Clean up code. Add a way to compare scores.

poker_ex/lib/poker_ex/card.ex

@@ -1,17 +1,14 @@
 defmodule PokerEx.Card do
-  @doc ~S"""
-  Holds functions that operate and symbolise a playing card.
-  """
-
   alias __MODULE__
 
   @valid_suits [:spades, :hearts, :diamonds, :clubs]
 
   @type suit() :: :hearts | :diamonds | :clubs | :spades
   @type rank() :: integer() | :jack | :queen | :king | :ace
-  @type t() :: %Card{suit: suit(), rank: rank()}
 
-  defstruct [:suit, :rank]
+  @type t() :: %Card{suit: suit(), rank: rank()}
+  defstruct suit: :required,
+            rank: :required
 
   defguard is_valid_suit(suit) when suit in @valid_suits
 
@@ -19,6 +16,17 @@ defmodule PokerEx.Card do
            when (is_integer(rank) and 2 <= rank and rank <= 10) or
                   rank in [:jack, :queen, :king, :ace]
 
+  @spec rank_to_number(rank()) :: integer()
+  def rank_to_number(rank) do
+    case rank do
+      :jack -> 11
+      :queen -> 12
+      :king -> 13
+      :ace -> 14
+      _ -> rank
+    end
+  end
+
   @doc ~S"""
   Checks if a given card is valid. To be valid, it should be the card
   string with a valid suit and rank, which are specified as module types.
@@ -80,19 +88,11 @@ defmodule PokerEx.Card do
 
   @spec compare(Card.t(), Card.t()) :: :lt | :eq | :gt
   def compare(first, second) do
-    case [first.rank, second.rank]
-         |> Enum.map(
-           &case &1 do
-             :jack -> 11
-             :queen -> 12
-             :king -> 13
-             :ace -> 14
-             n -> n
-           end
-         ) do
-      [f, s] when f < s -> :lt
-      [f, s] when f == s -> :eq
-      [f, s] when f > s -> :gt
+    [f_rank, s_rank] = [first.rank, second.rank] |> Enum.map(&rank_to_number/1)
+    cond do
+      f_rank < s_rank -> :lt
+      f_rank == s_rank -> :eq
+      f_rank > s_rank -> :gt
     end
   end
 

poker_ex/lib/poker_ex/combination.ex

@@ -1,5 +1,6 @@
 defmodule PokerEx.Combination do
-  alias PokerEx.Card, as: Card
+  import Bitwise
+  alias PokerEx.Card
 
   @type high_card() :: {:high_card, Card.t()}
   @type pair() :: {:pair, Card.t()}
@@ -24,20 +25,49 @@ defmodule PokerEx.Combination do
           | straight_flush()
           | royal_flush()
 
+  @spec means_to_number(score()) :: integer()
+  defp means_to_number({:high_card, %Card{rank: rank}}), do: Card.rank_to_number(rank)
+
+  defp means_to_number({:pair, %Card{rank: rank}}), do: Card.rank_to_number(rank)
+
+  defp means_to_number({:two_pair, {%Card{rank: rank1}, %Card{rank: rank2}}}),
+    do: [rank1, rank2] |> Enum.map(&Card.rank_to_number/1) |> Enum.sum()
+
+  defp means_to_number({:three_of_a_kind, %Card{rank: rank}}), do: Card.rank_to_number(rank)
+
+  defp means_to_number({:straight, {_begin, final}}), do: Card.rank_to_number(final)
+
+  defp means_to_number({:full_house, {%Card{rank: rank1}, %Card{rank: rank2}}}),
+    do: Card.rank_to_number(rank1) <<< (4 + Card.rank_to_number(rank2))
+
+  defp means_to_number({:four_of_a_kind, %Card{rank: rank}}), do: Card.rank_to_number(rank)
+
+  defp means_to_number({:straight_flush, {_suit, _begin, final}}), do: Card.rank_to_number(final)
+
+  defp means_to_number(_score), do: 0
+
+  @spec score_to_number(score()) :: integer()
+  defp score_to_number({score, means}) do
+    case score do
+      :high_card -> 0x000
+      :pair -> 0x100
+      :two_pair -> 0x200
+      :three_of_a_kind -> 0x300
+      :straight -> 0x400
+      :flush -> 0x500
+      :full_house -> 0x600
+      :four_of_a_kind -> 0x700
+      :straight_flush -> 0x800
+      :royal_flush -> 0x900
+    end + means_to_number({score, means})
+  end
+
   @spec straight?(ranks: [Card.rank()]) :: boolean
   defp straight?(ranks) when length(ranks) < 5, do: false
 
   defp straight?(ranks) do
     ranks
-    |> Enum.map(
-      &case &1 do
-        :jack -> 11
-        :queen -> 12
-        :king -> 13
-        :ace -> 14
-        n -> n
-      end
-    )
+    |> Enum.map(&Card.rank_to_number/1)
     |> Enum.chunk_every(2, 1, :discard)
     |> Enum.map(
       &case &1 do
@@ -142,6 +172,51 @@ defmodule PokerEx.Combination do
     end
   end
 
