GPEngine

import PackageDescription

let package = Package(
    name: "project_name",
    dependencies: [
        .package(url: "https://github.com/LuizZak/GPEngine.git", from: "4.0.0")
    ],
    targets: []
)

let myProvider = MyTypeProvider() // Implements SerializationTypeProvider

let gameSerializer = GameSerializer(typeProvider: myProvider)
let mySerialized = try gameSerializer.serialize(myEntity)

// .serialize(_:) returns a Serialized object, call .serialize() on it to receive a JSON that you can store:
let json = mySerialized.serialized()

// Store json somewhere...

let json = // Retrieve entity JSON from somewhere...

// Retrieve it back to a Serialized object
// If this fails, that means you got a bad JSON :(
let mySerialized = try Serialized.deserialized(from: json)

// Requires explicit ': Entity' type annotation
let myEntity: Entity = try gameSerializer.extract(from: mySerialized)

// If we reached here, entity was deserialized correctly! Success!

class Provider: BasicSerializationTypeProvider {
    // Requirement from `BasicSerializationTypeProvider`
    var serializableTypes: [(Serializable.Type, (JSON, JsonPath) throws -> Serializable))] = [
        (MySerializableComponent.self, MySerializableComponent.init),
        (MySerializableSubspace.self, MySerializableSubspace.init),
    ]

    // Now `serializedName(for:)`/`deserialized(from:)` are automatically stubbed using `serializableTypes` array.
}

/// Describes an object that can be serialized to and back from a JSON object.
/// Implementers of this protocol should take care of guaranteeing that the inner
/// state of the object remains the same when deserializing from a previously
/// serialized object.
public protocol Serializable {
    /// Serializes the state of this component into a JSON object.
    ///
    /// - returns: The serialized state for this object.
    func serialized() -> JSON
}

/// Initializes an instance of this type from a given serialized state.
///
/// - parameter json: A state that was previously serialized by an instance
/// of this type using `serialized()`
/// - parameter path: The full JSON path to the serialized object. Used for
/// diagnostics purposes.
/// - throws: Any type of error during deserialization.
(_ json: JSON, _ path: JsonPath) throws -> Serializable

struct MyComponent {
    let field: Int

    init(json: JSON, path: JsonPath) throws {
        field = try json[path: "field"].integer(prefixPath: path)
    }
}

try MyComponent(
    json: ["field": true],
    path: aPrefixPath
)
// Throws error: "Expected a value of type 'bool' but found a value of type 'int' @ <root>.aPrefixPath.field"