/*
 * 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.pig.impl.util;

import java.io.IOException;
import java.io.Serializable;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Properties;

import org.apache.hadoop.conf.Configuration;
import org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.MRConfiguration;

public class UDFContext {

    private Configuration jconf = null;
    private HashMap<UDFContextKey, Properties> udfConfs;
    private Properties clientSysProps;

    static final String CLIENT_SYS_PROPS = "pig.client.sys.props";
    static final String UDF_CONTEXT = "pig.udf.context";

    private static ThreadLocal<UDFContext> tss = new ThreadLocal<UDFContext>() {
        @Override
        public UDFContext initialValue() {
            return new UDFContext();
        }
    };

    private UDFContext() {
        udfConfs = new HashMap<UDFContextKey, Properties>();
    }

    /**
     * @return a Thread Local {@link UDFContext}
     */
    public static UDFContext getUDFContext() {
        return tss.get();
    }

    /*
     *  internal pig use only - should NOT be called from user code
     */
    public static void setUdfContext(UDFContext udfContext) {
        tss.set(udfContext);
    }

    /*
     *  internal pig use only - should NOT be called from user code
     */
    //@StaticDataCleanup
    public static void staticDataCleanup() {
        tss = new ThreadLocal<UDFContext>() {
            @Override
            public UDFContext initialValue() {
                return new UDFContext();
            }
        };
    }

    /*
     *  internal pig use only - should NOT be called from user code
     */
    HashMap<UDFContextKey, Properties> getUdfConfs() {
        return udfConfs;
    }


    /*
     *  internal pig use only - should NOT be called from user code
     */
    public void setClientSystemProps(Properties properties) {
        clientSysProps = properties;
    }

    /**
     * Get the System Properties (Read only) as on the client machine from where Pig
     * was launched. This will include command line properties passed at launch
     * time
     * @return client side System Properties including command line properties
     */
    public Properties getClientSystemProps() {
        return clientSysProps;
    }
    /**
     * Adds the JobConf to this singleton.  Will be
     * called on the backend by the Map and Reduce
     * functions so that UDFs can obtain the JobConf
     * on the backend.
     */
    public void addJobConf(Configuration conf) {
        jconf = conf;
    }

    /**
     * Get the JobConf.  This should only be called on
     * the backend.  It will return null on the frontend.
     * @return JobConf for this job.  This is a copy of the
     * JobConf.  Nothing written here will be kept by the system.
     * getUDFConf should be used for recording UDF specific
     * information.
     */
    public Configuration getJobConf() {
        if (jconf != null)  return new Configuration(jconf);
        else return null;
    }

    /**
     * Get a properties object that is specific to this UDF.
     * Note that if a given UDF is called multiple times in a script,
     * and each instance passes different arguments, then each will
     * be provided with different configuration object.
     * This can be used by loaders to pass their input object path
     * or URI and separate themselves from other instances of the
     * same loader.  Constructor arguments could also be used,
     * as they are available on both the front and back end.
     *
     * Note that this can only be used to share information
     * across instantiations of the same function in the front end
     * and between front end and back end.  It cannot be used to
     * share information between instantiations (that is, between
     * map and/or reduce instances) on the back end at runtime.
     * @param c of the UDF obtaining the properties object.
     * @param args String arguments that make this instance of
     * the UDF unique.
     * @return A reference to the properties object specific to
     * the calling UDF.  This is a reference, not a copy.
     * Any changes to this object will automatically be
     * propogated to other instances of the UDF calling this
     * function.
     */

    @SuppressWarnings("rawtypes")
    public Properties getUDFProperties(Class c, String[] args) {
        UDFContextKey k = generateKey(c, args);
        Properties p = udfConfs.get(k);
        if (p == null) {
            p = new Properties();
            udfConfs.put(k, p);
        }
        return p;
    }

