StepBuilder.playground

//: Playground - noun: a place where people can play

import UIKit

protocol OfflineRequestConvertible {}
extension String: OfflineRequestConvertible {}

struct OfflineAction {

    enum `Type` {
        case cache, get, delete
    }

    fileprivate(set) var type: Type?
    fileprivate(set) var request: OfflineRequestConvertible?
    fileprivate(set) var data: Data?
    fileprivate(set) var id: String?
    fileprivate(set) var encryptionKey: String?
    fileprivate(set) var keepAliveUntil: Date?
    fileprivate(set) var ifBefore: Date?
}

protocol BuildStep {
    func build() -> OfflineAction
}

protocol RequestStep {
    func toCache(_ request: OfflineRequestConvertible) -> DataStep
    func toGet(_ request: OfflineRequestConvertible) -> GetCommonsStep
    func toDelete(_ request: OfflineRequestConvertible) -> CommonsStep
}

protocol DataStep {
    func data(_ data: Data) -> CacheCommonsStep
}

protocol CommonsStep: BuildStep {
    func forId(_ id: String) -> Self
    func withEncryptionKey(_ encryptionKey: String) -> Self
}

protocol CacheCommonsStep: CommonsStep {
    func keepingAliveUntil(_ date: Date) -> Self
}

protocol GetCommonsStep: CommonsStep {
    func ifBefore(_ date: Date) -> Self
}

class OfflineActionBuilder {
    
    fileprivate var action: OfflineAction!
    
    init() {
        fatalError("This type cannot be constructed directly, use static var 'builder' instead.")
    }
    
    private init(_ action: OfflineAction) {
        self.action = action
    }
    
    static var builder: RequestStep {
        return OfflineActionBuilder(OfflineAction()) as RequestStep
    }
}

extension OfflineActionBuilder: RequestStep, DataStep, CommonsStep, CacheCommonsStep, GetCommonsStep {
    
    func toCache(_ request: OfflineRequestConvertible) -> DataStep {
        action.type = .cache
        action.request = request
        return self as DataStep
    }
    
    func toGet(_ request: OfflineRequestConvertible) -> GetCommonsStep {
        action.type = .get
        action.request = request
        return self as GetCommonsStep
    }
    
    func toDelete(_ request: OfflineRequestConvertible) -> CommonsStep {
        action.type = .delete
        action.request = request
        return self as CommonsStep
    }
    
    func data(_ data: Data) -> CacheCommonsStep {
        action.data = data
        return self as CacheCommonsStep
    }

    func forId(_ id: String) -> Self {
        action.id = id
        return self
    }

    func withEncryptionKey(_ encryptionKey: String) -> Self {
        action.encryptionKey = encryptionKey
        return self
    }

    func keepingAliveUntil(_ date: Date) -> Self {
        action.keepAliveUntil = date
        return self
    }

    func ifBefore(_ date: Date) -> Self {
        action.ifBefore = date
        return self
    }

    func build() -> OfflineAction {
        return action
    }
}

// Let's build here: