using System;
using System.Collections.Generic;

namespace DrillTools
{
    /// <summary>
    /// 钻带文本行结构，保留原始文本和行尾换行符。
    /// </summary>
    internal readonly record struct DrillTapeLine(string Text, string LineEnding);

    /// <summary>
    /// 钻带行解析器，将钻带文本按行拆分，保留原始换行符。
    /// </summary>
    internal static class DrillTapeLineParser
    {
        private static readonly char[] LineEndChars = { '\r', '\n' };

        /// <summary>
        /// 将文本内容按行拆分，保留每行的换行符。
        /// </summary>
        public static List<DrillTapeLine> SplitLines(string content)
        {
            var lines = new List<DrillTapeLine>();
            int index = 0;

            while (index < content.Length)
            {
                int lineEndIndex = content.IndexOfAny(LineEndChars, index);
                if (lineEndIndex < 0)
                {
                    lines.Add(new DrillTapeLine(content[index..], string.Empty));
                    return lines;
                }

                string text = content[index..lineEndIndex];
                string lineEnding;
                if (content[lineEndIndex] == '\r' && lineEndIndex + 1 < content.Length && content[lineEndIndex + 1] == '\n')
                {
                    lineEnding = "\r\n";
                    index = lineEndIndex + 2;
                }
                else
                {
                    lineEnding = content[lineEndIndex].ToString();
                    index = lineEndIndex + 1;
                }

                lines.Add(new DrillTapeLine(text, lineEnding));
            }

            if (content.Length == 0)
                lines.Add(new DrillTapeLine(string.Empty, string.Empty));

            return lines;
        }
    }
}