//
//  KeychainStorage.swift
//  KeychainStorage
//
//  Created by Javier Cicchelli on 11/12/2022.
//  Copyright © 2022 Röck+Cöde. All rights reserved.
//

import Foundation
import KeychainAccess
import SwiftUI

@propertyWrapper
public struct KeychainStorage<Model: Codable>: DynamicProperty {
    
    // MARK: Type aliases
    
    public typealias Value = Model
    
    // MARK: States
    
    @State private var value: Value?
    
    // MARK: Properties
    
    private let key: String
    private let keychain: Keychainable
    private let decoder: JSONDecoder = .init()
    private let encoder: JSONEncoder = .init()
    
    public var wrappedValue: Value? {
        get { value }
        nonmutating set {
            value = newValue
            
            do {
                if let newValue {
                    let encodedValue = try encoder.encode(newValue)
                    
                    try keychain.set(encodedValue, key: key, ignoringAttributeSynchronizable: true)
                } else {
                    try keychain.remove(key, ignoringAttributeSynchronizable: true)
                }
            } catch {
                assertionFailure("The '\(key)' key should have either be set or removed from the keychain storage.")
            }
        }
    }
    
    public var projectedValue: Binding<Value?> {
        .init { wrappedValue } set: { wrappedValue = $0 }
    }
    
    // MARK: Initialisers
    
    public init(
        key: String,
        defaultValue: Value? = nil,
        keychain: Keychainable = Keychain()
    ) {
        self.key = key
        self.keychain = keychain
        
        do {
            guard let data = try keychain.getData(key, ignoringAttributeSynchronizable: true) else {
                self._value = .init(initialValue: defaultValue)
                return
            }

            do {
                let model = try decoder.decode(Value.self, from: data)
                
                self._value = .init(initialValue: model)
            } catch {
                assertionFailure("The data for the '\(key)' key should have been decoded properly.")
            }
        } catch {
            assertionFailure("The data of the '\(key)' key should have been obtained from the keychain storage.")
        }
    }
    
}