/*
 * 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 "Firebase/Messaging/FIRMessagingRmqManager.h"

#import <sqlite3.h>

#import "Firebase/Messaging/FIRMessagingConstants.h"
#import "Firebase/Messaging/FIRMessagingDefines.h"
#import "Firebase/Messaging/FIRMessagingLogger.h"
#import "Firebase/Messaging/FIRMessagingPersistentSyncMessage.h"
#import "Firebase/Messaging/FIRMessagingUtilities.h"
#import "Firebase/Messaging/NSError+FIRMessaging.h"
#import "Firebase/Messaging/Protos/GtalkCore.pbobjc.h"

#ifndef _FIRMessagingRmqLogAndExit
#define _FIRMessagingRmqLogAndExit(stmt, return_value)   \
do {                              \
[self logErrorAndFinalizeStatement:stmt];  \
return return_value; \
} while(0)
#endif

#ifndef FIRMessagingRmqLogAndReturn
#define FIRMessagingRmqLogAndReturn(stmt)   \
do {                              \
[self logErrorAndFinalizeStatement:stmt];  \
return; \
} while(0)
#endif

#ifndef FIRMessaging_MUST_NOT_BE_MAIN_THREAD
#define FIRMessaging_MUST_NOT_BE_MAIN_THREAD()                                                 \
  do {                                                                                \
    NSAssert(![NSThread isMainThread], @"Must not be executing on the main thread."); \
  } while (0);
#endif



// table names
NSString *const kTableOutgoingRmqMessages = @"outgoingRmqMessages";
NSString *const kTableLastRmqId = @"lastrmqid";
NSString *const kOldTableS2DRmqIds = @"s2dRmqIds";
NSString *const kTableS2DRmqIds = @"s2dRmqIds_1";

// Used to prevent de-duping of sync messages received both via APNS and MCS.
NSString *const kTableSyncMessages = @"incomingSyncMessages";

static NSString *const kTablePrefix = @"";

// create tables
static NSString *const kCreateTableOutgoingRmqMessages =
    @"create TABLE IF NOT EXISTS %@%@ "
    @"(_id INTEGER PRIMARY KEY, "
    @"rmq_id INTEGER, "
    @"type INTEGER, "
    @"ts INTEGER, "
    @"data BLOB)";

static NSString *const kCreateTableLastRmqId =
    @"create TABLE IF NOT EXISTS %@%@ "
    @"(_id INTEGER PRIMARY KEY, "
    @"rmq_id INTEGER)";

static NSString *const kCreateTableS2DRmqIds =
    @"create TABLE IF NOT EXISTS %@%@ "
    @"(_id INTEGER PRIMARY KEY, "
    @"rmq_id TEXT)";

static NSString *const kCreateTableSyncMessages =
    @"create TABLE IF NOT EXISTS %@%@ "
    @"(_id INTEGER PRIMARY KEY, "
    @"rmq_id TEXT, "
    @"expiration_ts INTEGER, "
    @"apns_recv INTEGER, "
    @"mcs_recv INTEGER)";

static NSString *const kDropTableCommand =
    @"drop TABLE if exists %@%@";

// table infos
static NSString *const kRmqIdColumn = @"rmq_id";
static NSString *const kDataColumn = @"data";
static NSString *const kProtobufTagColumn = @"type";
static NSString *const kIdColumn = @"_id";

static NSString *const kOutgoingRmqMessagesColumns = @"rmq_id, type, data";

// Sync message columns
static NSString *const kSyncMessagesColumns = @"rmq_id, expiration_ts, apns_recv, mcs_recv";
// Message time expiration in seconds since 1970
static NSString *const kSyncMessageExpirationTimestampColumn = @"expiration_ts";
static NSString *const kSyncMessageAPNSReceivedColumn = @"apns_recv";
static NSString *const kSyncMessageMCSReceivedColumn = @"mcs_recv";

// Utility to create an NSString from a sqlite3 result code
NSString * _Nonnull FIRMessagingStringFromSQLiteResult(int result) {
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wunguarded-availability"
  const char *errorStr = sqlite3_errstr(result);
#pragma clang diagnostic pop
  NSString *errorString = [NSString stringWithFormat:@"%d - %s", result, errorStr];
  return errorString;
}

@interface FIRMessagingRmqManager () {
  sqlite3 *_database;
  /// Serial queue for database read/write operations.
  dispatch_queue_t _databaseOperationQueue;
}

