/// <summary>
/// State machine analysis of the provided message line, to minimize processing cost overhead.
/// </summary>
/// <param name="line">The message line.</param>
/// <returns>Returns a tuple indicating if this was a vote line, whether this line indicated
/// that this post should be ignored, and the encapsulated vote line, if applicable.</returns>
/// <exception cref="InvalidOperationException">Throws if it gets into an unknown state.</exception>
internal static (bool isVoteLine, bool flagIgnore, VoteLine voteLine) AnalyzeLine(string line)
{
bool isVoteLine = false;
bool flagIgnore = false;
VoteLine voteLine = null;
if (string.IsNullOrEmpty(line))
{
return(isVoteLine, flagIgnore, voteLine);
}
StringBuilder prefixSB = new StringBuilder();
StringBuilder markerSB = new StringBuilder();
StringBuilder taskSB = new StringBuilder();
StringBuilder contentSB = new StringBuilder();
StringBuilder tempContent = new StringBuilder();
MarkerType markerType = MarkerType.None;
int markerValue = 0;
int ignoreCharCount = 0;
Stack <TokenState> state = new Stack <TokenState>();
TokenState currentState = TokenState.None;
foreach (var ch in line)
{
switch (currentState)
{
case TokenState.None:
if (ch == whitespace)
{
continue;
}
else if (ch == openBBCode)
{
state.Push(currentState);
currentState = TokenState.BBCode;
}
else if (ch == prefixChar)
{
state.Push(currentState);
currentState = TokenState.Prefix;
prefixSB.Append(ch);
}
else if (ch == ignoreChar)
{
state.Push(currentState);
currentState = TokenState.Ignore;
ignoreCharCount = 1;
}
else if (ch == openBracket)
{
state.Push(currentState);
currentState = TokenState.Marker;
}
else
{
goto doneExamining;
}
break;
case TokenState.BBCode:
if (state.Peek() == TokenState.PostMarker)
{
tempContent.Append(ch);
}
if (ch == closeBBCode)
{
currentState = state.Pop();
}
break;
case TokenState.Ignore:
if (ch == ignoreChar)
{
ignoreCharCount++;
if (ignoreCharCount == 5)
{
flagIgnore = true;
goto doneExamining;
}
}
else if (ch == openBBCode)
{
state.Push(currentState);
currentState = TokenState.BBCode;
}
else
{
goto doneExamining;
}
break;
case TokenState.Prefix:
if (ch == whitespace)
{
continue;
}
else if (ch == prefixChar)
{
prefixSB.Append(ch);
}
else if (ch == openBBCode)
{
state.Push(currentState);
currentState = TokenState.BBCode;
}
else if (ch == openBracket)
{
currentState = TokenState.Marker;
}
else
{
goto doneExamining;
}
break;
case TokenState.Marker:
if (ch == whitespace)
{
continue;
}
else if (ch == openBBCode)
{
state.Push(currentState);
currentState = TokenState.BBCode;
}
else if (markerChars.Contains(ch))
{
markerSB.Append(ch);
}
else if (ch == closeBracket)
{
(markerType, markerValue) = GetMarkerType(markerSB.ToString());
if (markerType != MarkerType.None)
{
isVoteLine = true;
currentState = TokenState.PostMarker;
}
else
{
goto doneExamining;
}
}
else
{
goto doneExamining;
}
break;
case TokenState.PostMarker:
if (ch == whitespace)
{
continue;
}
else if (ch == openBracket && taskSB.Length == 0)
{
state.Push(currentState);
currentState = TokenState.Task;
}
else if (ch == openBBCode && taskSB.Length == 0)
{
state.Push(currentState);
currentState = TokenState.BBCode;
tempContent.Append(ch);
}
else
{
contentSB.Append(tempContent.ToString());
contentSB.Append(ch);
currentState = TokenState.Content;
}
break;
case TokenState.Task:
if (ch == closeBracket)
{
currentState = state.Pop();
}
else if (ch == openBBCode)
{
state.Push(currentState);
currentState = TokenState.BBCode;
}
else
{
taskSB.Append(ch);
}
break;
case TokenState.Content:
contentSB.Append(ch);
break;
default:
throw new InvalidOperationException($"Unknown token state value: {currentState}.");
}
}
doneExamining:
if (isVoteLine)
{
voteLine = new VoteLine(prefixSB.ToString(), markerSB.ToString(), taskSB.ToString(), contentSB.ToString(), markerType, markerValue);
}
return(isVoteLine, flagIgnore, voteLine);
}
