/// <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));
}
/// <summary>
/// Build a <see cref="FieldFragList"/> for more than one field.
/// </summary>
private FieldFragList GetFieldFragList(IFragListBuilder fragListBuilder,
FieldQuery fieldQuery, IndexReader reader, int docId,
ISet <string> matchedFields, int fragCharSize)
{
if (matchedFields.Count == 0)
{
throw new ArgumentException("matchedFields must contain at least on field name.");
}
FieldPhraseList[]
toMerge = new FieldPhraseList[matchedFields.Count];
int i = 0;
foreach (var matchedField in matchedFields)
{
FieldTermStack stack = new FieldTermStack(reader, docId, matchedField, fieldQuery);
toMerge[i++] = new FieldPhraseList(stack, fieldQuery, phraseLimit);
}
return(fragListBuilder.CreateFieldFragList(new FieldPhraseList(toMerge), fragCharSize));
}
/// <summary>
/// Build a <see cref="FieldFragList"/> for more than one field.
/// </summary>
private FieldFragList GetFieldFragList(IFragListBuilder fragListBuilder,
FieldQuery fieldQuery, IndexReader reader, int docId,
ISet <string> matchedFields, int fragCharSize)
{
IEnumerator <string> matchedFieldsItr = matchedFields.GetEnumerator();
if (!matchedFields.Any())
{
throw new ArgumentException("matchedFields must contain at least on field name.");
}
FieldPhraseList[]
toMerge = new FieldPhraseList[matchedFields.Count];
int i = 0;
while (matchedFieldsItr.MoveNext())
{
FieldTermStack stack = new FieldTermStack(reader, docId, matchedFieldsItr.Current, fieldQuery);
toMerge[i++] = new FieldPhraseList(stack, fieldQuery, phraseLimit);
}
return(fragListBuilder.CreateFieldFragList(new FieldPhraseList(toMerge), fragCharSize));
}
