/// <summary>
/// <para>
/// Generate suggestions by combining one or more of the passed-in terms into
/// single words. The returned <see cref="CombineSuggestion"/> contains both a
/// <see cref="SuggestWord"/> and also an array detailing which passed-in terms were
/// involved in creating this combination. The scores returned are equal to the
/// number of word combinations needed, also one less than the length of the
/// array <see cref="CombineSuggestion.OriginalTermIndexes"/>. Generally, a
/// suggestion with a lower score is preferred over a higher score.
/// </para>
/// <para>
/// To prevent two adjacent terms from being combined (for instance, if one is
/// mandatory and the other is prohibited), separate the two terms with
/// <see cref="WordBreakSpellChecker.SEPARATOR_TERM"/>
/// </para>
/// <para>
/// When suggestMode equals <see cref="SuggestMode.SUGGEST_WHEN_NOT_IN_INDEX"/>, each
/// suggestion will include at least one term not in the index.
/// </para>
/// <para>
/// When suggestMode equals <see cref="SuggestMode.SUGGEST_MORE_POPULAR"/>, each
/// suggestion will have the same, or better frequency than the most-popular
/// included term.
/// </para>
/// </summary>
/// <returns> an array of words generated by combining original terms </returns>
/// <exception cref="IOException"> If there is a low-level I/O error. </exception>
public virtual CombineSuggestion[] SuggestWordCombinations(Term[] terms, int maxSuggestions,
IndexReader ir, SuggestMode suggestMode = SuggestMode.SUGGEST_WHEN_NOT_IN_INDEX)
{
if (maxSuggestions < 1)
{
return(Arrays.Empty <CombineSuggestion>());
}
int[] origFreqs = null;
if (suggestMode != SuggestMode.SUGGEST_ALWAYS)
{
origFreqs = new int[terms.Length];
for (int i = 0; i < terms.Length; i++)
{
origFreqs[i] = ir.DocFreq(terms[i]);
}
}
int queueInitialCapacity = maxSuggestions > 10 ? 10 : maxSuggestions;
IComparer <CombineSuggestionWrapper> queueComparer = new CombinationsThenFreqComparer();
JCG.PriorityQueue <CombineSuggestionWrapper> suggestions = new JCG.PriorityQueue <CombineSuggestionWrapper>(queueInitialCapacity, queueComparer);
int thisTimeEvaluations = 0;
for (int i = 0; i < terms.Length - 1; i++)
{
if (terms[i].Equals(SEPARATOR_TERM))
{
continue;
}
string leftTermText = terms[i].Text;
int leftTermLength = leftTermText.CodePointCount(0, leftTermText.Length);
if (leftTermLength > maxCombineWordLength)
{
continue;
}
int maxFreq = 0;
int minFreq = int.MaxValue;
if (origFreqs != null)
{
maxFreq = origFreqs[i];
minFreq = origFreqs[i];
}
string combinedTermText = leftTermText;
int combinedLength = leftTermLength;
for (int j = i + 1; j < terms.Length && j - i <= maxChanges; j++)
{
if (terms[j].Equals(SEPARATOR_TERM))
{
break;
}
string rightTermText = terms[j].Text;
int rightTermLength = rightTermText.CodePointCount(0, rightTermText.Length);
combinedTermText += rightTermText;
combinedLength += rightTermLength;
if (combinedLength > maxCombineWordLength)
{
break;
}
if (origFreqs != null)
{
maxFreq = Math.Max(maxFreq, origFreqs[j]);
minFreq = Math.Min(minFreq, origFreqs[j]);
}
Term combinedTerm = new Term(terms[0].Field, combinedTermText);
int combinedTermFreq = ir.DocFreq(combinedTerm);
if (suggestMode != SuggestMode.SUGGEST_MORE_POPULAR || combinedTermFreq >= maxFreq)
{
if (suggestMode != SuggestMode.SUGGEST_WHEN_NOT_IN_INDEX || minFreq == 0)
{
if (combinedTermFreq >= minSuggestionFrequency)
{
int[] origIndexes = new int[j - i + 1];
origIndexes[0] = i;
for (int k = 1; k < origIndexes.Length; k++)
{
origIndexes[k] = i + k;
}
SuggestWord word = new SuggestWord();
word.Freq = combinedTermFreq;
word.Score = origIndexes.Length - 1;
word.String = combinedTerm.Text;
CombineSuggestionWrapper suggestion = new CombineSuggestionWrapper(new CombineSuggestion(word, origIndexes), (origIndexes.Length - 1));
suggestions.Enqueue(suggestion);
if (suggestions.Count > maxSuggestions)
{
suggestions.TryDequeue(out CombineSuggestionWrapper _);
}
}
}
}
thisTimeEvaluations++;
if (thisTimeEvaluations == maxEvaluations)
{
break;
}
}
}
CombineSuggestion[] combineSuggestions = new CombineSuggestion[suggestions.Count];
for (int i = suggestions.Count - 1; i >= 0; i--)
{
combineSuggestions[i] = suggestions.Dequeue().CombineSuggestion;
}
return(combineSuggestions);
}
internal CombineSuggestionWrapper(WordBreakSpellChecker outerInstance, CombineSuggestion combineSuggestion, int numCombinations)
{
this.outerInstance = outerInstance;
this.combineSuggestion = combineSuggestion;
this.numCombinations = numCombinations;
}
