using System;
using System.Text;

namespace Upsilon.Text
{
    public class SourceText
    {
        private readonly string[] _text;

        public SourceText(string text)
        {
            _text = text.Split('\n');
        }

        public string GetSpan(int startLine, int startPosition, int endLine, int endPosition)
        {
            if (startPosition < 0) startPosition = 0;
            if (startLine >= _text.Length)
                return string.Empty;
            if (startLine == endLine)
            {
                if (endPosition > _text[startLine].Length) endPosition = _text[startLine].Length;
                return _text[startLine].Substring(startPosition, endPosition - startPosition);
            }
            var sb = new StringBuilder();
            sb.Append(_text[startLine].Substring(startPosition));
            for (var i = startLine + 1; i < endLine; i++)
            {
                sb.Append(_text[i]);
            }

            if (endPosition > _text[endLine].Length) endPosition = _text[endLine].Length;
            sb.Append(_text[endLine].Substring(0, endPosition));
            return sb.ToString();
        }

        public string GetLine(int linePosition)
        {
            return _text[linePosition];

        }

        public string GetSpan(TextSpan span)
        {
            return GetSpan(span.StartLine, span.StartPosition, span.EndLine, span.EndPosition);
        }
    }
}