Improved loading of new and cached items.

Scrolling through large lists was a pain. The next page would only load
when the end of the list was reached, stopping the scroll action while the new
page was fetched.

This commits adds two items:

 * Artists, albums and playlists do not refresh data on resume, only
   using cached data until manually refreshed.
 * When manually refreshed, we initially fetch a few pages instead
   of only one. Also, on scroll, we try as best as we can to always keep
   10 pages (pages as in screen estate) worth of data loaded.

app/src/main/java/com/github/apognu/otter/activities/MainActivity.kt

@@ -408,7 +408,7 @@ class MainActivity : AppCompatActivity() {
       }
 
       now_playing_details_favorite?.let { now_playing_details_favorite ->
-        favoriteCheckRepository.fetch().untilNetwork(lifecycleScope, IO) { favorites, _, _ ->
+        favoriteCheckRepository.fetch().untilNetwork(lifecycleScope, IO) { favorites, _, _, _ ->
           lifecycleScope.launch(Main) {
             track.favorite = favorites.contains(track.id)
 

app/src/main/java/com/github/apognu/otter/activities/SearchActivity.kt

@@ -67,21 +67,21 @@ class SearchActivity : AppCompatActivity() {
           adapter.tracks.clear()
           adapter.notifyDataSetChanged()
 
-          artistsRepository.fetch(Repository.Origin.Network.origin).untilNetwork(lifecycleScope) { artists, _, _ ->
+          artistsRepository.fetch(Repository.Origin.Network.origin).untilNetwork(lifecycleScope) { artists, _, _, _ ->
             done++
 
             adapter.artists.addAll(artists)
             refresh()
           }
 
-          albumsRepository.fetch(Repository.Origin.Network.origin).untilNetwork(lifecycleScope) { albums, _, _ ->
+          albumsRepository.fetch(Repository.Origin.Network.origin).untilNetwork(lifecycleScope) { albums, _, _ ,_ ->
             done++
 
             adapter.albums.addAll(albums)
             refresh()
           }
 
-          tracksRepository.fetch(Repository.Origin.Network.origin).untilNetwork(lifecycleScope) { tracks, _, _ ->
+          tracksRepository.fetch(Repository.Origin.Network.origin).untilNetwork(lifecycleScope) { tracks, _, _, _ ->
             done++
 
             adapter.tracks.addAll(tracks)

app/src/main/java/com/github/apognu/otter/fragments/AlbumsFragment.kt

@@ -33,8 +33,9 @@ import kotlinx.coroutines.withContext
 class AlbumsFragment : FunkwhaleFragment<Album, AlbumsAdapter>() {
   override val viewRes = R.layout.fragment_albums
   override val recycler: RecyclerView get() = albums
+  override val alwaysRefresh = false
 
-  lateinit var artistTracksRepository: ArtistTracksRepository
+  private lateinit var artistTracksRepository: ArtistTracksRepository
 
   var artistId = 0
   var artistName = ""

app/src/main/java/com/github/apognu/otter/fragments/ArtistsFragment.kt

@@ -21,6 +21,7 @@ import kotlinx.android.synthetic.main.fragment_artists.*
 class ArtistsFragment : FunkwhaleFragment<Artist, ArtistsAdapter>() {
   override val viewRes = R.layout.fragment_artists
   override val recycler: RecyclerView get() = artists
+  override val alwaysRefresh = false
 
   companion object {
     fun openAlbums(context: Context?, artist: Artist, fragment: Fragment? = null, art: String? = null) {

app/src/main/java/com/github/apognu/otter/fragments/FavoritesFragment.kt

@@ -19,6 +19,7 @@ import kotlinx.coroutines.withContext
 class FavoritesFragment : FunkwhaleFragment<Track, FavoritesAdapter>() {
   override val viewRes = R.layout.fragment_favorites
   override val recycler: RecyclerView get() = favorites
+  override val alwaysRefresh = false
 
   override fun onCreate(savedInstanceState: Bundle?) {
     super.onCreate(savedInstanceState)

app/src/main/java/com/github/apognu/otter/fragments/FunkwhaleFragment.kt

@@ -28,14 +28,19 @@ abstract class FunkwhaleAdapter<D, VH : RecyclerView.ViewHolder> : RecyclerView.
 }
 
 abstract class FunkwhaleFragment<D : Any, A : FunkwhaleAdapter<D, *>> : Fragment() {
+  val INITIAL_PAGES = 5
+  val OFFSCREEN_PAGES = 10
+
   abstract val viewRes: Int
   abstract val recycler: RecyclerView
   open val layoutManager: RecyclerView.LayoutManager get() = LinearLayoutManager(context)
+  open val alwaysRefresh = true
 
