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/*
 * Copyright 2016 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package ratpack.jdbctx.internal;

import ratpack.exec.Blocking;
import ratpack.exec.Downstream;
import ratpack.exec.Operation;
import ratpack.exec.Promise;
import ratpack.func.Action;
import ratpack.func.Factory;
import ratpack.jdbctx.Transaction;

import java.sql.Connection;
import java.sql.Savepoint;
import java.util.ArrayDeque;
import java.util.Deque;
import java.util.Optional;

public class DefaultTransaction implements Transaction {

  private final Deque savepoints = new ArrayDeque<>(1);
  private final Factory connectionFactory;

  private volatile Connection connection;
  private boolean autoBind = true;

  public DefaultTransaction(Factory connectionFactory) {
    this.connectionFactory = connectionFactory;
  }

  @Override
  public Optional getConnection() {
    return Optional.ofNullable(connection);
  }

  @Override
  public  Promise wrap(Promise promise) {
    return promise.transform(up -> down ->
      begin()
        .onError(down::error)
        .then(() ->
          up.connect(new Downstream() {
            @Override
            public void success(T value) {
              commit()
                .onError(down::error)
                .then(() -> down.success(value));
            }

            @Override
            public void error(Throwable throwable) {
              rollback()
                .onError(e -> {
                  e.addSuppressed(throwable);
                  down.error(e);
                })
                .then(() -> down.error(throwable));
            }

            @Override
            public void complete() {
              commit()
                .onError(down::error)
                .then(down::complete);
            }
          })
        )
    );
  }

  @Override
  public Operation wrap(Operation operation) {
    return wrap(operation.promise()).operation();
  }

  @Override
  public Transaction autoBind(boolean autoBind) {
    this.autoBind = autoBind;
    return this;
  }

  @Override
  public boolean isAutoBind() {
    return autoBind;
  }

  @Override
  public Operation begin() {
    return Operation.flatten(() -> {
      if (connection == null) {
        return Blocking.op(() -> {
          connection = connectionFactory.create();
          try {
            connection.setAutoCommit(false);
          } catch (Exception e) {
            try {
              Connection connection = this.connection;
              this.connection = null;
              connection.close();
            } catch (Exception e1) {
              e1.addSuppressed(e);
              throw e1;
            }
            throw e;
          }
          if (autoBind) {
            bind();
          }
        });
      } else {
        return Blocking.get(connection::setSavepoint)
          .operation(savepoints::push);
      }
    });
  }

  @Override
  public Operation rollback() {
    return Operation.flatten(() -> {
      if (connection == null) {
        throw new IllegalStateException("Rollback attempted outside of a transaction.");
      }
      Savepoint savepoint = savepoints.poll();
      if (savepoint == null) {
        return dispose(Connection::rollback);
      } else {
        return Blocking.op(() -> connection.rollback(savepoint));
      }
    });
  }

  @Override
  public Operation commit() {
    return Operation.flatten(() -> {
      if (connection == null) {
        throw new IllegalStateException("Commit attempted outside of a transaction.");
      }
      Savepoint savepoint = savepoints.poll();
      if (savepoint == null) {
        return dispose(Connection::commit);
      } else {
        return Operation.noop();
      }
    });
  }

  private Operation dispose(Action disposal) {
    return Blocking.op(() -> {
      Connection connection = this.connection;
      this.connection = null;
      if (autoBind) {
        unbind();
      }
      if (connection != null) {
        try (Connection c = connection) {
          disposal.execute(c);
        }
      }
    });
  }

}