funkwhale-app-android/app/src/main/java/audio/funkwhale/ffa/repositories/HttpUpstream.kt

package audio.funkwhale.ffa.repositories

import android.net.Uri
import audio.funkwhale.ffa.utils.*
import com.github.kittinunf.fuel.Fuel
import com.github.kittinunf.fuel.core.FuelError
import com.github.kittinunf.fuel.core.ResponseDeserializable
import com.github.kittinunf.fuel.coroutines.awaitObjectResponseResult
import com.github.kittinunf.fuel.coroutines.awaitObjectResult
import com.github.kittinunf.result.Result
import com.google.gson.Gson
import kotlinx.coroutines.Dispatchers.IO
import kotlinx.coroutines.flow.Flow
import kotlinx.coroutines.flow.collect
import kotlinx.coroutines.flow.flow
import kotlinx.coroutines.flow.flowOn
import java.io.Reader
import java.lang.reflect.Type
import kotlin.math.ceil

class HttpUpstream<D : Any, R : OtterResponse<D>>(
  val behavior: Behavior,
  private val url: String,
  private val type: Type
) : Upstream<D> {
  enum class Behavior {
    Single, AtOnce, Progressive
  }

  override fun fetch(size: Int): Flow<Repository.Response<D>> = flow<Repository.Response<D>> {
    if (behavior == Behavior.Single && size != 0) return@flow

    val page = ceil(size / AppContext.PAGE_SIZE.toDouble()).toInt() + 1

    val url =
      Uri.parse(url)
        .buildUpon()
        .appendQueryParameter("page_size", AppContext.PAGE_SIZE.toString())
        .appendQueryParameter("page", page.toString())
        .appendQueryParameter("scope", Settings.getScopes().joinToString(","))
        .build()
        .toString()

    get(url).fold(
      { response ->
        val data = response.getData()

        when (behavior) {
          Behavior.Single -> emit(networkResponse(data, page, false))
          Behavior.Progressive -> emit(networkResponse(data, page, response.next != null))
          else -> {
            emit(networkResponse(data, page, response.next != null))
            if (response.next != null) fetch(size + data.size).collect { emit(it) }
          }
        }
      },
      { error ->
        when (error.exception) {
          is RefreshError -> EventBus.send(Event.LogOut)
          else -> emit(networkResponse(listOf(), page, false))
        }
      }
    )
  }.flowOn(IO)

  private fun networkResponse(data: List<D>, page: Int, hasMore: Boolean) = Repository.Response(
    Repository.Origin.Network,
    data,
    page,
    hasMore
  )

  class GenericDeserializer<T : OtterResponse<*>>(val type: Type) : ResponseDeserializable<T> {
    override fun deserialize(reader: Reader): T? {
      return Gson().fromJson(reader, type)
    }
  }

  suspend fun get(url: String): Result<R, FuelError> {
    return try {
      val request = Fuel.get(mustNormalizeUrl(url)).apply {
        if (!Settings.isAnonymous()) {
          header("Authorization", "Bearer ${Settings.getAccessToken()}")
        }
      }

      val (_, response, result) = request.awaitObjectResponseResult(GenericDeserializer<R>(type))

      if (response.statusCode == 401) {
        return retryGet(url)
      }

      result
    } catch (e: Exception) {
      Result.error(FuelError.wrap(e))
    }
  }

  private suspend fun retryGet(url: String): Result<R, FuelError> {
    return try {
      return if (HTTP.refresh()) {
        val request = Fuel.get(mustNormalizeUrl(url)).apply {
          if (!Settings.isAnonymous()) {
            header("Authorization", "Bearer ${Settings.getAccessToken()}")
          }
        }

        request.awaitObjectResult(GenericDeserializer(type))
      } else {
        Result.Failure(FuelError.wrap(RefreshError))
      }
    } catch (e: Exception) {
      Result.error(FuelError.wrap(e))
    }
  }
}