private static AbstractYearSpecification ParseToExpression(Queue <Token> unProcessedTokens,
AbstractYearSpecification from)
{
const String onlyRegex = "^only$";
if (Regex.IsMatch(unProcessedTokens.Peek().Value, onlyRegex))
{
// dequeue only token and discard
unProcessedTokens.Dequeue();
return(from);
}
return(YearSpecificationExpression.Parse(unProcessedTokens));
}
public static bool TryParse(Queue <Token> unProcessedTokens, out TzDbRule?tzDbRule)
{
// the value of the first token of every link entry is Rule
const String ruleRegex = "Rule";
if (Regex.IsMatch(unProcessedTokens.Peek().Value, ruleRegex))
{
try
{
// dequeue Rule token and discard
unProcessedTokens.Dequeue();
string name = unProcessedTokens.Dequeue().Value;
AbstractYearSpecification from = YearSpecificationExpression.Parse(unProcessedTokens);
AbstractYearSpecification to = ParseToExpression(unProcessedTokens, from);
string type = unProcessedTokens.Dequeue().Value;
MonthOfYear @in = MonthOfYearExpression.Parse(unProcessedTokens);
AbstractDayOfMonthSpecification on = DayOfMonthSpecificationExpression.Parse(unProcessedTokens);
AbstractTime at = TzDbTimeExpression.Parse(unProcessedTokens);
TimeSpan save = TimeSpanExpression.Parse(unProcessedTokens);
TimeZoneAbbreviationVariable letter = TimeZoneAbbreviationVariableExpression.Parse(unProcessedTokens);
tzDbRule = new TzDbRule(name, from, to, type, @in, on, at, save, letter);
Token endLineToken = unProcessedTokens.Dequeue();
// guard end of line token was present
if (endLineToken.TokenType != TokenType.EndLine)
{
string msg = String.Format(
"received unexpected token type:{0} when token type should have been {1}",
endLineToken.TokenType, TokenType.EndLine);
throw new Exception(msg);
}
return(true);
}
catch (Exception e)
{
string msg = String.Format("Unable to parse {0}", typeof(RuleExpression).Name);
throw new Exception(msg, e);
}
}
tzDbRule = null;
return(false);
}