@property(nonatomic, readwrite, strong) NSString *databaseName;
// map the category of an outgoing message with the number of messages for that category
// should always have two keys -- the app, gcm
@property(nonatomic, readwrite, strong) NSMutableDictionary *outstandingMessages;

// Outgoing RMQ persistent id
@property(nonatomic, readwrite, assign) int64_t rmqId;
@end

@implementation FIRMessagingRmqManager

- (instancetype)initWithDatabaseName:(NSString *)databaseName {
  self = [super init];
  if (self) {
    _databaseOperationQueue =
        dispatch_queue_create("com.google.firebase.messaging.database.rmq", DISPATCH_QUEUE_SERIAL);
    _databaseName = [databaseName copy];
    [self openDatabase];
    _outstandingMessages = [NSMutableDictionary dictionaryWithCapacity:2];
    _rmqId = -1;
  }
  return self;
}

- (void)dealloc {
  sqlite3_close(_database);
}

# pragma mark - RMQ ID

- (void)loadRmqId {
  if (self.rmqId >= 0) {
    return; // already done
  }

  [self loadInitialOutgoingPersistentId];
  if (self.outstandingMessages.count) {
    FIRMessagingLoggerDebug(kFIRMessagingMessageCodeRmqManager000,
                            @"Outstanding categories %ld",
                            _FIRMessaging_UL(self.outstandingMessages.count));
  }
}

/**
 * Initialize the 'initial RMQ':
 * - max ID of any message in the queue
 * - if the queue is empty, stored value in separate DB.
 *
 * Stream acks will remove from RMQ, when we remove the highest message we keep track
 * of its ID.
 */
- (void)loadInitialOutgoingPersistentId {

  // we shouldn't always trust the lastRmqId stored in the LastRmqId table, because
  // we only save to the LastRmqId table once in a while (after getting the lastRmqId sent
  // by the server after reconnect, and after getting a rmq ack from the server). The
  // rmq message with the highest rmq id tells the real story, so check against that first.

  __block int64_t rmqId;
  dispatch_sync(_databaseOperationQueue, ^{
    rmqId = [self queryHighestRmqId];
  });
  if (rmqId == 0) {
    dispatch_sync(_databaseOperationQueue, ^{
      rmqId = [self queryLastRmqId];
    });
  }
  self.rmqId = rmqId + 1;
}

#pragma mark - Save

/**
 * Save a message to RMQ2. Will populate the rmq2 persistent ID.
 */
- (void)saveRmqMessage:(GPBMessage *)message withCompletionHandler:(void(^)(BOOL success))handler {
  // send using rmq2manager
  // the wire format of rmq2 id is a string. However, we keep it as a long internally
  // in the database. So only convert the id to string when preparing for sending over
  // the wire.
  NSString *rmq2Id = FIRMessagingGetRmq2Id(message);
  if (![rmq2Id length]) {
    int64_t rmqId = [self nextRmqId];
    rmq2Id = [NSString stringWithFormat:@"%lld", rmqId];
    FIRMessagingSetRmq2Id(message, rmq2Id);
  }
  FIRMessagingProtoTag tag = FIRMessagingGetTagForProto(message);
  NSData *data = [message data];
  dispatch_async(_databaseOperationQueue, ^{
    BOOL success = [self saveMessageWithRmqId:[rmq2Id integerValue] tag:tag data:data];
    if (handler) {
      dispatch_async(dispatch_get_main_queue(), ^{
        handler(success);
      });
    }
  });
}

/**
 * This is called when we delete the largest outgoing message from queue.
 */
- (void)saveLastOutgoingRmqId:(int64_t)rmqID {
  dispatch_async(_databaseOperationQueue, ^{
    NSString *queryFormat = @"INSERT OR REPLACE INTO %@ (%@, %@) VALUES (?, ?)";
    NSString *query = [NSString stringWithFormat:queryFormat,
                       kTableLastRmqId, // table
                       kIdColumn, kRmqIdColumn]; // columns
    sqlite3_stmt *statement;
    if (sqlite3_prepare_v2(self->_database, [query UTF8String], -1, &statement, NULL) != SQLITE_OK) {
      FIRMessagingRmqLogAndReturn(statement);
    }
    if (sqlite3_bind_int(statement, 1, 1) != SQLITE_OK) {
      FIRMessagingRmqLogAndReturn(statement);
    }
    if (sqlite3_bind_int64(statement, 2, rmqID) != SQLITE_OK) {
      FIRMessagingRmqLogAndReturn(statement);
    }
    if (sqlite3_step(statement) != SQLITE_DONE) {
      FIRMessagingRmqLogAndReturn(statement);
    }
    sqlite3_finalize(statement);
  });
}

