Trio/FreeAPS/Sources/Helpers/PropertyWrappers/PersistedProperty.swift

import Foundation

/// Attention! Do not use this wrapper for mutating structure with `didSet` handler into property owner!
/// `didSet` will never called if structure mutate into itself (by "mutating functions").
@propertyWrapper struct Persisted<Value: Codable & Equatable> {
    var wrappedValue: Value {
        get { getValue() ?? initialValue }
        set { setValue(newValue) }
    }

    private func getValue() -> Value? {
        lock?.lock()
        defer { lock?.unlock() }
        return storage.getValue(Value.self, forKey: key)
    }

    private mutating func setValue(_ value: Value) {
        lock?.lock()
        defer { lock?.unlock() }
        storage.setValue(value, forKey: key)
    }

    private let key: String
    private let storage: KeyValueStorage
    private let lock: NSRecursiveLock?
    private let initialValue: Value
    var isInitialValue: Bool {
        if let value = getValue() {
            return value == initialValue
        }
        return true
    }

    init(
        wrappedValue: Value,
        key: String,
        storage: KeyValueStorage = UserDefaults.standard,
        lock: NSRecursiveLock? = nil
    ) {
        self.storage = storage
        self.key = key
        self.lock = lock
        initialValue = wrappedValue
        lock?.lock()
        defer { lock?.unlock() }
        if storage.getValue(Value.self, forKey: key) == nil {
            setValue(wrappedValue)
        }
    }
}

@propertyWrapper public struct PersistedProperty<Value> {
    let key: String
    let storageURL: URL

    public init(key: String) {
        self.key = key

        let documents: URL

        guard let localDocuments = try? FileManager.default.url(
            for: .documentDirectory,
            in: .userDomainMask,
            appropriateFor: nil,
            create: true
        ) else {
            preconditionFailure("Could not get a documents directory URL.")
        }
        documents = localDocuments
        storageURL = documents.appendingPathComponent(key + ".plist")
    }

    public var wrappedValue: Value? {
        get {
            do {
                let data = try Data(contentsOf: storageURL)

                guard let value = try PropertyListSerialization.propertyList(from: data, options: [], format: nil) as? Value
                else {
                    return nil
                }
                return value
            } catch {}
            return nil
        }
        set {
            guard let newValue = newValue else {
                do {
                    try FileManager.default.removeItem(at: storageURL)
                } catch {}
                return
            }
            do {
                let data = try PropertyListSerialization.data(fromPropertyList: newValue, format: .binary, options: 0)
                try data.write(to: storageURL, options: .atomic)

            } catch {}
        }
    }
}