CsvParser.cs

using System.Collections.Generic;
using System.IO;
using System.Text;
using static ParsecSharp.Parser;
using static ParsecSharp.Text;

namespace ParsecSharp.Examples;

// CSV parser, fairly compliant with RFC4180
public class CsvParser
{
    public static IParser<char, IReadOnlyCollection<string[]>> Parser { get; } = CreateParser();

    private static IParser<char, IReadOnlyCollection<string[]>> CreateParser()
    {
        // COMMA = %x2C ; == ','
        var comma = Char(',');

        // DQUOTE = %x22 ; == '"'
        var dquote = Char('"');

        // TEXTDATA = %x20-21 / %x23-2B / %x2D-7E ; == CHAR except ( COMMA / DQUOTE / CTL )
        // According to RFC, only ASCII characters are accepted, but this has been extended to include arbitrary characters.
        // Any characters except (comma / double quote / control characters, including newline)
        var textChar = Any().Except(comma, dquote, ControlChar());

        // escaped = DQUOTE *( TEXTDATA / COMMA / CR / LF / 2DQUOTE ) DQUOTE
        // Field value enclosed in double quotes.
        // Unlike the original definition, supported newline characters are only LF and CRLF.
        var escapedField =
            Many(Choice(textChar, comma, EndOfLine(), dquote.Right(dquote)))
                .Between(dquote)
                .AsString();

        // non-escaped = *TEXTDATA
        var nonEscapedField = Many(textChar).AsString();

        // field = ( escaped / non-escaped )
        var field = escapedField | nonEscapedField;

        // record = field *( COMMA field )
        var record = field.SeparatedBy1(comma).ToArray();

        // file = [header CRLF] record *( CRLF record ) [CRLF]
        // In this implementation the header and record are treated as the same.
        // Unlike the RFC definition, this requires trailing newline at the last record of the input.
        // *( record ( LF / CRLF ) )
        var csv = record.EndBy(EndOfLine());

        var parser = csv.End();

        return parser;
    }

    public IResult<char, IReadOnlyCollection<string[]>> Parse(string csv)
        => Parser.Parse(csv);

    public IResult<char, IReadOnlyCollection<string[]>> Parse(Stream csv)
        => Parser.Parse(csv);

    public IResult<char, IReadOnlyCollection<string[]>> Parse(Stream csv, Encoding encoding)
        => Parser.Parse(csv, encoding);
}