- (void)saveS2dMessageWithRmqId:(NSString *)rmqId {
  dispatch_async(_databaseOperationQueue, ^{
    NSString *insertFormat = @"INSERT INTO %@ (%@) VALUES (?)";
    NSString *insertSQL = [NSString stringWithFormat:insertFormat,
                           kTableS2DRmqIds,
                           kRmqIdColumn];
    sqlite3_stmt *insert_statement;
    if (sqlite3_prepare_v2(self->_database, [insertSQL UTF8String], -1, &insert_statement, NULL)
        != SQLITE_OK) {
      FIRMessagingRmqLogAndReturn(insert_statement);
    }
    if (sqlite3_bind_text(insert_statement,
                          1,
                          [rmqId UTF8String],
                          (int)[rmqId length],
                          SQLITE_STATIC) != SQLITE_OK) {
      FIRMessagingRmqLogAndReturn(insert_statement);
    }
    if (sqlite3_step(insert_statement) != SQLITE_DONE) {
      FIRMessagingRmqLogAndReturn(insert_statement);
    }
    sqlite3_finalize(insert_statement);
  });
}

#pragma mark - Query

- (int64_t)queryHighestRmqId {
  NSString *queryFormat = @"SELECT %@ FROM %@ ORDER BY %@ DESC LIMIT %d";
  NSString *query = [NSString stringWithFormat:queryFormat,
                     kRmqIdColumn, // column
                     kTableOutgoingRmqMessages, // table
                     kRmqIdColumn, // order by column
                     1]; // limit

  sqlite3_stmt *statement;
  int64_t highestRmqId = 0;
  if (sqlite3_prepare_v2(_database, [query UTF8String], -1, &statement, NULL) != SQLITE_OK) {
    _FIRMessagingRmqLogAndExit(statement, highestRmqId);
  }
  if (sqlite3_step(statement) == SQLITE_ROW) {
    highestRmqId = sqlite3_column_int64(statement, 0);
  }
  sqlite3_finalize(statement);
  return highestRmqId;
}

- (int64_t)queryLastRmqId {
  NSString *queryFormat = @"SELECT %@ FROM %@ ORDER BY %@ DESC LIMIT %d";
  NSString *query = [NSString stringWithFormat:queryFormat,
                     kRmqIdColumn, // column
                     kTableLastRmqId, // table
                     kRmqIdColumn, // order by column
                     1]; // limit

  sqlite3_stmt *statement;
  int64_t lastRmqId = 0;
  if (sqlite3_prepare_v2(_database, [query UTF8String], -1, &statement, NULL) != SQLITE_OK) {
    _FIRMessagingRmqLogAndExit(statement, lastRmqId);
  }
  if (sqlite3_step(statement) == SQLITE_ROW) {
    lastRmqId = sqlite3_column_int64(statement, 0);
  }
  sqlite3_finalize(statement);
  return lastRmqId;
}

- (NSArray *)unackedS2dRmqIds {
  __block NSMutableArray *rmqIDArray = [NSMutableArray array];
  dispatch_sync(_databaseOperationQueue, ^{
    NSString *queryFormat = @"SELECT %@ FROM %@ ORDER BY %@ ASC";
    NSString *query = [NSString stringWithFormat:queryFormat,
                       kRmqIdColumn,
                       kTableS2DRmqIds,
                       kRmqIdColumn];
    sqlite3_stmt *statement;
    if (sqlite3_prepare_v2(self->_database, [query UTF8String], -1, &statement, NULL) != SQLITE_OK) {
      FIRMessagingLoggerDebug(kFIRMessagingMessageCodeRmq2PersistentStore005,
                              @"Could not find s2d ids");
      FIRMessagingRmqLogAndReturn(statement);
    }
    while (sqlite3_step(statement) == SQLITE_ROW) {
      const char *rmqID = (char *)sqlite3_column_text(statement, 0);
      [rmqIDArray addObject:[NSString stringWithUTF8String:rmqID]];
    }
    sqlite3_finalize(statement);
  });
  return rmqIDArray;
}

