/*
 * Copyright © 2017-2019 WireGuard LLC. All Rights Reserved.
 * SPDX-License-Identifier: Apache-2.0
 */
package com.wireguard.android.model

import android.content.BroadcastReceiver
import android.content.Context
import android.content.Intent
import android.os.Build
import android.util.Log
import android.widget.Toast
import androidx.databinding.BaseObservable
import androidx.databinding.Bindable
import com.wireguard.android.Application.Companion.get
import com.wireguard.android.Application.Companion.getBackend
import com.wireguard.android.Application.Companion.getTunnelManager
import com.wireguard.android.BR
import com.wireguard.android.R
import com.wireguard.android.backend.Statistics
import com.wireguard.android.backend.Tunnel
import com.wireguard.android.configStore.ConfigStore
import com.wireguard.android.databinding.ObservableSortedKeyedArrayList
import com.wireguard.android.util.ErrorMessages
import com.wireguard.android.util.UserKnobs
import com.wireguard.android.util.applicationScope
import com.wireguard.config.Config
import kotlinx.coroutines.CompletableDeferred
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.SupervisorJob
import kotlinx.coroutines.async
import kotlinx.coroutines.awaitAll
import kotlinx.coroutines.flow.first
import kotlinx.coroutines.launch
import kotlinx.coroutines.withContext

/**
 * Maintains and mediates changes to the set of available WireGuard tunnels,
 */
class TunnelManager(private val configStore: ConfigStore) : BaseObservable() {
    private val tunnels = CompletableDeferred<ObservableSortedKeyedArrayList<String, ObservableTunnel>>()
    private val context: Context = get()
    private val tunnelMap: ObservableSortedKeyedArrayList<String, ObservableTunnel> = ObservableSortedKeyedArrayList(TunnelComparator)
    private var haveLoaded = false

    private fun addToList(name: String, config: Config?, state: Tunnel.State): ObservableTunnel {
        val tunnel = ObservableTunnel(this, name, config, state)
        tunnelMap.add(tunnel)
        return tunnel
    }

    suspend fun getTunnels(): ObservableSortedKeyedArrayList<String, ObservableTunnel> = tunnels.await()

    suspend fun create(name: String, config: Config?): ObservableTunnel = withContext(Dispatchers.Main.immediate) {
        if (Tunnel.isNameInvalid(name))
            throw IllegalArgumentException(context.getString(R.string.tunnel_error_invalid_name))
        if (tunnelMap.containsKey(name))
            throw IllegalArgumentException(context.getString(R.string.tunnel_error_already_exists, name))
        addToList(name, withContext(Dispatchers.IO) { configStore.create(name, config!!) }, Tunnel.State.DOWN)
    }

    suspend fun delete(tunnel: ObservableTunnel) = withContext(Dispatchers.Main.immediate) {
        val originalState = tunnel.state
        val wasLastUsed = tunnel == lastUsedTunnel
        // Make sure nothing touches the tunnel.
        if (wasLastUsed)
            lastUsedTunnel = null
        tunnelMap.remove(tunnel)
        try {
            if (originalState == Tunnel.State.UP)
                withContext(Dispatchers.IO) { getBackend().setState(tunnel, Tunnel.State.DOWN, null) }
            try {
                withContext(Dispatchers.IO) { configStore.delete(tunnel.name) }
            } catch (e: Throwable) {
                if (originalState == Tunnel.State.UP)
                    withContext(Dispatchers.IO) { getBackend().setState(tunnel, Tunnel.State.UP, tunnel.config) }
                throw e
            }
        } catch (e: Throwable) {
            // Failure, put the tunnel back.
            tunnelMap.add(tunnel)
            if (wasLastUsed)
                lastUsedTunnel = tunnel
            throw e
        }
    }

    @get:Bindable
    var lastUsedTunnel: ObservableTunnel? = null
        private set(value) {
            if (value == field) return
            field = value
            notifyPropertyChanged(BR.lastUsedTunnel)
            applicationScope.launch { UserKnobs.setLastUsedTunnel(value?.name) }
        }

    suspend fun getTunnelConfig(tunnel: ObservableTunnel): Config = withContext(Dispatchers.Main.immediate) {
        tunnel.onConfigChanged(withContext(Dispatchers.IO) { configStore.load(tunnel.name) })!!
    }

    fun onCreate() {
        applicationScope.launch {
            try {
                onTunnelsLoaded(withContext(Dispatchers.IO) { configStore.enumerate() }, withContext(Dispatchers.IO) { getBackend().runningTunnelNames })
            } catch (e: Throwable) {
                Log.e(TAG, Log.getStackTraceString(e))
            }
        }
    }

    private fun onTunnelsLoaded(present: Iterable<String>, running: Collection<String>) {
        for (name in present)
            addToList(name, null, if (running.contains(name)) Tunnel.State.UP else Tunnel.State.DOWN)
        applicationScope.launch {
            val lastUsedName = UserKnobs.lastUsedTunnel.first()
            if (lastUsedName != null)
                lastUsedTunnel = tunnelMap[lastUsedName]
            haveLoaded = true
            restoreState(true)
            tunnels.complete(tunnelMap)
        }
    }

    private fun refreshTunnelStates() {
        applicationScope.launch {
            try {
                val running = withContext(Dispatchers.IO) { getBackend().runningTunnelNames }
                for (tunnel in tunnelMap)
                    tunnel.onStateChanged(if (running.contains(tunnel.name)) Tunnel.State.UP else Tunnel.State.DOWN)
            } catch (e: Throwable) {
                Log.e(TAG, Log.getStackTraceString(e))
            }
        }
    }

