/**
 * 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.hcatalog.mapreduce;

import java.io.IOException;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.Map;
import java.util.HashMap;
import java.util.List;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapreduce.InputFormat;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.JobContext;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.util.ReflectionUtils;
import org.apache.hadoop.util.StringUtils;

import org.apache.hcatalog.common.HCatConstants;
import org.apache.hcatalog.common.HCatUtil;
import org.apache.hcatalog.data.HCatRecord;
import org.apache.hcatalog.data.schema.HCatFieldSchema;
import org.apache.hcatalog.data.schema.HCatSchema;

public abstract class HCatBaseInputFormat 
  extends InputFormat<WritableComparable, HCatRecord> {
  
  /**
   * get the schema for the HCatRecord data returned by HCatInputFormat.
   * 
   * @param context the jobContext
   * @throws IllegalArgumentException
   */
  private Class<? extends InputFormat> inputFileFormatClass;

  // TODO needs to go in InitializeInput? as part of InputJobInfo
  public static HCatSchema getOutputSchema(JobContext context) 
    throws IOException {
    String os = context.getConfiguration().get(
                                HCatConstants.HCAT_KEY_OUTPUT_SCHEMA);
    if (os == null) {
      return getTableSchema(context);
    } else {
      return (HCatSchema) HCatUtil.deserialize(os);
    }
  }
  
  /**
   * Set the schema for the HCatRecord data returned by HCatInputFormat.
   * @param job the job object
   * @param hcatSchema the schema to use as the consolidated schema
   */
  public static void setOutputSchema(Job job,HCatSchema hcatSchema) 
    throws IOException {
    job.getConfiguration().set(HCatConstants.HCAT_KEY_OUTPUT_SCHEMA, 
                               HCatUtil.serialize(hcatSchema));
  }

  protected static
    org.apache.hadoop.mapred.InputFormat<WritableComparable, Writable>
    getMapRedInputFormat (JobConf job, Class inputFormatClass) throws IOException {
      return (
          org.apache.hadoop.mapred.InputFormat<WritableComparable, Writable>) 
        ReflectionUtils.newInstance(inputFormatClass, job);
  }

  /**
   * Logically split the set of input files for the job. Returns the
   * underlying InputFormat's splits
   * @param jobContext the job context object
   * @return the splits, an HCatInputSplit wrapper over the storage
   *         handler InputSplits
   * @throws IOException or InterruptedException
   */
  @Override
  public List<InputSplit> getSplits(JobContext jobContext)
  throws IOException, InterruptedException {

    //Get the job info from the configuration,
    //throws exception if not initialized
    InputJobInfo inputJobInfo;
    try {
      inputJobInfo = getJobInfo(jobContext);
    } catch (Exception e) {
      throw new IOException(e);
    }

    List<InputSplit> splits = new ArrayList<InputSplit>();
    List<PartInfo> partitionInfoList = inputJobInfo.getPartitions();
    if(partitionInfoList == null ) {
      //No partitions match the specified partition filter
      return splits;
    }

    HCatStorageHandler storageHandler;
    JobConf jobConf;
    Configuration conf = jobContext.getConfiguration();
    //For each matching partition, call getSplits on the underlying InputFormat
    for(PartInfo partitionInfo : partitionInfoList) {
      jobConf = HCatUtil.getJobConfFromContext(jobContext);
      setInputPath(jobConf, partitionInfo.getLocation());
      Map<String,String> jobProperties = partitionInfo.getJobProperties();

      HCatSchema allCols = new HCatSchema(new LinkedList<HCatFieldSchema>());
      for(HCatFieldSchema field: 
          inputJobInfo.getTableInfo().getDataColumns().getFields())
          allCols.append(field);
      for(HCatFieldSchema field: 
          inputJobInfo.getTableInfo().getPartitionColumns().getFields())
          allCols.append(field);

      HCatUtil.copyJobPropertiesToJobConf(jobProperties, jobConf);

      storageHandler = HCatUtil.getStorageHandler(
          jobConf, partitionInfo);

      //Get the input format
      Class inputFormatClass = storageHandler.getInputFormatClass();
      org.apache.hadoop.mapred.InputFormat inputFormat = 
                            getMapRedInputFormat(jobConf, inputFormatClass);

      //Call getSplit on the InputFormat, create an
      //HCatSplit for each underlying split
      //NumSplits is 0 for our purposes
      org.apache.hadoop.mapred.InputSplit[] baseSplits = 
        inputFormat.getSplits(jobConf, 0);

      for(org.apache.hadoop.mapred.InputSplit split : baseSplits) {
        splits.add(new HCatSplit(
            partitionInfo,
            split,allCols));
      }
    }

    return splits;
  }

  /**
   * Create the RecordReader for the given InputSplit. Returns the underlying
   * RecordReader if the required operations are supported and schema matches
   * with HCatTable schema. Returns an HCatRecordReader if operations need to
   * be implemented in HCat.
   * @param split the split
   * @param taskContext the task attempt context
   * @return the record reader instance, either an HCatRecordReader(later) or
   *         the underlying storage handler's RecordReader
   * @throws IOException or InterruptedException
   */
  @Override
  public RecordReader<WritableComparable, HCatRecord> 
  createRecordReader(InputSplit split,
      TaskAttemptContext taskContext) throws IOException, InterruptedException {

