//
//  ConfigurationManager.swift
//  LearnMapKit
//
//  Centralized configuration management
//

import Foundation
import Combine
import MapKit

// MARK: - App Configuration
struct AppConfiguration: Equatable {
    let dataSource: DataSourceConfiguration
    let displaySettings: DisplaySettings
    let mapSettings: MapSettings
    let networkSettings: NetworkSettings

    static let `default` = AppConfiguration(
        dataSource: NetworkDataSourceConfiguration(
            hostname: "64.226.23.78",
            port: 30003
        ),
        displaySettings: DisplaySettings(),
        mapSettings: MapSettings(),
        networkSettings: NetworkSettings()
    )
}

// MARK: - Display Settings
struct DisplaySettings: Equatable {
    var showAircraftLabels: Bool = true
    var showAltitude: Bool = true
    var showSpeed: Bool = false
    var aircraftHistoryLength: Int = 10
    var updateInterval: TimeInterval = 1.0
    var theme: AppTheme = .system

    enum AppTheme: String, CaseIterable {
        case light, dark, system
    }
}

// MARK: - Map Settings
struct MapSettings: Equatable {
    var defaultCenter: CLLocationCoordinate2D = CLLocationCoordinate2D(
        latitude: 55.90159,
        longitude: -3.53154
    )
    var defaultSpan: MKCoordinateSpan = MKCoordinateSpan(
        latitudeDelta: 0.1,
        longitudeDelta: 0.1
    )
    var mapStyle: MapStyle = .hybrid
    var showTerrain: Bool = true

    enum MapStyle: String, CaseIterable {
        case standard, hybrid, satellite

        var mkMapType: MKMapType {
            switch self {
            case .standard: return .standard
            case .hybrid: return .hybrid
            case .satellite: return .satellite
            }
        }
    }

    // Custom equality to handle CLLocationCoordinate2D
    static func == (lhs: MapSettings, rhs: MapSettings) -> Bool {
        lhs.defaultCenter.latitude == rhs.defaultCenter.latitude &&
        lhs.defaultCenter.longitude == rhs.defaultCenter.longitude &&
        lhs.defaultSpan.latitudeDelta == rhs.defaultSpan.latitudeDelta &&
        lhs.defaultSpan.longitudeDelta == rhs.defaultSpan.longitudeDelta &&
        lhs.mapStyle == rhs.mapStyle &&
        lhs.showTerrain == rhs.showTerrain
    }
}

// MARK: - Network Settings
struct NetworkSettings: Equatable {
    var connectionTimeout: TimeInterval = 10.0
    var reconnectAttempts: Int = 3
    var bufferSize: Int = 1024
    var enableHeartbeat: Bool = true
    var heartbeatInterval: TimeInterval = 30.0
}

// MARK: - Configuration Manager Protocol
protocol ConfigurationManager: AnyObject {
    var currentConfiguration: AnyPublisher<AppConfiguration, Never> { get }
    var hasUnsavedChanges: AnyPublisher<Bool, Never> { get }

    func getCurrentConfiguration() -> AppConfiguration
    func updateConfiguration(_ configuration: AppConfiguration) async
    func updateDataSource(_ dataSource: DataSourceConfiguration) async
    func updateDisplaySettings(_ settings: DisplaySettings) async
    func updateMapSettings(_ settings: MapSettings) async
    func updateNetworkSettings(_ settings: NetworkSettings) async
    func resetToDefaults() async
    func saveConfiguration() async throws
    func validateConfiguration(_ configuration: AppConfiguration) -> ConfigurationValidationResult
}

// MARK: - Validation
struct ConfigurationValidationResult {
    let isValid: Bool
    let errors: [String]
    let warnings: [String]

    static let valid = ConfigurationValidationResult(isValid: true, errors: [], warnings: [])
}

// MARK: - Default Implementation
@MainActor
class DefaultConfigurationManager: ConfigurationManager {

    // MARK: - Published Properties
    var currentConfiguration: AnyPublisher<AppConfiguration, Never> {
        configurationSubject.eraseToAnyPublisher()
    }

    var hasUnsavedChanges: AnyPublisher<Bool, Never> {
        hasChangesSubject.eraseToAnyPublisher()
    }

    // MARK: - Private Properties
    private let configurationSubject: CurrentValueSubject<AppConfiguration, Never>
    private let hasChangesSubject = CurrentValueSubject<Bool, Never>(false)
    private var savedConfiguration: AppConfiguration
    private let userDefaults = UserDefaults.standard

    // MARK: - Keys for UserDefaults
    private enum Keys {
        static let configuration = "app_configuration"
    }

    init() {
        // Load configuration from UserDefaults or use default
        if let data = userDefaults.data(forKey: Keys.configuration),
           let configuration = try? JSONDecoder().decode(AppConfiguration.self, from: data) {
            self.savedConfiguration = configuration
        } else {
            self.savedConfiguration = AppConfiguration.default
        }

        self.configurationSubject = CurrentValueSubject(savedConfiguration)

