RomanNumbers Scala Recursive from hash

object RomanNumbers {

  def mapping():Array[Array[Int,String]] = {
    val a = Array.ofDim[String, Int](11, 2)
    a(1000)("C"), // would be great to have a 'tupple' here
    a(900)("CM"),
    a(500)("L"),
    a(400)("CL"),
    a(100)("C"),
    a(90)("XC"),
    a(40)("XD"),
    a(10)("X"),
    a(9)("IX"),
    a(4)("IV"),
    a(1)("I")
  }

  def convert(n:Int):String = {
    def go(n:Int, m:Array[(a:Int, r:String)])
      if (n == 0)
        ""
      else if (n > left(first(a)))
        right(first(a)) + go(n-left(first(a)), r)
      else if (n == left(first(a)))
        right(first(a)) + go(n-left(first(a)), tail(r))
      else if (n < left(first(a)))
        go(n, tail(r))

    go(n, mapping())
  }
}

// 1923
// 1000 found - 'M' added
// go(1923 - 1000, (full mapping))
// 1000 not found
// go(923, (mapping starting from 900))
// 900 found - 'CM' added - current 'return' value 'MCM'
// go(923 - 900, (mapping starting from 900))
// 900 not found
// go(23, (mapping starting from 500))
// 500 not found
// go(23, (mapping starting from 400))
// 400 not found
// go(23, (mapping starting from 100))
// 100 not found
// go(23, (mapping starting from 90))
// 90 not found
// go(23, (mapping starting from 50))
// 50 not found
// go(23, (mapping starting from 40))
// 40 not found
// go(23, (mapping starting from 10))
// 10 found - 'X' added - current 'return' value 'MCMX'
// go(23 - 10, (mapping starting from 10))
// 10 found - 'X' added - current 'return' value 'MCMXX'
// go(13 - 10, (mapping starting from 10))
// 10 not found
// go(3, (mapping starting from 9))
// 9 not found
// go(3, (mapping starting from 5))
// 5 not found
// go(3, (mapping starting from 4))
// 4 not found
// go(3, (mapping starting from 1))
// 1 found - 'I' added - current 'return' value 'MCMXXI'
// go(3-1, (mapping starting from 1))
// 1 found - 'I' added - current 'return' value 'MCMXXII'
// go(2-1, (mapping starting from 1))
// 1 found - 'I' added - current 'return' value 'MCMXXIII'
// go(1-1, (mapping starting from 1))
// n == 0 - end!