#pragma mark - FIRMessagingRMQScanner protocol

#pragma mark - Remove
- (void)removeRmqMessagesWithRmqIds:(NSArray *)rmqIds {
  if (![rmqIds count]) {
    return;
  }
  int64_t maxRmqId = -1;
  for (NSString *rmqId in rmqIds) {
    int64_t rmqIdValue = [rmqId longLongValue];
    if (rmqIdValue > maxRmqId) {
      maxRmqId = rmqIdValue;
    }
  }
  maxRmqId++;
  if (maxRmqId >= self.rmqId) {
    [self saveLastOutgoingRmqId:maxRmqId];
  }
  [self deleteMessagesFromTable:kTableOutgoingRmqMessages withRmqIds:rmqIds];
}

- (void)removeS2dIds:(NSArray *)s2dIds {
  [self deleteMessagesFromTable:kTableS2DRmqIds withRmqIds:s2dIds];
}

#pragma mark - Sync Messages

- (FIRMessagingPersistentSyncMessage *)querySyncMessageWithRmqID:(NSString *)rmqID {
  __block FIRMessagingPersistentSyncMessage *persistentMessage;
  dispatch_sync(_databaseOperationQueue, ^{
    NSString *queryFormat = @"SELECT %@ FROM %@ WHERE %@ = '%@'";
    NSString *query = [NSString stringWithFormat:queryFormat,
                       kSyncMessagesColumns, // SELECT (rmq_id, expiration_ts, apns_recv, mcs_recv)
                       kTableSyncMessages,   // FROM sync_rmq
                       kRmqIdColumn,         // WHERE rmq_id
                       rmqID];

    sqlite3_stmt *stmt;
    if (sqlite3_prepare_v2(self->_database, [query UTF8String], -1, &stmt, NULL) != SQLITE_OK) {
      [self logError];
      sqlite3_finalize(stmt);
      return;
    }

    const int rmqIDColumn = 0;
    const int expirationTimestampColumn = 1;
    const int apnsReceivedColumn = 2;
    const int mcsReceivedColumn = 3;

    int count = 0;

    while (sqlite3_step(stmt) == SQLITE_ROW) {
      NSString *rmqID =
          [NSString stringWithUTF8String:(char *)sqlite3_column_text(stmt, rmqIDColumn)];
      int64_t expirationTimestamp = sqlite3_column_int64(stmt, expirationTimestampColumn);
      BOOL apnsReceived = sqlite3_column_int(stmt, apnsReceivedColumn);
      BOOL mcsReceived = sqlite3_column_int(stmt, mcsReceivedColumn);

      // create a new persistent message
      persistentMessage =
          [[FIRMessagingPersistentSyncMessage alloc] initWithRMQID:rmqID expirationTime:expirationTimestamp];
      persistentMessage.apnsReceived = apnsReceived;
      persistentMessage.mcsReceived = mcsReceived;

      count++;
    }
    sqlite3_finalize(stmt);
  });

  return persistentMessage;
}

- (void)deleteSyncMessageWithRmqID:(NSString *)rmqID {
  [self deleteMessagesFromTable:kTableSyncMessages withRmqIds:@[rmqID]];
}

- (void)deleteExpiredOrFinishedSyncMessages {
  dispatch_async(_databaseOperationQueue, ^{
    int64_t now = FIRMessagingCurrentTimestampInSeconds();
    NSString *deleteSQL = @"DELETE FROM %@ "
                          @"WHERE %@ < %lld OR "  // expirationTime < now
                          @"(%@ = 1 AND %@ = 1)";  // apns_received = 1 AND mcs_received = 1
    NSString *query = [NSString stringWithFormat:deleteSQL,
                       kTableSyncMessages,
                       kSyncMessageExpirationTimestampColumn,
                       now,
                       kSyncMessageAPNSReceivedColumn,
                       kSyncMessageMCSReceivedColumn];
    sqlite3_stmt *stmt;
    if (sqlite3_prepare_v2(self->_database, [query UTF8String], -1, &stmt, NULL) != SQLITE_OK) {
      FIRMessagingRmqLogAndReturn(stmt);
    }

    if (sqlite3_step(stmt) != SQLITE_DONE) {
      FIRMessagingRmqLogAndReturn(stmt);
    }

    sqlite3_finalize(stmt);
    int deleteCount = sqlite3_changes(self->_database);
    if (deleteCount > 0) {
      FIRMessagingLoggerDebug(kFIRMessagingMessageCodeSyncMessageManager001,
                              @"Successfully deleted %d sync messages from store", deleteCount);
    }
  });
}

