/*
 * 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.lucene.document;


import java.util.*;

import org.apache.lucene.index.IndexReader;  // for javadoc
import org.apache.lucene.index.IndexableField;
import org.apache.lucene.search.IndexSearcher;  // for javadoc
import org.apache.lucene.search.ScoreDoc; // for javadoc
import org.apache.lucene.util.BytesRef;

Documents are the unit of indexing and search. A Document is a set of fields. Each field has a name and a textual value. A field may be stored with the document, in which case it is returned with search hits on the document. Thus each document should typically contain one or more stored fields which uniquely identify it. 
Note that fields which are not stored are not available in documents retrieved from the index, e.g. with ScoreDoc.doc or IndexReader.document(int). /** Documents are the unit of indexing and search.
 *
 * A Document is a set of fields.  Each field has a name and a textual value.
 * A field may be {@link org.apache.lucene.index.IndexableFieldType#stored() stored} with the document, in which
 * case it is returned with search hits on the document.  Thus each document
 * should typically contain one or more stored fields which uniquely identify
 * it.
 *
 * <p>Note that fields which are <i>not</i> {@link org.apache.lucene.index.IndexableFieldType#stored() stored} are
 * <i>not</i> available in documents retrieved from the index, e.g. with {@link
 * ScoreDoc#doc} or {@link IndexReader#document(int)}.
 */

public final class Document implements Iterable<IndexableField> {

  private final List<IndexableField> fields = new ArrayList<>();

  
Constructs a new document with no fields. /** Constructs a new document with no fields. */
  public Document() {}
  
  @Override
  public Iterator<IndexableField> iterator() {
    return fields.iterator();
  }

  
Adds a field to a document.  Several fields may be added with
the same name.  In this case, if the fields are indexed, their text is
treated as though appended for the purposes of search.
 Note that add like the removeField(s) methods only makes sense 
prior to adding a document to an index. These methods cannot
be used to change the content of an existing index! In order to achieve this,
a document has to be deleted from an index and a new changed version of that
document has to be added.
/**
   * <p>Adds a field to a document.  Several fields may be added with
   * the same name.  In this case, if the fields are indexed, their text is
   * treated as though appended for the purposes of search.</p>
   * <p> Note that add like the removeField(s) methods only makes sense 
   * prior to adding a document to an index. These methods cannot
   * be used to change the content of an existing index! In order to achieve this,
   * a document has to be deleted from an index and a new changed version of that
   * document has to be added.</p>
   */
  public final void add(IndexableField field) {
    fields.add(field);
  }
  
  
Removes field with the specified name from the document.
If multiple fields exist with this name, this method removes the first field that has been added.
If there is no field with the specified name, the document remains unchanged.
 Note that the removeField(s) methods like the add method only make sense 
prior to adding a document to an index. These methods cannot
be used to change the content of an existing index! In order to achieve this,
a document has to be deleted from an index and a new changed version of that
document has to be added.
/**
   * <p>Removes field with the specified name from the document.
   * If multiple fields exist with this name, this method removes the first field that has been added.
   * If there is no field with the specified name, the document remains unchanged.</p>
   * <p> Note that the removeField(s) methods like the add method only make sense 
   * prior to adding a document to an index. These methods cannot
   * be used to change the content of an existing index! In order to achieve this,
   * a document has to be deleted from an index and a new changed version of that
   * document has to be added.</p>
   */
  public final void removeField(String name) {
    Iterator<IndexableField> it = fields.iterator();
    while (it.hasNext()) {
      IndexableField field = it.next();
      if (field.name().equals(name)) {
        it.remove();
        return;
      }
    }
  }
  
  
Removes all fields with the given name from the document.
If there is no field with the specified name, the document remains unchanged.
 Note that the removeField(s) methods like the add method only make sense 
prior to adding a document to an index. These methods cannot
be used to change the content of an existing index! In order to achieve this,
a document has to be deleted from an index and a new changed version of that
document has to be added.
/**
   * <p>Removes all fields with the given name from the document.
   * If there is no field with the specified name, the document remains unchanged.</p>
   * <p> Note that the removeField(s) methods like the add method only make sense 
   * prior to adding a document to an index. These methods cannot
   * be used to change the content of an existing index! In order to achieve this,
   * a document has to be deleted from an index and a new changed version of that
   * document has to be added.</p>
   */
  public final void removeFields(String name) {
    Iterator<IndexableField> it = fields.iterator();
    while (it.hasNext()) {
      IndexableField field = it.next();
      if (field.name().equals(name)) {
        it.remove();
      }
    }
  }


