public IEnumerable <SiteAccessEntry> GetSiteAccessEntries(IEnumerable <Token> tokens)
{
var result = new List <SiteAccessEntry>();
var parseState = new SiteAccessParseState();
var comparer = StringComparer.OrdinalIgnoreCase;
using (var enumerator = tokens.GetEnumerator())
{
string lastFieldValue = null;
while (enumerator.MoveTo(TokenType.Field))
{
var fieldValue = enumerator.Current.Value;
if (!ExpectedFields.Contains(fieldValue))
{
continue;
}
//Reset the state when we have encountered a new "User-agent" field not immediately after another
if (!string.IsNullOrEmpty(lastFieldValue) && !comparer.Equals(lastFieldValue, UserAgentField) && comparer.Equals(fieldValue, UserAgentField))
{
result.Add(parseState.AsEntry());
parseState.Reset();
}
//When we have seen a field for the first time that isn't a User-agent, default to all User-agents (written as "*")
if (string.IsNullOrEmpty(lastFieldValue) && !comparer.Equals(fieldValue, UserAgentField))
{
parseState.UserAgents.Add("*");
}
lastFieldValue = fieldValue;
if (comparer.Equals(fieldValue, UserAgentField))
{
if (enumerator.StepOverTo(TokenType.Value, TokenType.FieldValueDelimiter))
{
parseState.UserAgents.Add(enumerator.Current.Value);
}
}
else if (comparer.Equals(fieldValue, AllowField) || comparer.Equals(fieldValue, DisallowField))
{
var pathRule = comparer.Equals(fieldValue, DisallowField) ? PathRuleType.Disallow : PathRuleType.Allow;
var pathValue = string.Empty;
if (enumerator.StepOverTo(TokenType.Value, TokenType.FieldValueDelimiter))
{
pathValue = enumerator.Current.Value;
}
if (pathRule == PathRuleType.Allow && string.IsNullOrEmpty(pathValue))
{
//Only disallow can be blank (no "Value" token) - See Section 4 of RFC
continue;
}
parseState.PathRules.Add(new SiteAccessPathRule
{
RuleType = pathRule,
Path = pathValue
});
}
else if (comparer.Equals(fieldValue, CrawlDelayField))
{
if (enumerator.StepOverTo(TokenType.Value, TokenType.FieldValueDelimiter))
{
if (int.TryParse(enumerator.Current.Value, out var parsedCrawlDelay))
{
parseState.CrawlDelay = parsedCrawlDelay;
}
}
}
}
result.Add(parseState.AsEntry());
}
return(result);
}
public IEnumerable <SiteAccessEntry> GetSiteAccessEntries(IEnumerable <Token> tokens)
{
//TODO: Refactor the implementation to not be as nasty as it is :(
var result = new List <SiteAccessEntry>();
var parseState = new SiteAccessParseState();
var valueSteppingTokens = new[] { TokenType.FieldValueDelimiter };
var expectedFields = new[] { "User-agent", "Allow", "Disallow", "Crawl-delay" };
using (var enumerator = tokens.GetEnumerator())
{
var lastFieldValue = string.Empty;
while (enumerator.MoveTo(TokenType.Field))
{
var fieldCurrent = enumerator.Current;
if (!expectedFields.Contains(fieldCurrent.Value))
{
continue;
}
//Reset the state when we have encountered a new "User-agent" field not immediately after another
if (lastFieldValue != string.Empty && lastFieldValue != "User-agent" && fieldCurrent.Value == "User-agent")
{
result.Add(parseState.AsEntry());
parseState.Reset();
}
//When we have seen a field for the first time that isn't a User-agent, default to all User-agents
if (lastFieldValue == string.Empty && fieldCurrent.Value != "User-agent")
{
parseState.UserAgents.Add("*");
}
lastFieldValue = fieldCurrent.Value;
if (fieldCurrent.Value == "User-agent")
{
if (enumerator.StepOverTo(TokenType.Value, valueSteppingTokens))
{
parseState.UserAgents.Add(enumerator.Current.Value);
}
}
else if (fieldCurrent.Value == "Allow" || fieldCurrent.Value == "Disallow")
{
var pathRule = fieldCurrent.Value == "Disallow" ? PathRuleType.Disallow : PathRuleType.Allow;
var pathValue = string.Empty;
if (enumerator.StepOverTo(TokenType.Value, valueSteppingTokens))
{
pathValue = enumerator.Current.Value;
}
if (pathRule == PathRuleType.Allow && pathValue == null)
{
//Only disallow can be blank (no "Value" token) - See Section 4 of RFC
continue;
}
parseState.PathRules.Add(new SiteAccessPathRule
{
RuleType = pathRule,
Path = pathValue
});
}
else if (fieldCurrent.Value == "Crawl-delay")
{
if (enumerator.StepOverTo(TokenType.Value, valueSteppingTokens))
{
if (int.TryParse(enumerator.Current.Value, out int parsedInt))
{
parseState.CrawlDelay = parsedInt;
}
}
}
}
result.Add(parseState.AsEntry());
}
return(result);
}