- (void)saveSyncMessageWithRmqID:(NSString *)rmqID
                  expirationTime:(int64_t)expirationTime
                    apnsReceived:(BOOL)apnsReceived
                     mcsReceived:(BOOL)mcsReceived {
  dispatch_async(_databaseOperationQueue, ^{
    NSString *insertFormat = @"INSERT INTO %@ (%@, %@, %@, %@) VALUES (?, ?, ?, ?)";
    NSString *insertSQL = [NSString stringWithFormat:insertFormat,
                           kTableSyncMessages, // Table name
                           kRmqIdColumn, // rmq_id
                           kSyncMessageExpirationTimestampColumn, // expiration_ts
                           kSyncMessageAPNSReceivedColumn, // apns_recv
                           kSyncMessageMCSReceivedColumn /* mcs_recv */];

    sqlite3_stmt *stmt;

    if (sqlite3_prepare_v2(self->_database, [insertSQL UTF8String], -1, &stmt, NULL) != SQLITE_OK) {
      FIRMessagingRmqLogAndReturn(stmt);
    }

    if (sqlite3_bind_text(stmt, 1, [rmqID UTF8String], (int)[rmqID length], NULL) != SQLITE_OK) {
      FIRMessagingRmqLogAndReturn(stmt);
    }

    if (sqlite3_bind_int64(stmt, 2, expirationTime) != SQLITE_OK) {
      FIRMessagingRmqLogAndReturn(stmt);
    }

    if (sqlite3_bind_int(stmt, 3, apnsReceived ? 1 : 0) != SQLITE_OK) {
      FIRMessagingRmqLogAndReturn(stmt);
    }

    if (sqlite3_bind_int(stmt, 4, mcsReceived ? 1 : 0) != SQLITE_OK) {
      FIRMessagingRmqLogAndReturn(stmt);
    }

    if (sqlite3_step(stmt) != SQLITE_DONE) {
      FIRMessagingRmqLogAndReturn(stmt);
    }
    sqlite3_finalize(stmt);
    FIRMessagingLoggerInfo(kFIRMessagingMessageCodeSyncMessageManager004,
                             @"Added sync message to cache: %@", rmqID);
  });

}

- (void)updateSyncMessageViaAPNSWithRmqID:(NSString *)rmqID {
  dispatch_async(_databaseOperationQueue, ^{
    if (![self updateSyncMessageWithRmqID:rmqID
                                     column:kSyncMessageAPNSReceivedColumn
                                      value:YES]) {
      FIRMessagingLoggerError(kFIRMessagingMessageCodeSyncMessageManager005,
                              @"Failed to update APNS state for sync message %@", rmqID);
    }
  });
}

- (void)updateSyncMessageViaMCSWithRmqID:(NSString *)rmqID {
  dispatch_async(_databaseOperationQueue, ^{
    if (![self updateSyncMessageWithRmqID:rmqID
                                     column:kSyncMessageMCSReceivedColumn
                                      value:YES]) {
      FIRMessagingLoggerError(kFIRMessagingMessageCodeSyncMessageManager006,
                                   @"Failed to update MCS state for sync message %@", rmqID);
    }
  });
}

- (BOOL)updateSyncMessageWithRmqID:(NSString *)rmqID
                            column:(NSString *)column
                             value:(BOOL)value{
  FIRMessaging_MUST_NOT_BE_MAIN_THREAD();
  NSString *queryFormat = @"UPDATE %@ "  // Table name
                          @"SET %@ = %d "  // column=value
                          @"WHERE %@ = ?";  // condition
  NSString *query = [NSString stringWithFormat:queryFormat,
                     kTableSyncMessages,
                     column,
                     value ? 1 : 0,
                     kRmqIdColumn];
  sqlite3_stmt *stmt;

  if (sqlite3_prepare_v2(_database, [query UTF8String], -1, &stmt, NULL) != SQLITE_OK) {
    _FIRMessagingRmqLogAndExit(stmt, NO);
  }

  if (sqlite3_bind_text(stmt, 1, [rmqID UTF8String], (int)[rmqID length], NULL) != SQLITE_OK) {
    _FIRMessagingRmqLogAndExit(stmt, NO);
  }

  if (sqlite3_step(stmt) != SQLITE_DONE) {
    _FIRMessagingRmqLogAndExit(stmt, NO);
  }

  sqlite3_finalize(stmt);
  return YES;

