/topics/%ld", i];
    [pendingTopics addOperationForTopic:topic
                             withAction:FIRMessagingTopicActionSubscribe
                             completion:nil];
  }
  XCTAssertEqual(pendingTopics.numberOfBatches, 1);
}

- (void)testAddTopicsWithDifferentActions {
  FIRMessagingPendingTopicsList *pendingTopics = [[FIRMessagingPendingTopicsList alloc] init];
  pendingTopics.delegate = self.notReadyDelegate;

  [pendingTopics addOperationForTopic:@"/topics/0"
                           withAction:FIRMessagingTopicActionSubscribe
                           completion:nil];
  [pendingTopics addOperationForTopic:@"/topics/1"
                           withAction:FIRMessagingTopicActionUnsubscribe
                           completion:nil];
  [pendingTopics addOperationForTopic:@"/topics/2"
                           withAction:FIRMessagingTopicActionSubscribe
                           completion:nil];
  XCTAssertEqual(pendingTopics.numberOfBatches, 3);
}

- (void)testBatchSizeReductionAfterSuccessfulTopicUpdate {
  FIRMessagingPendingTopicsList *pendingTopics = [[FIRMessagingPendingTopicsList alloc] init];
  pendingTopics.delegate = self.alwaysReadyDelegate;

  XCTestExpectation *batchSizeReductionExpectation =
      [self expectationWithDescription:@"Batch size was reduced after topic suscription"];

  FIRMessaging_WEAKIFY(self)
  self.alwaysReadyDelegate.subscriptionHandler =
      ^(NSString *topic,
        FIRMessagingTopicAction action,
        FIRMessagingTopicOperationCompletion completion) {
    // Simulate that the handler is generally called asynchronously
    dispatch_async(dispatch_get_main_queue(), ^{
      FIRMessaging_STRONGIFY(self)
      if (action == FIRMessagingTopicActionUnsubscribe) {
        XCTAssertEqual(pendingTopics.numberOfBatches, 1);
        [batchSizeReductionExpectation fulfill];
      }
      completion(nil);
    });
  };

  [pendingTopics addOperationForTopic:@"/topics/0"
                           withAction:FIRMessagingTopicActionSubscribe
                           completion:nil];
  [pendingTopics addOperationForTopic:@"/topics/1"
                           withAction:FIRMessagingTopicActionSubscribe
                           completion:nil];
  [pendingTopics addOperationForTopic:@"/topics/2"
                           withAction:FIRMessagingTopicActionSubscribe
                           completion:nil];
  [pendingTopics addOperationForTopic:@"/topics/1"
                           withAction:FIRMessagingTopicActionUnsubscribe
                           completion:nil];

  [self waitForExpectationsWithTimeout:5.0 handler:nil];
}

- (void)testCompletionOfTopicUpdatesInSameThread {
  FIRMessagingPendingTopicsList *pendingTopics = [[FIRMessagingPendingTopicsList alloc] init];
  pendingTopics.delegate = self.alwaysReadyDelegate;

  XCTestExpectation *allOperationsSucceededed =
      [self expectationWithDescription:@"All queued operations succeeded"];

  self.alwaysReadyDelegate.subscriptionHandler =
      ^(NSString *topic,
        FIRMessagingTopicAction action,
        FIRMessagingTopicOperationCompletion completion) {
    // Typically, our callbacks happen asynchronously, but to ensure resilience,
    // call back the operation on the same thread it was called in.
    completion(nil);
  };

  self.alwaysReadyDelegate.updateHandler = ^{
    if (pendingTopics.numberOfBatches == 0) {
      [allOperationsSucceededed fulfill];
    }
  };

  [pendingTopics addOperationForTopic:@"/topics/0"
                           withAction:FIRMessagingTopicActionSubscribe
                           completion:nil];
  [pendingTopics addOperationForTopic:@"/topics/1"
                           withAction:FIRMessagingTopicActionSubscribe
                           completion:nil];
  [pendingTopics addOperationForTopic:@"/topics/2"
                           withAction:FIRMessagingTopicActionSubscribe
                           completion:nil];

  [self waitForExpectationsWithTimeout:5.0 handler:nil];
}

- (void)testAddingTopicToCurrentBatchWhileCurrentBatchTopicsInFlight {

  FIRMessagingPendingTopicsList *pendingTopics = [[FIRMessagingPendingTopicsList alloc] init];
  pendingTopics.delegate = self.alwaysReadyDelegate;

  NSString *stragglerTopic = @"/topics/straggler";
  XCTestExpectation *stragglerTopicWasAddedToInFlightOperations =
  [self expectationWithDescription:@"The topic was added to in-flight operations"];

  self.alwaysReadyDelegate.subscriptionHandler =
      ^(NSString *topic,
        FIRMessagingTopicAction action,
        FIRMessagingTopicOperationCompletion completion) {
    if ([topic isEqualToString:stragglerTopic]) {
      [stragglerTopicWasAddedToInFlightOperations fulfill];
    }
    // Add a 0.5 second delay to the completion, to give time to add a straggler before the batch
    // is completed
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.5 * NSEC_PER_SEC)),
                   dispatch_get_main_queue(), ^{
                     completion(nil);
                   });
  };

  // This is a normal topic, which should start fairly soon, but take a while to complete
  [pendingTopics addOperationForTopic:@"/topics/0"
                           withAction:FIRMessagingTopicActionSubscribe
                           completion:nil];
  // While waiting for the first topic to complete, we add another topic after a slight delay
  dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.25 * NSEC_PER_SEC)),
                 dispatch_get_main_queue(),
                 ^{
    [pendingTopics addOperationForTopic:stragglerTopic
                             withAction:FIRMessagingTopicActionSubscribe
                             completion:nil];
  });

  [self waitForExpectationsWithTimeout:5.0 handler:nil];
}

@end