/*
 * Copyright 2008-present MongoDB, Inc.
 *
 * 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 com.mongodb.async.client;

import com.mongodb.ReadConcern;
import com.mongodb.ReadPreference;
import com.mongodb.async.SingleResultCallback;
import com.mongodb.binding.AsyncClusterBinding;
import com.mongodb.binding.AsyncConnectionSource;
import com.mongodb.binding.AsyncReadWriteBinding;
import com.mongodb.binding.AsyncSingleServerBinding;
import com.mongodb.connection.AsyncConnection;
import com.mongodb.connection.ClusterType;
import com.mongodb.connection.Server;
import com.mongodb.connection.ServerDescription;
import com.mongodb.internal.session.ClientSessionContext;
import com.mongodb.selector.ReadPreferenceServerSelector;
import com.mongodb.session.SessionContext;

import static com.mongodb.assertions.Assertions.notNull;

class ClientSessionBinding implements AsyncReadWriteBinding {
    private final AsyncClusterBinding wrapped;
    private final ClientSession session;
    private final boolean ownsSession;
    private final ClientSessionContext sessionContext;

    ClientSessionBinding(final ClientSession session, final boolean ownsSession, final AsyncReadWriteBinding wrapped) {
        this.wrapped = notNull("wrapped", ((AsyncClusterBinding) wrapped));
        this.ownsSession = ownsSession;
        this.session = notNull("session", session);
        this.sessionContext = new AsyncClientSessionContext(session);
    }

    @Override
    public ReadPreference getReadPreference() {
        return wrapped.getReadPreference();
    }

    @Override
    public void getReadConnectionSource(final SingleResultCallback<AsyncConnectionSource> callback) {
        wrapped.getReadConnectionSource(new SingleResultCallback<AsyncConnectionSource>() {
            @Override
            public void onResult(final AsyncConnectionSource result, final Throwable t) {
                if (t != null) {
                    callback.onResult(null, t);
                } else {
                    wrapConnectionSource(result, callback);
                }
            }
        });
    }

    public void getWriteConnectionSource(final SingleResultCallback<AsyncConnectionSource> callback) {
        wrapped.getWriteConnectionSource(new SingleResultCallback<AsyncConnectionSource>() {
            @Override
            public void onResult(final AsyncConnectionSource result, final Throwable t) {
                if (t != null) {
                    callback.onResult(null, t);
                } else {
                    wrapConnectionSource(result, callback);
                }
            }
        });
    }

    @Override
    public SessionContext getSessionContext() {
        return sessionContext;
    }

    private void wrapConnectionSource(final AsyncConnectionSource connectionSource,
                                      final SingleResultCallback<AsyncConnectionSource> callback) {
        if (isActiveShardedTxn()) {
            if (session.getPinnedServerAddress() == null) {
                wrapped.getCluster().selectServerAsync(
                        new ReadPreferenceServerSelector(wrapped.getReadPreference()),
                        new SingleResultCallback<Server>() {
                            @Override
                            public void onResult(final Server server, final Throwable t) {
                                if (t != null) {
                                    callback.onResult(null, t);
                                } else {
                                    session.setPinnedServerAddress(server.getDescription().getAddress());
                                    setSingleServerBindingConnectionSource(callback);
                                }
                            }
                        });
            } else {
                setSingleServerBindingConnectionSource(callback);
            }
        } else {
            callback.onResult(new SessionBindingAsyncConnectionSource(connectionSource), null);
        }
    }

    private void setSingleServerBindingConnectionSource(final SingleResultCallback<AsyncConnectionSource> callback) {
        final AsyncSingleServerBinding binding =
                new AsyncSingleServerBinding(wrapped.getCluster(), session.getPinnedServerAddress(), wrapped.getReadPreference());
        binding.getWriteConnectionSource(new SingleResultCallback<AsyncConnectionSource>() {
            @Override
            public void onResult(final AsyncConnectionSource result, final Throwable t) {
                binding.release();
                if (t != null) {
                    callback.onResult(null, t);
                } else {
                    callback.onResult(new SessionBindingAsyncConnectionSource(result), null);
                }
            }
        });
    }

    @Override
    public int getCount() {
        return wrapped.getCount();
    }

    @Override
    public AsyncReadWriteBinding retain() {
        wrapped.retain();
        return this;
    }

    @Override
    public void release() {
        wrapped.release();
        closeSessionIfCountIsZero();
    }

    private void closeSessionIfCountIsZero() {
        if (getCount() == 0 && ownsSession) {
            session.close();
        }
    }

    private boolean isActiveShardedTxn() {
        return session.hasActiveTransaction() && wrapped.getCluster().getDescription().getType() == ClusterType.SHARDED;
    }

    private class SessionBindingAsyncConnectionSource implements AsyncConnectionSource {
        private AsyncConnectionSource wrapped;

        SessionBindingAsyncConnectionSource(final AsyncConnectionSource wrapped) {
            this.wrapped = wrapped;
        }

        @Override
        public ServerDescription getServerDescription() {
            return wrapped.getServerDescription();
        }

        @Override
        public SessionContext getSessionContext() {
            return sessionContext;
        }

        @Override
        public void getConnection(final SingleResultCallback<AsyncConnection> callback) {
            wrapped.getConnection(callback);
        }

        @Override
        public AsyncConnectionSource retain() {
            wrapped = wrapped.retain();
            return this;
        }

        @Override
        public int getCount() {
            return wrapped.getCount();
        }

        @Override
        public void release() {
            wrapped.release();
            closeSessionIfCountIsZero();
        }
    }

    private final class AsyncClientSessionContext extends ClientSessionContext implements SessionContext {

        private final ClientSession clientSession;

        AsyncClientSessionContext(final ClientSession clientSession) {
            super(clientSession);
            this.clientSession = clientSession;
        }


        @Override
        public boolean isImplicitSession() {
            return ownsSession;
        }

        @Override
        public boolean notifyMessageSent() {
            return clientSession.notifyMessageSent();
        }

        @Override
        public boolean hasActiveTransaction() {
            return clientSession.hasActiveTransaction();
        }

        @Override
        public ReadConcern getReadConcern() {
            if (clientSession.hasActiveTransaction()) {
                return clientSession.getTransactionOptions().getReadConcern();
            } else {
                return wrapped.getSessionContext().getReadConcern();
            }
        }
    }
}