ViewController.swift

//
//  Copyright (c) 2017 Google 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.
//

import UIKit

import FirebaseAuth
import FirebaseDatabase

class ViewController: UIViewController {

  var ref: DatabaseReference!

  func persistenceReference() {
    // [START keep_synchronized]
    let scoresRef = Database.database().reference(withPath: "scores")
    scoresRef.keepSynced(true)
    // [END keep_synchronized]

    // [START stop_sync]
    scoresRef.keepSynced(false)
    // [END stop_sync]
  }

  func loadCached() {
    // [START load_cached]
    let scoresRef = Database.database().reference(withPath: "scores")
    scoresRef.queryOrderedByValue().queryLimited(toLast: 4).observe(.childAdded) { snapshot in
      print("The \(snapshot.key) dinosaur's score is \(snapshot.value ?? "null")")
    }
    // [END load_cached]

    // [START load_more_cached]
    scoresRef.queryOrderedByValue().queryLimited(toLast: 2).observe(.childAdded) { snapshot in
      print("The \(snapshot.key) dinosaur's score is \(snapshot.value ?? "null")")
    }
    // [END load_more_cached]

    // [START disconnected]
    let presenceRef = Database.database().reference(withPath: "disconnectmessage");
    // Write a string when this client loses connection
    presenceRef.onDisconnectSetValue("I disconnected!")
    // [END disconnected]

    // [START remove_disconnect]
    presenceRef.onDisconnectRemoveValue { error, reference in
      if let error = error {
        print("Could not establish onDisconnect event: \(error)")
      }
    }
    // [END remove_disconnect]

    // [START cancel_disconnect]
    presenceRef.onDisconnectSetValue("I disconnected")
    // some time later when we change our minds
    presenceRef.cancelDisconnectOperations()
    // [END cancel_disconnect]

    // [START test_connection]
    let connectedRef = Database.database().reference(withPath: ".info/connected")
    connectedRef.observe(.value, with: { snapshot in
      if snapshot.value as? Bool ?? false {
        print("Connected")
      } else {
        print("Not connected")
      }
    })
    // [END test_connection]

    // [START last_online]
    let userLastOnlineRef = Database.database().reference(withPath: "users/morgan/lastOnline")
    userLastOnlineRef.onDisconnectSetValue(ServerValue.timestamp())
    // [END last_online]

    // [START clock_skew]
    let offsetRef = Database.database().reference(withPath: ".info/serverTimeOffset")
    offsetRef.observe(.value, with: { snapshot in
      if let offset = snapshot.value as? TimeInterval {
        print("Estimated server time in milliseconds: \(Date().timeIntervalSince1970 * 1000 + offset)")
      }
    })
    // [END clock_skew]
  }

  func writeNewUser(_ user: FirebaseAuth.User, withUsername username: String) {
    // [START rtdb_write_new_user]
    ref.child("users").child(user.uid).setValue(["username": username])
    // [END rtdb_write_new_user]
  }

  func writeNewUserWithCompletion(_ user: FirebaseAuth.User, withUsername username: String) async {
    // [START rtdb_write_new_user_completion]
    do {
      try await ref.child("users").child(user.uid).setValue(["username": username])
      print("Data saved successfully!")
    } catch {
      print("Data could not be saved: \(error).")
    }
    // [END rtdb_write_new_user_completion]
  }

  func singleUseFetchData(uid: String) async {
    let ref = Database.database().reference()
    // [START single_value_get_data]
    do {
      let snapshot = try await ref.child("users/\(uid)/username").getData()
      let userName = snapshot.value as? String ?? "Unknown"
    } catch {
      print(error)
    }
    // [END single_value_get_data]
  }

  func emulatorSettings() {
    // [START rtdb_emulator_connect]
        // In almost all cases the ns (namespace) is your project ID.
    let db = Database.database(url:"http://127.0.0.1:9000?ns=YOUR_DATABASE_NAMESPACE")
    // [END rtdb_emulator_connect]
  }

  func flushRealtimeDatabase() { 
    // [START rtdb_emulator_flush]
	// With a DatabaseReference, write nil to clear the database.
	Database.database().reference().setValue(nil)
	// [END rtdb_emulator_flush]  
  }

  func incrementStars(forPost postID: String, byUser userID: String) {
    // [START rtdb_post_stars_increment]
    let updates = [
      "posts/\(postID)/stars/\(userID)": true,
      "posts/\(postID)/starCount": ServerValue.increment(1),
      "user-posts/\(postID)/stars/\(userID)": true,
      "user-posts/\(postID)/starCount": ServerValue.increment(1)
    ] as [String : Any]
    Database.database().reference().updateChildValues(updates)
    // [END rtdb_post_stars_increment]
  }

}

func combinedExample() {
  // [START combined]
  // since I can connect from multiple devices, we store each connection instance separately
  // any time that connectionsRef's value is null (i.e. has no children) I am offline
  let myConnectionsRef = Database.database().reference(withPath: "users/morgan/connections")

  // stores the timestamp of my last disconnect (the last time I was seen online)
  let lastOnlineRef = Database.database().reference(withPath: "users/morgan/lastOnline")

  let connectedRef = Database.database().reference(withPath: ".info/connected")

  connectedRef.observe(.value, with: { snapshot in
    // only handle connection established (or I've reconnected after a loss of connection)
    guard snapshot.value as? Bool ?? false else { return }

    // add this device to my connections list
    let con = myConnectionsRef.childByAutoId()

    // when this device disconnects, remove it.
    con.onDisconnectRemoveValue()

    // The onDisconnect() call is before the call to set() itself. This is to avoid a race condition
    // where you set the user's presence to true and the client disconnects before the
    // onDisconnect() operation takes effect, leaving a ghost user.

    // this value could contain info about the device or a timestamp instead of just true
    con.setValue(true)

    // when I disconnect, update the last time I was seen online
    lastOnlineRef.onDisconnectSetValue(ServerValue.timestamp())
  })
  // [END combined]
}