import Darwin
import FamilyControls
import Foundation
import PolicyCore

struct NativeState: Codable {
    var snapshot: Snapshot?
    var selection = FamilyActivitySelection()
    var selectionRevision = UUID().uuidString
    var observation = Observation()
    var generation: String?
    var policyKey: String?
    var thresholds: [Int] = []
    var monitoringReady = false
    var shielded = false
    var lastEvent = "Not configured"
    var monitoringError: String?
}

enum LocalError: LocalizedError {
    case message(String)
    var errorDescription: String? {
        switch self { case .message(let value): return value }
    }
}

enum StateStore {
    /// A process-wide UserDefaults cache is not sufficient: the app and extension both write.
    /// Lock one file while atomically replacing another. Corrupt state is never reset to defaults.
    static func withState<T>(_ operation: (inout NativeState) throws -> T) throws -> T {
        guard let group = Bundle.main.object(forInfoDictionaryKey: "APCAppGroup") as? String,
              let directory = FileManager.default.containerURL(forSecurityApplicationGroupIdentifier: group) else {
            throw LocalError.message("App Group unavailable. Check signing and APC_APP_GROUP on all targets.")
        }
        let lockPath = directory.appendingPathComponent("state.lock").path
        let fd = open(lockPath, O_CREAT | O_RDWR, S_IRUSR | S_IWUSR)
        guard fd >= 0 else { throw LocalError.message("Cannot open the shared-state lock") }
        defer { close(fd) }
        guard flock(fd, LOCK_EX) == 0 else { throw LocalError.message("Cannot lock shared state") }
        defer { flock(fd, LOCK_UN) }
        let file = directory.appendingPathComponent("state.json")
        var state = NativeState()
        if FileManager.default.fileExists(atPath: file.path) {
            state = try WireCoding.decoder().decode(NativeState.self, from: Data(contentsOf: file))
        }
        let result = try operation(&state)
        try WireCoding.encoder().encode(state).write(to: file, options: .atomic)
        try FileManager.default.setAttributes(
            [.protectionKey: FileProtectionType.completeUntilFirstUserAuthentication], atPath: file.path
        )
        return result
    }
}