package nya.kitsunyan.foxydroid.service

import android.app.NotificationChannel
import android.app.NotificationManager
import android.app.PendingIntent
import android.app.Service
import android.app.job.JobParameters
import android.app.job.JobService
import android.content.Intent
import android.graphics.Color
import android.text.SpannableStringBuilder
import android.text.style.ForegroundColorSpan
import androidx.appcompat.view.ContextThemeWrapper
import androidx.core.app.NotificationCompat
import androidx.fragment.app.Fragment
import io.reactivex.rxjava3.android.schedulers.AndroidSchedulers
import io.reactivex.rxjava3.core.Observable
import io.reactivex.rxjava3.disposables.Disposable
import io.reactivex.rxjava3.schedulers.Schedulers
import io.reactivex.rxjava3.subjects.PublishSubject
import nya.kitsunyan.foxydroid.BuildConfig
import nya.kitsunyan.foxydroid.Common
import nya.kitsunyan.foxydroid.MainActivity
import nya.kitsunyan.foxydroid.R
import nya.kitsunyan.foxydroid.content.Preferences
import nya.kitsunyan.foxydroid.database.Database
import nya.kitsunyan.foxydroid.entity.ProductItem
import nya.kitsunyan.foxydroid.entity.Repository
import nya.kitsunyan.foxydroid.index.RepositoryUpdater
import nya.kitsunyan.foxydroid.utility.RxUtils
import nya.kitsunyan.foxydroid.utility.extension.android.*
import nya.kitsunyan.foxydroid.utility.extension.resources.*
import nya.kitsunyan.foxydroid.utility.extension.text.*
import java.lang.ref.WeakReference
import java.util.concurrent.TimeUnit
import kotlin.math.*

class SyncService: Service() {
  companion object {
    private const val ACTION_CANCEL = "${BuildConfig.APPLICATION_ID}.intent.action.CANCEL"

    private val stateSubject = PublishSubject.create<State>()
    private val finishSubject = PublishSubject.create<Unit>()
  }

  private sealed class State {
    data class Connecting(val name: String): State()
    data class Syncing(val name: String, val stage: RepositoryUpdater.Stage,
      val read: Long, val total: Long?): State()
    object Finishing: State()
  }

  private class Task(val repositoryId: Long, val manual: Boolean)
  private data class CurrentTask(val task: Task?, val disposable: Disposable,
    val hasUpdates: Boolean, val lastState: State)
  private enum class Started { NO, AUTO, MANUAL }

  private var started = Started.NO
  private val tasks = mutableListOf<Task>()
  private var currentTask: CurrentTask? = null

  private var updateNotificationBlockerFragment: WeakReference<Fragment>? = null

  enum class SyncRequest { AUTO, MANUAL, FORCE }

  inner class Binder: android.os.Binder() {
    val finish: Observable<Unit>
      get() = finishSubject

    private fun sync(ids: List<Long>, request: SyncRequest) {
      val cancelledTask = cancelCurrentTask { request == SyncRequest.FORCE && it.task?.repositoryId in ids }
      cancelTasks { !it.manual && it.repositoryId in ids }
      val currentIds = tasks.asSequence().map { it.repositoryId }.toSet()
      val manual = request != SyncRequest.AUTO
      tasks += ids.asSequence().filter { it !in currentIds &&
        it != currentTask?.task?.repositoryId }.map { Task(it, manual) }
      handleNextTask(cancelledTask?.hasUpdates == true)
      if (request != SyncRequest.AUTO && started == Started.AUTO) {
        started = Started.MANUAL
        handleSetStarted()
        currentTask?.lastState?.let { publishForegroundState(true, it) }
      }
    }

    fun sync(request: SyncRequest) {
      val ids = Database.RepositoryAdapter.getAll(null)
        .asSequence().filter { it.enabled }.map { it.id }.toList()
      sync(ids, request)
    }

    fun sync(repository: Repository) {
      if (repository.enabled) {
        sync(listOf(repository.id), SyncRequest.FORCE)
      }
    }