    suspend fun restoreState(force: Boolean) {
        if (!haveLoaded || (!force && !UserKnobs.restoreOnBoot.first()))
            return
        val previouslyRunning = UserKnobs.runningTunnels.first()
        if (previouslyRunning.isEmpty()) return
        withContext(Dispatchers.IO) {
            try {
                tunnelMap.filter { previouslyRunning.contains(it.name) }.map { async(Dispatchers.IO + SupervisorJob()) { setTunnelState(it, Tunnel.State.UP) } }.awaitAll()
            } catch (e: Throwable) {
                Log.e(TAG, Log.getStackTraceString(e))
            }
        }
    }

    suspend fun saveState() {
        UserKnobs.setRunningTunnels(tunnelMap.filter { it.state == Tunnel.State.UP }.map { it.name }.toSet())
    }

    suspend fun setTunnelConfig(tunnel: ObservableTunnel, config: Config): Config = withContext(Dispatchers.Main.immediate) {
        tunnel.onConfigChanged(withContext(Dispatchers.IO) {
            getBackend().setState(tunnel, tunnel.state, config)
            configStore.save(tunnel.name, config)
        })!!
    }

    suspend fun setTunnelName(tunnel: ObservableTunnel, name: String): String = withContext(Dispatchers.Main.immediate) {
        if (Tunnel.isNameInvalid(name))
            throw IllegalArgumentException(context.getString(R.string.tunnel_error_invalid_name))
        if (tunnelMap.containsKey(name)) {
            throw IllegalArgumentException(context.getString(R.string.tunnel_error_already_exists, name))
        }
        val originalState = tunnel.state
        val wasLastUsed = tunnel == lastUsedTunnel
        // Make sure nothing touches the tunnel.
        if (wasLastUsed)
            lastUsedTunnel = null
        tunnelMap.remove(tunnel)
        var throwable: Throwable? = null
        var newName: String? = null
        try {
            if (originalState == Tunnel.State.UP)
                withContext(Dispatchers.IO) { getBackend().setState(tunnel, Tunnel.State.DOWN, null) }
            withContext(Dispatchers.IO) { configStore.rename(tunnel.name, name) }
            newName = tunnel.onNameChanged(name)
            if (originalState == Tunnel.State.UP)
                withContext(Dispatchers.IO) { getBackend().setState(tunnel, Tunnel.State.UP, tunnel.config) }
        } catch (e: Throwable) {
            throwable = e
            // On failure, we don't know what state the tunnel might be in. Fix that.
            getTunnelState(tunnel)
        }
        // Add the tunnel back to the manager, under whatever name it thinks it has.
        tunnelMap.add(tunnel)
        if (wasLastUsed)
            lastUsedTunnel = tunnel
        if (throwable != null)
            throw throwable
        newName!!
    }

    suspend fun setTunnelState(tunnel: ObservableTunnel, state: Tunnel.State): Tunnel.State = withContext(Dispatchers.Main.immediate) {
        var newState = tunnel.state
        var throwable: Throwable? = null
        try {
            newState = withContext(Dispatchers.IO) { getBackend().setState(tunnel, state, tunnel.getConfigAsync()) }
            if (newState == Tunnel.State.UP)
                lastUsedTunnel = tunnel
        } catch (e: Throwable) {
            throwable = e
        }
        tunnel.onStateChanged(newState)
        saveState()
        if (throwable != null)
            throw throwable
        newState
    }

    class IntentReceiver : BroadcastReceiver() {
        override fun onReceive(context: Context, intent: Intent?) {
            applicationScope.launch {
                val manager = getTunnelManager()
                if (intent == null) return@launch
                val action = intent.action ?: return@launch
                if ("com.wireguard.android.action.REFRESH_TUNNEL_STATES" == action) {
                    manager.refreshTunnelStates()
                    return@launch
                }
                if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M || !UserKnobs.allowRemoteControlIntents.first())
                    return@launch
                val state: Tunnel.State
                state = when (action) {
                    "com.wireguard.android.action.SET_TUNNEL_UP" -> Tunnel.State.UP
                    "com.wireguard.android.action.SET_TUNNEL_DOWN" -> Tunnel.State.DOWN
                    else -> return@launch
                }
                val tunnelName = intent.getStringExtra("tunnel") ?: return@launch
                val tunnels = manager.getTunnels()
                val tunnel = tunnels[tunnelName] ?: return@launch
                try {
                    manager.setTunnelState(tunnel, state)
                } catch (e: Throwable) {
                    Toast.makeText(context, ErrorMessages[e], Toast.LENGTH_LONG).show()
                }
            }
        }
    }

    suspend fun getTunnelState(tunnel: ObservableTunnel): Tunnel.State = withContext(Dispatchers.Main.immediate) {
        tunnel.onStateChanged(withContext(Dispatchers.IO) { getBackend().getState(tunnel) })
    }

    suspend fun getTunnelStatistics(tunnel: ObservableTunnel): Statistics = withContext(Dispatchers.Main.immediate) {
        tunnel.onStatisticsChanged(withContext(Dispatchers.IO) { getBackend().getStatistics(tunnel) })!!
    }

    companion object {
        private const val TAG = "WireGuard/TunnelManager"
    }
}