  
Returns an array of byte arrays for of the fields that have the name specified
as the method parameter.  This method returns an empty
array when there are no matching fields.  It never
returns null.
Params:
name – the name of the field
Returns:
a BytesRef[] of binary field values/**
  * Returns an array of byte arrays for of the fields that have the name specified
  * as the method parameter.  This method returns an empty
  * array when there are no matching fields.  It never
  * returns null.
  *
  * @param name the name of the field
  * @return a <code>BytesRef[]</code> of binary field values
  */
  public final BytesRef[] getBinaryValues(String name) {
    final List<BytesRef> result = new ArrayList<>();
    for (IndexableField field : fields) {
      if (field.name().equals(name)) {
        final BytesRef bytes = field.binaryValue();
        if (bytes != null) {
          result.add(bytes);
        }
      }
    }
  
    return result.toArray(new BytesRef[result.size()]);
  }
  
  
Returns an array of bytes for the first (or only) field that has the name
specified as the method parameter. This method will return null
if no binary fields with the specified name are available.
There may be non-binary fields with the same name.
Params:
name – the name of the field.
Returns:
a BytesRef containing the binary field value or null/**
  * Returns an array of bytes for the first (or only) field that has the name
  * specified as the method parameter. This method will return <code>null</code>
  * if no binary fields with the specified name are available.
  * There may be non-binary fields with the same name.
  *
  * @param name the name of the field.
  * @return a <code>BytesRef</code> containing the binary field value or <code>null</code>
  */
  public final BytesRef getBinaryValue(String name) {
    for (IndexableField field : fields) {
      if (field.name().equals(name)) {
        final BytesRef bytes = field.binaryValue();
        if (bytes != null) {
          return bytes;
        }
      }
    }
    return null;
  }

  
Returns a field with the given name if any exist in this document, or
null.  If multiple fields exists with this name, this method returns the
first value added.
/** Returns a field with the given name if any exist in this document, or
   * null.  If multiple fields exists with this name, this method returns the
   * first value added.
   */
  public final IndexableField getField(String name) {
    for (IndexableField field : fields) {
      if (field.name().equals(name)) {
        return field;
      }
    }
    return null;
  }

  
Returns an array of IndexableFields with the given name. This method returns an empty array when there are no matching fields. It never returns null. 
Params:
name – the name of the field
Returns:
a Field[] array/**
   * Returns an array of {@link IndexableField}s with the given name.
   * This method returns an empty array when there are no
   * matching fields.  It never returns null.
   *
   * @param name the name of the field
   * @return a <code>Field[]</code> array
   */
  public IndexableField[] getFields(String name) {
    List<IndexableField> result = new ArrayList<>();
    for (IndexableField field : fields) {
      if (field.name().equals(name)) {
        result.add(field);
      }
    }

    return result.toArray(new IndexableField[result.size()]);
  }
  
  
Returns a List of all the fields in a document.
Note that fields which are not stored are
not available in documents retrieved from the index, e.g. IndexSearcher.doc(int) or IndexReader.document(int). 
Returns:
an immutable List<Field>/** Returns a List of all the fields in a document.
   * <p>Note that fields which are <i>not</i> stored are
   * <i>not</i> available in documents retrieved from the
   * index, e.g. {@link IndexSearcher#doc(int)} or {@link
   * IndexReader#document(int)}.
   * 
   * @return an immutable <code>List&lt;Field&gt;</code> 
   */
  public final List<IndexableField> getFields() {
    return Collections.unmodifiableList(fields);
  }
  
  private final static String[] NO_STRINGS = new String[0];

  
Returns an array of values of the field specified as the method parameter. This method returns an empty array when there are no matching fields. It never returns null. For a numeric StoredField it returns the string value of the number. If you want the actual numeric field instances back, use getFields. 
Params:
name – the name of the field
Returns:
a String[] of field values/**
   * Returns an array of values of the field specified as the method parameter.
   * This method returns an empty array when there are no
   * matching fields.  It never returns null.
   * For a numeric {@link StoredField} it returns the string value of the number. If you want
   * the actual numeric field instances back, use {@link #getFields}.
   * @param name the name of the field
   * @return a <code>String[]</code> of field values
   */
  public final String[] getValues(String name) {
    List<String> result = new ArrayList<>();
    for (IndexableField field : fields) {
      if (field.name().equals(name) && field.stringValue() != null) {
        result.add(field.stringValue());
      }
    }
    
    if (result.size() == 0) {
      return NO_STRINGS;
    }
    
    return result.toArray(new String[result.size()]);
  }

  
Returns the string value of the field with the given name if any exist in this document, or null. If multiple fields exist with this name, this method returns the first value added. If only binary fields with this name exist, returns null. For a numeric StoredField it returns the string value of the number. If you want the actual numeric field instance back, use getField. /** Returns the string value of the field with the given name if any exist in
   * this document, or null.  If multiple fields exist with this name, this
   * method returns the first value added. If only binary fields with this name
   * exist, returns null.
   * For a numeric {@link StoredField} it returns the string value of the number. If you want
   * the actual numeric field instance back, use {@link #getField}.
   */
  public final String get(String name) {
    for (IndexableField field : fields) {
      if (field.name().equals(name) && field.stringValue() != null) {
        return field.stringValue();
      }
    }
    return null;
  }
  
  
Prints the fields of a document for human consumption. /** Prints the fields of a document for human consumption. */
  @Override
  public final String toString() {
    StringBuilder buffer = new StringBuilder();
    buffer.append("Document<");
    for (int i = 0; i < fields.size(); i++) {
      IndexableField field = fields.get(i);
      buffer.append(field.toString());
      if (i != fields.size()-1) {
        buffer.append(" ");
      }
    }
    buffer.append(">");
    return buffer.toString();
  }

  
Removes all the fields from document. /** Removes all the fields from document. */
  public void clear() {
    fields.clear();
  }
}