}

# pragma mark - Database

- (NSString *)pathForDatabase {
  NSString *dbNameWithExtension = [NSString stringWithFormat:@"%@.sqlite", _databaseName];
  NSArray *paths = NSSearchPathForDirectoriesInDomains(FIRMessagingSupportedDirectory(),
                                                  NSUserDomainMask,
                                                  YES);
  NSArray *components = @[
                     paths.lastObject,
                     kFIRMessagingSubDirectoryName,
                     dbNameWithExtension
                     ];
  return [NSString pathWithComponents:components];
}

- (void)createTableWithName:(NSString *)tableName command:(NSString *)command {
  FIRMessaging_MUST_NOT_BE_MAIN_THREAD();
  char *error;
  NSString *createDatabase = [NSString stringWithFormat:command, kTablePrefix, tableName];
  if (sqlite3_exec(self->_database, [createDatabase UTF8String], NULL, NULL, &error) != SQLITE_OK) {
    // remove db before failing
    [self removeDatabase];
    NSString *errorMessage = [NSString stringWithFormat:@"Couldn't create table: %@ %@",
                              kCreateTableOutgoingRmqMessages,
                              [NSString stringWithCString:error encoding:NSUTF8StringEncoding]];
    FIRMessagingLoggerError(kFIRMessagingMessageCodeRmq2PersistentStoreErrorCreatingTable,
                            @"%@",
                            errorMessage);
    NSAssert(NO, errorMessage);
  }
}

- (void)dropTableWithName:(NSString *)tableName {
  FIRMessaging_MUST_NOT_BE_MAIN_THREAD();
  char *error;
    NSString *dropTableSQL = [NSString stringWithFormat:kDropTableCommand, kTablePrefix, tableName];
    if (sqlite3_exec(self->_database, [dropTableSQL UTF8String], NULL, NULL, &error) != SQLITE_OK) {
      FIRMessagingLoggerError(kFIRMessagingMessageCodeRmq2PersistentStore002,
                            @"Failed to remove table %@", tableName);
    }
}

- (void)removeDatabase {
  // Ensure database is removed in a sync queue as this sometimes makes test have race conditions.
  dispatch_sync(_databaseOperationQueue, ^{
    NSString *path = [self pathForDatabase];
    [[NSFileManager defaultManager] removeItemAtPath:path error:nil];
  });
}

- (void)openDatabase {
  dispatch_async(_databaseOperationQueue, ^{
    NSFileManager *fileManager = [NSFileManager defaultManager];
    NSString *path = [self pathForDatabase];

    BOOL didOpenDatabase = YES;
    if (![fileManager fileExistsAtPath:path]) {
      // We've to separate between different versions here because of backwards compatbility issues.
      int result = sqlite3_open_v2([path UTF8String],
                                   &self->_database,
                                   SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_FILEPROTECTION_NONE,
                                   NULL);
      if (result != SQLITE_OK) {
        NSString *errorString = FIRMessagingStringFromSQLiteResult(result);
        NSString *errorMessage =
            [NSString stringWithFormat:@"Could not open existing RMQ database at path %@, error: %@",
                                       path,
                                       errorString];
        FIRMessagingLoggerError(kFIRMessagingMessageCodeRmq2PersistentStoreErrorOpeningDatabase,
                                @"%@",
                                errorMessage);
        NSAssert(NO, errorMessage);
        return;
      }
      [self createTableWithName:kTableOutgoingRmqMessages
                        command:kCreateTableOutgoingRmqMessages];

      [self createTableWithName:kTableLastRmqId command:kCreateTableLastRmqId];
      [self createTableWithName:kTableS2DRmqIds command:kCreateTableS2DRmqIds];
    } else {
      // Calling sqlite3_open should create the database, since the file doesn't exist.
      int result = sqlite3_open_v2([path UTF8String],
                                   &self->_database,
                                   SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_FILEPROTECTION_NONE,
                                   NULL);
      if (result != SQLITE_OK) {
        NSString *errorString = FIRMessagingStringFromSQLiteResult(result);
        NSString *errorMessage =
            [NSString stringWithFormat:@"Could not create RMQ database at path %@, error: %@",
                                       path,
                                       errorString];
        FIRMessagingLoggerError(kFIRMessagingMessageCodeRmq2PersistentStoreErrorCreatingDatabase,
                                @"%@",
                                errorMessage);
        NSAssert(NO, errorMessage);
        didOpenDatabase = NO;
      } else {
        [self updateDBWithStringRmqID];
      }
    }

    if (didOpenDatabase) {
      [self createTableWithName:kTableSyncMessages command:kCreateTableSyncMessages];
    }
  });
}

