private static void ParseClauseWords(List <string> clauseWords, SelectWhereGroup currentGroup)
{
if (clauseWords.Any())
{
var negate = false;
var index = 0;
var startWord = clauseWords[index];
if (string.Equals(startWord, "select"))
{
// todo recursion select statement
throw new NotSupportedException("Inner Select not currently supported.");
}
var leftExpression = ParseWhereColumn(startWord);
var nextWord = clauseWords[++index];
if (nextWord == "not")
{
negate = true;
nextWord = clauseWords[++index];
}
if (nextWord.In("=", "<", ">", "!"))
{
var comparison = "";
for (; index < clauseWords.Count - 1; index++)
{
comparison += clauseWords[index];
}
var comparisonOperator = SelectWhereComparisonOperatorEnum.None;
switch (comparison)
{
case "=":
comparisonOperator = SelectWhereComparisonOperatorEnum.Equal;
break;
case "<>":
comparisonOperator = SelectWhereComparisonOperatorEnum.NotEqual;
break;
case "!=":
comparisonOperator = SelectWhereComparisonOperatorEnum.NotEqual;
break;
case "<":
comparisonOperator = SelectWhereComparisonOperatorEnum.LessThan;
break;
case "!<":
negate = true;
comparisonOperator = SelectWhereComparisonOperatorEnum.LessThan;
break;
case "<=":
comparisonOperator = SelectWhereComparisonOperatorEnum.LessEqualThan;
break;
case ">":
comparisonOperator = SelectWhereComparisonOperatorEnum.GreaterThan;
break;
case "!>":
negate = true;
comparisonOperator = SelectWhereComparisonOperatorEnum.GreaterThan;
break;
case ">=":
comparisonOperator = SelectWhereComparisonOperatorEnum.GreaterEqualThan;
break;
default:
throw new Exception($"Found unexpected comparison operator '{comparisonOperator}'");
}
nextWord = clauseWords[index];
var rightExpression = ParseWhereColumn(nextWord);
var clause = new SelectWhereComparison(leftExpression, comparisonOperator, rightExpression)
{
Negate = negate
};
currentGroup.Clauses.Add(clause);
}
if (nextWord == "like")
{
nextWord = clauseWords[++index];
var rightExpression = ParseWhereColumn(nextWord);
if (++index < clauseWords.Count)
{
throw new Exception("Found unexpected tokens after 'LIKE' clause.");
}
var clause = new SelectWhereLike(leftExpression, rightExpression)
{
Negate = negate
};
currentGroup.Clauses.Add(clause);
}
if (nextWord == "is")
{
if (negate)
{
throw new Exception("'NOT' must come after 'IS'.");
}
nextWord = clauseWords[++index];
if (nextWord.NotIn("not", "null"))
{
throw new Exception("Expecting 'NOT' or 'NULL' after 'IS'.");
}
if (nextWord == "not")
{
negate = true;
nextWord = clauseWords[++index];
if (nextWord.NotIn("null"))
{
throw new Exception("Expecting 'NULL' after 'IS NOT'.");
}
}
if (nextWord != "null")
{
throw new Exception("Expecting 'NULL' after 'IS'.");
}
if (++index < clauseWords.Count)
{
throw new Exception("Found unexpected tokens after 'IS' clause.");
}
var clause = new SelectWhereNull(leftExpression)
{
Negate = negate
};
currentGroup.Clauses.Add(clause);
}
}
clauseWords.Clear();
}
public TokenParserResults Parse(ParseArgs <SelectStatement> parseArgs)
{
var selectStatement = parseArgs.Statement;
var args = parseArgs.StatementArgs;
var results = new TokenParserResults();
var words = GetWords != null
? GetWords(args).ToList()
: ParserUtils.GetWords(args).ToList();
if (words.Any())
{
var currentGroup = new SelectWhereGroup();
var groupStack = new Stack <SelectWhereGroup>();
var clauseWords = new List <string>();
for (int i = 0; i < words.Count; i++)
{
var word = words[i];
if (word.In("(", ")", "and", "or"))
{
ParseClauseWords(clauseWords, currentGroup);
}
if (word == "(")
{
groupStack.Push(currentGroup);
var newGroup = new SelectWhereGroup();
currentGroup.Clauses.Add(newGroup);
currentGroup = newGroup;
}
else if (word == ")")
{
currentGroup = groupStack.Pop();
}
else if (word == "or")
{
var clauseOperator = new SelectWhereOperator(SelectWhereClauseOperatorEnum.Or);
currentGroup.Clauses.Add(clauseOperator);
}
else if (word == "and")
{
var clauseOperator = new SelectWhereOperator(SelectWhereClauseOperatorEnum.And);
currentGroup.Clauses.Add(clauseOperator);
}
else
{
clauseWords.Add(word);
}
}
ParseClauseWords(clauseWords, currentGroup);
selectStatement.Where = currentGroup.Clauses;
}
return(results);
}
