Caching toots (#809)

* Initial timeline cache implementation

* Fix build/DI errors for caching

* Rename timeline entities tables. Add migration. Add DB scheme file.

* Fix uniqueness problem, change offline strategy, improve mapping

* Try to merge in new statuses, fix bottom loading, fix saving spans.

* Fix reblogs IDs, fix inserting elements from top

* Send one more request to get latest timeline statuses

* Give Timeline placeholders string id. Rewrite Either in Kotlin

* Initial placeholder implementation for caching

* Fix crash on removing overlap statuses

* Migrate counters to long

* Remove unused counters. Add minimal TimelineDAOTest

* Fix bug with placeholder ID

* Update cache in response to events. Refactor TimelineCases

* Fix crash, reduce number of placeholders

* Fix crash, fix filtering, improve placeholder handling

* Fix migration, add 8-9 migration test

* Fix initial timeline update, remove more placeholders

* Add cleanup for old statuses

* Fix cleanup

* Delete ExampleInstrumentedTest

* Improve timeline UX regarding caching

* Fix typos

* Fix initial timeline update

* Cleanup/fix initial timeline update

* Workaround for weird behavior of first post on initial tl update.

* Change counter types back to int

* Clear timeline cache on logout

* Fix loading when timeline is completely empty

* Fix androidx migration issues

* Fix tests

* Apply caching feedback

* Save account emojis to cache

* Fix warnings and bugs

app/src/main/java/com/keylesspalace/tusky/appstore/CacheUpdater.kt

@@ -0,0 +1,47 @@
+package com.keylesspalace.tusky.appstore
+
+import com.keylesspalace.tusky.db.AccountManager
+import com.keylesspalace.tusky.db.AppDatabase
+import io.reactivex.Single
+import io.reactivex.disposables.Disposable
+import io.reactivex.schedulers.Schedulers
+import javax.inject.Inject
+
+class CacheUpdater @Inject constructor(
+        eventHub: EventHub,
+        accountManager: AccountManager,
+        val appDatabase: AppDatabase
+) {
+
+    private val disposable: Disposable
+
+    init {
+        val timelineDao = appDatabase.timelineDao()
+        disposable = eventHub.events.subscribe { event ->
+            val accountId = accountManager.activeAccount?.id ?: return@subscribe
+            when (event) {
+                is FavoriteEvent ->
+                    timelineDao.setFavourited(accountId, event.statusId, event.favourite)
+                is ReblogEvent ->
+                    timelineDao.setReblogged(accountId, event.statusId, event.reblog)
+                is UnfollowEvent ->
+                    timelineDao.removeAllByUser(accountId, event.accountId)
+                is StatusDeletedEvent ->
+                    timelineDao.delete(accountId, event.statusId)
+            }
+        }
+    }
+
+    fun stop() {
+        this.disposable.dispose()
+    }
+
+    fun clearForUser(accountId: Long) {
+        Single.fromCallable {
+            appDatabase.timelineDao().removeAllForAccount(accountId)
+            appDatabase.timelineDao().removeAllUsersForAccount(accountId)
+        }
+                .subscribeOn(Schedulers.io())
+                .subscribe()
+    }
+}