    HCatSplit hcatSplit = InternalUtil.castToHCatSplit(split);
    PartInfo partitionInfo = hcatSplit.getPartitionInfo();
    JobContext jobContext = taskContext;

    HCatStorageHandler storageHandler = HCatUtil.getStorageHandler(
        jobContext.getConfiguration(), partitionInfo);
    
    JobConf jobConf = HCatUtil.getJobConfFromContext(jobContext);
    Map<String, String> jobProperties = partitionInfo.getJobProperties();
    HCatUtil.copyJobPropertiesToJobConf(jobProperties, jobConf);

    Map<String,String> valuesNotInDataCols = getColValsNotInDataColumns(
        getOutputSchema(jobContext),partitionInfo
        );

    return new HCatRecordReader(storageHandler, valuesNotInDataCols);
  }


  /**
   * gets values for fields requested by output schema which will not be in the data
   */
  private static Map<String,String> getColValsNotInDataColumns(HCatSchema outputSchema,
      PartInfo partInfo){
    HCatSchema dataSchema = partInfo.getPartitionSchema();
    Map<String,String> vals = new HashMap<String,String>();
    for (String fieldName : outputSchema.getFieldNames()){
      if (dataSchema.getPosition(fieldName) == null){
        // this entry of output is not present in the output schema
        // so, we first check the table schema to see if it is a part col
        
        if (partInfo.getPartitionValues().containsKey(fieldName)){
          vals.put(fieldName, partInfo.getPartitionValues().get(fieldName));
        } else {
          vals.put(fieldName, null);
        }
      }
    }
    return vals;
  }

  /**
   * Gets the HCatTable schema for the table specified in the HCatInputFormat.setInput call
   * on the specified job context. This information is available only after HCatInputFormat.setInput
   * has been called for a JobContext.
   * @param context the context
   * @return the table schema
   * @throws IOException if HCatInputFormat.setInput has not been called 
   *                     for the current context
   */
  public static HCatSchema getTableSchema(JobContext context) 
  throws IOException {
    InputJobInfo inputJobInfo = getJobInfo(context);
      HCatSchema allCols = new HCatSchema(new LinkedList<HCatFieldSchema>());
      for(HCatFieldSchema field: 
          inputJobInfo.getTableInfo().getDataColumns().getFields())
          allCols.append(field);
      for(HCatFieldSchema field: 
          inputJobInfo.getTableInfo().getPartitionColumns().getFields())
          allCols.append(field);
    return allCols;
  }

  /**
   * Gets the InputJobInfo object by reading the Configuration and deserializing
   * the string. If InputJobInfo is not present in the configuration, throws an
   * exception since that means HCatInputFormat.setInput has not been called.
   * @param jobContext the job context
   * @return the InputJobInfo object
   * @throws IOException the exception
   */
  private static InputJobInfo getJobInfo(JobContext jobContext) 
    throws IOException {
    String jobString = jobContext.getConfiguration().get(
                                  HCatConstants.HCAT_KEY_JOB_INFO);
    if( jobString == null ) {
      throw new IOException("job information not found in JobContext."
         + " HCatInputFormat.setInput() not called?");
    }

    return (InputJobInfo) HCatUtil.deserialize(jobString);
  }

  private void setInputPath(JobConf jobConf, String location) 
  throws IOException{

    // ideally we should just call FileInputFormat.setInputPaths() here - but
    // that won't work since FileInputFormat.setInputPaths() needs
    // a Job object instead of a JobContext which we are handed here

    int length = location.length();
    int curlyOpen = 0;
    int pathStart = 0;
    boolean globPattern = false;
    List<String> pathStrings = new ArrayList<String>();

    for (int i=0; i<length; i++) {
      char ch = location.charAt(i);
      switch(ch) {
      case '{' : {
        curlyOpen++;
        if (!globPattern) {
          globPattern = true;
        }
        break;
      }
      case '}' : {
        curlyOpen--;
        if (curlyOpen == 0 && globPattern) {
          globPattern = false;
        }
        break;
      }
      case ',' : {
        if (!globPattern) {
          pathStrings.add(location.substring(pathStart, i));
          pathStart = i + 1 ;
        }
        break;
      }
      }
    }
    pathStrings.add(location.substring(pathStart, length));

    Path[] paths = StringUtils.stringToPath(pathStrings.toArray(new String[0]));

    FileSystem fs = FileSystem.get(jobConf);
    Path path = paths[0].makeQualified(fs);
    StringBuilder str = new StringBuilder(StringUtils.escapeString(
                                                          path.toString()));
    for(int i = 1; i < paths.length;i++) {
      str.append(StringUtils.COMMA_STR);
      path = paths[i].makeQualified(fs);
      str.append(StringUtils.escapeString(path.toString()));
    }

    jobConf.set("mapred.input.dir", str.toString());
  }

}