/*
 * Copyright 2021 Google LLC
 *
 * 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 FirebaseFirestore
import Foundation

#if compiler(>=5.5.2) && canImport(_Concurrency)
  @available(iOS 13, tvOS 13, macOS 10.15, macCatalyst 13, watchOS 7, *)
  public extension Firestore {
    /// Loads a Firestore bundle into the local cache.
    /// - Parameter bundleData: Data from the bundle to be loaded.
    /// - Throws: `Error` if the bundle data cannot be parsed.
    /// - Returns: The final `LoadBundleTaskProgress` that contains the total number of documents loaded.
    func loadBundle(_ bundleData: Data) async throws -> LoadBundleTaskProgress {
      return try await withCheckedThrowingContinuation { continuation in
        self.loadBundle(bundleData) { progress, error in
          if let err = error {
            continuation.resume(throwing: err)
          } else {
            // Our callbacks guarantee that we either return an error or a progress event.
            continuation.resume(returning: progress!)
          }
        }
      }
    }

    /// Loads a Firestore bundle into the local cache.
    /// - Parameter bundleStream: An input stream from which the bundle can be read.
    /// - Throws: `Error` if the bundle stream cannot be parsed.
    /// - Returns: The final `LoadBundleTaskProgress` that contains the total number of documents loaded.
    func loadBundle(_ bundleStream: InputStream) async throws -> LoadBundleTaskProgress {
      return try await withCheckedThrowingContinuation { continuation in
        self.loadBundle(bundleStream) { progress, error in
          if let err = error {
            continuation.resume(throwing: err)
          } else {
            // Our callbacks guarantee that we either return an error or a progress event.
            continuation.resume(returning: progress!)
          }
        }
      }
    }

    /// Executes the given updateBlock and then attempts to commit the changes applied within an atomic
    /// transaction.
    ///
    /// The maximum number of writes allowed in a single transaction is 500, but note that each usage of
    /// `FieldValue.serverTimestamp()`, `FieldValue.arrayUnion()`, `FieldValue.arrayRemove()`, or
    /// `FieldValue.increment()` inside a transaction counts as an additional write.
    ///
    /// In the `updateBlock`, a set of reads and writes can be performed atomically using the
    /// `Transaction` object passed to the block. After the `updateBlock` is run, Firestore will attempt
    /// to apply the changes to the server. If any of the data read has been modified outside of this
    /// transaction since being read, then the transaction will be retried by executing the `updateBlock`
    /// again. If the transaction still fails after 5 retries, then the transaction will fail.
    ///
    /// Since the `updateBlock` may be executed multiple times, it should avoiding doing anything that
    /// would cause side effects.
    ///
    /// Any value maybe be returned from the `updateBlock`. If the transaction is successfully committed,
    /// then the completion block will be passed that value. The `updateBlock` also has an `NSError` out
    /// parameter. If this is set, then the transaction will not attempt to commit, and the given error
    /// will be returned.
    ///
    /// The `Transaction` object passed to the `updateBlock` contains methods for accessing documents
    /// and collections. Unlike other firestore access, data accessed with the transaction will not
    /// reflect local changes that have not been committed. For this reason, it is required that all
    /// reads are performed before any writes. Transactions must be performed while online. Otherwise,
    /// reads will fail, the final commit will fail, and this function will return an error.
    ///
    /// - Parameter updateBlock The block to execute within the transaction context.
    /// - Throws Throws an error if the transaction could not be committed, or if an error was explicitly specified in the `updateBlock` parameter.
    /// - Returns Returns the value returned in the `updateBlock` parameter if no errors occurred.
    func runTransaction(_ updateBlock: @escaping (Transaction, NSErrorPointer)
      -> Any?) async throws -> Any? {
      // This needs to be wrapped in order to express a nullable return value upon success.
      // See https://github.com/firebase/firebase-ios-sdk/issues/9426 for more details.
      return try await withCheckedThrowingContinuation { continuation in
        self.runTransaction(updateBlock) { anyValue, error in
          if let err = error {
            continuation.resume(throwing: err)
          } else {
            continuation.resume(returning: anyValue)
          }
        }
      }
    }
  }
#endif
