firestore/swift/firestore-smoketest/SolutionCountersViewController.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 FirebaseCore
import FirebaseFirestore

class SolutionCountersController: UIViewController {

  var db: Firestore!

  override func viewDidLoad() {
    super.viewDidLoad()
    db = Firestore.firestore()
  }

  // [START counter_structs]
  // counters/${ID}
  struct Counter {
    let numShards: Int

    init(numShards: Int) {
      self.numShards = numShards
    }
  }

  // counters/${ID}/shards/${NUM}
  struct Shard {
    let count: Int

    init(count: Int) {
      self.count = count
    }
  }
  // [END counter_structs]

  // [START create_counter]
  func createCounter(ref: DocumentReference, numShards: Int) async {
    do {
      try await ref.setData(["numShards": numShards])
      for i in 0...numShards {
        try await ref.collection("shards").document(String(i)).setData(["count": 0])
      }
    } catch {
      // ...
    }
  }
  // [END create_counter]

  // [START increment_counter]
  func incrementCounter(ref: DocumentReference, numShards: Int) {
    // Select a shard of the counter at random
    let shardId = Int(arc4random_uniform(UInt32(numShards)))
    let shardRef = ref.collection("shards").document(String(shardId))

    shardRef.updateData([
      "count": FieldValue.increment(Int64(1))
    ])
  }
  // [END increment_counter]

  // [START get_count]
  func getCount(ref: DocumentReference) async {
    do {
      let querySnapshot = try await ref.collection("shards").getDocuments()
      var totalCount = 0
      for document in querySnapshot.documents {
        let count = document.data()["count"] as! Int
        totalCount += count
      }

      print("Total count is \(totalCount)")
    } catch {
      // handle error
    }
  }
  // [END get_count]
}