    /**
     * Get a properties object that is specific to this UDF.
     * Note that if a given UDF is called multiple times in a script,
     * they will all be provided the same configuration object.  It
     * is up to the UDF to make sure the multiple instances do not
     * stomp on each other.
     *
     * It is guaranteed that this properties object will be separate
     * from that provided to any other UDF.
     *
     * Note that this can only be used to share information
     * across instantiations of the same function in the front end
     * and between front end and back end.  It cannot be used to
     * share information between instantiations (that is, between
     * map and/or reduce instances) on the back end at runtime.
     * @param c of the UDF obtaining the properties object.
     * @return A reference to the properties object specific to
     * the calling UDF.  This is a reference, not a copy.
     * Any changes to this object will automatically be
     * propogated to other instances of the UDF calling this
     * function.
     */
    @SuppressWarnings("rawtypes")
    public Properties getUDFProperties(Class c) {
        UDFContextKey k = generateKey(c, null);
        Properties p = udfConfs.get(k);
        if (p == null) {
            p = new Properties();
            udfConfs.put(k, p);
        }
        return p;
    }


    /**
     * Serialize the UDF specific information into an instance
     * of JobConf.  This function is intended to be called on
     * the front end in preparation for sending the data to the
     * backend.
     * @param conf JobConf to serialize into
     * @throws IOException if underlying serialization throws it
     */
    public void serialize(Configuration conf) throws IOException {
        conf.set(UDF_CONTEXT, ObjectSerializer.serialize(udfConfs));
        conf.set(CLIENT_SYS_PROPS, ObjectSerializer.serialize(clientSysProps));
    }


    /**
     * Populate the udfConfs field.  This function is intended to
     * be called by Map.configure or Reduce.configure on the backend.
     * It assumes that addJobConf has already been called.
     * @throws IOException if underlying deseralization throws it
     */
    @SuppressWarnings("unchecked")
    public void deserialize() throws IOException {
        udfConfs = (HashMap<UDFContextKey, Properties>)ObjectSerializer.deserialize(jconf.get(UDF_CONTEXT));
        clientSysProps = (Properties)ObjectSerializer.deserialize(
                jconf.get(CLIENT_SYS_PROPS));
    }

    private UDFContextKey generateKey(Class<?> c, String[] args) {
        return new UDFContextKey(c.getName(), args);
    }

    public void reset() {
        udfConfs.clear();
    }

    public boolean isUDFConfEmpty() {
        return udfConfs.isEmpty();
    }

    /**
     * Convenience method for UDF code to check where it runs (see PIG-2576)
     * @return boolean type value
     */
    public boolean isFrontend() {
        // mapred.task.id is for MR1
        // mapreduce.job.application.attempt.id is for MR2
        return (this.jconf == null
                || (jconf.get(MRConfiguration.TASK_ID) == null &&
                    jconf.get(MRConfiguration.JOB_APPLICATION_ATTEMPT_ID) == null));
    }

    /**
     * Make a shallow copy of the context.
     */
    @Override
    public UDFContext clone() {
    	UDFContext other = new UDFContext();
    	other.clientSysProps = this.clientSysProps;
    	other.jconf = this.jconf;
    	other.udfConfs = this.udfConfs;
    	return other;
    }

    /**
     * Class that acts as key for hashmap in UDFContext,
     *  it holds the class and args of the udf, and
     *  implements equals() and hashCode()
     */
    static class UDFContextKey implements Serializable{

        private static final long serialVersionUID = 1;
        private String className;
        private String[] args;

        UDFContextKey(String className, String [] args){
            this.className = className;
            this.args = args;
        }

        String getClassName() {
            return className;
        }

        String[] getArgs() {
            return args;
        }

        @Override
        public String toString() {
            return "UDFContextKey [className=" + className + ", args="
                    + Arrays.toString(args) + "]";
        }

        @Override
        public int hashCode() {
            final int prime = 31;
            int result = 1;
            result = prime * result + Arrays.hashCode(args);
            result = prime * result
                    + ((className == null) ? 0 : className.hashCode());
            return result;
        }

        @Override
        public boolean equals(Object obj) {
            if (this == obj)
                return true;
            if (obj == null)
                return false;
            if (getClass() != obj.getClass())
                return false;
            UDFContextKey other = (UDFContextKey) obj;
            if (!Arrays.equals(args, other.args))
                return false;
            if (className == null) {
                if (other.className != null)
                    return false;
            } else if (!className.equals(other.className))
                return false;
            return true;
        }
    }

}