/// <summary>
/// return the best fragment.
/// </summary>
/// <param name="fieldQuery"><see cref="FieldQuery"/> object</param>
/// <param name="reader"><see cref="IndexReader"/> of the index</param>
/// <param name="docId">document id to be highlighted</param>
/// <param name="fieldName">field of the document to be highlighted</param>
/// <param name="fragCharSize">the length (number of chars) of a fragment</param>
/// <param name="fragListBuilder"><see cref="IFragListBuilder"/> object</param>
/// <param name="fragmentsBuilder"><see cref="IFragmentsBuilder"/> object</param>
/// <param name="preTags">pre-tags to be used to highlight terms</param>
/// <param name="postTags">post-tags to be used to highlight terms</param>
/// <param name="encoder">an encoder that generates encoded text</param>
/// <returns>the best fragment (snippet) string</returns>
/// <exception cref="IOException">If there is a low-level I/O error</exception>
public string GetBestFragment(FieldQuery fieldQuery, IndexReader reader, int docId,
string fieldName, int fragCharSize,
IFragListBuilder fragListBuilder, IFragmentsBuilder fragmentsBuilder,
string[] preTags, string[] postTags, IEncoder encoder)
{
FieldFragList fieldFragList = GetFieldFragList(fragListBuilder, fieldQuery, reader, docId, fieldName, fragCharSize);
return(fragmentsBuilder.CreateFragment(reader, docId, fieldName, fieldFragList, preTags, postTags, encoder));
}
/// <summary>
/// Return the best fragments. Matches are scanned from <paramref name="matchedFields"/> and turned into fragments against
/// <paramref name="storedField"/>. The highlighting may not make sense if <paramref name="matchedFields"/> has matches with offsets that don't
/// correspond features in <paramref name="storedField"/>. It will outright throw a <see cref="IndexOutOfRangeException"/>
/// if <paramref name="matchedFields"/> produces offsets outside of <paramref name="storedField"/>. As such it is advisable that all
/// <paramref name="matchedFields"/> share the same source as <paramref name="storedField"/> or are at least a prefix of it.
/// </summary>
/// <param name="fieldQuery"><see cref="FieldQuery"/> object</param>
/// <param name="reader"><see cref="IndexReader"/> of the index</param>
/// <param name="docId">document id to be highlighted</param>
/// <param name="storedField">field of the document that stores the text</param>
/// <param name="matchedFields">fields of the document to scan for matches</param>
/// <param name="fragCharSize">the length (number of chars) of a fragment</param>
/// <param name="maxNumFragments">maximum number of fragments</param>
/// <param name="fragListBuilder"><see cref="IFragListBuilder"/> object</param>
/// <param name="fragmentsBuilder"><see cref="IFragmentsBuilder"/> object</param>
/// <param name="preTags">pre-tags to be used to highlight terms</param>
/// <param name="postTags">post-tags to be used to highlight terms</param>
/// <param name="encoder">an encoder that generates encoded text</param>
/// <returns>
/// created fragments or null when no fragments created.
