ThreadBacked.swift

//
// Copyright 2021 Signal Messenger, LLC
// SPDX-License-Identifier: AGPL-3.0-only
//

import Foundation

// Thread local
@propertyWrapper
public struct ThreadBacked<Value> {
    private let key: String
    private let defaultValue: Value

    public init(key: String, defaultValue: Value) {
        self.key = key
        self.defaultValue = defaultValue
    }

    public var wrappedValue: Value {
        get {
            guard let value = Thread.current.threadDictionary[key] else {
                return defaultValue
            }
            guard let value = value as? Value else {
                owsFailDebug("Unexpected value: \(type(of: value))")
                return defaultValue
            }
            return value
        }
        set {
            Thread.current.threadDictionary[key] = newValue
        }
    }
}