C# port of my Java string library (https://github.com/jamiemansfield/string)

StringReader.cs

/*
 * This file is part of string, licensed under the MIT License (MIT).
 *
 * Copyright (c) Jamie Mansfield <https://www.jamiemansfield.me/>
 * Copyright (c) contributors
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

using System;

namespace AOC2020.Utils
{
    /// <summary>
    /// Reader for strings.
    /// </summary>
    public class StringReader
    {
        public StringReader(string source)
        {
            Source = source;
        }

        public string Source { get; }

        /// <summary>
        /// The length of the source string.
        /// </summary>
        public int Length => Source.Length;

        /// <summary>
        /// The index (position) of the character currently being read.
        /// </summary>
        public int Index { get; private set; }

        /// <summary>
        /// The count of remaining characters to be read from the source.
        /// </summary>
        public int Remaining => Length - Index;

        /// <summary>
        /// Establishes whether a character is available to be read in the given offset.
        /// </summary>
        /// <param name="offset">How many characters ahead of the index (defaults to 1)</param>
        /// <returns><code>true</code> if there is a character to read; <code>false</code> otherwise</returns>
        public bool Available(int offset = 1) => Index + offset <= Length;

        /// <summary>
        /// Advances the index by the given length.
        /// </summary>
        /// <param name="length">How much to advance by</param>
        public void Skip(int length) => Index += length;

        /// <summary>
        /// Gets the character at the index and offset, without incrementing the index.
        /// </summary>
        /// <param name="offset">How many characters ahead of the index (defaults to 0)</param>
        /// <returns>The character</returns>
        /// <exception cref="ArgumentOutOfRangeException">If <paramref name="offset"/> is out of range</exception>
        public char Peek(int offset = 0) => Source[Index + Verify(offset)];

        /// <summary>
        /// Gets the character at the index and offset, incrementing the index.
        /// </summary>
        /// <param name="offset">How many characters ahead of the index (defaults to 0)</param>
        /// <returns>The character</returns>
        /// <exception cref="ArgumentOutOfRangeException">If <paramref name="offset"/> is out of range</exception>
        public char Advance(int offset = 0) => Source[(Index += Verify(offset) + 1) - 1];

        /// <summary>
        /// Gets a substring from the source.
        /// </summary>
        /// <param name="start">The starting index</param>
        /// <param name="end">The ending index</param>
        /// <returns>The substring</returns>
        public string Substring(int start, int end) => Source.Substring(start, end - start);

        private int Verify(int offset)
        {
            if (Available(offset)) return offset;
            throw new ArgumentOutOfRangeException(nameof(offset), "No character available");
        }
    }
}