    fun cancelAuto(): Boolean {
      val removed = cancelTasks { !it.manual }
      val currentTask = cancelCurrentTask { it.task?.manual == false }
      handleNextTask(currentTask?.hasUpdates == true)
      return removed || currentTask != null
    }

    fun setUpdateNotificationBlocker(fragment: Fragment?) {
      updateNotificationBlockerFragment = fragment?.let(::WeakReference)
      if (fragment != null) {
        notificationManager.cancel(Common.NOTIFICATION_ID_UPDATES)
      }
    }

    fun setEnabled(repository: Repository, enabled: Boolean): Boolean {
      Database.RepositoryAdapter.put(repository.enable(enabled))
      if (enabled) {
        if (repository.id != currentTask?.task?.repositoryId && !tasks.any { it.repositoryId == repository.id }) {
          tasks += Task(repository.id, true)
          handleNextTask(false)
        }
      } else {
        cancelTasks { it.repositoryId == repository.id }
        val cancelledTask = cancelCurrentTask { it.task?.repositoryId == repository.id }
        handleNextTask(cancelledTask?.hasUpdates == true)
      }
      return true
    }

    fun isCurrentlySyncing(repositoryId: Long): Boolean {
      return currentTask?.task?.repositoryId == repositoryId
    }

    fun deleteRepository(repositoryId: Long): Boolean {
      val repository = Database.RepositoryAdapter.get(repositoryId)
      return repository != null && run {
        setEnabled(repository, false)
        Database.RepositoryAdapter.markAsDeleted(repository.id)
        true
      }
    }
  }

  private val binder = Binder()
  override fun onBind(intent: Intent): Binder = binder

  private var stateDisposable: Disposable? = null

  override fun onCreate() {
    super.onCreate()

    if (Android.sdk(26)) {
      NotificationChannel(Common.NOTIFICATION_CHANNEL_SYNCING,
        getString(R.string.syncing), NotificationManager.IMPORTANCE_LOW)
        .apply { setShowBadge(false) }
        .let(notificationManager::createNotificationChannel)
      NotificationChannel(Common.NOTIFICATION_CHANNEL_UPDATES,
        getString(R.string.updates), NotificationManager.IMPORTANCE_LOW)
        .let(notificationManager::createNotificationChannel)
    }

    stateDisposable = stateSubject
      .sample(500L, TimeUnit.MILLISECONDS, AndroidSchedulers.mainThread())
      .subscribe { publishForegroundState(false, it) }
  }

  override fun onDestroy() {
    super.onDestroy()

    stateDisposable?.dispose()
    stateDisposable = null
    cancelTasks { true }
    cancelCurrentTask { true }
  }

  override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
    if (intent?.action == ACTION_CANCEL) {
      tasks.clear()
      val cancelledTask = cancelCurrentTask { it.task != null }
      handleNextTask(cancelledTask?.hasUpdates == true)
    }
    return START_NOT_STICKY
  }

  private fun cancelTasks(condition: (Task) -> Boolean): Boolean {
    return tasks.removeAll(condition)
  }

  private fun cancelCurrentTask(condition: ((CurrentTask) -> Boolean)): CurrentTask? {
    return currentTask?.let {
      if (condition(it)) {
        currentTask = null
        it.disposable.dispose()
        RepositoryUpdater.await()
        it
      } else {
        null
      }
    }
  }

  private fun showNotificationError(repository: Repository, exception: Exception) {
    notificationManager.notify("repository-${repository.id}", Common.NOTIFICATION_ID_SYNCING, NotificationCompat
      .Builder(this, Common.NOTIFICATION_CHANNEL_SYNCING)
      .setSmallIcon(android.R.drawable.stat_sys_warning)
      .setColor(ContextThemeWrapper(this, R.style.Theme_Main_Light)
        .getColorFromAttr(R.attr.colorAccent).defaultColor)
      .setContentTitle(getString(R.string.error_syncing_format, repository.name))
      .setContentText(getString(when (exception) {
        is RepositoryUpdater.UpdateException -> when (exception.errorType) {
          RepositoryUpdater.ErrorType.NETWORK -> R.string.network_error_description
          RepositoryUpdater.ErrorType.HTTP -> R.string.http_error_description
          RepositoryUpdater.ErrorType.VALIDATION -> R.string.validation_index_error_description
          RepositoryUpdater.ErrorType.PARSING -> R.string.parsing_index_error_description
        }
        else -> R.string.unknown_error_description
      }))
      .build())
  }

