LeadKit/Sources/Classes/Services/NetworkService.swift

//
//  Copyright (c) 2017 Touch Instinct
//
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//
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//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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import RxSwift
import RxCocoa
import Alamofire
import ObjectMapper
import RxAlamofire

/// Base network service implementation build on top of LeadKit extensions for Alamofire.
/// Has an ability to automatically show / hide network activity indicator
open class NetworkService {

    /// Enable synchronization for setting variable from different thread
    private let lock = NSRecursiveLock()

    private let requestCountVariable = Variable<Int>(0)
    private var disposeBag = DisposeBag()

    private let acceptableStatusCodes: [Int]
    public let sessionManager: Alamofire.SessionManager

    var requestCount: Driver<Int> {
        return requestCountVariable.asDriver()
    }

    /// - Parameter sessionManager: Alamofire.SessionManager to use for requests
    /// Creates new instance of NetworkService with given Alamofire session manager
    ///
    /// - Parameters:
    ///   - sessionManager: Alamofire.SessionManager to use for requests.
    ///   - acceptableStatusCodes: Validates that the response has a status code in the specified sequence.
    public init(sessionManager: Alamofire.SessionManager,
                acceptableStatusCodes: [Int] = Alamofire.SessionManager.defaultAcceptableStatusCodes) {

        self.sessionManager = sessionManager
        self.acceptableStatusCodes = acceptableStatusCodes

        bindToApplicationActivityIndicator()
    }

    /// Perform reactive request to get mapped ObservableMappable model and http response
    ///
    /// - Parameter parameters: api parameters to pass Alamofire
    /// - Returns: Observable of tuple containing (HTTPURLResponse, ObservableMappable)
    public func rxRequest<T: ObservableMappable>(with parameters: ApiRequestParameters)
        -> Observable<(response: HTTPURLResponse, model: T)> where T.ModelType == T {

            return sessionManager.rx.responseObservableModel(requestParameters: parameters,
                                                             acceptableStatusCodes: acceptableStatusCodes)
                .counterTracking(for: self)
    }

    /// Perform reactive request to get mapped ImmutableMappable model and http response
    ///
    /// - Parameter parameters: api parameters to pass Alamofire
    /// - Returns: Observable of tuple containing (HTTPURLResponse, ImmutableMappable)
    public func rxRequest<T: ImmutableMappable>(with parameters: ApiRequestParameters)
        -> Observable<(response: HTTPURLResponse, model: T)> {

            return sessionManager.rx.responseModel(requestParameters: parameters,
                                                   acceptableStatusCodes: acceptableStatusCodes)
                .counterTracking(for: self)
    }

    /// Shows network activity indicator when requests in executed. Works only on iOS.
    public func bindToApplicationActivityIndicator() {
        bindActivityIndicator()?.disposed(by: disposeBag)
    }

    /// Disable showing network activity indicator.
    public func unbindToApplicationActivityIndicator() {
        disposeBag = DisposeBag()
    }

}

private extension NetworkService {

    func increaseRequestCounter() {
        lock.lock()
        requestCountVariable.value += 1
        lock.unlock()
    }

    func decreaseRequestCounter() {
        lock.lock()
        requestCountVariable.value -= 1
        lock.unlock()
    }

}

public extension Observable {

    /// Increase and descrease NetworkService request counter on subscribe and dispose
    /// (used to show / hide activity indicator)
    ///
    /// - Parameter networkService: NetworkService to operate on it
    /// - Returns: The source sequence with the side-effecting behavior applied.
    func counterTracking(for networkService: NetworkService) -> Observable<Observable.E> {
        return `do`(onSubscribe: {
            networkService.increaseRequestCounter()
        }, onDispose: {
            networkService.decreaseRequestCounter()
        })
    }

}