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SergiiVlasiuk's solution

to ETL in the Scala Track

Published at Aug 17 2019 · 0 comments
Instructions
Test suite
Solution

We are going to do the Transform step of an Extract-Transform-Load.

ETL

Extract-Transform-Load (ETL) is a fancy way of saying, "We have some crufty, legacy data over in this system, and now we need it in this shiny new system over here, so we're going to migrate this."

(Typically, this is followed by, "We're only going to need to run this once." That's then typically followed by much forehead slapping and moaning about how stupid we could possibly be.)

The goal

We're going to extract some scrabble scores from a legacy system.

The old system stored a list of letters per score:

  • 1 point: "A", "E", "I", "O", "U", "L", "N", "R", "S", "T",
  • 2 points: "D", "G",
  • 3 points: "B", "C", "M", "P",
  • 4 points: "F", "H", "V", "W", "Y",
  • 5 points: "K",
  • 8 points: "J", "X",
  • 10 points: "Q", "Z",

The shiny new scrabble system instead stores the score per letter, which makes it much faster and easier to calculate the score for a word. It also stores the letters in lower-case regardless of the case of the input letters:

  • "a" is worth 1 point.
  • "b" is worth 3 points.
  • "c" is worth 3 points.
  • "d" is worth 2 points.
  • Etc.

Your mission, should you choose to accept it, is to transform the legacy data format to the shiny new format.

Notes

A final note about scoring, Scrabble is played around the world in a variety of languages, each with its own unique scoring table. For example, an "E" is scored at 2 in the Māori-language version of the game while being scored at 4 in the Hawaiian-language version.

The Scala exercises assume an SBT project scheme. The exercise solution source should be placed within the exercise directory/src/main/scala. The exercise unit tests can be found within the exercise directory/src/test/scala.

To run the tests simply run the command sbt test in the exercise directory.

For more detailed info about the Scala track see the help page.

Source

The Jumpstart Lab team http://jumpstartlab.com

Submitting Incomplete Solutions

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EtlTest.scala

import org.scalatest.{Matchers, FunSuite}

/** @version 1.0.0 */
class EtlTest extends FunSuite with Matchers {

  test("a single letter") {
    Etl.transform(Map(1 -> Seq("A"))) should be(Map("a" -> 1))
  }

  test("single score with multiple letters") {
    pending
    Etl.transform(Map(1 -> Seq("A", "E", "I", "O", "U"))) should be(Map("a" -> 1,
      "e" -> 1, "i" -> 1, "o" -> 1, "u" -> 1))
  }

  test("multiple scores with multiple letters") {
    pending
    Etl.transform(Map(1 -> Seq("A", "E"), 2 -> Seq("D", "G"))) should be(Map("a" -> 1,
      "d" -> 2, "e" -> 1, "g" -> 2))
  }

  test("multiple scores with differing numbers of letters") {
    pending
    Etl.transform(Map(1 -> Seq("A", "E", "I", "O", "U", "L", "N", "R", "S", "T"),
      2 -> Seq("D", "G"), 3 -> Seq("B", "C", "M", "P"), 4 -> Seq("F", "H", "V", "W", "Y"),
      5 -> Seq("K"), 8 -> Seq("J", "X"), 10 -> Seq("Q", "Z"))) should be(Map("a" -> 1,
        "b" -> 3, "c" -> 3, "d" -> 2, "e" -> 1, "f" -> 4, "g" -> 2, "h" -> 4,
        "i" -> 1, "j" -> 8, "k" -> 5, "l" -> 1, "m" -> 3, "n" -> 1, "o" -> 1, 
        "p" -> 3, "q" -> 10, "r" -> 1, "s" -> 1, "t" -> 1, "u" -> 1, "v" -> 4,
        "w" -> 4, "x" -> 8, "y" -> 4, "z" -> 10))
  }
}
object Etl {
  def transform(intToStrings: Map[Int, Seq[String]]): Map[String, Int] = {
    intToStrings.flatMap { case (number, letters) =>
//      letters.map { letter => letter.toLowerCase -> number }
      letters.map( letter => letter.toLowerCase -> number )
    }
  }
}

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