/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.heron.streamlet.impl;

import java.io.Serializable;
import java.util.Map;
import java.util.function.Supplier;

import org.apache.heron.api.metric.IMetric;
import org.apache.heron.api.state.State;
import org.apache.heron.api.topology.TopologyContext;
import org.apache.heron.streamlet.Context;

/**
 * Context is the information available at runtime for operators like transform.
 * It contains basic things like config, runtime information like task,
 * the stream that it is operating on, ProcessState, etc.
 */
public class ContextImpl implements Context {
  private TopologyContext topologyContext;
  private Map<String, Object> topologyConfig;
  private State<Serializable, Serializable> state;

  public ContextImpl(TopologyContext topologyContext, Map<String, Object> topologyConfig,
                     State<Serializable, Serializable> state) {
    this.topologyContext = topologyContext;
    this.topologyConfig = topologyConfig;
    this.state = state;
  }

  @Override
  public int getTaskId() {
    return topologyContext.getThisTaskId();
  }

  @Override
  public Map<String, Object> getConfig() {
    return topologyConfig;
  }

  @Override
  public String getStreamName() {
    return topologyContext.getThisStreams().iterator().next();
  }

  @Override
  public int getStreamPartition() {
    return topologyContext.getThisTaskIndex();
  }

  @Override
  public <T> void registerMetric(String metricName, int collectionInterval,
                             Supplier<T> metricFn) {
    topologyContext.registerMetric(metricName, new StreamletMetric<T>(metricFn),
        collectionInterval);
  }

  @Override
  public State<Serializable, Serializable> getState() {
    return state;
  }

  private class StreamletMetric<T> implements IMetric<T> {
    private Supplier<T> metricFn;
    StreamletMetric(Supplier<T> metricFn) {
      this.metricFn = metricFn;
    }

    @Override
    public T getValueAndReset() {
      return metricFn.get();
    }
  }
}