   lateinit var repository: Repository<D, *>
   lateinit var adapter: A
 
   private var initialFetched = false
+  private var moreLoading = false
   private var listener: Job? = null
 
   override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
@@ -51,7 +56,11 @@ abstract class FunkwhaleFragment<D : Any, A : FunkwhaleAdapter<D, *>> : Fragment
     (repository.upstream as? HttpUpstream<*, *>)?.let { upstream ->
       if (upstream.behavior == HttpUpstream.Behavior.Progressive) {
         recycler.setOnScrollChangeListener { _, _, _, _, _ ->
-          if (recycler.computeVerticalScrollOffset() > 0 && !recycler.canScrollVertically(1)) {
+          val offset = recycler.computeVerticalScrollOffset()
+          val left = recycler.computeVerticalScrollRange() - recycler.height - offset
+
+          if (initialFetched && !moreLoading && offset > 0 && left < (recycler.height * OFFSCREEN_PAGES)) {
+            moreLoading = true
             fetch(Repository.Origin.Network.origin, adapter.data.size)
           }
         }
@@ -60,7 +69,7 @@ abstract class FunkwhaleFragment<D : Any, A : FunkwhaleAdapter<D, *>> : Fragment
 
     fetch(Repository.Origin.Cache.origin)
 
-    if (adapter.data.isEmpty()) {
+    if (alwaysRefresh && adapter.data.isEmpty()) {
       fetch(Repository.Origin.Network.origin)
     }
   }
@@ -91,11 +100,11 @@ abstract class FunkwhaleFragment<D : Any, A : FunkwhaleAdapter<D, *>> : Fragment
   private fun fetch(upstreams: Int = Repository.Origin.Network.origin, size: Int = 0) {
     var first = size == 0
 
-    if (upstreams == Repository.Origin.Network.origin) {
+    if (!moreLoading && upstreams == Repository.Origin.Network.origin) {
       swiper?.isRefreshing = true
     }
 
-    repository.fetch(upstreams, size).untilNetwork(lifecycleScope, IO) { data, isCache, hasMore ->
+    repository.fetch(upstreams, size).untilNetwork(lifecycleScope, IO) { data, isCache, page, hasMore ->
       lifecycleScope.launch(Main) {
         if (isCache) {
           adapter.data = data.toMutableList()
@@ -112,10 +121,16 @@ abstract class FunkwhaleFragment<D : Any, A : FunkwhaleAdapter<D, *>> : Fragment
 
         adapter.data.addAll(data)
 
-        if (!hasMore) {
-          swiper?.isRefreshing = false
+        (repository.upstream as? HttpUpstream<*, *>)?.let { upstream ->
+          when (upstream.behavior) {
+            HttpUpstream.Behavior.Progressive -> if (!hasMore || page >= INITIAL_PAGES) swiper?.isRefreshing = false
+            HttpUpstream.Behavior.AtOnce -> if (!hasMore) swiper?.isRefreshing = false
+            HttpUpstream.Behavior.Single -> if (!hasMore) swiper?.isRefreshing = false
+          }
+        }
 
-          withContext(IO) {
+        when (hasMore) {
+          false -> withContext(IO) {
             if (adapter.data.isNotEmpty()) {
               try {
                 repository.cacheId?.let { cacheId ->
@@ -129,6 +144,21 @@ abstract class FunkwhaleFragment<D : Any, A : FunkwhaleAdapter<D, *>> : Fragment
               }
             }
           }
+
+          true -> {
+            moreLoading = false
+
+            (repository.upstream as? HttpUpstream<*, *>)?.let { upstream ->
+              if (upstream.behavior == HttpUpstream.Behavior.Progressive) {
+                if (page < INITIAL_PAGES) {
+                  moreLoading = true
+                  fetch(Repository.Origin.Network.origin, adapter.data.size)
+                } else {
+                  initialFetched = true
+                }
+              }
+            }
+          }
         }
 
         when (first) {

app/src/main/java/com/github/apognu/otter/repositories/HttpUpstream.kt

@@ -41,18 +41,19 @@ class HttpUpstream<D : Any, R : FunkwhaleResponse<D>>(val behavior: Behavior, pr
       { response ->
         val data = response.getData()
 
