Day 2

Mix.install([{:kino, github: "livebook-dev/kino"}])

Common

input = Kino.Input.textarea("Input file")

Part 1

# A: Rock
# B: Paper
# C: Scissors

# X: Rock
# Y: Paper
# Z: Scissors

# Values
# Rock: 1 point
# Paper: 2 points
# Scissors: 3 points

# Loss: 0
# Tie: 3 points
# Win: 6 points

defmodule RockPaperScissor do
  defp point_for_shape("X"), do: 1
  defp point_for_shape("Y"), do: 2
  defp point_for_shape("Z"), do: 3

  defp point_for_round("A", "X"), do: 3
  defp point_for_round("A", "Y"), do: 6
  defp point_for_round("A", "Z"), do: 0

  defp point_for_round("B", "X"), do: 0
  defp point_for_round("B", "Y"), do: 3
  defp point_for_round("B", "Z"), do: 6

  defp point_for_round("C", "X"), do: 6
  defp point_for_round("C", "Y"), do: 0
  defp point_for_round("C", "Z"), do: 3

  def points_for_round([them, me]) do
    point_for_shape(me) + point_for_round(them, me)
  end
end

input
|> Kino.Input.read()
|> String.split("\n", trim: true)
|> Enum.map(fn round ->
  round
  |> String.split(" ", trim: true)
  |> RockPaperScissor.points_for_round()
end)
|> Enum.sum()

Part 2

# A: Rock
# B: Paper
# C: Scissors

# X: Need to lose
# Y: Need to draw
# Z: Need to Win

# Values
# Rock: 1 point
# Paper: 2 points
# Scissors: 3 points

# Loss: 0
# Tie: 3 points
# Win: 6 points

defmodule RockPaperScissor do
  defp point_for_round_result("X"), do: 0
  defp point_for_round_result("Y"), do: 3
  defp point_for_round_result("Z"), do: 6

  # Scissor
  defp point_for_shape_to_play("A", "X"), do: 3
  # Rock
  defp point_for_shape_to_play("A", "Y"), do: 1
  # Paper
  defp point_for_shape_to_play("A", "Z"), do: 2

  # Rock
  defp point_for_shape_to_play("B", "X"), do: 1
  # Paper
  defp point_for_shape_to_play("B", "Y"), do: 2
  # Scissor
  defp point_for_shape_to_play("B", "Z"), do: 3

  # Paper
  defp point_for_shape_to_play("C", "X"), do: 2
  # Scissor
  defp point_for_shape_to_play("C", "Y"), do: 3
  # Rock
  defp point_for_shape_to_play("C", "Z"), do: 1

  def points_for_round_result([them, result]) do
    point_for_round_result(result) + point_for_shape_to_play(them, result)
  end
end

input
|> Kino.Input.read()
|> String.split("\n", trim: true)
|> Enum.map(fn round ->
  round
  |> String.split(" ", trim: true)
  |> RockPaperScissor.points_for_round_result()
end)
|> Enum.sum()