//
//  SettingsService.swift
//  AutoCatCore
//
//  Created by Selim Mustafaev on 17.08.2024.
//  Copyright © 2024 Selim Mustafaev. All rights reserved.
//

import SwiftUI

@Observable
public final class SettingsService: SettingsServiceProtocol {
    
    public static let shared = SettingsService(defaults: .standard)
 
    let defaults: UserDefaults
    var observations: [NSKeyValueObservation] = []
    
    let jsonEncoder = JSONEncoder()
    let jsonDecoder = JSONDecoder()
    
    public var user: User {
        get {
            if let data = userData {
                let result = try? jsonDecoder.decode(User.self, from: data)
                return result ?? User()
            } else {
                return User()
            }
        }
        
        set {
            if let json = try? jsonEncoder.encode(newValue) {
                userData = json
            }
        }
    }
    
    public var userData: Data? = nil {
        didSet {
            defaults.user = userData
        }
    }

    public var recognizeAlternativeOrder: Bool = false {
        didSet {
            defaults.recognizeAlternativeOrder = recognizeAlternativeOrder
        }
    }
    
    public var recognizeShortenedNumbers: Bool = false {
        didSet {
            defaults.recognizeShortenedNumbers = recognizeShortenedNumbers
        }
    }
    
    public var defaultRegion: String = "161" {
        didSet {
            defaults.defaultRegion = defaultRegion
        }
    }
    
    public var recordBeep: Bool = false {
        didSet {
            defaults.recordBeep = recordBeep
        }
    }
    
    public var showDebugInfo: Bool = false {
        didSet {
            defaults.showDebugInfo = showDebugInfo
        }
    }
    
    public var useTestBackend: Bool = false {
        didSet {
            defaults.useTestBackend = useTestBackend
        }
    }
    
    public init(defaults: UserDefaults) {
        self.defaults = defaults
        
        observe(key: \.recognizeAlternativeOrder, for: \.recognizeAlternativeOrder)
        observe(key: \.recognizeShortenedNumbers, for: \.recognizeShortenedNumbers)
        observe(key: \.defaultRegion, for: \.defaultRegion)
        observe(key: \.recordBeep, for: \.recordBeep)
        observe(key: \.showDebugInfo, for: \.showDebugInfo)
        observe(key: \.useTestBackend, for: \.useTestBackend)
        observe(key: \.user, for: \.userData)
        
        register(defaultValues: [
            .recognizeAlternativeOrder: false,
            .recognizeShortenedNumbers: false,
            .defaultRegion: "761",
            .recordBeep: false,
            .showDebugInfo: false,
            .useTestBackend: false
        ])
    }
    
    deinit {
        observations.forEach { $0.invalidate() }
    }
    
    func observe<T>(key userDefaultsKey: KeyPath<UserDefaults,T>, for settingsKey: ReferenceWritableKeyPath<SettingsService,T>) where T: Equatable {
        let observation = defaults.observe(userDefaultsKey, options: [.initial, .new]) { [weak self] _, change in
            guard let self else { return }
            
            if let new = change.newValue, self[keyPath: settingsKey] != new {
                self[keyPath: settingsKey] = new
            }
        }
        observations.append(observation)
    }
    
    func register(defaultValues: [SettingsKey: Any]) {
        defaults.register(defaults: defaultValues.reduce(into: [:], { (partialResult: inout [String: Any], tuple) in
            partialResult[tuple.key.rawValue] = tuple.value
        }))
    }
}