vpnhotspotmod/mobile/src/main/java/be/mygod/vpnhotspot/TetheringService.kt

package be.mygod.vpnhotspot

import android.content.Intent
import android.content.IntentFilter
import be.mygod.vpnhotspot.App.Companion.app
import be.mygod.vpnhotspot.net.Routing
import be.mygod.vpnhotspot.net.TetherType
import be.mygod.vpnhotspot.net.TetheringManager
import be.mygod.vpnhotspot.net.monitor.IpNeighbourMonitor
import be.mygod.vpnhotspot.net.wifi.WifiDoubleLock
import be.mygod.vpnhotspot.util.Event0
import be.mygod.vpnhotspot.util.broadcastReceiver
import be.mygod.vpnhotspot.widget.SmartSnackbar
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.GlobalScope
import kotlinx.coroutines.launch
import timber.log.Timber

class TetheringService : IpNeighbourMonitoringService() {
    companion object {
        const val EXTRA_ADD_INTERFACES = "interface.add"
        const val EXTRA_REMOVE_INTERFACE = "interface.remove"
    }

    inner class Binder : android.os.Binder() {
        val routingsChanged = Event0()

        fun isActive(iface: String): Boolean = synchronized(routings) { routings.containsKey(iface) }
    }

    private val binder = Binder()
    private val routings = HashMap<String, Routing?>()
    private var locked = false
    private var receiverRegistered = false
    private val receiver = broadcastReceiver { _, intent ->
        val extras = intent.extras ?: return@broadcastReceiver
        synchronized(routings) {
            for (iface in routings.keys - TetheringManager.getTetheredIfaces(extras))
                routings.remove(iface)?.revert()
            updateRoutingsLocked()
        }
    }
    override val activeIfaces get() = synchronized(routings) { routings.keys.toList() }

    private fun updateRoutingsLocked() {
        if (locked && routings.keys.all { !TetherType.ofInterface(it).isWifi }) {
            WifiDoubleLock.release()
            locked = false
        }
        if (routings.isEmpty()) {
            unregisterReceiver()
            ServiceNotification.stopForeground(this)
            stopSelf()
        } else {
            if (!receiverRegistered) {
                receiverRegistered = true
                registerReceiver(receiver, IntentFilter(TetheringManager.ACTION_TETHER_STATE_CHANGED))
                app.onPreCleanRoutings[this] = {
                    synchronized(routings) { for (iface in routings.keys) routings.put(iface, null)?.stop() }
                }
                app.onRoutingsCleaned[this] = { synchronized(routings) { updateRoutingsLocked() } }
                IpNeighbourMonitor.registerCallback(this)
            }
            val disableIpv6 = app.pref.getBoolean("service.disableIpv6", true)
            val iterator = routings.iterator()
            while (iterator.hasNext()) {
                val (downstream, value) = iterator.next()
                if (value != null) continue
                try {
                    routings[downstream] = Routing(downstream).apply {
                        try {
                            if (app.dhcpWorkaround) dhcpWorkaround()
                            // system tethering already has working forwarding rules
                            // so it doesn't make sense to add additional forwarding rules
                            forward()
                            if (app.masquerade) masquerade()
                            if (disableIpv6) disableIpv6()
                            commit()
                        } catch (e: Exception) {
                            revert()
                            throw e
                        }
                    }
                } catch (e: Exception) {
                    Timber.w(e)
                    SmartSnackbar.make(e).show()
                    iterator.remove()
                }
            }
            if (routings.isEmpty()) {
                updateRoutingsLocked()
                return
            }
            updateNotification()
        }
        GlobalScope.launch(Dispatchers.Main) { binder.routingsChanged() }
    }

    override fun onBind(intent: Intent?) = binder

    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
        if (intent != null) {
            val ifaces = intent.getStringArrayExtra(EXTRA_ADD_INTERFACES) ?: emptyArray()
            synchronized(routings) {
                for (iface in ifaces) {
                    routings[iface] = null
                    if (TetherType.ofInterface(iface).isWifi && !locked) {
                        WifiDoubleLock.acquire()
                        locked = true
                    }
                }
                routings.remove(intent.getStringExtra(EXTRA_REMOVE_INTERFACE))?.revert()
                updateRoutingsLocked()
            }
        } else if (routings.isEmpty()) stopSelf(startId)
        return START_NOT_STICKY
    }

    override fun onDestroy() {
        routings.values.forEach { it?.revert() }    // force clean to prevent leakage
        unregisterReceiver()
        super.onDestroy()
    }

    private fun unregisterReceiver() {
        if (receiverRegistered) {
            unregisterReceiver(receiver)
            app.onPreCleanRoutings -= this
            app.onRoutingsCleaned -= this
            IpNeighbourMonitor.unregisterCallback(this)
            receiverRegistered = false
        }
    }
}