//
//  Copyright (c) 2017 Touch Instinct
//
//  Permission is hereby granted, free of charge, to any person obtaining a copy
//  of this software and associated documentation files (the "Software"), to deal
//  in the Software without restriction, including without limitation the rights
//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//  copies of the Software, and to permit persons to whom the Software is
//  furnished to do so, subject to the following conditions:
//
//  The above copyright notice and this permission notice shall be included in
//  all copies or substantial portions of the Software.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
//  THE SOFTWARE.
//

import RxSwift
import RxCocoa
import Alamofire
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 behaviour relay from different thread
    private let lock = NSRecursiveLock()

    private let requestCountRelay = BehaviorRelay(value: 0)
    private var disposeBag = DisposeBag()

    public let configuration: NetworkServiceConfiguration
    public let sessionManager: SessionManager

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

    /// - Parameter sessionManager: Alamofire.SessionManager to use for requests
    /// Creates new instance of NetworkService with given Alamofire session manager
    ///
    /// - Parameters:
    ///   - configuration: instance of NetworkServiceConfiguration to configure network service.
    public init(configuration: NetworkServiceConfiguration) {

        self.configuration = configuration
        self.sessionManager = configuration.sessionManager
        bindToApplicationActivityIndicator()
    }

    /// Perform reactive request to get mapped ObservableMappable model and http response
    ///
    /// - Parameter parameters: api parameters to pass Alamofire
    /// - Parameter decoder: json decoder to decode response data
    /// - Returns: Observable of tuple containing (HTTPURLResponse, ObservableMappable)
    public func rxObservableRequest<T: ObservableMappable>(with parameters: ApiRequestParameters,
                                                           decoder: JSONDecoder = JSONDecoder())
        -> Observable<(response: HTTPURLResponse, model: T)> {

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

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

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

    /// Shows network activity indicator when requests in executed. Works only on iOS.
    public func bindToApplicationActivityIndicator() {
        // Fatal error: `drive*` family of methods can be only called from `MainThread`
        DispatchQueue.main.async {
            self.bindActivityIndicator()?.disposed(by: self.disposeBag)
        }
    }

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

}

private extension NetworkService {

    func increaseRequestCounter() {
        lock.lock()
        requestCountRelay.accept(requestCountRelay.value + 1)
        lock.unlock()
    }

    func decreaseRequestCounter() {
        lock.lock()
        requestCountRelay.accept(requestCountRelay.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()
        })
    }

}