+  @doc ~S"""
+  Compares two scores and returns their equality.
+
+  When players have the same score, the one with the highest means for
+  this score (i.e., the cards with which the score is obtained) is the winner.
+
+  ## Examples
+
+      iex> import PokerEx.Card
+      iex> hand1 = [~p"S3", ~p"C4", ~p"H5", ~p"D6", ~p"C7"]
+      iex> hand2 = [~p"C4", ~p"H5", ~p"D6", ~p"C7", ~p"S8"]
+      iex> [score1, score2] = [hand1, hand2] |> Enum.map(&PokerEx.Combination.evaluate_hand/1)
+      iex> [score1, score2]
+      [{:straight, {3, 7}}, {:straight, {4, 8}}]
+      iex> compare(score1, score2)
+      :lt
+
+      iex> import PokerEx.Card
+      iex> hand1 = [~p"S3", ~p"S5", ~p"S6", ~p"S7", ~p"S8"]
+      iex> hand2 = [~p"C4", ~p"H5", ~p"D6", ~p"C7", ~p"S8"]
+      iex> [score1, score2] = [hand1, hand2] |> Enum.map(&PokerEx.Combination.evaluate_hand/1)
+      iex> [score1, score2]
+      [{:flush, :spades}, {:straight, {4, 8}}]
+      iex> compare(score1, score2)
+      :gt
+
+      iex> import PokerEx.Card
+      iex> hand1 = [~p"S3", ~p"C4", ~p"H5", ~p"D6", ~p"C7"]
+      iex> hand2 = [~p"S3", ~p"C4", ~p"H5", ~p"D6", ~p"C7"]
+      iex> [score1, score2] = [hand1, hand2] |> Enum.map(&PokerEx.Combination.evaluate_hand/1)
+      iex> [score1, score2]
+      [{:straight, {3, 7}}, {:straight, {3, 7}}]
+      iex> compare(score1, score2)
+      :eq
+  """
+  @spec compare(score(), score()) :: :lt | :eq | :gt
+  def compare(score1, score2) do
+    [s1, s2] = [score1, score2] |> Enum.map(&score_to_number/1)
+    cond do
+      s1 < s2 -> :lt
+      s1 == s2 -> :eq
+      s1 > s2 -> :gt
+    end
+  end
+
   @doc ~S"""
   Finds the highest combination that can be made using the hand and the cards
   that are present.
@@ -155,19 +230,19 @@ defmodule PokerEx.Combination do
       iex> import PokerEx.Card
       iex> PokerEx.Combination.evaluate_hand [~p"C10", ~p"CJ", ~p"CQ", ~p"CK", ~p"CA"]
       {:royal_flush, :clubs}
-  
+
       iex> import PokerEx.Card
       iex> PokerEx.Combination.evaluate_hand [~p"CA", ~p"CA", ~p"CA", ~p"CK", ~p"CK"]
       {:full_house, {%PokerEx.Card{suit: :clubs, rank: :ace}, %PokerEx.Card{suit: :clubs, rank: :king}}}
-      
+
       iex> import PokerEx.Card
       iex> PokerEx.Combination.evaluate_hand [~p"CA", ~p"CA", ~p"CA", ~p"D2", ~p"D3"]
       {:three_of_a_kind, %PokerEx.Card{suit: :clubs, rank: :ace}}
-      
+
       iex> import PokerEx.Card
       iex> PokerEx.Combination.evaluate_hand [~p"CA", ~p"CA", ~p"D2", ~p"D3", ~p"D4"]
       {:pair, %PokerEx.Card{suit: :clubs, rank: :ace}}
-      
+
       iex> import PokerEx.Card
       iex> PokerEx.Combination.evaluate_hand [~p"CA", ~p"CK", ~p"DJ", ~p"D2", ~p"H7"]
       {:high_card, %PokerEx.Card{suit: :clubs, rank: :ace}}