/*
 * 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 "FIRMessagingClient.h"

#import <GoogleUtilities/GULReachabilityChecker.h>

#import "FIRMessaging.h"
#import "FIRMessagingConnection.h"
#import "FIRMessagingConstants.h"
#import "FIRMessagingDataMessageManager.h"
#import "FIRMessagingDefines.h"
#import "FIRMessagingLogger.h"
#import "FIRMessagingRegistrar.h"
#import "FIRMessagingRmqManager.h"
#import "FIRMessagingTopicsCommon.h"
#import "FIRMessagingUtilities.h"
#import "NSError+FIRMessaging.h"

static const NSTimeInterval kConnectTimeoutInterval = 40.0;
static const NSTimeInterval kReconnectDelayInSeconds = 2 * 60; // 2 minutes

static const NSUInteger kMaxRetryExponent = 10;  // 2^10 = 1024 seconds ~= 17 minutes

static NSString *const kFIRMessagingMCSServerHost = @"mtalk.google.com";
static NSUInteger const kFIRMessagingMCSServerPort = 5228;

// register device with checkin
typedef void(^FIRMessagingRegisterDeviceHandler)(NSError *error);

static NSString *FIRMessagingServerHost() {
  static NSString *serverHost = nil;
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
    NSDictionary *environment = [[NSProcessInfo processInfo] environment];
    NSString *customServerHostAndPort = environment[@"FCM_MCS_HOST"];
    NSString *host = [customServerHostAndPort componentsSeparatedByString:@":"].firstObject;
    if (host) {
      serverHost = host;
    } else {
      serverHost = kFIRMessagingMCSServerHost;
    }
  });
  return serverHost;
}

static NSUInteger FIRMessagingServerPort() {
  static NSUInteger serverPort = kFIRMessagingMCSServerPort;
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
    NSDictionary *environment = [[NSProcessInfo processInfo] environment];
    NSString *customServerHostAndPort = environment[@"FCM_MCS_HOST"];
    NSArray<NSString *> *components = [customServerHostAndPort componentsSeparatedByString:@":"];
    NSUInteger port = (NSUInteger)[components.lastObject integerValue];
    if (port != 0) {
      serverPort = port;
    }
  });
  return serverPort;
}

@interface FIRMessagingClient () <FIRMessagingConnectionDelegate>

@property(nonatomic, readwrite, weak) id<FIRMessagingClientDelegate> clientDelegate;
@property(nonatomic, readwrite, strong) FIRMessagingConnection *connection;
@property(nonatomic, readwrite, strong) FIRMessagingRegistrar *registrar;

@property(nonatomic, readwrite, strong) NSString *senderId;

// FIRMessagingService owns these instances
@property(nonatomic, readwrite, weak) FIRMessagingRmqManager *rmq2Manager;
@property(nonatomic, readwrite, weak) GULReachabilityChecker *reachability;

@property(nonatomic, readwrite, assign) int64_t lastConnectedTimestamp;
@property(nonatomic, readwrite, assign) int64_t lastDisconnectedTimestamp;
@property(nonatomic, readwrite, assign) NSUInteger connectRetryCount;

// Should we stay connected to MCS or not. Should be YES throughout the lifetime
// of a MCS connection. If set to NO it signifies that an existing MCS connection
// should be disconnected.
@property(nonatomic, readwrite, assign) BOOL stayConnected;
@property(nonatomic, readwrite, assign) NSTimeInterval connectionTimeoutInterval;

// Used if the MCS connection suddenly breaksdown in the middle and we want to reconnect
// with some permissible delay we schedule a reconnect and set it to YES and when it's
// scheduled this will be set back to NO.
@property(nonatomic, readwrite, assign) BOOL didScheduleReconnect;

// handlers
@property(nonatomic, readwrite, copy) FIRMessagingConnectCompletionHandler connectHandler;

@end

@implementation FIRMessagingClient

- (instancetype)init {
  FIRMessagingInvalidateInitializer();
}

- (instancetype)initWithDelegate:(id<FIRMessagingClientDelegate>)delegate
                    reachability:(GULReachabilityChecker *)reachability
                     rmq2Manager:(FIRMessagingRmqManager *)rmq2Manager {
  self = [super init];
  if (self) {
    _reachability = reachability;
    _clientDelegate = delegate;
    _rmq2Manager = rmq2Manager;
    _registrar = [[FIRMessagingRegistrar alloc] init];
    _connectionTimeoutInterval = kConnectTimeoutInterval;
    // Listen for checkin fetch notifications, as connecting to MCS may have failed due to
    // missing checkin info (while it was being fetched).
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(checkinFetched:)
                                                 name:kFIRMessagingCheckinFetchedNotification
                                               object:nil];
  }
  return self;
}

