/**
 * 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.thrift;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.nio.ByteBuffer;

import org.apache.thrift.protocol.TField;
import org.apache.thrift.protocol.TProtocol;
import org.apache.thrift.protocol.TProtocolException;
import org.apache.thrift.protocol.TStruct;

public abstract class TUnion<T extends TUnion<?,?>, F extends TFieldIdEnum> implements TBase<T, F> {

  protected Object value_;
  protected F setField_;

  protected TUnion() {
    setField_ = null;
    value_ = null;
  }

  protected TUnion(F setField, Object value) {
    setFieldValue(setField, value);
  }

  protected TUnion(TUnion<T, F> other) {
    if (!other.getClass().equals(this.getClass())) {
      throw new ClassCastException();
    }
    setField_ = other.setField_;
    value_ = deepCopyObject(other.value_);
  }

  private static Object deepCopyObject(Object o) {
    if (o instanceof TBase) {
      return ((TBase)o).deepCopy();
    } else if (o instanceof ByteBuffer) {
      return TBaseHelper.copyBinary((ByteBuffer)o);
    } else if (o instanceof List) {
      return deepCopyList((List)o);
    } else if (o instanceof Set) {
      return deepCopySet((Set)o);
    } else if (o instanceof Map) {
      return deepCopyMap((Map)o);
    } else {
      return o;
    }
  }

  private static Map deepCopyMap(Map<Object, Object> map) {
    Map copy = new HashMap();
    for (Map.Entry<Object, Object> entry : map.entrySet()) {
      copy.put(deepCopyObject(entry.getKey()), deepCopyObject(entry.getValue()));
    }
    return copy;
  }

  private static Set deepCopySet(Set set) {
    Set copy = new HashSet();
    for (Object o : set) {
      copy.add(deepCopyObject(o));
    }
    return copy;
  }

  private static List deepCopyList(List list) {
    List copy = new ArrayList(list.size());
    for (Object o : list) {
      copy.add(deepCopyObject(o));
    }
    return copy;
  }

  public F getSetField() {
    return setField_;
  }

  public Object getFieldValue() {
    return value_;
  }

  public Object getFieldValue(F fieldId) {
    if (fieldId != setField_) {
      throw new IllegalArgumentException("Cannot get the value of field " + fieldId + " because union's set field is " + setField_);
    }

    return getFieldValue();
  }

  public Object getFieldValue(int fieldId) {
    return getFieldValue(enumForId((short)fieldId));
  }

  public boolean isSet() {
    return setField_ != null;
  }

  public boolean isSet(F fieldId) {
    return setField_ == fieldId;
  }

  public boolean isSet(int fieldId) {
    return isSet(enumForId((short)fieldId));
  }

  public void read(TProtocol iprot) throws TException {
    setField_ = null;
    value_ = null;

    iprot.readStructBegin();

    TField field = iprot.readFieldBegin();

    value_ = readValue(iprot, field);
    if (value_ != null) {
      setField_ = enumForId(field.id);
    }

    iprot.readFieldEnd();
    // this is so that we will eat the stop byte. we could put a check here to
    // make sure that it actually *is* the stop byte, but it's faster to do it
    // this way.
    iprot.readFieldBegin();
    iprot.readStructEnd();
  }

  public void setFieldValue(F fieldId, Object value) {
    checkType(fieldId, value);
    setField_ = fieldId;
    value_ = value;
  }

  public void setFieldValue(int fieldId, Object value) {
    setFieldValue(enumForId((short)fieldId), value);
  }

  public void write(TProtocol oprot) throws TException {
    if (getSetField() == null || getFieldValue() == null) {
      throw new TProtocolException("Cannot write a TUnion with no set value!");
    }
    oprot.writeStructBegin(getStructDesc());
    oprot.writeFieldBegin(getFieldDesc(setField_));
    writeValue(oprot);
    oprot.writeFieldEnd();
    oprot.writeFieldStop();
    oprot.writeStructEnd();
  }

  /**
   * Implementation should be generated so that we can efficiently type check 
   * various values.
   * @param setField
   * @param value
   */
  protected abstract void checkType(F setField, Object value) throws ClassCastException;

  /**
   * Implementation should be generated to read the right stuff from the wire 
   * based on the field header. 
   * @param field
   * @return
   */
  protected abstract Object readValue(TProtocol iprot, TField field) throws TException;

  protected abstract void writeValue(TProtocol oprot) throws TException;

  protected abstract TStruct getStructDesc();

  protected abstract TField getFieldDesc(F setField);

  protected abstract F enumForId(short id);

  @Override
  public String toString() {
    StringBuilder sb = new StringBuilder();
    sb.append("<");
    sb.append(this.getClass().getSimpleName());
    sb.append(" ");

    if (getSetField() != null) {
      Object v = getFieldValue();
      sb.append(getFieldDesc(getSetField()).name);
      sb.append(":");
      if(v instanceof ByteBuffer) {
        TBaseHelper.toString((ByteBuffer)v, sb);
      } else {
        sb.append(v.toString());
      }
    }
    sb.append(">");
    return sb.toString();
  }

  public final void clear() {
    this.setField_ = null;
    this.value_ = null;
  }
}