/**
 * 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.utils;

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;

import org.apache.pig.EvalFunc;
import org.apache.pig.data.DataBag;
import org.apache.pig.data.DataType;
import org.apache.pig.data.Tuple;
import org.apache.pig.impl.logicalLayer.schema.Schema;
import org.apache.pig.impl.util.Utils;

/**
 * This UDF can be used to check that a tuple presented by HCatLoader has the
 * right types for the fields
 * 
 * Usage is :
 * 
 * register testudf.jar;
 * a = load 'numbers' using HCatLoader(...);
 * b = foreach a generate HCatTypeCheck('intnum1000:int,id:int,intnum5:int,intnum100:int,intnum:int,longnum:long,floatnum:float,doublenum:double', *);
 * store b into 'output';
 * 
 * The schema string (the first argument to the UDF) is of the form one would provide in a 
 * pig load statement.
 * 
 * The output should only contain the value '1' in all rows. (This UDF returns
 * the integer value 1 if all fields have the right type, else throws IOException)
 *  
 */
public class HCatTypeCheck extends EvalFunc<Integer> {

    static HashMap<Byte, Class<?>> typeMap = new HashMap<Byte, Class<?>>();
    
    @Override
    public Integer exec(Tuple input) throws IOException {
        String schemaStr = (String) input.get(0);
        Schema s = null;
        try {
            s = getSchemaFromString(schemaStr);
        } catch (Exception e) {
            throw new IOException(e);
        }
        for(int i = 0; i < s.size(); i++) {
            check(s.getField(i).type, input.get(i+1)); // input.get(i+1) since input.get(0) is the schema;
        }
        return 1;
    }
    
    static {    
        typeMap.put(DataType.INTEGER, Integer.class);
        typeMap.put(DataType.LONG, Long.class);
        typeMap.put(DataType.FLOAT, Float.class);
        typeMap.put(DataType.DOUBLE, Double.class);
        typeMap.put(DataType.CHARARRAY, String.class);
        typeMap.put(DataType.TUPLE, Tuple.class);
        typeMap.put(DataType.MAP, Map.class);
        typeMap.put(DataType.BAG, DataBag.class);
    }
    
    
    
    private void die(String expectedType, Object o) throws IOException {
        throw new IOException("Expected " + expectedType + ", got " +  
              o.getClass().getName());
    }
    
    
    private String check(Byte type, Object o) throws IOException {
        if(o == null) {
            return "";
        }
        if(check(typeMap.get(type), o)) {
            if(type.equals(DataType.MAP)) {
                Map<String, String> m = (Map<String, String>) o;
                check(m);
            } else if(type.equals(DataType.BAG)) {
                DataBag bg = (DataBag) o;
                for (Tuple tuple : bg) {
                    Map<String, String> m = (Map<String, String>) tuple.get(0);
                    check(m);
                }
            } else if(type.equals(DataType.TUPLE)) {
                Tuple t = (Tuple) o;
                if(!check(Integer.class, t.get(0)) ||
                        !check(String.class, t.get(1)) ||
                                !check(Double.class, t.get(2))) {
                    die("t:tuple(num:int,str:string,dbl:double)", t);
                }
            }
        } else {
            die(typeMap.get(type).getName(), o);
        }
        return o.toString();
    }
    
    /**
    * @param m
    * @throws IOException 
    */
    private void check(Map<String, String> m) throws IOException {
      for(Entry<String, String> e: m.entrySet()) {
          // just access key and value to ensure they are correct
          if(!check(String.class, e.getKey())) {
              die("String", e.getKey());
          }
          if(!check(String.class, e.getValue())) {
              die("String", e.getValue());
          }
      }
      
    }
    
    private boolean check(Class<?> expected, Object actual) {
        if(actual == null) {
            return true;
        }
        return expected.isAssignableFrom(actual.getClass());
    }

    Schema getSchemaFromString(String schemaString) throws Exception {
        /** ByteArrayInputStream stream = new ByteArrayInputStream(schemaString.getBytes()) ;
        QueryParser queryParser = new QueryParser(stream) ;
        Schema schema = queryParser.TupleSchema() ;
        Schema.setSchemaDefaultType(schema, org.apache.pig.data.DataType.BYTEARRAY);
        return schema;
        */
        return Utils.getSchemaFromString(schemaString);
    }

}