Part2. Implement optional for SQLite

storio-common/src/main/java/com/pushtorefresh/storio2/Optional.java

@@ -0,0 +1,72 @@
+package com.pushtorefresh.storio2;
+
+import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
+
+public final class Optional<T> {
+
+    @NonNull
+    private transient static final Optional<?> EMPTY = new Optional<Object>(null);
+
+    @Nullable
+    private final T value;
+
+    private Optional(@Nullable T value) {
+        this.value = value;
+    }
+
+    @NonNull
+    public static <T> Optional<T> empty() {
+        //noinspection unchecked
+        return (Optional<T>) EMPTY;
+    }
+
+    @NonNull
+    public static <T> Optional<T> of(@Nullable T value) {
+        //noinspection unchecked
+        return value == null ? (Optional<T>) EMPTY : new Optional<T>(value);
+    }
+
+    @NonNull
+    public T get() {
+        if (value == null)
+            throw new NullPointerException();
+        return value;
+    }
+
+    public boolean isPresent() {
+        return value != null;
+    }
+
+    @NonNull
+    public T or(@NonNull T defaultValue) {
+        return value != null ? value : defaultValue;
+    }
+
+    @Nullable
+    public T orNull() {
+        return value;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+
+        Optional<?> optional = (Optional<?>) o;
+
+        return value != null ? value.equals(optional.value) : optional.value == null;
+    }
+
+    @Override
+    public int hashCode() {
+        return value != null ? value.hashCode() : 0;
+    }
+
+    @Override
+    public String toString() {
+        return "Optional{" +
+                "value=" + value +
+                '}';
+    }
+}

storio-common/src/main/java/com/pushtorefresh/storio2/operations/PreparedOperation.java

@@ -2,7 +2,6 @@
 
 import android.support.annotation.CheckResult;
 import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
 import android.support.annotation.WorkerThread;
 
 import io.reactivex.BackpressureStrategy;
@@ -26,7 +25,7 @@ public interface PreparedOperation<Result, Data> {
      *
      * @return nullable result of operation.
      */
-    @Nullable
+    @NonNull
     @WorkerThread
     Result executeAsBlocking();
 

storio-common/src/test/java/com/pushtorefresh/storio2/OptionalTest.java

@@ -0,0 +1,103 @@
+package com.pushtorefresh.storio2;
+
+import com.pushtorefresh.storio2.test.ToStringChecker;
+
+import org.assertj.core.api.ThrowableAssert;
+import org.junit.Test;
+
+import nl.jqno.equalsverifier.EqualsVerifier;
+
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.assertj.core.api.Java6Assertions.assertThat;
+
+public class OptionalTest {
+
+    @Test
+    public void emptyHasNullValue() {
+        assertThat(Optional.empty().orNull()).isEqualTo(null);
+    }
+
+    @Test
+    public void emptyReturnsTheSameInstance() {
+        assertThat(Optional.empty()).isSameAs(Optional.empty());
+    }
+
+    @Test
+    public void ofNullValueReturnsEmpty() {
+        assertThat(Optional.of(null)).isSameAs(Optional.empty());
+    }
+
+    @Test
+    public void ofNotNullValueReturnsEqualInstances() {
+        assertThat(Optional.of("some value"))
+                .isEqualTo(Optional.of("some value"));
+    }
+
+    @Test
+    public void getReturnsValueIfPresent() {
+        assertThat(Optional.of("some value").get()).isEqualTo("some value");
+    }
+
+    @Test
+    public void getThrowsIfNull() {
+        final Optional<Object> empty = Optional.empty();
+        assertThatThrownBy(new ThrowableAssert.ThrowingCallable() {
+            @Override
+            public void call() throws Throwable {
+                empty.get();
+            }
+        }).isInstanceOf(NullPointerException.class)
+                .hasMessage(null)
+                .hasNoCause();
+    }
+
+    @Test
+    public void isPresentReturnsTrueIfNotNull() {
+        assertThat(Optional.of("some value").isPresent()).isTrue();
+    }
+
+    @Test
+    public void isPresentReturnsFalseIfNull() {
+        assertThat(Optional.empty().isPresent()).isFalse();
+    }
+
+    @Test
+    public void orReturnsValueIfPresent() {
+        assertThat(Optional.of("some value").or("default value")).
+                isEqualTo("some value");
+    }
+
+    @Test
+    public void orReturnsDefaultIfNotPresent() {
+        assertThat(Optional.empty().or("default value")).
+                isEqualTo("default value");
+    }
+
+
+    @Test
+    public void orNullReturnsValueIfPresent() {
+        assertThat(Optional.of("some value").orNull()).
+                isEqualTo("some value");
+    }
+
+    @Test
+    public void orNullReturnsNullIfNotPresent() {
+        assertThat(Optional.empty().orNull()).isNull();
+    }
+
+    @Test
+    public void verifyEqualsAndHashCodeImplementation() {
+        EqualsVerifier
+                .forClass(Optional.class)
+                .allFieldsShouldBeUsed()
+                .withPrefabValues(Optional.class, Optional.of("some value"), Optional.of("another value"))
+                .verify();
+    }
+
+    @Test
+    public void checkToStringImplementation() {
+        ToStringChecker
+                .forClass(Optional.class)
+                .check();
+    }
+}

