/// <summary>
/// build specification from rsql query
/// </summary>
/// <param name="queryCollection"></param>
/// <returns></returns>
private Expression <Func <T, bool> > Build(IQueryCollection queryCollection)
{
var result = QueryExpressionHelper.True <T>();
if (queryCollection.TryGetValue(_autumnSettings.QueryField, out var query))
{
result = GetOrRegistryQuery(query, _autumnSettings);
}
return(result);
}
private static Expression <Func <T, bool> > GetOrRegistryQuery(string query, AutumnSettings autumnSettings)
{
lock (QueryExpressionHelper.QueriesCache)
{
if (string.IsNullOrWhiteSpace(query))
{
return(QueryExpressionHelper.True <T>());
}
var hash = Hash($"{typeof(T).FullName}?{query}");
if (QueryExpressionHelper.QueriesCache.TryGetValue(hash, out Expression <Func <T, bool> > result))
{
return(result);
}
var antlrInputStream = new AntlrInputStream(query);
var lexer = new QueryLexer(antlrInputStream);
var commonTokenStream = new CommonTokenStream(lexer);
var parser = new QueryParser(commonTokenStream);
var eval = parser.or();
var visitor = new DefaultQueryVisitor <T>(autumnSettings.NamingStrategy);
result = visitor.VisitOr(eval);
QueryExpressionHelper.QueriesCache.Set(hash, result);
return(result);
}
}