        // Monitor for changes
        setupChangeMonitoring()
    }

    // MARK: - ConfigurationManager Implementation
    func getCurrentConfiguration() -> AppConfiguration {
        configurationSubject.value
    }

    func updateConfiguration(_ configuration: AppConfiguration) async {
        configurationSubject.send(configuration)
        checkForChanges()
    }

    func updateDataSource(_ dataSource: DataSourceConfiguration) async {
        var current = getCurrentConfiguration()
        current = AppConfiguration(
            dataSource: dataSource,
            displaySettings: current.displaySettings,
            mapSettings: current.mapSettings,
            networkSettings: current.networkSettings
        )
        await updateConfiguration(current)
    }

    func updateDisplaySettings(_ settings: DisplaySettings) async {
        var current = getCurrentConfiguration()
        current = AppConfiguration(
            dataSource: current.dataSource,
            displaySettings: settings,
            mapSettings: current.mapSettings,
            networkSettings: current.networkSettings
        )
        await updateConfiguration(current)
    }

    func updateMapSettings(_ settings: MapSettings) async {
        var current = getCurrentConfiguration()
        current = AppConfiguration(
            dataSource: current.dataSource,
            displaySettings: current.displaySettings,
            mapSettings: settings,
            networkSettings: current.networkSettings
        )
        await updateConfiguration(current)
    }

    func updateNetworkSettings(_ settings: NetworkSettings) async {
        var current = getCurrentConfiguration()
        current = AppConfiguration(
            dataSource: current.dataSource,
            displaySettings: current.displaySettings,
            mapSettings: current.mapSettings,
            networkSettings: settings
        )
        await updateConfiguration(current)
    }

    func resetToDefaults() async {
        await updateConfiguration(AppConfiguration.default)
    }

    func saveConfiguration() async throws {
        let current = getCurrentConfiguration()
        let data = try JSONEncoder().encode(current)
        userDefaults.set(data, forKey: Keys.configuration)
        savedConfiguration = current
        hasChangesSubject.send(false)
    }

    func validateConfiguration(_ configuration: AppConfiguration) -> ConfigurationValidationResult {
        var errors: [String] = []
        var warnings: [String] = []

        // Validate data source
        switch configuration.dataSource.sourceType {
        case .file(let path):
            if !FileManager.default.fileExists(atPath: path) {
                errors.append("File does not exist at path: \(path)")
            }
        case .network(let host, let port):
            if host.isEmpty {
                errors.append("Network hostname cannot be empty")
            }
            if port <= 0 || port > 65535 {
                errors.append("Invalid port number: \(port)")
            }
        case .test:
            warnings.append("Using test data source")
        }

        // Validate display settings
        if configuration.displaySettings.updateInterval < 0.1 {
            errors.append("Update interval must be at least 0.1 seconds")
        }
        if configuration.displaySettings.aircraftHistoryLength < 1 {
            errors.append("Aircraft history length must be at least 1")
        }

        // Validate network settings
        if configuration.networkSettings.connectionTimeout < 1.0 {
            errors.append("Connection timeout must be at least 1 second")
        }
        if configuration.networkSettings.reconnectAttempts < 0 {
            errors.append("Reconnect attempts cannot be negative")
        }

        return ConfigurationValidationResult(
            isValid: errors.isEmpty,
            errors: errors,
            warnings: warnings
        )
    }

    // MARK: - Private Methods
    private func setupChangeMonitoring() {
        configurationSubject
            .dropFirst() // Skip initial value
            .sink { [weak self] _ in
                self?.checkForChanges()
            }
            .store(in: &cancellables)
    }

    private func checkForChanges() {
        let hasChanges = getCurrentConfiguration() != savedConfiguration
        hasChangesSubject.send(hasChanges)
    }

    private var cancellables = Set<AnyCancellable>()
}

// MARK: - Extensions for Codable Support
extension AppConfiguration: Codable {
    // Custom coding keys and implementation would be needed here
    // for proper serialization of the configuration
}

extension DisplaySettings: Codable {}
extension NetworkSettings: Codable {}

extension MapSettings: Codable {
    enum CodingKeys: String, CodingKey {
        case defaultCenterLatitude, defaultCenterLongitude
        case defaultSpanLatitudeDelta, defaultSpanLongitudeDelta
        case mapStyle, showTerrain
    }

    init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)

        let latitude = try container.decode(Double.self, forKey: .defaultCenterLatitude)
        let longitude = try container.decode(Double.self, forKey: .defaultCenterLongitude)
        defaultCenter = CLLocationCoordinate2D(latitude: latitude, longitude: longitude)

        let latDelta = try container.decode(Double.self, forKey: .defaultSpanLatitudeDelta)
        let lonDelta = try container.decode(Double.self, forKey: .defaultSpanLongitudeDelta)
        defaultSpan = MKCoordinateSpan(latitudeDelta: latDelta, longitudeDelta: lonDelta)

        mapStyle = try container.decode(MapStyle.self, forKey: .mapStyle)
        showTerrain = try container.decode(Bool.self, forKey: .showTerrain)
    }

    func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: CodingKeys.self)

        try container.encode(defaultCenter.latitude, forKey: .defaultCenterLatitude)
        try container.encode(defaultCenter.longitude, forKey: .defaultCenterLongitude)
        try container.encode(defaultSpan.latitudeDelta, forKey: .defaultSpanLatitudeDelta)
        try container.encode(defaultSpan.longitudeDelta, forKey: .defaultSpanLongitudeDelta)
        try container.encode(mapStyle, forKey: .mapStyle)
        try container.encode(showTerrain, forKey: .showTerrain)
    }
}