  private val stateNotificationBuilder by lazy { NotificationCompat
    .Builder(this, Common.NOTIFICATION_CHANNEL_SYNCING)
    .setSmallIcon(R.drawable.ic_sync)
    .setColor(ContextThemeWrapper(this, R.style.Theme_Main_Light)
      .getColorFromAttr(R.attr.colorAccent).defaultColor)
    .addAction(0, getString(R.string.cancel), PendingIntent.getService(this, 0,
      Intent(this, this::class.java).setAction(ACTION_CANCEL), PendingIntent.FLAG_UPDATE_CURRENT)) }

  private fun publishForegroundState(force: Boolean, state: State) {
    if (force || currentTask?.lastState != state) {
      currentTask = currentTask?.copy(lastState = state)
      if (started == Started.MANUAL) {
        startForeground(Common.NOTIFICATION_ID_SYNCING, stateNotificationBuilder.apply {
          when (state) {
            is State.Connecting -> {
              setContentTitle(getString(R.string.syncing_format, state.name))
              setContentText(getString(R.string.connecting))
              setProgress(0, 0, true)
            }
            is State.Syncing -> {
              setContentTitle(getString(R.string.syncing_format, state.name))
              when (state.stage) {
                RepositoryUpdater.Stage.DOWNLOAD -> {
                  if (state.total != null) {
                    setContentText("${state.read.formatSize()} / ${state.total.formatSize()}")
                    setProgress(100, (100f * state.read / state.total).roundToInt(), false)
                  } else {
                    setContentText(state.read.formatSize())
                    setProgress(0, 0, true)
                  }
                }
                RepositoryUpdater.Stage.PROCESS -> {
                  val progress = state.total?.let { 100f * state.read / it }?.roundToInt()
                  setContentText(getString(R.string.processing_format, "${progress ?: 0}%"))
                  setProgress(100, progress ?: 0, progress == null)
                }
                RepositoryUpdater.Stage.MERGE -> {
                  val progress = (100f * state.read / (state.total ?: state.read)).roundToInt()
                  setContentText(getString(R.string.merging_format, "${state.read} / ${state.total ?: state.read}"))
                  setProgress(100, progress, false)
                }
                RepositoryUpdater.Stage.COMMIT -> {
                  setContentText(getString(R.string.saving_details))
                  setProgress(0, 0, true)
                }
              }
            }
            is State.Finishing -> {
              setContentTitle(getString(R.string.syncing))
              setContentText(null)
              setProgress(0, 0, true)
            }
          }::class
        }.build())
      }
    }
  }

  private fun handleSetStarted() {
    startAnyService(Intent(this, this::class.java))
    stateNotificationBuilder.setWhen(System.currentTimeMillis())
  }

