/*
 * 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.facebook.presto.connector.jmx;

import com.facebook.presto.common.predicate.NullableValue;
import com.facebook.presto.common.predicate.TupleDomain;
import com.facebook.presto.spi.ColumnHandle;
import com.facebook.presto.spi.ConnectorSession;
import com.facebook.presto.spi.ConnectorSplit;
import com.facebook.presto.spi.ConnectorSplitSource;
import com.facebook.presto.spi.ConnectorTableLayoutHandle;
import com.facebook.presto.spi.FixedSplitSource;
import com.facebook.presto.spi.NodeManager;
import com.facebook.presto.spi.connector.ConnectorSplitManager;
import com.facebook.presto.spi.connector.ConnectorTransactionHandle;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;

import javax.inject.Inject;

import java.util.List;
import java.util.Optional;

import static com.facebook.presto.common.predicate.TupleDomain.fromFixedValues;
import static com.facebook.presto.common.type.VarcharType.createUnboundedVarcharType;
import static com.facebook.presto.connector.jmx.JmxMetadata.NODE_COLUMN_NAME;
import static com.google.common.base.Preconditions.checkState;
import static io.airlift.slice.Slices.utf8Slice;
import static java.util.Objects.requireNonNull;
import static java.util.stream.Collectors.toList;

public class JmxSplitManager
        implements ConnectorSplitManager
{
    private final NodeManager nodeManager;

    @Inject
    public JmxSplitManager(NodeManager nodeManager)
    {
        this.nodeManager = requireNonNull(nodeManager, "nodeManager is null");
    }

    @Override
    public ConnectorSplitSource getSplits(
            ConnectorTransactionHandle transaction,
            ConnectorSession session,
            ConnectorTableLayoutHandle layout,
            SplitSchedulingContext splitSchedulingContext)
    {
        JmxTableLayoutHandle jmxLayout = (JmxTableLayoutHandle) layout;
        JmxTableHandle tableHandle = jmxLayout.getTable();
        TupleDomain<ColumnHandle> predicate = jmxLayout.getConstraint();

        //TODO is there a better way to get the node column?
        Optional<JmxColumnHandle> nodeColumnHandle = tableHandle.getColumnHandles().stream()
                .filter(jmxColumnHandle -> jmxColumnHandle.getColumnName().equals(NODE_COLUMN_NAME))
                .findFirst();
        checkState(nodeColumnHandle.isPresent(), "Failed to find %s column", NODE_COLUMN_NAME);

        List<ConnectorSplit> splits = nodeManager.getAllNodes().stream()
                .filter(node -> {
                    NullableValue value = NullableValue.of(createUnboundedVarcharType(), utf8Slice(node.getNodeIdentifier()));
                    return predicate.overlaps(fromFixedValues(ImmutableMap.of(nodeColumnHandle.get(), value)));
                })
                .map(node -> new JmxSplit(tableHandle, ImmutableList.of(node.getHostAndPort())))
                .collect(toList());

        return new FixedSplitSource(splits);
    }
}