- (void)teardown {
  FIRMessagingLoggerDebug(kFIRMessagingMessageCodeClient000, @"");
  self.stayConnected = NO;

  // Clear all the handlers
  self.connectHandler = nil;

  [self.connection teardown];

  // Stop all subscription requests
  [self.registrar cancelAllRequests];

  _FIRMessagingDevAssert(self.connection.state == kFIRMessagingConnectionNotConnected, @"Did not disconnect");
  [NSObject cancelPreviousPerformRequestsWithTarget:self];

  [[NSNotificationCenter defaultCenter] removeObserver:self];
}

- (void)cancelAllRequests {
  // Stop any checkin requests or any subscription requests
  [self.registrar cancelAllRequests];

  // Stop any future connection requests to MCS
  if (self.stayConnected && self.isConnected && !self.isConnectionActive) {
    self.stayConnected = NO;
    [NSObject cancelPreviousPerformRequestsWithTarget:self];
  }
}

#pragma mark - FIRMessaging subscribe

- (void)updateSubscriptionWithToken:(NSString *)token
                              topic:(NSString *)topic
                            options:(NSDictionary *)options
                       shouldDelete:(BOOL)shouldDelete
                            handler:(FIRMessagingTopicOperationCompletion)handler {

  _FIRMessagingDevAssert(handler != nil, @"Invalid handler to FIRMessaging subscribe");

  FIRMessagingTopicOperationCompletion completion = ^void(NSError *error) {
    if (error) {
      FIRMessagingLoggerError(kFIRMessagingMessageCodeClient001, @"Failed to subscribe to topic %@",
                              error);
    } else {
      if (shouldDelete) {
        FIRMessagingLoggerInfo(kFIRMessagingMessageCodeClient002,
                               @"Successfully unsubscribed from topic %@", topic);
      } else {
        FIRMessagingLoggerInfo(kFIRMessagingMessageCodeClient003,
                               @"Successfully subscribed to topic %@", topic);
      }
    }
    handler(error);
  };

  [self.registrar updateSubscriptionToTopic:topic
                                  withToken:token
                                    options:options
                               shouldDelete:shouldDelete
                                    handler:completion];
}

#pragma mark - MCS Connection

- (BOOL)isConnected {
  return self.stayConnected && self.connection.state != kFIRMessagingConnectionNotConnected;
}

- (BOOL)isConnectionActive {
  return self.stayConnected && self.connection.state == kFIRMessagingConnectionSignedIn;
}

- (BOOL)shouldStayConnected {
  return self.stayConnected;
}

- (void)retryConnectionImmediately:(BOOL)immediately {
  // Do not connect to an invalid host or an invalid port
  if (!self.stayConnected || !self.connection.host || self.connection.port == 0) {
    FIRMessagingLoggerDebug(kFIRMessagingMessageCodeClient004,
                            @"FIRMessaging connection will not reconnect to MCS. "
                            @"Stay connected: %d",
                            self.stayConnected);
    return;
  }
  if (self.isConnectionActive) {
    FIRMessagingLoggerDebug(kFIRMessagingMessageCodeClient005,
                            @"FIRMessaging Connection skip retry, active");
    // already connected and logged in.
    // Heartbeat alarm is set and will force close the connection
    return;
  }
  if (self.isConnected) {
    // already connected and logged in.
    // Heartbeat alarm is set and will force close the connection
    FIRMessagingLoggerDebug(kFIRMessagingMessageCodeClient006,
                            @"FIRMessaging Connection skip retry, connected");
    return;
  }

  if (immediately) {
    FIRMessagingLoggerDebug(kFIRMessagingMessageCodeClient007,
                            @"Try to connect to MCS immediately");
    [self tryToConnect];
  } else {
    FIRMessagingLoggerDebug(kFIRMessagingMessageCodeClient008, @"Try to connect to MCS lazily");
    // Avoid all the other logic that we have in other clients, since this would always happen
    // when the app is in the foreground and since the FIRMessaging connection isn't shared with any other
    // app we can be more aggressive in reconnections
    if (!self.didScheduleReconnect) {
      FIRMessaging_WEAKIFY(self);
      dispatch_after(dispatch_time(DISPATCH_TIME_NOW,
                                   (int64_t)(kReconnectDelayInSeconds * NSEC_PER_SEC)),
                     dispatch_get_main_queue(), ^{
                         FIRMessaging_STRONGIFY(self);
                         self.didScheduleReconnect = NO;
                         [self tryToConnect];
                     });

      self.didScheduleReconnect = YES;
    }
  }
}

- (void)connectWithHandler:(FIRMessagingConnectCompletionHandler)handler {
  if (self.isConnected) {
    NSError *error = [NSError fcm_errorWithCode:kFIRMessagingErrorCodeAlreadyConnected
                                       userInfo:@{
        NSLocalizedFailureReasonErrorKey: @"FIRMessaging is already connected",
        }];
    handler(error);
    return;
  }
  self.lastDisconnectedTimestamp = FIRMessagingCurrentTimestampInMilliseconds();
  self.connectHandler = handler;
  [self connect];
}

