csv.scala

package cats.parse
package examples

import cats.implicits._

import Parser.{char, charWhere, charsWhile, string1}

object Csv {

  def mkString(p: Parser1[Char]): Parser[String] =
    p.rep.map(_.mkString)

  val parser: Parser[Vector[Vector[String]]] = {

    val quote: Parser1[Unit] = char('"')
    val notQuote: Parser1[Char] = charWhere(_ != '"')
    val escapedQuote: Parser1[Char] = string1("\"\"").as('"')

    val standardField: Parser[String] =
      charsWhile(c => c != '"' && c != ',').string
    val quotedField : Parser[String] =
      quote *> mkString(notQuote orElse1 escapedQuote) <* quote
    val field: Parser[String] =
      quotedField orElse standardField

    val row: Parser[Vector[String]] =
      (field ~ (quote *> field).rep).map { case (x, xs) => (x :: xs).toVector }
    val lineBreak: Parser1[Unit] =
      string1("\r\n") orElse1 char('\n')
    val rows: Parser[Vector[Vector[String]]] =
      (row.with1 <* lineBreak).rep.map(_.toVector)

    rows
  }
}