LehrerApp/LehrerApp.WebUntis/TabSeparatedTextReader.cs

using System.Text;

namespace LehrerApp.WebUntis;

internal static class TabSeparatedTextReader
{
    public static List<List<string>> ParseRows(string content, char separator)
    {
        var rows = new List<List<string>>();
        var row = new List<string>();
        var field = new StringBuilder();
        var inQuotes = false;

        for (var index = 0; index < content.Length; index++)
        {
            var character = content[index];
            if (character == '"')
            {
                if (inQuotes && index + 1 < content.Length && content[index + 1] == '"')
                {
                    field.Append('"');
                    index++;
                }
                else
                {
                    inQuotes = !inQuotes;
                }
                continue;
            }

            if (!inQuotes && character == separator)
            {
                row.Add(field.ToString());
                field.Clear();
                continue;
            }

            if (!inQuotes && character == '\n')
            {
                row.Add(field.ToString());
                rows.Add(row);
                row = [];
                field.Clear();
                continue;
            }

            if (!inQuotes && character == '\r') continue;
            field.Append(character);
        }

        row.Add(field.ToString());
        if (row.Count > 1 || !string.IsNullOrWhiteSpace(row[0])) rows.Add(row);
        return rows;
    }
}