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makafakachka's solution

to ETL in the Delphi Pascal Track

Published at May 25 2019 · 0 comments
Instructions
Test suite
Solution

Note:

This exercise has changed since this solution was written.

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.

Testing

In order to run the tests for this track, you will need to install DUnitX. Please see the installation instructions for more information.

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For example, if you're submitting ubob.pas for the Bob exercise, the submit command would be something like exercism submit <path_to_exercism_dir>/delphi/bob/ubob.pas.

Source

The Jumpstart Lab team http://jumpstartlab.com

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uETLtests.pas

unit uETLtests;

interface
uses
  System.Generics.Collections, DUnitX.TestFramework;

const
  CanonicalVersion = '1.0.0';

type

  [TestFixture]
  testETL = class(TObject)
  private
    procedure CompareDictionaries(Expected, Actual: TDictionary<String, integer>);
  public
    [Test]
    procedure Validate_CompareDictionaries;

    [Test]
//    [Ignore('Comment the "[Ignore]" statement to run the test')]
    procedure A_single_letter;

    [Test]
    [Ignore]
    procedure Single_score_with_multiple_letters;

    [Test]
    [Ignore]
    procedure Multiple_scores_with_multiple_letters;

    [Test]
    [Ignore]
    procedure Multiple_scores_with_differing_numbers_of_letters;
  end;

implementation
uses SysUtils, uETL;

procedure testETL.CompareDictionaries(Expected, Actual: TDictionary<String, Integer>);
var expectedPair: TPair<string, Integer>;
begin
  Assert.AreEqual(Expected.Count, Actual.Count);
  for expectedPair in Expected do
  begin
    Assert.IsTrue(Actual.ContainsKey(expectedPair.Key));
    Assert.AreEqual(expectedPair.Value, Actual[expectedPair.Key]);
  end;
end;

procedure testETL.Validate_CompareDictionaries;
var expected, actual: TDictionary<String, integer>;
begin
  expected := TDictionary<String, integer>.Create;
  expected.Add('r',5);
  expected.Add('a',10);
  expected.Add('n',15);
  expected.Add('d',20);
  expected.Add('o',25);
  expected.Add('m',30);

  actual := TDictionary<String, Integer>.create(expected);

  CompareDictionaries(expected, actual);
end;

procedure testETL.A_single_letter;
var aList: TList<string>;
    old: TDictionary<integer, TList<string>>;
    expected: TDictionary<string, integer>;
begin
  aList := TList<string>.Create;
  aList.Add('A');
  old := TDictionary<integer, TList<string>>.Create;
  old.Add(1, aList);

  expected := TDictionary<string, integer>.Create;
  expected.Add('a', 1);

  CompareDictionaries(expected, ETL.Transform(old));
end;

procedure testETL.Single_score_with_multiple_letters;
var aList: TList<string>;
    old: TDictionary<integer, TList<string>>;
    expected: TDictionary<string, integer>;
begin
  aList := TList<string>.create;
  aList.AddRange(['A','E','I','O','U']);
  old := TDictionary<integer, TList<string>>.Create;
  old.Add(1, aList);

  expected := TDictionary<string, integer>.Create;
  expected.Add('a',1);
  expected.Add('e',1);
  expected.Add('i',1);
  expected.Add('o',1);
  expected.Add('u',1);

  CompareDictionaries(expected, ETL.Transform(old));
end;

procedure testETL.Multiple_scores_with_multiple_letters;
var aList: TList<string>;
    old: TDictionary<integer, TList<string>>;
    expected: TDictionary<string, integer>;
begin
  aList := TList<string>.Create;
  aList.Add('A');
  aList.Add('E');
  old := TDictionary<integer, TList<string>>.Create;
  old.Add(1, aList);
  aList := TList<string>.Create;
  aList.Add('D');
  aList.Add('G');
  old.Add(2, aList);

  expected := TDictionary<string, integer>.Create;
  expected.Add('a',1);
  expected.Add('d',2);
  expected.Add('e',1);
  expected.Add('g',2);

  CompareDictionaries(expected, ETL.Transform(old));
end;

procedure testETL.Multiple_scores_with_differing_numbers_of_letters;
var aList: TList<string>;
    old: TDictionary<integer, TList<string>>;
    expected: TDictionary<string, integer>;
begin
  aList := TList<string>.Create;
  aList.AddRange(['A','E','I','O','U','L','N','R','S','T']);
  old := TDictionary<integer, TList<string>>.Create;
  old.Add(1, aList);

  aList := TList<string>.Create;
  aList.AddRange(['D','G']);
  old.Add(2, aList);

  aList := TList<string>.Create;
  aList.AddRange(['B','C','M','P']);
  old.Add(3, aList);

  aList := TList<string>.Create;
  aList.AddRange(['F','H','V','W','Y']);
  old.Add(4, aList);

  aList := TList<string>.Create;
  aList.Add('K');
  old.Add(5, aList);

  aList := TList<string>.Create;
  aList.AddRange(['J','X']);
  old.Add(8, aList);

  aList := TList<string>.Create;
  aList.AddRange(['Q','Z']);
  old.Add(10, aList);

  expected := TDictionary<string, integer>.Create;
  expected.Add('a',1);
  expected.Add('b',3);
  expected.Add('c',3);
  expected.Add('d',2);
  expected.Add('e',1);
  expected.Add('f',4);
  expected.Add('g',2);
  expected.Add('h',4);
  expected.Add('i',1);
  expected.Add('j',8);
  expected.Add('k',5);
  expected.Add('l',1);
  expected.Add('m',3);
  expected.Add('n',1);
  expected.Add('o',1);
  expected.Add('p',3);
  expected.Add('q',10);
  expected.Add('r',1);
  expected.Add('s',1);
  expected.Add('t',1);
  expected.Add('u',1);
  expected.Add('v',4);
  expected.Add('w',4);
  expected.Add('x',8);
  expected.Add('y',4);
  expected.Add('z',10);

  CompareDictionaries(expected, ETL.Transform(old));
end;

initialization
  TDUnitX.RegisterTestFixture(testETL);
end.
unit uETL;

interface

uses
  System.Generics.Collections;

type
  ETL = class
    class function Transform(
      old: TDictionary<Integer, TList<String>>): TDictionary<String, Integer>;
  end;

implementation

uses
  System.Sysutils;

{ ETL }

class function ETL.Transform(
  old: TDictionary<Integer, TList<String>>): TDictionary<String, Integer>;

  procedure InsertToDict(letters: TList<String>; score: Integer);
  begin
    for var letter in letters do
      Result.Add(letter.ToLower, score);
  end;

begin
  Result := TDictionary<String, Integer>.Create;
  for var score in old.Keys do
    InsertToDict(old[score], score);
end;

end.

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