-        if (behavior == Behavior.Progressive || response.next == null) {
-          emit(Repository.Response(Repository.Origin.Network, data, false))
-        } else {
-          emit(Repository.Response(Repository.Origin.Network, data, true))
+        when (behavior) {
+          Behavior.Progressive -> emit(Repository.Response(Repository.Origin.Network, data, page, response.next != null))
+          else -> {
+            emit(Repository.Response(Repository.Origin.Network, data, page, response.next != null))
 
-          fetch(size + data.size).collect { emit(it) }
+            fetch(size + data.size).collect { emit(it) }
+          }
         }
       },
       { error ->
         when (error.exception) {
           is RefreshError -> EventBus.send(Event.LogOut)
-          else -> emit(Repository.Response(Repository.Origin.Network, listOf(), false))
+          else -> emit(Repository.Response(Repository.Origin.Network, listOf(), page,false))
         }
       }
     )

app/src/main/java/com/github/apognu/otter/repositories/Repository.kt

@@ -1,6 +1,7 @@
 package com.github.apognu.otter.repositories
 
 import android.content.Context
+import com.github.apognu.otter.utils.AppContext
 import com.github.apognu.otter.utils.Cache
 import com.github.apognu.otter.utils.CacheItem
 import kotlinx.coroutines.CoroutineScope
@@ -8,6 +9,7 @@ import kotlinx.coroutines.Dispatchers.IO
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.flow.*
 import java.io.BufferedReader
+import kotlin.math.ceil
 
 interface Upstream<D> {
   fun fetch(size: Int = 0): Flow<Repository.Response<D>>
@@ -21,7 +23,7 @@ abstract class Repository<D : Any, C : CacheItem<D>> {
     Network(0b10)
   }
 
-  data class Response<D>(val origin: Origin, val data: List<D>, val hasMore: Boolean)
+  data class Response<D>(val origin: Origin, val data: List<D>, val page: Int, val hasMore: Boolean)
 
   abstract val context: Context?
   abstract val cacheId: String?
@@ -39,7 +41,7 @@ abstract class Repository<D : Any, C : CacheItem<D>> {
     cacheId?.let { cacheId ->
       Cache.get(context, cacheId)?.let { reader ->
         uncache(reader)?.let { cache ->
-          emit(Response(Origin.Cache, cache.data, false))
+          emit(Response(Origin.Cache, cache.data, ceil(cache.data.size / AppContext.PAGE_SIZE.toDouble()).toInt(), false))
         }
       }
     }
@@ -48,8 +50,8 @@ abstract class Repository<D : Any, C : CacheItem<D>> {
   private fun fromNetwork(size: Int) = flow {
     upstream
       .fetch(size)
-      .map { response -> Response(Origin.Network, onDataFetched(response.data), response.hasMore) }
-      .collect { response -> emit(Response(Origin.Network, response.data, response.hasMore)) }
+      .map { response -> Response(Origin.Network, onDataFetched(response.data), response.page, response.hasMore) }
+      .collect { response -> emit(Response(Origin.Network, response.data, response.page, response.hasMore)) }
   }
 
   protected open fun onDataFetched(data: List<D>) = data

app/src/main/java/com/github/apognu/otter/utils/Extensions.kt

@@ -17,10 +17,10 @@ import kotlinx.coroutines.flow.collect
 import kotlinx.coroutines.launch
 import kotlin.coroutines.CoroutineContext
 
-inline fun <D> Flow<Repository.Response<D>>.untilNetwork(scope: CoroutineScope, context: CoroutineContext = Main, crossinline callback: (data: List<D>, isCache: Boolean, hasMore: Boolean) -> Unit) {
+inline fun <D> Flow<Repository.Response<D>>.untilNetwork(scope: CoroutineScope, context: CoroutineContext = Main, crossinline callback: (data: List<D>, isCache: Boolean, page: Int, hasMore: Boolean) -> Unit) {
   scope.launch(context) {
     collect { data ->
-      callback(data.data, data.origin == Repository.Origin.Cache, data.hasMore)
+      callback(data.data, data.origin == Repository.Origin.Cache, data.page, data.hasMore)
     }
   }
 }

app/src/main/res/xml/security.xml

@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="utf-8"?>
+<network-security-config xmlns:tools="http://schemas.android.com/tools">
+  <base-config>
+    <trust-anchors>
+
+      <certificates src="system" />
+
+      <certificates
+        src="user"
+        tools:ignore="AcceptsUserCertificates" />
+
+    </trust-anchors>
+  </base-config>
+</network-security-config>