storio-content-resolver/src/main/java/com/pushtorefresh/storio2/contentresolver/operations/get/PreparedGetObject.java

@@ -53,7 +53,7 @@ public class PreparedGetObject<T> extends PreparedGet<T> {
      */
     @SuppressWarnings({"ConstantConditions", "NullableProblems"})
     @WorkerThread
-    @Nullable
+    @NonNull
     @Override
     public T executeAsBlocking() {
         try {

storio-sample-app/src/main/java/com/pushtorefresh/storio2/sample/ui/fragment/TweetsFragment.java

@@ -13,6 +13,7 @@
 import android.view.ViewGroup;
 import android.widget.Toast;
 
+import com.pushtorefresh.storio2.Optional;
 import com.pushtorefresh.storio2.sample.R;
 import com.pushtorefresh.storio2.sample.SampleApp;
 import com.pushtorefresh.storio2.sample.db.entities.Tweet;
@@ -216,21 +217,24 @@ public void onUpdateTweet(@NonNull final Long tweetId) {
                 .prepare()
                 .asRxSingle()
                 // 2.
-                .map(new Function<Tweet, Tweet>() {
+                .map(new Function<Optional<Tweet>, Optional<Tweet>>() {
                     @Override
-                    public Tweet apply(Tweet tweet) {
+                    @NonNull
+                    public Optional<Tweet> apply(@NonNull Optional<Tweet> tweet) {
                         // We can get NULL in parameter so we check it
-                        return tweet == null ? tweet :
-                                Tweet.newTweet(tweetId, tweet.author() + "+", tweet.content());
+                        return tweet.isPresent()
+                                ? Optional.of(Tweet.newTweet(tweetId, tweet.get().author() + "+", tweet.get().content()))
+                                : tweet;
                     }
                 })
                 // 3.
-                .flatMap(new Function<Tweet, Single<?>>() {
+                .flatMap(new Function<Optional<Tweet>, Single<?>>() {
                     @Override
-                    public Single<?> apply(Tweet tweet) {
+                    @NonNull
+                    public Single<?> apply(Optional<Tweet> tweet) {
                         return storIOSQLite
                                 .put()
-                                .object(tweet)
+                                .object(tweet.get())
                                 .prepare()
                                 .asRxSingle();
                     }
@@ -239,7 +243,7 @@ public Single<?> apply(Tweet tweet) {
                 .observeOn(mainThread())
                 .subscribe(new Consumer<Object>() {
                     @Override
-                    public void accept(Object o) {
+                    public void accept(@NonNull Object o) {
 
                     }
                 }, new Consumer<Throwable>() {

storio-sqlite/src/main/java/com/pushtorefresh/storio2/sqlite/Interceptor.java

@@ -1,7 +1,6 @@
 package com.pushtorefresh.storio2.sqlite;
 
 import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
 
 import com.pushtorefresh.storio2.operations.PreparedOperation;
 
