funkwhale-android/app/src/main/java/audio/funkwhale/ffa/activities/DownloadsActivity.kt

package audio.funkwhale.ffa.activities

import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import androidx.lifecycle.lifecycleScope
import androidx.recyclerview.widget.LinearLayoutManager
import audio.funkwhale.ffa.adapters.DownloadsAdapter
import audio.funkwhale.ffa.databinding.ActivityDownloadsBinding
import audio.funkwhale.ffa.utils.Event
import audio.funkwhale.ffa.utils.EventBus
import audio.funkwhale.ffa.utils.getMetadata
import com.google.android.exoplayer2.offline.Download
import com.google.android.exoplayer2.offline.DownloadManager
import kotlinx.coroutines.Dispatchers.Default
import kotlinx.coroutines.Dispatchers.Main
import kotlinx.coroutines.delay
import kotlinx.coroutines.launch
import kotlinx.coroutines.withContext
import org.koin.java.KoinJavaComponent.inject

class DownloadsActivity : AppCompatActivity() {

  private lateinit var adapter: DownloadsAdapter
  private lateinit var binding: ActivityDownloadsBinding
  private val exoDownloadManager: DownloadManager by inject(DownloadManager::class.java)

  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)

    binding = ActivityDownloadsBinding.inflate(layoutInflater)

    setContentView(binding.root)

    binding.downloads.itemAnimator = null

    adapter = DownloadsAdapter(layoutInflater, this, DownloadChangedListener()).also {
      it.setHasStableIds(true)

      binding.downloads.layoutManager = LinearLayoutManager(this)
      binding.downloads.adapter = it
    }

    lifecycleScope.launch(Default) {
      while (true) {
        delay(1000)
        refreshProgress()
      }
    }
  }

  override fun onResume() {
    super.onResume()

    lifecycleScope.launch(Default) {
      EventBus.get().collect { event ->
        if (event is Event.DownloadChanged) {
          refreshTrack(event.download)
        }
      }
    }

    refresh()
  }

  private fun refresh() {
    lifecycleScope.launch(Main) {
      adapter.downloads.clear()
      exoDownloadManager.downloadIndex.getDownloads()
        .use { cursor ->
          while (cursor.moveToNext()) {
            val download = cursor.download

            download.getMetadata()?.let { info ->
              adapter.downloads.add(
                info.apply { this.download = download }
              )
            }
          }
        }
      adapter.notifyDataSetChanged()
    }
  }

  private suspend fun refreshTrack(download: Download) {
    download.getMetadata()?.let { info ->
      adapter.downloads.withIndex().associate { it.value to it.index }
        .filter { it.key.id == info.id }.toList().getOrNull(0)?.let { match ->
          if (download.state != info.download?.state) {
            withContext(Main) {
              adapter.downloads[match.second] = info.apply {
                this.download = download
              }

              adapter.notifyItemChanged(match.second)
            }
          }
        }
    }
  }

  private suspend fun refreshProgress() {
    exoDownloadManager.downloadIndex.getDownloads()
      .use { cursor ->
        while (cursor.moveToNext()) {
          val download = cursor.download

          download.getMetadata()?.let { info ->
            adapter.downloads.withIndex().associate { it.value to it.index }
              .filter { it.key.id == info.id }.toList().getOrNull(0)?.let { match ->
                if (download.state == Download.STATE_DOWNLOADING &&
                  download.percentDownloaded != (info.download?.percentDownloaded ?: 0)
                ) {
                  withContext(Main) {
                    adapter.downloads[match.second] = info.apply {
                      this.download = download
                    }

                    adapter.notifyItemChanged(match.second)
                  }
                }
              }
          }
        }
      }
  }

  inner class DownloadChangedListener : DownloadsAdapter.OnDownloadChangedListener {
    override fun onItemRemoved(index: Int) {
      adapter.downloads.removeAt(index)
      adapter.notifyDataSetChanged()
    }
  }
}