- (void)connect {
  // reset retry counts
  self.connectRetryCount = 0;

  if (self.isConnected) {
    return;
  }

  self.stayConnected = YES;
  if (![self.registrar tryToLoadValidCheckinInfo]) {
    // Checkin info is not available. This may be due to the checkin still being fetched.
    if (self.connectHandler) {
      NSError *error = [NSError errorWithFCMErrorCode:kFIRMessagingErrorCodeMissingDeviceID];
      self.connectHandler(error);
    }
    FIRMessagingLoggerDebug(kFIRMessagingMessageCodeClient009,
                            @"Failed to connect to MCS. No deviceID and secret found.");
    // Return for now. If checkin is, in fact, retrieved, the
    // |kFIRMessagingCheckinFetchedNotification| will be fired.
    return;
  }
  [self setupConnectionAndConnect];
}

- (void)disconnect {
  // user called disconnect
  // We don't want to connect later even if no network is available.
  [self disconnectWithTryToConnectLater:NO];
}

/**
 *  Disconnect the current client connection. Also explicitly stop and connction retries.
 *
 *  @param tryToConnectLater If YES will try to connect later when sending upstream messages
 *                           else if NO do not connect again until user explicitly calls
 *                           connect.
 */
- (void)disconnectWithTryToConnectLater:(BOOL)tryToConnectLater {

  self.stayConnected = tryToConnectLater;
  [self.connection signOut];
  _FIRMessagingDevAssert(self.connection.state == kFIRMessagingConnectionNotConnected,
                @"FIRMessaging connection did not disconnect");

  // since we can disconnect while still trying to establish the connection it's required to
  // cancel all performSelectors else the object might be retained
  [NSObject cancelPreviousPerformRequestsWithTarget:self
                                           selector:@selector(tryToConnect)
                                             object:nil];
  [NSObject cancelPreviousPerformRequestsWithTarget:self
                                           selector:@selector(didConnectTimeout)
                                             object:nil];
  self.connectHandler = nil;
}

#pragma mark - Checkin Notification
- (void)checkinFetched:(NSNotification *)notification {
  // A failed checkin may have been the reason for the connection failure. Attempt a connection
  // if the checkin fetched notification is fired.
  if (self.stayConnected && !self.isConnected) {
    [self connect];
  }
}

#pragma mark - Messages

- (void)sendMessage:(GPBMessage *)message {
  [self.connection sendProto:message];
}

- (void)sendOnConnectOrDrop:(GPBMessage *)message {
  [self.connection sendOnConnectOrDrop:message];
}

#pragma mark - FIRMessagingConnectionDelegate

- (void)connection:(FIRMessagingConnection *)fcmConnection
    didCloseForReason:(FIRMessagingConnectionCloseReason)reason {

  self.lastDisconnectedTimestamp = FIRMessagingCurrentTimestampInMilliseconds();

  if (reason == kFIRMessagingConnectionCloseReasonSocketDisconnected) {
    // Cancel the not-yet-triggered timeout task before rescheduling, in case the previous sign in
    // failed, due to a connection error caused by bad network.
    [NSObject cancelPreviousPerformRequestsWithTarget:self
                                             selector:@selector(didConnectTimeout)
                                               object:nil];
  }
  if (self.stayConnected) {
    [self scheduleConnectRetry];
  }
}

- (void)didLoginWithConnection:(FIRMessagingConnection *)fcmConnection {
  // Cancel the not-yet-triggered timeout task.
  [NSObject cancelPreviousPerformRequestsWithTarget:self
                                           selector:@selector(didConnectTimeout)
                                             object:nil];
  self.connectRetryCount = 0;
  self.lastConnectedTimestamp = FIRMessagingCurrentTimestampInMilliseconds();


  [self.dataMessageManager setDeviceAuthID:self.registrar.deviceAuthID
                               secretToken:self.registrar.secretToken];
  if (self.connectHandler) {
    self.connectHandler(nil);
    // notified the third party app with the registrationId.
    // we don't want them to know about the connection status and how it changes
    // so remove this handler
    self.connectHandler = nil;
  }
}

