public static IExpression ParseEachTermWithPrefix(string query, string prefix, ITermCorrector corrector)
{
IExpression result = Parse(query, corrector);
IExpression prefixExpression = null;
string[] pieces = query.Split(' ', '\t', '\n', '\r');
foreach (string piece in pieces)
{
// Make sure no already prefixed item to be add a new prefix
if (piece.Split(':').Length == 1)
{
if (piece.Length >= 2)
{
IExpression part = Parse(prefix + piece, corrector);
prefixExpression = LogicOrExpression.Join(prefixExpression, part);
}
}
}
if (prefixExpression != null)
{
return(LogicAndExpression.Join(result, prefixExpression));
}
else
{
return(new TermExpression(""));
}
}
/// <summary>
/// Parse a single piece of the entire search query into an Expression form using corrector
/// </summary>
/// <param name="term">A truncated piece contains no delimiters</param>
/// <param name="corrector">Corrector to be used to add suggestions to the expression</param>
/// <returns>IExpression contains the original term and the suggestions of the word</returns>
private static IExpression ParseTerm(string term, ITermCorrector corrector)
{
IExpression result = new TermExpression(term);
if (corrector != null)
{
foreach (string correction in corrector.Correct(term))
{
if (correction != term)
{
IExpression expr = new TermExpression(correction);
result = LogicOrExpression.Join(result, expr);
}
}
}
return(result);
}
/// <summary>
/// Parse the search query by building a logic expression tree of single terms
/// </summary>
/// <param name="query">Original search query</param>
/// <param name="corrector">Correct single term into an expression</param>
/// <returns>Expression tree (Join AndExpression for different terms and join OrExpression for corrections)</returns>
public static IExpression Parse(string query, ITermCorrector corrector)
{
if (String.IsNullOrEmpty(query))
{
return(new TermExpression(String.Empty));
}
query = query.ToLowerInvariant();
string[] pieces = query.Split(' ', '\t', '\n', '\r');
IExpression result = null;
foreach (string piece in pieces)
{
IExpression expr = null;
// Scan the possibilities of AndNot and Or
if (piece.Length > 1)
{
if (piece.Contains('|'))
{
string[] orPieces = piece.Split('|');
foreach (string orPiece in orPieces)
{
expr = LogicOrExpression.Join(expr, Parse(orPiece, corrector));
}
result = LogicAndExpression.Join(result, expr);
continue;
}
else if (piece[0] == '-')
{
expr = ParseTerm(piece.Substring(1), corrector);
result = LogicAndNotExpression.Join(result, expr);
continue;
}
}
// By default, use And to connect
expr = ParseTerm(piece, corrector);
result = LogicAndExpression.Join(result, expr);
}
return(result);
}