Spans.cs

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/* 
 * 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.
 */

using System;
using System.Collections.Generic;

namespace Lucene.Net.Search.Spans
{
    
    /// <summary>Expert: an enumeration of span matches.  Used to implement span searching.
    /// Each span represents a range of term positions within a document.  Matches
    /// are enumerated in order, by increasing document number, within that by
    /// increasing start position and finally by increasing end position. 
    /// </summary>
    public abstract class Spans
    {
        /// <summary>Move to the next match, returning true iff any such exists. </summary>
        public abstract bool Next();
        
        /// <summary>Skips to the first match beyond the current, whose document number is
        /// greater than or equal to <i>target</i>. <p/>Returns true iff there is such
        /// a match.  <p/>Behaves as if written: <code>
        /// boolean skipTo(int target) {
        /// do {
        /// if (!next())
        /// return false;
        /// } while (target > doc());
        /// return true;
        /// }
        /// </code>
        /// Most implementations are considerably more efficient than that.
        /// </summary>
        public abstract bool SkipTo(int target);
        
        /// <summary>Returns the document number of the current match.  Initially invalid. </summary>
        public abstract int Doc();
        
        /// <summary>Returns the start position of the current match.  Initially invalid. </summary>
        public abstract int Start();
        
        /// <summary>Returns the end position of the current match.  Initially invalid. </summary>
        public abstract int End();

        /// <summary> Returns the payload data for the current span.
        /// This is invalid until <see cref="Next()" /> is called for
        /// the first time.
        /// This method must not be called more than once after each call
        /// of <see cref="Next()" />. However, most payloads are loaded lazily,
        /// so if the payload data for the current position is not needed,
        /// this method may not be called at all for performance reasons. An ordered
        /// SpanQuery does not lazy load, so if you have payloads in your index and
        /// you do not want ordered SpanNearQuerys to collect payloads, you can
        /// disable collection with a constructor option.<br/>
        /// 
        /// Note that the return type is a collection, thus the ordering should not be relied upon.
        /// <br/>
        /// <p/><font color="#FF0000">
        /// WARNING: The status of the <b>Payloads</b> feature is experimental.
        /// The APIs introduced here might change in the future and will not be
        /// supported anymore in such a case.</font><p/>
        /// 
        /// </summary>
        /// <returns> a List of byte arrays containing the data of this payload, otherwise null if isPayloadAvailable is false </returns>
        /// <throws>  java.io.IOException </throws>
        // TODO: Remove warning after API has been finalized
        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1024:UsePropertiesWhereAppropriate")]
        public abstract ICollection<byte[]> GetPayload();

        /// <summary> Checks if a payload can be loaded at this position.
        /// <p/>
        /// Payloads can only be loaded once per call to
        /// <see cref="Next()" />.
        /// 
        /// </summary>
        /// <returns> true if there is a payload available at this position that can be loaded </returns>
        public abstract bool IsPayloadAvailable();
    }
}