STITCH-2526: Add findOne() functionality (#104)

.gitignore

@@ -64,3 +64,8 @@ fastlane/readme.md
 
 # mac
 .DS_Store
+
+# eclipse
+.project
+.classpath
+.settings/

android/services/mongodb-remote/src/androidTest/java/com/mongodb/stitch/android/services/mongodb/remote/RemoteMongoClientIntTests.kt

@@ -15,6 +15,7 @@ import com.mongodb.stitch.core.auth.providers.anonymous.AnonymousCredential
 import com.mongodb.stitch.core.internal.common.BsonUtils
 import com.mongodb.stitch.core.services.mongodb.remote.OperationType
 import com.mongodb.stitch.core.services.mongodb.remote.RemoteCountOptions
+import com.mongodb.stitch.core.services.mongodb.remote.RemoteFindOptions
 import com.mongodb.stitch.core.services.mongodb.remote.RemoteUpdateOptions
 import com.mongodb.stitch.core.testutils.CustomType
 import org.bson.BsonDocument
@@ -131,6 +132,61 @@ class RemoteMongoClientIntTests : BaseStitchAndroidIntTest() {
         }
     }
 
+    @Test
+    fun testFindOne() {
+        val coll = getTestColl()
+
+        val doc1 = Document("hello", "world1")
+        val doc2 = Document("hello", "world2")
+        val doc3 = Document("hello", "world3")
+
+        // Test findOne() on empty collection with no filter and no options
+        assertNull(Tasks.await(coll.findOne()))
+
+        // Insert a document into the collection
+        Tasks.await(coll.insertOne(doc1))
+        assertEquals(1, Tasks.await(coll.count()))
+
+        // Test findOne() with no filter and no options
+        assertEquals(withoutId(Tasks.await(coll.findOne())), withoutId(doc1))
+
+        // Test findOne() with filter and no options
+        val result = Tasks.await(coll.findOne(Document("hello", "world1")))
+        assertEquals(withoutId(result), withoutId(doc1))
+
+        // Test findOne() with filter that does not match any documents and no options
+        assertNull(Tasks.await(coll.findOne(Document("hello", "worldDNE"))))
+
+        // Insert 2 more documents into the collection
+        Tasks.await(coll.insertMany(listOf(doc2, doc3)))
+        assertEquals(3, Tasks.await(coll.count()))
+
+        // test findOne() with projection and sort options
+        val projection = Document("hello", 1)
+        projection["_id"] = 0
+        val result2 = Tasks.await(coll.findOne(Document(), RemoteFindOptions()
+                .limit(2)
+                .projection(projection)
+                .sort(Document("hello", 1))))
+        assertEquals(result2, withoutId(doc1))
+
+        val result3 = Tasks.await(coll.findOne(Document(), RemoteFindOptions()
+                .limit(2)
+                .projection(projection)
+                .sort(Document("hello", -1))))
+        assertEquals(result3, withoutId(doc3))
+
+        // test findOne() properly fails
+        try {
+            Tasks.await(coll.findOne(Document("\$who", 1)))
+            fail()
+        } catch (ex: ExecutionException) {
+            assertTrue(ex.cause is StitchServiceException)
+            val svcEx = ex.cause as StitchServiceException
+            assertEquals(StitchServiceErrorCode.MONGODB_ERROR, svcEx.errorCode)
+        }
+    }
+
     @Test
     fun testFind() {
         val coll = getTestColl()

android/services/mongodb-remote/src/main/java/com/mongodb/stitch/android/services/mongodb/remote/RemoteMongoCollection.java

@@ -22,6 +22,7 @@
 import com.mongodb.stitch.core.services.mongodb.remote.ChangeStream;
 import com.mongodb.stitch.core.services.mongodb.remote.RemoteCountOptions;
 import com.mongodb.stitch.core.services.mongodb.remote.RemoteDeleteResult;
+import com.mongodb.stitch.core.services.mongodb.remote.RemoteFindOptions;
 import com.mongodb.stitch.core.services.mongodb.remote.RemoteInsertManyResult;
 import com.mongodb.stitch.core.services.mongodb.remote.RemoteInsertOneResult;
 import com.mongodb.stitch.core.services.mongodb.remote.RemoteUpdateOptions;
@@ -130,6 +131,63 @@ <NewDocumentT> RemoteMongoCollection<NewDocumentT> withDocumentClass(
    */
   Task<Long> count(final Bson filter, final RemoteCountOptions options);
 