/// size of the array can be less than <paramref name="maxNumFragments"/>
/// </returns>
/// <exception cref="IOException">If there is a low-level I/O error</exception>
public string[] GetBestFragments(FieldQuery fieldQuery, IndexReader reader, int docId,
string storedField, ISet <string> matchedFields, int fragCharSize, int maxNumFragments,
IFragListBuilder fragListBuilder, IFragmentsBuilder fragmentsBuilder,
string[] preTags, string[] postTags, IEncoder encoder)
{
FieldFragList fieldFragList =
GetFieldFragList(fragListBuilder, fieldQuery, reader, docId, matchedFields, fragCharSize);
return(fragmentsBuilder.CreateFragments(reader, docId, storedField, fieldFragList, maxNumFragments,
preTags, postTags, encoder));
}
public virtual string CreateFragment(IndexReader reader, int docId,
string fieldName, FieldFragList fieldFragList, string[] preTags, string[] postTags,
IEncoder encoder)
{
string[]
fragments = CreateFragments(reader, docId, fieldName, fieldFragList, 1,
preTags, postTags, encoder);
if (fragments == null || fragments.Length == 0)
{
return(null);
}
return(fragments[0]);
}
public virtual string[] CreateFragments(IndexReader reader, int docId,
string fieldName, FieldFragList fieldFragList, int maxNumFragments,
string[] preTags, string[] postTags, IEncoder encoder)
{
if (maxNumFragments < 0)
{
throw new ArgumentException("maxNumFragments(" + maxNumFragments + ") must be positive number.");
}
IList <WeightedFragInfo> fragInfos = fieldFragList.FragInfos;
Field[]
values = GetFields(reader, docId, fieldName);
if (values.Length == 0)
{
return(null);
}
if (discreteMultiValueHighlighting && values.Length > 1)
{
fragInfos = DiscreteMultiValueHighlighting(fragInfos, values);
}
fragInfos = GetWeightedFragInfoList(fragInfos);
int limitFragments = maxNumFragments < fragInfos.Count ? maxNumFragments : fragInfos.Count;
List <string> fragments = new List <string>(limitFragments);
StringBuilder buffer = new StringBuilder();
int[] nextValueIndex = { 0 };
for (int n = 0; n < limitFragments; n++)
{
WeightedFragInfo fragInfo = fragInfos[n];
fragments.Add(MakeFragment(buffer, nextValueIndex, values, fragInfo, preTags, postTags, encoder));
}
return(fragments.ToArray(/* new String[fragments.size()] */));
}
protected virtual FieldFragList CreateFieldFragList(FieldPhraseList fieldPhraseList, FieldFragList fieldFragList, int fragCharSize)
{
if (fragCharSize < minFragCharSize)
{
throw new ArgumentException("fragCharSize(" + fragCharSize + ") is too small. It must be " + minFragCharSize + " or higher.");
}
List <WeightedPhraseInfo> wpil = new List <WeightedPhraseInfo>();
using (IteratorQueue <WeightedPhraseInfo> queue = new IteratorQueue <WeightedPhraseInfo>(fieldPhraseList.PhraseList.GetEnumerator()))
{
WeightedPhraseInfo phraseInfo = null;
int startOffset = 0;
while ((phraseInfo = queue.Top()) != null)
{
// if the phrase violates the border of previous fragment, discard it and try next phrase
if (phraseInfo.StartOffset < startOffset)
{
queue.RemoveTop();
continue;
}
wpil.Clear();
int currentPhraseStartOffset = phraseInfo.StartOffset;
int currentPhraseEndOffset = phraseInfo.EndOffset;
int spanStart = Math.Max(currentPhraseStartOffset - margin, startOffset);
int spanEnd = Math.Max(currentPhraseEndOffset, spanStart + fragCharSize);
if (AcceptPhrase(queue.RemoveTop(), currentPhraseEndOffset - currentPhraseStartOffset, fragCharSize))
{
wpil.Add(phraseInfo);
}
while ((phraseInfo = queue.Top()) != null)
{ // pull until we crossed the current spanEnd
if (phraseInfo.EndOffset <= spanEnd)
{
currentPhraseEndOffset = phraseInfo.EndOffset;
if (AcceptPhrase(queue.RemoveTop(), currentPhraseEndOffset - currentPhraseStartOffset, fragCharSize))
{
wpil.Add(phraseInfo);
}
}
else
{
break;
}
}
if (wpil.Count == 0)
{
continue;
}
int matchLen = currentPhraseEndOffset - currentPhraseStartOffset;
// now recalculate the start and end position to "center" the result
int newMargin = Math.Max(0, (fragCharSize - matchLen) / 2); // matchLen can be > fragCharSize prevent IAOOB here
spanStart = currentPhraseStartOffset - newMargin;
if (spanStart < startOffset)
{
spanStart = startOffset;
}
// whatever is bigger here we grow this out
spanEnd = spanStart + Math.Max(matchLen, fragCharSize);
startOffset = spanEnd;
fieldFragList.Add(spanStart, spanEnd, wpil);
}
}
return(fieldFragList);
}
public virtual string CreateFragment(IndexReader reader, int docId,
string fieldName, FieldFragList fieldFragList)
{
return(CreateFragment(reader, docId, fieldName, fieldFragList,
m_preTags, m_postTags, NULL_ENCODER));
}
