GParse/source/GParse/QuoteAwareParser.cs

namespace GParse;

public class QuoteAwareParser(string delimiter, string openQuote, string closeQuote) : ITextParser
{
	public IEnumerable<string> Parse(ITextInputProvider textInputProvider) => Parse(textInputProvider.GetText());

	public IEnumerable<string> Parse(string text)
	{
		if (delimiter == openQuote || delimiter == closeQuote)
			throw new ArgumentException("Delimiter cannot be the same as the quotes.");

		int size = text.Length;
		int delimiterSize = delimiter.Length;
		int openQuoteSize = openQuote.Length;
		int closeQuoteSize = closeQuote.Length;
		int index = 0;
		bool inQuote = false;
		int tokenStartIndex = 0;

		while (index <= size - 1)
		{
			if (!inQuote && (text.SafeSubstring(index, openQuoteSize) == openQuote))
			{
				// Enter quotes.
				inQuote = true;
				index += openQuoteSize - 1;
			}
			else if (inQuote && (text.SafeSubstring(index, closeQuoteSize) == closeQuote))
			{
				inQuote = false;
				index += closeQuoteSize - 1;
			}
			else if (!inQuote && (text.SafeSubstring(index, delimiterSize) == delimiter))
			{
				string token = text.SafeSubstring(tokenStartIndex, index - tokenStartIndex);
				yield return token;

				tokenStartIndex = index + delimiterSize;
				index += delimiterSize - 1;
			}

			index++;
		}

		if (inQuote)
			throw new ParseException("Unterminated quotation in input string.");

		string lastToken = text.SafeSubstring(tokenStartIndex, index - tokenStartIndex);
		yield return lastToken;
	}
}