+  /**
+   * Finds a document in the collection.
+   *
+   * @return  a task containing the result of the find one operation
+   */
+  Task<DocumentT> findOne();
+
+  /**
+   * Finds a document in the collection.
+   *
+   * @param resultClass the class to decode each document into
+   * @param <ResultT>   the target document type
+   * @return a task containing the result of the find one operation
+   */
+  <ResultT> Task<ResultT> findOne(final Class<ResultT> resultClass);
+
+  /**
+   * Finds a document in the collection.
+   *
+   * @param filter the query filter
+   * @return  a task containing the result of the find one operation
+   */
+  Task<DocumentT> findOne(final Bson filter);
+
+  /**
+   * Finds a document in the collection.
+   *
+   * @param filter      the query filter
+   * @param resultClass the class to decode each document into
+   * @param <ResultT>   the target document type of the iterable.
+   * @return  a task containing the result of the find one operation
+   */
+  <ResultT> Task<ResultT> findOne(final Bson filter, final Class<ResultT> resultClass);
+
+  /**
+   * Finds a document in the collection.
+   *
+   * @param filter the query filter
+   * @param options A RemoteFindOptions struct
+   * @return  a task containing the result of the find one operation
+   */
+  Task<DocumentT> findOne(final Bson filter, final RemoteFindOptions options);
+
+  /**
+   * Finds a document in the collection.
+   *
+   * @param filter      the query filter
+   * @param options     A RemoteFindOptions struct
+   * @param resultClass the class to decode each document into
+   * @param <ResultT>   the target document type of the iterable.
+   * @return  a task containing the result of the find one operation
+   */
+  <ResultT> Task<ResultT> findOne(
+          final Bson filter,
+          final RemoteFindOptions options,
+          final Class<ResultT> resultClass);
+
   /**
    * Finds all documents in the collection.
    *

android/services/mongodb-remote/src/main/java/com/mongodb/stitch/android/services/mongodb/remote/internal/RemoteMongoCollectionImpl.java

@@ -28,6 +28,7 @@
 import com.mongodb.stitch.core.services.mongodb.remote.ChangeStream;
 import com.mongodb.stitch.core.services.mongodb.remote.RemoteCountOptions;
 import com.mongodb.stitch.core.services.mongodb.remote.RemoteDeleteResult;
+import com.mongodb.stitch.core.services.mongodb.remote.RemoteFindOptions;
 import com.mongodb.stitch.core.services.mongodb.remote.RemoteInsertManyResult;
 import com.mongodb.stitch.core.services.mongodb.remote.RemoteInsertOneResult;
 import com.mongodb.stitch.core.services.mongodb.remote.RemoteUpdateOptions;
@@ -140,6 +141,107 @@ public Long call() {
     });
   }
 
+
+  /**
+   * Finds a document in the collection
+   *
+   * @return  a task containing the result of the find one operation
+   */
+  public Task<DocumentT> findOne() {
+    return dispatcher.dispatchTask(new Callable<DocumentT>() {
+      @Override
+      public DocumentT call() {
+        return proxy.findOne();
+      }
+    });
+  }
+
+  /**
+   * Finds a document in the collection.
+   *
+   * @param resultClass the class to decode each document into
+   * @param <ResultT>   the target document type
+   * @return a task containing the result of the find one operation
+   */
+  public <ResultT> Task<ResultT> findOne(final Class<ResultT> resultClass) {
+    return dispatcher.dispatchTask(new Callable<ResultT>() {
+      @Override
+      public ResultT call() {
+        return proxy.findOne(resultClass);
+      }
+    });
+  }
+
+  /**
+   * Finds a document in the collection.
+   *
+   * @param filter the query filter
+   * @return  a task containing the result of the find one operation
+   */
+  public Task<DocumentT> findOne(final Bson filter) {
+    return dispatcher.dispatchTask(new Callable<DocumentT>() {
+      @Override
+      public DocumentT call() {
+        return proxy.findOne(filter);
+      }
+    });
+  }
+
+  /**
+   * Finds a document in the collection.
+   *
+   * @param filter      the query filter
+   * @param resultClass the class to decode each document into
+   * @param <ResultT>   the target document type of the iterable.
+   * @return  a task containing the result of the find one operation
+   */
+  public <ResultT> Task<ResultT> findOne(final Bson filter, final Class<ResultT> resultClass) {
+    return dispatcher.dispatchTask(new Callable<ResultT>() {
+      @Override
+      public ResultT call() {
+        return proxy.findOne(filter, resultClass);
+      }
+    });
+  }
+
+  /**
+   * Finds a document in the collection.
+   *
+   * @param filter the query filter
+   * @param options A RemoteFindOptions struct
+   * @return  a task containing the result of the find one operation
+   */
+  public Task<DocumentT> findOne(final Bson filter, final RemoteFindOptions options) {
+    return dispatcher.dispatchTask(new Callable<DocumentT>() {
+      @Override
+      public DocumentT call() {
+        return proxy.findOne(filter, options);
+      }
+    });
+  }
+
+  /**
+   * Finds a document in the collection.
+   *
+   * @param filter      the query filter
+   * @param options     A RemoteFindOptions struct
+   * @param resultClass the class to decode each document into
+   * @param <ResultT>   the target document type of the iterable.
+   * @return  a task containing the result of the find one operation
+   */
+  public <ResultT> Task<ResultT> findOne(
+          final Bson filter,
+          final RemoteFindOptions options,
+          final Class<ResultT> resultClass) {
+    return dispatcher.dispatchTask(new Callable<ResultT>() {
+      @Override
+      public ResultT call() {
+        return proxy.findOne(filter, options, resultClass);
+      }
+    });
+  }
+
+
   /**
    * Finds all documents in the collection.
    *

core/sdk/src/main/java/com/mongodb/stitch/core/auth/internal/CoreStitchAuth.java

@@ -53,9 +53,13 @@
 import javax.annotation.Nullable;
 import javax.annotation.meta.When;
 
