/// <summary>
/// Parses the source code searching for the longest matching term text from the specified terms.
/// It returns the index of the longest matching term or -1, if there is no matching term at the specified source position.
/// </summary>
/// <param name="source">The source of an extension.</param>
/// <param name="textSelector">The selector of term text at the specified 0 based index.</param>
/// <param name="accept">if set to <c>true</c> accepts the position after parsed longest text.</param>
/// <param name="charComparer">The character comparer.</param>
/// <param name="termsCount">The number of terms.</param>
/// <returns>The index of the longest matching text or -1, if there is no matching text at the specified source position.</returns>
public static int ParseLongestMatchingString(this IParsingContextStream source, int termsCount, Func <int, string> textSelector, bool accept = false, IEqualityComparer <char> charComparer = null)
{
var text = Enumerable.Range(0, termsCount).Select(textSelector).ToArray();
var matchedTermIdx = -1;
using (var ctx = source.GetFurtherContext())
{
//go through all character indexes from 0 to longest matching term
// for each term check if character at specified position matches
// if char matches and it is last character, temporary accept position and exclude term by setting to null
// if char doesn't match -> exclude term by setting to null
// if there are no more matching terms -> break
// if accept true and matchedTermIdx > -1 -> accept
// return matchedTermIndex
var charPosition = -1;
while (ctx.MoveNext())
{
charPosition++;
var current = ctx.Current;
var matchingTermsCount = 0;
for (var termIdx = 0; termIdx < text.Length; termIdx++)
{
var currentTerm = text[termIdx];
if (currentTerm != null)
{
if (currentTerm.Length <= charPosition)
{
text[termIdx] = null;
}
if (Equals(currentTerm[charPosition], current, charComparer))
{
if (currentTerm.Length == charPosition + 1)
{
matchedTermIdx = termIdx;
ctx.Accept();
text[termIdx] = null;
}
else
{
matchingTermsCount++;
}
}
else
{
text[termIdx] = null;
}
}
}
if (matchingTermsCount <= 0)
{
break;
}
}
}
if (accept && matchedTermIdx >= 0)
{
source.Accept();
}
return(matchedTermIdx);
}