using System;
using System.Collections.Generic;
using System.Text;

namespace StgSharp.Script
{
    public static class CodeLineHelper
    {
        public static string SliceAndTrim(this string line, int startIndex, int length)
        {
            if (line == null) throw new ArgumentNullException(nameof(line));
            if (startIndex < 0 || startIndex >= line.Length)
                throw new ArgumentOutOfRangeException(nameof(startIndex));
            if (length < 0 || startIndex + length > line.Length)
                throw new ArgumentOutOfRangeException(nameof(length));

            ReadOnlySpan<char> sourceSpan = line.AsSpan();
            ReadOnlySpan<char> subSpan = sourceSpan.Slice(startIndex, length);

            int start = 0;
            while (start < subSpan.Length && char.IsWhiteSpace(subSpan[start]))
            {
                start++;
            }
            int end = subSpan.Length - 1;
            while (end >= start && char.IsWhiteSpace(subSpan[end]))
            {
                end--;
            }
            if (start > end)
            {
                return string.Empty;
            }
            int finalLength = end - start + 1;

            return new string(subSpan.Slice(start, finalLength));
        }

        public static string SliceAndTrim(this string line, int startIndex)
        {
            if (line == null) throw new ArgumentNullException(nameof(line));
            if (startIndex < 0 || startIndex >= line.Length)
                throw new ArgumentOutOfRangeException(nameof(startIndex));

            ReadOnlySpan<char> sourceSpan = line.AsSpan();
            ReadOnlySpan<char> subSpan = sourceSpan.Slice(startIndex);

            int start = 0;
            while (start < subSpan.Length && char.IsWhiteSpace(subSpan[start]))
            {
                start++;
            }
            int end = subSpan.Length - 1;
            while (end >= start && char.IsWhiteSpace(subSpan[end]))
            {
                end--;
            }
            if (start > end)
            {
                return string.Empty;
            }
            int finalLength = end - start + 1;

            return new string(subSpan.Slice(start, finalLength));
        }
    }
}