// FuelBoard shared model — compiled into BOTH the app and the widget extension.
// Kept Foundation-only so both targets can compile it (no SwiftUI dependency).
//
// Storage strategy (same as WidgetBoard — proven on free SideStore accounts):
//   App-group UserDefaults + Keychain (generic password). Keychain first:
//   shared group $(AppIdentifierPrefix)com.apt.fuelboard.shared is listed FIRST
//   in the entitlements so it is the default access group. Read order:
//   keychain → app-group defaults → fallback.

import Foundation
import Security

// MARK: - Fuel types

struct Coordinate: Equatable, Codable {
    let lat: Double
    let lng: Double
}

enum FuelType: String, Codable, CaseIterable, Identifiable {
    case e10    // Unleaded 95 (E10)
    case e5     // Premium 97/98 (E5)
    case diesel // B7 diesel

    var id: String { rawValue }

    var displayName: String {
        switch self {
        case .e10: return "E10 Unleaded"
        case .e5: return "E5 Premium"
        case .diesel: return "Diesel"
        }
    }
}

// MARK: - Station model

struct FuelStation: Identifiable, Codable, Equatable {
    let id: String
    let name: String
    let brand: String
    let address: String
    let postcode: String
    let lat: Double
    let lng: Double
    /// Price per fuel type in pence per litre. Missing type = station doesn't sell it.
    let prices: [FuelType: Double]
    /// Updated timestamp (seconds since 1970) — nil for sample data.
    let priceUpdated: TimeInterval?

    /// Cheap haversine distance to a location, in km.
    func distanceKM(to lat2: Double, lng2: Double) -> Double {
        let r = 6371.0
        let dLat = (lat2 - lat) * .pi / 180
        let dLng = (lng2 - lng) * .pi / 180
        let a = sin(dLat / 2) * sin(dLat / 2) +
                cos(lat * .pi / 180) * cos(lat2 * .pi / 180) *
                sin(dLng / 2) * sin(dLng / 2)
        return r * 2 * atan2(sqrt(a), sqrt(1 - a))
    }

    /// Apple Maps directions URL — used by the widget tap and app rows.
    var mapsDirectionsURL: URL? {
        URL(string: "http://maps.apple.com/?daddr=\(lat),\(lng)&t=d")
    }
}

// MARK: - Shared store

struct FuelStore {
    static let appGroupSuite = "group.com.apt.fuelboard"
    static let stationsKey = "fuelboard.stations"      // [FuelStation] JSON
    static let locationKey = "fuelboard.lastLocation"  // "lat,lng,timestamp"
    static let fuelKey = "fuelboard.selectedFuel"      // FuelType raw value

    // MARK: Stations

    static func loadStations() -> [FuelStation] {
        if let data = keychainData(service: stationsKey),
           let stations = try? JSONDecoder().decode([FuelStation].self, from: data),
           !stations.isEmpty {
            return stations
        }
        if let defaults = UserDefaults(suiteName: appGroupSuite),
           let data = defaults.data(forKey: stationsKey),
           let stations = try? JSONDecoder().decode([FuelStation].self, from: data),
           !stations.isEmpty {
            return stations
        }
        return []
    }

    static func saveStations(_ stations: [FuelStation]) {
        if let data = try? JSONEncoder().encode(stations) {
            UserDefaults(suiteName: appGroupSuite)?.set(data, forKey: stationsKey)
            writeKeychain(data: data, service: stationsKey)
        }
    }

    // MARK: Last known location ("lat,lng,unixTime")

    static func loadLocation() -> Coordinate? {
        let raw = loadString(service: locationKey)
        let parts = raw?.split(separator: ",").compactMap { Double($0) }
        guard let parts, parts.count == 3 else { return nil }
        return Coordinate(lat: parts[0], lng: parts[1])
    }

    static func saveLocation(lat: Double, lng: Double, date: Date = Date()) {
        saveString("\(lat),\(lng),\(date.timeIntervalSince1970)", service: locationKey)
    }

    // MARK: Selected fuel

    static func loadSelectedFuel() -> FuelType {
        if let raw = loadString(service: fuelKey), let fuel = FuelType(rawValue: raw) {
            return fuel
        }
        return .e10
    }

    static func saveSelectedFuel(_ fuel: FuelType) {
        saveString(fuel.rawValue, service: fuelKey)
    }

    // MARK: Low-level keychain helpers

    private static func keychainData(service: String) -> Data? {
        var query: [String: Any] = [
            kSecClass as String: kSecClassGenericPassword,
            kSecAttrService as String: service,
            kSecReturnData as String: true,
            kSecMatchLimit as String: kSecMatchLimitOne,
        ]
        var item: CFTypeRef?
        let status = SecItemCopyMatching(query as CFDictionary, &item)
        guard status == errSecSuccess, let data = item as? Data else { return nil }
        return data
    }

    private static func writeKeychain(data: Data, service: String) {
        let deleteQuery: [String: Any] = [
            kSecClass as String: kSecClassGenericPassword,
            kSecAttrService as String: service,
        ]
        SecItemDelete(deleteQuery as CFDictionary)
        let addQuery: [String: Any] = [
            kSecClass as String: kSecClassGenericPassword,
            kSecAttrService as String: service,
            kSecAttrAccessible as String: kSecAttrAccessibleAfterFirstUnlock,
            kSecValueData as String: data,
        ]
        SecItemAdd(addQuery as CFDictionary, nil)
    }

    private static func loadString(service: String) -> String? {
        if let data = keychainData(service: service) {
            return String(data: data, encoding: .utf8)
        }
        if let defaults = UserDefaults(suiteName: appGroupSuite) {
            return defaults.string(forKey: service)
        }
        return nil
    }

    private static func saveString(_ value: String, service: String) {
        UserDefaults(suiteName: appGroupSuite)?.set(value, forKey: service)
        writeKeychain(data: Data(value.utf8), service: service)
    }
}