Result.swift

public typealias JSON = [String: Any]

public enum Result<A> {
    case success(A)
    case failure(Error)

    public var isSuccess: Bool {
        switch self {
        case .success:
            return true
        case .failure:
            return false
        }
    }

    public var value: A? {
        guard case .success(let v) = self else { return nil }
        return v
    }

    public var error: Error? {
        switch self {
        case .success:
            return nil
        case .failure(let error):
            return error
        }
    }
}

// MARK: - Initialize

extension Result {
    public init(_ value: A?, or error: Error) {
        if let value = value {
            self = .success(value)
        } else {
            self = .failure(error)
        }
    }
}

// MARK: - CustomStringConvertible

extension Result: CustomStringConvertible {

    public var description: String {
        switch self {
        case .success:
            return "SUCCESS"
        case .failure:
            return "FAILURE"
        }
    }
}

// MARK: - CustomDebugStringConvertible

extension Result: CustomDebugStringConvertible {

    public var debugDescription: String {
        switch self {
        case .success(let value):
            return "SUCCESS: \(value)"
        case .failure(let error):
            return "FAILURE: \(error)"
        }
    }
}