/*
 * Copyright 2020 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 Foundation
import FirebaseFunctions
import FirebaseSharedSwift

public extension Functions {
  /**
   * Creates a reference to the Callable HTTPS trigger with the given name, the type of an `Encodable`
   * request and the type of a `Decodable` response.
   *
   * - Parameter name: The name of the Callable HTTPS trigger
   * - Parameter requestType: The type of the `Encodable` entity to use for requests to this `Callable`
   * - Parameter responseType: The type of the `Decodable` entity to use for responses from this `Callable`
   */
  func httpsCallable<Request: Encodable,
    Response: Decodable>(_ name: String,
                         requestType: Request.Type,
                         responseType: Response.Type)
    -> Callable<Request, Response> {
    return Callable(callable: httpsCallable(name))
  }
}

/**
 * A `Callable` is reference to a particular Callable HTTPS trigger in Cloud Functions.
 */
public struct Callable<Request: Encodable, Response: Decodable> {
  /**
   * The timeout to use when calling the function. Defaults to 60 seconds.
   */
  public var timeoutInterval: TimeInterval {
    get {
      callable.timeoutInterval
    }
    set {
      callable.timeoutInterval = newValue
    }
  }

  enum CallableError: Error {
    case internalError
  }

  private let callable: HTTPSCallable
  init(callable: HTTPSCallable) {
    self.callable = callable
  }

  /**
   * Executes this Callable HTTPS trigger asynchronously.
   *
   * The data passed into the trigger must be of the generic `Request` type:
   *
   * The request to the Cloud Functions backend made by this method automatically includes a
   * Firebase Instance ID token to identify the app instance. If a user is logged in with Firebase
   * Auth, an auth ID token for the user is also automatically included.
   *
   * Firebase Instance ID sends data to the Firebase backend periodically to collect information
   * regarding the app instance. To stop this, see `[FIRInstanceID deleteIDWithHandler:]`. It
   * resumes with a new Instance ID the next time you call this method.
   *
   * - Parameter data: Parameters to pass to the trigger.
   * - Parameter completion: The block to call when the HTTPS request has completed.
   *
   * - Throws: An error if any value throws an error during encoding.
   */
  public func call(_ data: Request,
                   encoder: StructureEncoder = StructureEncoder(),
                   decoder: StructureDecoder = StructureDecoder(),
                   completion: @escaping (Result<Response, Error>)
                     -> Void) throws {
    let encoded = try encoder.encode(data)

    callable.call(encoded) { result, error in
      do {
        if let result = result {
          let decoded = try decoder.decode(Response.self, from: result.data)
          completion(.success(decoded))
        } else if let error = error {
          completion(.failure(error))
        } else {
          completion(.failure(CallableError.internalError))
        }
      } catch {
        completion(.failure(error))
      }
    }
  }

  #if compiler(>=5.5) && canImport(_Concurrency)
    /**
     * Executes this Callable HTTPS trigger asynchronously.
     *
     * The data passed into the trigger must be of the generic `Request` type:
     *
     * The request to the Cloud Functions backend made by this method automatically includes a
     * Firebase Instance ID token to identify the app instance. If a user is logged in with Firebase
     * Auth, an auth ID token for the user is also automatically included.
     *
     * Firebase Instance ID sends data to the Firebase backend periodically to collect information
     * regarding the app instance. To stop this, see `[FIRInstanceID deleteIDWithHandler:]`. It
     * resumes with a new Instance ID the next time you call this method.
     *
     * - Parameter data: The `Request` representing the data to pass to the trigger.
     *
     * - Throws: An error if any value throws an error during encoding.
     * - Throws: An error if any value throws an error during decoding.
     * - Throws: An error if the callable fails to complete
     *
     * - Returns: The decoded `Response` value
     */
    @available(iOS 15, tvOS 15, macOS 12, watchOS 8, *)
    public func call(_ data: Request,
                     encoder: StructureEncoder = StructureEncoder(),
                     decoder: StructureDecoder =
                       StructureDecoder()) async throws -> Response {
      let encoded = try encoder.encode(data)
      let result = try await callable.call(encoded)
      return try decoder.decode(Response.self, from: result.data)
    }
  #endif
}