//
//  ViewModelling.swift
//  Headlines
//
//  Created by Callum Trounce on 02/05/2019.
//  Copyright © 2019 Callum Trounce. All rights reserved.
//

import Foundation

/// Indicates presentation state
///
/// - idle: not loading / doing anything
/// - loading: loading data.
/// - result: result has been recieved.
enum PresentationState<T> {
    case idle
    case loading
    case result(Result<T, Error>)
}

/// Protocol which defines basic requirements for viewmodelling.
protocol ViewModelling {

    associatedtype ResultData

    /// Indicate current state
    var currentState: PresentationState<ResultData> { get set }

    /// Quick way to access the current data stored within the current state.
    var data: ResultData? { get }

    /// Closure indicating that the current state has been updated.
    var stateUpdated: ((PresentationState<ResultData>) -> Void)? { get set }

    /// Indicate that the view controller has finished loading
    func viewDidLoad()

    /// Clean / wipe data, expectation is to clear memory
    func clean()
}

/// Indicates that the data source can be refreshed.
protocol Refreshing {

    /// Indicate that the refresh has been pulled on the table view
    func refreshPulled()
}