package it.vigtig.dm509.linearalgebra.dsl

import scala.util.parsing.combinator._

case class Coefficient(factor: Double, id: String)
case class Line(lhs: List[Coefficient], rhs: Double)

trait LinearSystemDSL extends JavaTokenParsers with RegexParsers {

  def num: Parser[Double] = floatingPointNumber ^^ (_.toDouble)
  def char: Parser[String] = """[a-zA-Z]""".r
  def id: Parser[String] = char ~ rep(char | floatingPointNumber) ^^ (x => x._1 + x._2.mkString)
  def op: Parser[String] = "+" | "-"
  def factor: Parser[Coefficient] = ((num ~ id) | id) ^^ {
    case (num: Double) ~ (id: String) => Coefficient(num, id)
    case id: String => Coefficient(1d, id)
  }
  def lhs: Parser[List[Coefficient]] = factor ~ rep(op ~ factor) ^^ (x => x._1 :: x._2.map {
    case "+" ~ f => f
    case "-" ~ Coefficient(f, id) => Coefficient(-f, id)
  })
  def line: Parser[Line] = lhs ~ "=" ~ num ^^ {
    case lhs ~ _ ~ rhs => Line(lhs, rhs)
  }
  def system: Parser[List[Line]] = rep(line)

}

object LinearSystemDSLTest extends App with LinearSystemDSL {

  val program =
    """
    2X + Y - Z = 8
    -3X - Y + 2Z = -11
    -2X + Y + 2Z = -3
    """

  val pr = parseAll(system, program).get.mkString("\n")
  println(parseAll(factor, "10.7X"))
  println(pr)

}