@@ -12,15 +11,15 @@
  */
 public interface Interceptor {
 
-    @Nullable
+    @NonNull
     <Result, Data> Result intercept(@NonNull PreparedOperation<Result, Data> operation, @NonNull Chain chain);
 
     /**
      * Encapsulates logic of proceeding from one interceptor to another.
      */
     interface Chain {
 
-        @Nullable
+        @NonNull
         <Result, Data> Result proceed(@NonNull PreparedOperation<Result, Data> operation);
     }
 }

storio-sqlite/src/main/java/com/pushtorefresh/storio2/sqlite/LoggingInterceptor.java

@@ -2,7 +2,6 @@
 
 import android.os.SystemClock;
 import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
 import android.util.Log;
 
 import com.pushtorefresh.storio2.operations.PreparedOperation;
@@ -33,7 +32,7 @@ private LoggingInterceptor(@NonNull Logger logger) {
         this.logger = logger;
     }
 
-    @Nullable
+    @NonNull
     @Override
     public <Result, Data> Result intercept(@NonNull PreparedOperation<Result, Data> operation, @NonNull Chain chain) {
         final long startMillis = SystemClock.elapsedRealtime();

storio-sqlite/src/main/java/com/pushtorefresh/storio2/sqlite/impl/ChainImpl.java

@@ -1,7 +1,6 @@
 package com.pushtorefresh.storio2.sqlite.impl;
 
 import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
 
 import com.pushtorefresh.storio2.operations.PreparedOperation;
 import com.pushtorefresh.storio2.sqlite.Interceptor;
@@ -37,7 +36,7 @@ public ChainImpl(@NonNull ListIterator<Interceptor> interceptors) {
         this.interceptors = interceptors;
     }
 
-    @Nullable // can be null on PreparedGetObject
+    @NonNull
     @Override
     public <Result, Data> Result proceed(@NonNull PreparedOperation<Result, Data> operation) {
         if (!interceptors.hasNext()) {
@@ -55,8 +54,7 @@ public <Result, Data> Result proceed(@NonNull PreparedOperation<Result, Data> op
         // Call the nextChain nextInterceptor in the chain.
         final Interceptor nextInterceptor = interceptors.next();
         final ChainImpl nextChain = new ChainImpl(interceptors);
-        final Result result = nextInterceptor.intercept(operation, nextChain);
 
-        return result;
+        return nextInterceptor.intercept(operation, nextChain);
     }
 }

storio-sqlite/src/main/java/com/pushtorefresh/storio2/sqlite/operations/delete/PreparedDelete.java

@@ -1,7 +1,6 @@
 package com.pushtorefresh.storio2.sqlite.operations.delete;
 
 import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
 import android.support.annotation.WorkerThread;
 
 import com.pushtorefresh.storio2.operations.PreparedWriteOperation;
@@ -37,7 +36,7 @@ public abstract class PreparedDelete<T, Data> implements PreparedWriteOperation<
      * @return non-null result of Delete Operation.
      */
     @WorkerThread
-    @Nullable
+    @NonNull
     public final T executeAsBlocking() {
         return buildChain(storIOSQLite.interceptors(), getRealCallInterceptor())
                 .proceed(this);

storio-sqlite/src/main/java/com/pushtorefresh/storio2/sqlite/operations/delete/PreparedDeleteByQuery.java

@@ -112,6 +112,7 @@ public <Result, Data> Result intercept(@NonNull PreparedOperation<Result, Data>
                     );
                     storIOSQLite.lowLevel().notifyAboutChanges(changes);
                 }
+                //noinspection unchecked
                 return (Result) deleteResult;
             } catch (Exception exception) {
                 throw new StorIOException("Error has occurred during Delete operation. query = " + deleteQuery, exception);

storio-sqlite/src/main/java/com/pushtorefresh/storio2/sqlite/operations/get/PreparedGet.java

@@ -51,7 +51,7 @@ public abstract class PreparedGet<Result> implements PreparedOperation<Result, G
      * @return result of an operation. Can be null in get(Object).
      */
     @WorkerThread
-    @Nullable
+    @NonNull
     public final Result executeAsBlocking() {
         return buildChain(storIOSQLite.interceptors(), getRealCallInterceptor())
                 .proceed(this);