- (void)updateDBWithStringRmqID {
  dispatch_async(_databaseOperationQueue, ^{
    [self createTableWithName:kTableS2DRmqIds command:kCreateTableS2DRmqIds];
    [self dropTableWithName:kOldTableS2DRmqIds];
  });
}

#pragma mark - Scan

/**
 * We don't have a 'getMessages' method - it would require loading in memory
 * the entire content body of all messages.
 *
 * Instead we iterate and call 'resend' for each message.
 *
 * This is called:
 *  - on connect MCS, to resend any outstanding messages
 *  - init
 */
- (void)scanWithRmqMessageHandler:(FIRMessagingRmqMessageHandler)rmqMessageHandler {
  dispatch_async(_databaseOperationQueue, ^{
    NSMutableDictionary *messages = [NSMutableDictionary dictionary];
    static NSString *queryFormat = @"SELECT %@ FROM %@ WHERE %@ != 0 ORDER BY %@ ASC";
    NSString *query = [NSString stringWithFormat:queryFormat,
                       kOutgoingRmqMessagesColumns, // select (rmq_id, type, data)
                       kTableOutgoingRmqMessages, // from table
                       kRmqIdColumn, // where
                       kRmqIdColumn]; // order by
    sqlite3_stmt *statement;
    if (sqlite3_prepare_v2(self->_database, [query UTF8String], -1, &statement, NULL) != SQLITE_OK) {
      [self logError];
      sqlite3_finalize(statement);
      if (rmqMessageHandler) {
        dispatch_async(dispatch_get_main_queue(),^{
          rmqMessageHandler(messages);
        });
      }
    }
    // can query sqlite3 for this but this is fine
    const int rmqIdColumnNumber = 0;
    const int typeColumnNumber = 1;
    const int dataColumnNumber = 2;
    while (sqlite3_step(statement) == SQLITE_ROW) {
      int64_t rmqId = sqlite3_column_int64(statement, rmqIdColumnNumber);
      int8_t type = sqlite3_column_int(statement, typeColumnNumber);
      const void *bytes = sqlite3_column_blob(statement, dataColumnNumber);
      int length = sqlite3_column_bytes(statement, dataColumnNumber);

      NSData *data = [NSData dataWithBytes:bytes length:length];
      GPBMessage *proto = [FIRMessagingGetClassForTag((FIRMessagingProtoTag)type) parseFromData:data error:NULL];
      [messages addEntriesFromDictionary:@{@(rmqId): proto}];
    }
    sqlite3_finalize(statement);
    if (rmqMessageHandler) {
      dispatch_async(dispatch_get_main_queue(),^{
        rmqMessageHandler(messages);
      });
    }
  });
}

#pragma mark - Private

- (BOOL)saveMessageWithRmqId:(int64_t)rmqId
                         tag:(int8_t)tag
                        data:(NSData *)data {
  FIRMessaging_MUST_NOT_BE_MAIN_THREAD();
  NSString *insertFormat = @"INSERT INTO %@ (%@, %@, %@) VALUES (?, ?, ?)";
  NSString *insertSQL = [NSString stringWithFormat:insertFormat,
                         kTableOutgoingRmqMessages, // table
                         kRmqIdColumn, kProtobufTagColumn, kDataColumn /* columns */];
  sqlite3_stmt *insert_statement;
  if (sqlite3_prepare_v2(self->_database, [insertSQL UTF8String], -1, &insert_statement, NULL)
      != SQLITE_OK) {
    _FIRMessagingRmqLogAndExit(insert_statement, NO);
  }
  if (sqlite3_bind_int64(insert_statement, 1, rmqId) != SQLITE_OK) {
    _FIRMessagingRmqLogAndExit(insert_statement, NO);
  }
  if (sqlite3_bind_int(insert_statement, 2, tag) != SQLITE_OK) {
    _FIRMessagingRmqLogAndExit(insert_statement, NO);
  }
  if (sqlite3_bind_blob(insert_statement, 3, [data bytes], (int)[data length], NULL) != SQLITE_OK) {
    _FIRMessagingRmqLogAndExit(insert_statement, NO);
  }
  if (sqlite3_step(insert_statement) != SQLITE_DONE) {
    _FIRMessagingRmqLogAndExit(insert_statement, NO);
  }

  sqlite3_finalize(insert_statement);

  return YES;
}

- (void)deleteMessagesFromTable:(NSString *)tableName
                    withRmqIds:(NSArray *)rmqIds {
  dispatch_async(_databaseOperationQueue, ^{
    BOOL isRmqIDString = NO;
    // RmqID is a string only for outgoing messages
    if ([tableName isEqualToString:kTableS2DRmqIds] ||
        [tableName isEqualToString:kTableSyncMessages]) {
      isRmqIDString = YES;
    }

