Persistable.swift

//
//  Persistable.swift
//

import Foundation
import Disk

public protocol Persistable: Codable {
    init()
    init?(_: [String: Any])
    static func load() -> Self
    static func save(_ obj: Self)
    static var persistenceFileName: String { get }
}

extension Persistable {
    public static func load() -> Self {
        if let manager = try? Disk.retrieve(Self.persistencePath, from: .documents, as: Self.self) {
            return manager
        } else if let data = try? Disk.retrieve(Self.persistencePath, from: .documents, as: Data.self),
            let object = try? JSONSerialization.jsonObject(with: data, options: []),
            let dictionary = object as? [String: Any],
            let stored = Self.init(dictionary)
        {
            return stored
        }
    
        return Self()
    }

    public static func save(_ obj: Self) {
        try? Disk.save(obj, to: .documents, as: Self.persistencePath)
    }

    public static var persistencePath: String {
        return self.persistenceFileName.appending(".json")
    }
    
    public init?(_: [String: Any]) {
        return nil
    }
}