using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using NUnit.Framework;

namespace TableParser
{
    [TestFixture]
    public class QuotedFieldTaskTests
    {
        [TestCase("''", 0, "", 2)]
        [TestCase("'a'", 0, "a", 3)]
        [TestCase(@"""\\""", 0, @"\", 4)]
        [TestCase(@"hello world ""hello world 'hello'""", 12, "hello world 'hello'", 21)]
        public void Test(string line, int startIndex, string expectedValue, int expectedLength)
        {
            var actualToken = QuotedFieldTask.ReadQuotedField(line, startIndex);
            Assert.AreEqual(actualToken, new Token(expectedValue, startIndex, expectedLength));
        }
    }

    class QuotedFieldTask
    {
        public static Token ReadQuotedField(string line, int startIndex)
        {
            var newLine = new StringBuilder();
            var stopIndex = 0;
            var index = startIndex + 1;
            var length = 0;
            while (index < line.Length)
            {
                if (line[index] == '\\' && (line[index + 1] == '\"'
                    || line[index + 1] == '\''))
                {
                    if (line.Length - 1 == index + 1)
                        break;
                    newLine.Append(line[index + 1]);
                    index += 2;
                    length++;
                    continue;
                }
                if (line[index] == '\\')
                {
                    index++;
                    if (index >= line.Length)
                        break;
                }
                if (line[index] == line[startIndex])
                {
                    stopIndex = index;
                    break;
                }
                newLine.Append(line[index]);
                index++;
            }
            if (stopIndex == 0)
                length += line.Length - startIndex;
            else
                length += stopIndex - startIndex + 1;
            return new Token(newLine.ToString(), startIndex, length);
        }
    }
}