    NSMutableString *delete = [NSMutableString stringWithFormat:@"DELETE FROM %@ WHERE ", tableName];

    NSString *toDeleteArgument = [NSString stringWithFormat:@"%@ = ? OR ", kRmqIdColumn];

    int toDelete = (int)[rmqIds count];
    if (toDelete == 0) {
      return;
    }
    int maxBatchSize = 100;
    int start = 0;
    int deleteCount = 0;
    while (start < toDelete) {

      // construct the WHERE argument
      int end = MIN(start + maxBatchSize, toDelete);
      NSMutableString *whereArgument = [NSMutableString string];
      for (int i = start; i < end; i++) {
        [whereArgument appendString:toDeleteArgument];
      }
      // remove the last * OR * from argument
      NSRange range = NSMakeRange([whereArgument length] -4, 4);
      [whereArgument deleteCharactersInRange:range];
      NSString *deleteQuery = [NSString stringWithFormat:@"%@ %@", delete, whereArgument];


      // sqlite update
      sqlite3_stmt *delete_statement;
      if (sqlite3_prepare_v2(self->_database, [deleteQuery UTF8String],
                             -1, &delete_statement, NULL) != SQLITE_OK) {
        FIRMessagingRmqLogAndReturn(delete_statement);
      }

      // bind values
      int rmqIndex = 0;
      int placeholderIndex = 1; // placeholders in sqlite3 start with 1
      for (NSString *rmqId in rmqIds) { // objectAtIndex: is O(n) -- would make it slow
        if (rmqIndex < start) {
          rmqIndex++;
          continue;
        } else if (rmqIndex >= end) {
          break;
        } else {
          if (isRmqIDString) {
            if (sqlite3_bind_text(delete_statement,
                                  placeholderIndex,
                                  [rmqId UTF8String],
                                  (int)[rmqId length],
                                  SQLITE_STATIC) != SQLITE_OK) {
              FIRMessagingLoggerDebug(kFIRMessagingMessageCodeRmq2PersistentStore003,
                                      @"Failed to bind rmqID %@", rmqId);
              FIRMessagingLoggerError(kFIRMessagingMessageCodeSyncMessageManager007,
                @"Failed to delete sync message %@", rmqId);
              continue;
            }
          } else {
            int64_t rmqIdValue = [rmqId longLongValue];
            sqlite3_bind_int64(delete_statement, placeholderIndex, rmqIdValue);
          }
          placeholderIndex++;
        }
        rmqIndex++;
        FIRMessagingLoggerInfo(kFIRMessagingMessageCodeSyncMessageManager008,
                               @"Successfully deleted sync message from cache %@", rmqId);
      }
      if (sqlite3_step(delete_statement) != SQLITE_DONE) {
        FIRMessagingRmqLogAndReturn(delete_statement);
      }
      sqlite3_finalize(delete_statement);
      deleteCount += sqlite3_changes(self->_database);
      start = end;
    }

    // if we are here all of our sqlite queries should have succeeded
    FIRMessagingLoggerDebug(kFIRMessagingMessageCodeRmq2PersistentStore004,
                            @"Trying to delete %d s2D ID's, successfully deleted %d",
                            toDelete, deleteCount);
  });
}

- (int64_t)nextRmqId {
  return ++self.rmqId;
}

- (NSString *)lastErrorMessage {
  return [NSString stringWithFormat:@"%s", sqlite3_errmsg(_database)];
}

- (int)lastErrorCode {
  return sqlite3_errcode(_database);
}

- (void)logError {
  FIRMessagingLoggerError(kFIRMessagingMessageCodeRmq2PersistentStore006,
                          @"Error: code (%d) message: %@", [self lastErrorCode],
                          [self lastErrorMessage]);
}

- (void)logErrorAndFinalizeStatement:(sqlite3_stmt *)stmt {
  [self logError];
  sqlite3_finalize(stmt);
}
@end