// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause

package com.tailscale.ipn.ui.viewModel

import android.app.Activity
import android.content.Context
import android.content.ContextWrapper
import android.content.Intent
import android.util.Log
import androidx.lifecycle.ViewModel
import androidx.lifecycle.viewModelScope
import com.tailscale.ipn.App
import com.tailscale.ipn.IPNReceiver
import com.tailscale.ipn.ui.localapi.Client
import com.tailscale.ipn.ui.model.Ipn
import com.tailscale.ipn.ui.model.IpnLocal
import com.tailscale.ipn.ui.model.UserID
import com.tailscale.ipn.ui.notifier.Notifier
import com.tailscale.ipn.ui.util.set
import kotlinx.coroutines.flow.MutableStateFlow
import kotlinx.coroutines.flow.StateFlow
import kotlinx.coroutines.launch

/**
 * Base model for most models in this application. Provides common facilities for watching IPN
 * notifications, managing login/logout, updating preferences, etc.
 */
open class IpnViewModel : ViewModel() {
  protected val TAG = this::class.simpleName

  val loggedInUser: StateFlow<IpnLocal.LoginProfile?> = MutableStateFlow(null)
  val loginProfiles: StateFlow<List<IpnLocal.LoginProfile>?> = MutableStateFlow(null)

  // The userId associated with the current node. ie: The logged in user.
  private var selfNodeUserId: UserID? = null

  init {
    viewModelScope.launch {
      Notifier.state.collect {
        // Reload the user profiles on all state transitions to ensure loggedInUser is correct
        viewModelScope.launch { loadUserProfiles() }
      }
    }

    // This will observe the userId of the current node and reload our user profiles if
    // we discover it has changed (e.g. due to a login or user switch)
    viewModelScope.launch {
      Notifier.netmap.collect {
        it?.SelfNode?.User.let {
          if (it != selfNodeUserId) {
            selfNodeUserId = it
            viewModelScope.launch { loadUserProfiles() }
          }
        }
      }
    }

    viewModelScope.launch { loadUserProfiles() }
    Log.d(TAG, "Created")
  }

  protected fun Context.findActivity(): Activity? =
      when (this) {
        is Activity -> this
        is ContextWrapper -> baseContext.findActivity()
        else -> null
      }

  private fun loadUserProfiles() {
    Client(viewModelScope).profiles { result ->
      result.onSuccess(loginProfiles::set).onFailure {
        Log.e(TAG, "Error loading profiles: ${it.message}")
      }
    }

    Client(viewModelScope).currentProfile { result ->
      result
          .onSuccess { loggedInUser.set(if (it.isEmpty()) null else it) }
          .onFailure { Log.e(TAG, "Error loading current profile: ${it.message}") }
    }
  }

  fun toggleVpn() {
    when (Notifier.state.value) {
      Ipn.State.Running -> stopVPN()
      else -> startVPN()
    }
  }

  fun startVPN() {
    val context = App.getApplication().applicationContext
    val intent = Intent(context, IPNReceiver::class.java)
    intent.action = IPNReceiver.INTENT_CONNECT_VPN
    context.sendBroadcast(intent)
  }

  fun stopVPN() {
    val context = App.getApplication().applicationContext
    val intent = Intent(context, IPNReceiver::class.java)
    intent.action = IPNReceiver.INTENT_DISCONNECT_VPN
    context.sendBroadcast(intent)
  }

  fun login(completionHandler: (Result<Unit>) -> Unit = {}) {
    Client(viewModelScope).startLoginInteractive { result ->
      result
          .onSuccess { Log.d(TAG, "Login started: $it") }
          .onFailure { Log.e(TAG, "Error starting login: ${it.message}") }
      completionHandler(result)
    }
  }

  fun logout(completionHandler: (Result<String>) -> Unit = {}) {
    Client(viewModelScope).logout { result ->
      result
          .onSuccess { Log.d(TAG, "Logout started: $it") }
          .onFailure { Log.e(TAG, "Error starting logout: ${it.message}") }
      completionHandler(result)
    }
  }

  fun switchProfile(profile: IpnLocal.LoginProfile, completionHandler: (Result<String>) -> Unit) {
    Client(viewModelScope).switchProfile(profile) {
      startVPN()
      completionHandler(it)
    }
  }

  fun addProfile(completionHandler: (Result<String>) -> Unit) {
    Client(viewModelScope).addProfile {
      if (it.isSuccess) {
        login {}
      }
      startVPN()
      completionHandler(it)
    }
  }

  fun deleteProfile(profile: IpnLocal.LoginProfile, completionHandler: (Result<String>) -> Unit) {
    Client(viewModelScope).deleteProfile(profile) {
      viewModelScope.launch { loadUserProfiles() }
      completionHandler(it)
    }
  }

  // The below handle all types of preference modifications typically invoked by the UI.
  // Callers generally shouldn't care about the returned prefs value - the source of
  // truth is the IPNModel, who's prefs flow will change in value to reflect the true
  // value of the pref setting in the back end (and will match the value returned here).
  // Generally, you will want to inspect the returned value in the callback for errors
  // to indicate why a particular setting did not change in the interface.
  //
  // Usage:
  // - User/Interface changed to new value.  Render the new value.
  // - Submit the new value to the PrefsEditor
  // - Observe the prefs on the IpnModel and update the UI when/if the value changes.
  //   For a typical flow, the changed value should reflect the value already shown.
  // - Inform the user of any error which may have occurred
  //
  // The "toggle' functions here will attempt to set the pref value to the inverse of
  // what is currently known in the IpnModel.prefs.  If IpnModel.prefs is not available,
  // the callback will be called with a NO_PREFS error
  fun setWantRunning(wantRunning: Boolean, callback: (Result<Ipn.Prefs>) -> Unit) {
    Ipn.MaskedPrefs().WantRunning = wantRunning
    Client(viewModelScope).editPrefs(Ipn.MaskedPrefs(), callback)
  }

  fun toggleShieldsUp(callback: (Result<Ipn.Prefs>) -> Unit) {
    val prefs =
        Notifier.prefs.value
            ?: run {
              callback(Result.failure(Exception("no prefs")))
              return@toggleShieldsUp
            }

    val prefsOut = Ipn.MaskedPrefs()
    prefsOut.ShieldsUp = !prefs.ShieldsUp
    Client(viewModelScope).editPrefs(prefsOut, callback)
  }

  fun toggleRouteAll(callback: (Result<Ipn.Prefs>) -> Unit) {
    val prefs =
        Notifier.prefs.value
            ?: run {
              callback(Result.failure(Exception("no prefs")))
              return@toggleRouteAll
            }

    val prefsOut = Ipn.MaskedPrefs()
    prefsOut.RouteAll = !prefs.RouteAll
    Client(viewModelScope).editPrefs(prefsOut, callback)
  }
}