  private fun handleNextTask(hasUpdates: Boolean) {
    if (currentTask == null) {
      if (tasks.isNotEmpty()) {
        val task = tasks.removeAt(0)
        val repository = Database.RepositoryAdapter.get(task.repositoryId)
        if (repository != null && repository.enabled) {
          val lastStarted = started
          val newStarted = if (task.manual || lastStarted == Started.MANUAL) Started.MANUAL else Started.AUTO
          started = newStarted
          if (newStarted == Started.MANUAL && lastStarted != Started.MANUAL) {
            handleSetStarted()
          }
          val initialState = State.Connecting(repository.name)
          publishForegroundState(true, initialState)
          val unstable = Preferences[Preferences.Key.UpdateUnstable]
          lateinit var disposable: Disposable
          disposable = RepositoryUpdater
            .update(repository, unstable) { stage, progress, total ->
              if (!disposable.isDisposed) {
                stateSubject.onNext(State.Syncing(repository.name, stage, progress, total))
              }
            }
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe { result, throwable ->
              currentTask = null
              throwable?.printStackTrace()
              if (throwable != null && task.manual) {
                showNotificationError(repository, throwable as Exception)
              }
              handleNextTask(result == true || hasUpdates)
            }
          currentTask = CurrentTask(task, disposable, hasUpdates, initialState)
        } else {
          handleNextTask(hasUpdates)
        }
      } else if (started != Started.NO) {
        if (hasUpdates && Preferences[Preferences.Key.UpdateNotify]) {
          val disposable = RxUtils
            .querySingle { Database.ProductAdapter
              .query(true, true, "", "", ProductItem.Order.NAME, it)
              .use { it.asSequence().map(Database.ProductAdapter::transformItem).toList() } }
            .subscribeOn(Schedulers.io())
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe { result, throwable ->
              throwable?.printStackTrace()
              currentTask = null
              handleNextTask(false)
              val blocked = updateNotificationBlockerFragment?.get()?.isAdded == true
              if (!blocked && result != null && result.isNotEmpty()) {
                displayUpdatesNotification(result)
              }
            }
          currentTask = CurrentTask(null, disposable, true, State.Finishing)
        } else {
          finishSubject.onNext(Unit)
          val needStop = started == Started.MANUAL
          started = Started.NO
          if (needStop) {
            stopForeground(true)
            stopSelf()
          }
        }
      }
    }
  }

  private fun displayUpdatesNotification(productItems: List<ProductItem>) {
    val maxUpdates = 5
    fun <T> T.applyHack(callback: T.() -> Unit): T = apply(callback)
    notificationManager.notify(Common.NOTIFICATION_ID_UPDATES, NotificationCompat
      .Builder(this, Common.NOTIFICATION_CHANNEL_UPDATES)
      .setSmallIcon(R.drawable.ic_new_releases)
      .setContentTitle(getString(R.string.new_updates_available))
      .setContentText(resources.getQuantityString(R.plurals.new_updates_description_format,
        productItems.size, productItems.size))
      .setColor(ContextThemeWrapper(this, R.style.Theme_Main_Light)
        .getColorFromAttr(R.attr.colorAccent).defaultColor)
      .setContentIntent(PendingIntent.getActivity(this, 0, Intent(this, MainActivity::class.java)
        .setAction(MainActivity.ACTION_UPDATES), PendingIntent.FLAG_UPDATE_CURRENT))
      .setStyle(NotificationCompat.InboxStyle().applyHack {
        for (productItem in productItems.take(maxUpdates)) {
          val builder = SpannableStringBuilder(productItem.name)
          builder.setSpan(ForegroundColorSpan(Color.BLACK), 0, builder.length,
            SpannableStringBuilder.SPAN_EXCLUSIVE_EXCLUSIVE)
          builder.append(' ').append(productItem.version)
          addLine(builder)
        }
        if (productItems.size > maxUpdates) {
          val summary = getString(R.string.plus_more_format, productItems.size - maxUpdates)
          if (Android.sdk(24)) {
            addLine(summary)
          } else {
            setSummaryText(summary)
          }
        }
      })
      .build())
  }

  class Job: JobService() {
    private var syncParams: JobParameters? = null
    private var syncDisposable: Disposable? = null
    private val syncConnection = Connection<Binder>(SyncService::class.java, onBind = {
      syncDisposable = it.binder.finish.subscribe { _ ->
        val params = syncParams
        if (params != null) {
          syncParams = null
          syncDisposable?.dispose()
          syncDisposable = null
          it.connection.unbind(this)
          jobFinished(params, false)
        }
      }
      it.binder.sync(SyncRequest.AUTO)
    }, onUnbind = {
      syncDisposable?.dispose()
      syncDisposable = null
      it.binder.cancelAuto()
      val params = syncParams
      if (params != null) {
        syncParams = null
        jobFinished(params, true)
      }
    })

    override fun onStartJob(params: JobParameters): Boolean {
      syncParams = params
      syncConnection.bind(this)
      return true
    }

    override fun onStopJob(params: JobParameters): Boolean {
      syncParams = null
      syncDisposable?.dispose()
      syncDisposable = null
      val reschedule = syncConnection.binder?.cancelAuto() == true
      syncConnection.unbind(this)
      return reschedule
    }
  }
}