day 2 part 1

lib/aoc_runner.ex

@@ -8,10 +8,9 @@ defmodule AOCRunner do
     Enum.reduce_while(
       {nil, advent.init_state()},
       fn line, acc -> line
-        |> advent.to_command()
+        |> then(fn line ->
-        |> then(fn command ->
             {u, state} = acc
-            {u, advent.apply_command(command, state)}
+            {u, advent.execute(line, state)}
           end)
         |> then(fn {u, s} ->
             if (line |> is_empty()) && (u |> is_empty()) do

lib/day2.ex

@@ -0,0 +1,101 @@
+defmodule Day2 do
+  def init_state() do
+    score_with_points(0)
+  end
+
+  defp score_with_points(p) do
+    %{score: p}
+  end
+
+  defp parse_match(line) do
+    [p1, p2] = String.split(line, " ") |> Enum.map(&String.trim/1)
+    match = parse_match(p1, p2)
+
+    match
+  end
+
+  defp parse_match(left, right) do
+    {parse_move(left, :left), parse_move(right, :right)}
+  end
+
+  defp parse_move(move, side) do
+    case side do
+      :left -> case move do
+        "A" -> :rock
+        "B" -> :paper
+        "C" -> :scissors
+      end
+      :right -> case move do
+        "X" -> :rock
+        "Y" -> :paper
+        "Z" -> :scissors
+      end
+    end
+  end
+
+  defp points_from_player_move(match) do
+    {_, player_move} = match
+
+    case player_move do
+      :rock -> 1
+      :paper -> 2
+      :scissors -> 3
+    end
+  end
+
+  defp sort_(a, b) do
+    if a == b do
+      0
+    else
+      case a do
+        :rock -> case b do
+          :paper -> -1
+          :scissors -> 1
+        end
+        :paper -> case b do
+          :rock -> 1
+          :scissors -> -1
+        end
+        :scissors -> case b do
+          :rock -> -1
+          :paper -> 1
+        end
+      end
+    end
+  end
+
+  defp outcome(match) do
+    {opponent, player} = match
+    case sort_(player, opponent) do
+      1 -> :win
+      0 -> :draw
+      -1 -> :loss
+    end
+  end
+
+  defp points_from_outcome(match) do
+    case outcome(match) do
+      :win -> 6
+      :draw -> 3
+      :loss -> 0
+    end
+  end
+
+  def execute(line, state) do
+    if line |> String.trim() |> String.length == 0 do
+      state
+    else
+      match = parse_match(line)
+      
+      score_with_points(
+        state.score + 
+        points_from_player_move(match) +
+        points_from_outcome(match))
+
+    end
+  end
+
+  def get_answer(state) do
+    state.score
+  end
+end

main.exs

@@ -1 +1 @@
-AOCRunner.run(Day1)
+AOCRunner.run(Day2)