package org.neo4j.driver;
   
   import org.neo4j.driver.exception.Neo4jClientException;
   import org.neo4j.driver.v1.*;
   
   import java.util.Spliterator;
   import java.util.stream.Stream;
   import java.util.stream.StreamSupport;
   
  import static java.util.Spliterators.spliterator;
  
  /**
   * Main class of this project that handles database actions.
   */
  public class Neo4jClient {
  
      /**
       * Singleton instance of the client.
       */
      private static Neo4jClient client;
  
      /**
       * Neo4j driver instance.
       */
      private Driver driver;
  
      /**
       * Constructor of Neo4j client.
       * It just create a Neo4j driver instance with the help of the <code>neo4j-driver.properties</code> file.
       */
      private Neo4jClient() throws Exception {
          // Load the configuration
          Configuration config = new Configuration();
  
          // Create the Neo4j driver instance
          this.driver = GraphDatabase.driver(config.getStringOrDefault("neo4j.url", "bolt://localhost"),
                  AuthTokens.basic(config.getStringOrDefault("neo4j.user", "neo4j"), config.getStringOrDefault("neo4j.password", "neo4j")),
                  config.toDriverConfig());
      }
  
      /**
       * Retrieve the singleton instance.
       *
       * @return The Neo4jClient
       */
      private static synchronized Neo4jClient getInstance() {
          if (client == null) {
              try {
                  client = new Neo4jClient();
              } catch (Exception e) {
                  // just cast the exception to a runtime,
                  // to avoid to have a signature error on this method.
                  throw new RuntimeException(e);
              }
          }
  
          return client;
      }
  
      /**
       * Destructor of this object.
       * It close all underlying object if needed.
       */
      public static void destroy() {
          if (client != null) {
              client.driver.close();
              client = null;
          }
      }
  
  
      /*-------------------------------*/
      /*       Auto Commit mode        */
      /*-------------------------------*/
  
      /**
       * Execute a read cypher query with parameters to Neo4j.
       */
      private static Stream<Record> run(String query, Value parameters, AccessMode mode, String bookmarkId) {
          UncheckedCloseable close = null;
          try {
              Session session = getInstance().driver.session(mode, bookmarkId);
              close = UncheckedCloseable.wrap(session);
              StatementResult result = session.run(query, parameters);
              return StreamSupport.stream(spliterator(result, Long.MAX_VALUE, Spliterator.ORDERED), false).onClose(close);
          } catch (Exception e) {
              if (close != null) {
                  try {
                      close.close();
                  } catch (Exception ex) {
                      e.addSuppressed(ex);
                  }
              }
              throw new Neo4jClientException(e);
          }
      }
  
      /**
       * Execute a read cypher query to Neo4j.
      */
     public static Stream<Record> read(String query) {
         return run(query, Values.EmptyMap, AccessMode.READ, null);
     }
 
     /**
      * Execute a read cypher query to Neo4j with a bookmarkId.
      */
     public static Stream<Record> read(String query, String bookmarkId) {
         return run(query, Values.EmptyMap, AccessMode.READ, bookmarkId);
     }
 
     /**
      * Execute a read cypher query to Neo4j with parameters.
      */
     public static Stream<Record> read(String query, Value parameters) {
         return run(query, parameters, AccessMode.READ, null);
     }
 
     /**
      * Execute a read cypher query to Neo4j with parameters and bookmarkId.
      */
     public static Stream<Record> read(String query, Value parameters, String bookmarkId) {
         return run(query, parameters, AccessMode.READ, bookmarkId);
     }
 
     /**
      * Execute a write cypher query to Neo4j.
      */
     public static Stream<Record> write(String query) {
         return run(query, Values.EmptyMap, AccessMode.WRITE, null);
     }
 
     /**
      * Execute a write cypher query to Neo4j with a bookmarkId.
      */
     public static Stream<Record> write(String query, String bookmarkId) {
         return run(query, Values.EmptyMap, AccessMode.WRITE, bookmarkId);
     }
 
     /**
      * Execute a write cypher query to Neo4j with parameters.
      */
     public static Stream<Record> write(String query, Value parameters) {
         return run(query, parameters, AccessMode.WRITE, null);
     }
 
     /**
      * Execute a write cypher query to Neo4j with parameters and bookmarkId.
      */
     public static Stream<Record> write(String query, Value parameters, String bookmarkId) {
         return run(query, parameters, AccessMode.WRITE, bookmarkId);
     }
 
 
     /*-------------------------------*/
 	/*       Transaction mode        */
 	/*-------------------------------*/
 
     /**
      * Return a Client transaction corresponding the <code>mode</code>\ and <code>bookmarkId</code>.
      */
     private static Neo4jTransaction getTransaction(AccessMode mode, String bookmarkId) {
         return new Neo4jTransaction(getInstance().driver.session(mode, bookmarkId));
     }
 
     /**
      * Retrieve a read transaction.
      */
     public static Neo4jTransaction getReadTransaction() {
         return getTransaction(AccessMode.READ, null);
     }
 
     /**
      * Retrieve a read transaction with a bookmarkId.
      */
     public static Neo4jTransaction getReadTransaction(String bookmarkId) {
         return getTransaction(AccessMode.READ, bookmarkId);
     }
 
     /**
      * Retrieve a write.
      */
     public static Neo4jTransaction getWriteTransaction() {
         return getTransaction(AccessMode.WRITE, null);
     }
 
     /**
      * Retrieve a write transaction with a bookmarkId.
      */
     public static Neo4jTransaction getWriteTransaction(String bookmarkId) {
         return getTransaction(AccessMode.WRITE, bookmarkId);
     }
 
 }