+import org.bson.BsonType;
 import org.bson.Document;
 import org.bson.codecs.Decoder;
+import org.bson.codecs.DecoderContext;
+import org.bson.codecs.configuration.CodecRegistries;
 import org.bson.codecs.configuration.CodecRegistry;
+import org.bson.json.JsonReader;
 
 /**
  * CoreStitchAuth is responsible for authenticating clients as well as acting as a client for
@@ -249,7 +253,15 @@ public <T> T doAuthenticatedRequest(final StitchAuthRequest stitchReq,
                                       final Decoder<T> resultDecoder) {
     final Response response = doAuthenticatedRequest(stitchReq);
     try {
-      return BsonUtils.parseValue(IoUtils.readAllToString(response.getBody()), resultDecoder);
+      final String bodyStr = IoUtils.readAllToString(response.getBody());
+      final JsonReader bsonReader = new JsonReader(bodyStr);
+
+      // We must check this condition because the decoder will throw trying to decode null
+      if (bsonReader.readBsonType() == BsonType.NULL) {
+        return null;
+      }
+      return resultDecoder.decode(bsonReader, DecoderContext.builder().build());
+
     } catch (final Exception e) {
       throw new StitchRequestException(e, StitchRequestErrorCode.DECODING_ERROR);
     }
@@ -276,8 +288,17 @@ public <T> T doAuthenticatedRequest(
     final Response response = doAuthenticatedRequest(stitchReq);
 
     try {
-      return BsonUtils.parseValue(IoUtils.readAllToString(
-          response.getBody()), resultClass, codecRegistry);
+      final String bodyStr = IoUtils.readAllToString(response.getBody());
+      final JsonReader bsonReader = new JsonReader(bodyStr);
+
+      // We must check this condition because the decoder will throw trying to decode null
+      if (bsonReader.readBsonType() == BsonType.NULL) {
+        return null;
+      }
+
+      final CodecRegistry newReg =
+              CodecRegistries.fromRegistries(BsonUtils.DEFAULT_CODEC_REGISTRY, codecRegistry);
+      return newReg.get(resultClass).decode(bsonReader, DecoderContext.builder().build());
     } catch (final Exception e) {
       throw new StitchRequestException(e, StitchRequestErrorCode.DECODING_ERROR);
     }

core/services/mongodb-remote/src/main/java/com/mongodb/stitch/core/services/mongodb/remote/internal/CoreRemoteMongoCollection.java

@@ -21,6 +21,7 @@
 import com.mongodb.stitch.core.services.mongodb.remote.ChangeEvent;
 import com.mongodb.stitch.core.services.mongodb.remote.RemoteCountOptions;
 import com.mongodb.stitch.core.services.mongodb.remote.RemoteDeleteResult;
+import com.mongodb.stitch.core.services.mongodb.remote.RemoteFindOptions;
 import com.mongodb.stitch.core.services.mongodb.remote.RemoteInsertManyResult;
 import com.mongodb.stitch.core.services.mongodb.remote.RemoteInsertOneResult;
 import com.mongodb.stitch.core.services.mongodb.remote.RemoteUpdateOptions;
@@ -103,6 +104,63 @@ <NewDocumentT> CoreRemoteMongoCollection<NewDocumentT> withDocumentClass(
    */
   long count(final Bson filter, final RemoteCountOptions options);
 
+  /**
+   * Finds a document in the collection
+   *
+   * @return the resulting document
+   */
+  DocumentT findOne();
+
+  /**
+   * Finds a document in the collection.
+   *
+   * @param resultClass the class to decode each document into
+   * @param <ResultT>   the target document type
+   * @return the resulting document
+   */
+  <ResultT> ResultT findOne(final Class<ResultT> resultClass);
+
+  /**
+   * Finds a document in the collection.
+   *
+   * @param filter the query filter
+   * @return the resulting document
+   */
+  DocumentT findOne(final Bson filter);
+
+  /**
+   * Finds a document in the collection.
+   *
+   * @param filter      the query filter
+   * @param resultClass the class to decode each document into
+   * @param <ResultT>   the target document type of the iterable.
+   * @return the resulting document
+   */
+  <ResultT> ResultT findOne(final Bson filter, final Class<ResultT> resultClass);
+
+  /**
+   * Finds a document in the collection.
+   *
+   * @param filter the query filter
+   * @param options A RemoteFindOptions struct
+   * @return the resulting document
+   */
+  DocumentT findOne(final Bson filter, final RemoteFindOptions options);
+
+  /**
+   * Finds a document in the collection.
+   *
+   * @param filter      the query filter
+   * @param options     A RemoteFindOptions struct
+   * @param resultClass the class to decode each document into
+   * @param <ResultT>   the target document type of the iterable.
+   * @return the resulting document
+   */
+  <ResultT> ResultT findOne(
+          final Bson filter,
+          final RemoteFindOptions options,
+          final Class<ResultT> resultClass);
+
   /**
    * Finds all documents in the collection.
    *