//
//  PacketTunnelProvider.swift
//  Passepartout
//
//  Created by Davide De Rosa on 2/24/24.
//  Copyright (c) 2024 Davide De Rosa. All rights reserved.
//
//  https://github.com/passepartoutvpn
//
//  This file is part of Passepartout.
//
//  Passepartout is free software: you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  (at your option) any later version.
//
//  Passepartout is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU General Public License for more details.
//
//  You should have received a copy of the GNU General Public License
//  along with Passepartout.  If not, see <http://www.gnu.org/licenses/>.
//

import CommonLibrary
@preconcurrency import NetworkExtension
import PassepartoutKit

final class PacketTunnelProvider: NEPacketTunnelProvider, @unchecked Sendable {

    @MainActor
    private let context: TunnelContext = .shared

    @MainActor
    private let dependencies: Dependencies = .shared

    private var fwd: NEPTPForwarder?

    override func startTunnel(options: [String: NSObject]? = nil) async throws {
        PassepartoutConfiguration.shared.configureLogging(
            to: BundleConfiguration.urlForTunnelLog,
            parameters: Constants.shared.log,
            logsPrivateData: UserDefaults.appGroup.bool(forKey: AppPreference.logsPrivateData.key)
        )
        do {
            fwd = try await NEPTPForwarder(
                provider: self,
                decoder: dependencies.neProtocolCoder(),
                registry: dependencies.registry,
                environment: dependencies.tunnelEnvironment(),
                profileBlock: context.processor.willStart
            )
            guard let fwd else {
                fatalError("NEPTPForwarder nil without throwing error?")
            }
            try await checkEligibility(of: fwd.profile, environment: dependencies.tunnelEnvironment())
            try await fwd.startTunnel(options: options)
        } catch {
            pp_log(.app, .fault, "Unable to start tunnel: \(error)")
            PassepartoutConfiguration.shared.flushLog()
            throw error
        }
    }

    override func stopTunnel(with reason: NEProviderStopReason) async {
        await fwd?.stopTunnel(with: reason)
        fwd = nil
        PassepartoutConfiguration.shared.flushLog()
    }

    override func cancelTunnelWithError(_ error: (any Error)?) {
        PassepartoutConfiguration.shared.flushLog()
        super.cancelTunnelWithError(error)
    }

    override func handleAppMessage(_ messageData: Data) async -> Data? {
        await fwd?.handleAppMessage(messageData)
    }

    override func wake() {
        fwd?.wake()
    }

    override func sleep() async {
        await fwd?.sleep()
    }
}

// MARK: - Eligibility

@MainActor
private extension PacketTunnelProvider {
    func checkEligibility(of profile: Profile, environment: TunnelEnvironment) async throws {
        await context.iapManager.reloadReceipt()
        do {
            try context.iapManager.verify(profile)
        } catch {
            let error = PassepartoutError(.App.ineligibleProfile)
            environment.setEnvironmentValue(error.code, forKey: TunnelEnvironmentKeys.lastErrorCode)
            pp_log(.app, .fault, "Verification failed for profile \(profile.id), shutting down: \(error)")
            throw error
        }
    }
}