- (void)connectionDidRecieveMessage:(GtalkDataMessageStanza *)message {
  NSDictionary *parsedMessage = [self.dataMessageManager processPacket:message];
  if ([parsedMessage count]) {
    [self.dataMessageManager didReceiveParsedMessage:parsedMessage];
  }
}

- (int)connectionDidReceiveAckForRmqIds:(NSArray *)rmqIds {
  NSSet *rmqIDSet = [NSSet setWithArray:rmqIds];
  NSMutableArray *messagesSent = [NSMutableArray arrayWithCapacity:rmqIds.count];
  [self.rmq2Manager scanWithRmqMessageHandler:nil
                           dataMessageHandler:^(int64_t rmqId, GtalkDataMessageStanza *stanza) {
                             NSString *rmqIdString = [NSString stringWithFormat:@"%lld", rmqId];
                             if ([rmqIDSet containsObject:rmqIdString]) {
                               [messagesSent addObject:stanza];
                             }
                           }];
  for (GtalkDataMessageStanza *message in messagesSent) {
    [self.dataMessageManager didSendDataMessageStanza:message];
  }
  return [self.rmq2Manager removeRmqMessagesWithRmqIds:rmqIds];
}

#pragma mark - Private

- (void)setupConnectionAndConnect {
  [self setupConnection];
  [self tryToConnect];
}

- (void)setupConnection {
  NSString *host = FIRMessagingServerHost();
  NSUInteger port = FIRMessagingServerPort();
  _FIRMessagingDevAssert([host length] > 0 && port != 0, @"Invalid port or host");

  if (self.connection != nil) {
    // if there is an old connection, explicitly sign it off.
    [self.connection signOut];
    self.connection.delegate = nil;
  }
  self.connection = [[FIRMessagingConnection alloc] initWithAuthID:self.registrar.deviceAuthID
                                                    token:self.registrar.secretToken
                                                     host:host
                                                     port:port
                                                  runLoop:[NSRunLoop mainRunLoop]
                                              rmq2Manager:self.rmq2Manager
                                               fcmManager:self.dataMessageManager];
  self.connection.delegate = self;
}

- (void)tryToConnect {
  if (!self.stayConnected) {
    return;
  }

  // Cancel any other pending signin requests.
  [NSObject cancelPreviousPerformRequestsWithTarget:self
                                           selector:@selector(tryToConnect)
                                             object:nil];

  // Do not re-sign in if there is already a connection in progress.
  if (self.connection.state != kFIRMessagingConnectionNotConnected) {
    return;
  }

  _FIRMessagingDevAssert(self.registrar.deviceAuthID.length > 0 &&
                 self.registrar.secretToken.length > 0 &&
                 self.connection != nil,
                 @"Invalid state cannot connect");

  self.connectRetryCount = MIN(kMaxRetryExponent, self.connectRetryCount + 1);
  [self performSelector:@selector(didConnectTimeout)
             withObject:nil
             afterDelay:self.connectionTimeoutInterval];
  [self.connection signIn];
}

- (void)didConnectTimeout {
  _FIRMessagingDevAssert(self.connection.state != kFIRMessagingConnectionSignedIn,
                @"Invalid state for MCS connection");

  if (self.stayConnected) {
    [self.connection signOut];
    [self scheduleConnectRetry];
  }
}

#pragma mark - Schedulers

- (void)scheduleConnectRetry {
  GULReachabilityStatus status = self.reachability.reachabilityStatus;
  BOOL isReachable = (status == kGULReachabilityViaWifi || status == kGULReachabilityViaCellular);
  if (!isReachable) {
    FIRMessagingLoggerDebug(kFIRMessagingMessageCodeClient010,
                            @"Internet not reachable when signing into MCS during a retry");

    FIRMessagingConnectCompletionHandler handler = [self.connectHandler copy];
    // disconnect before issuing a callback
    [self disconnectWithTryToConnectLater:YES];
    NSError *error =
        [NSError errorWithDomain:@"No internet available, cannot connect to FIRMessaging"
                            code:kFIRMessagingErrorCodeNetwork
                        userInfo:nil];
    if (handler) {
      handler(error);
      self.connectHandler = nil;
    }
    return;
  }

  NSUInteger retryInterval = [self nextRetryInterval];

  FIRMessagingLoggerDebug(kFIRMessagingMessageCodeClient011,
                          @"Failed to sign in to MCS, retry in %lu seconds",
                          _FIRMessaging_UL(retryInterval));
  [self performSelector:@selector(tryToConnect) withObject:nil afterDelay:retryInterval];
}

- (NSUInteger)nextRetryInterval {
  return 1u << self.connectRetryCount;
}

@end