Added implementaion for common repository

app/src/main/java/com/sirekanyan/knigopis/repository/common/CommonRepository.kt

@@ -0,0 +1,28 @@
+package com.sirekanyan.knigopis.repository.common
+
+import com.sirekanyan.knigopis.common.NetworkChecker
+import io.reactivex.Completable
+import io.reactivex.Flowable
+import io.reactivex.Maybe
+import io.reactivex.Single
+
+abstract class CommonRepository<T>(private val networkChecker: NetworkChecker) {
+
+    abstract fun loadFromNetwork(): Single<T>
+
+    abstract fun findCached(): Maybe<T>
+
+    abstract fun saveToCache(data: T): Completable
+
+    fun observe(): Flowable<T> =
+        if (networkChecker.isNetworkAvailable()) {
+            findCached().concatWith(
+                loadFromNetwork()
+                    .doOnSuccess { saveToCache(it).blockingAwait() }
+                    .toMaybe()
+            )
+        } else {
+            findCached().toFlowable()
+        }
+
+}