Day 2

Mix.install([
  {:kino, "~> 0.5.0"}
])

input = Kino.Input.textarea("Paste input here:")

Part 1

opponent_map = %{"A" => :rock, "B" => :paper, "C" => :scissor}
elf_map = %{"X" => :rock, "Y" => :paper, "Z" => :scissor}
choice_point = %{rock: 1, paper: 2, scissor: 3}

play_result = fn
  :rock, :scissor ->
    6

  :scissor, :paper ->
    6

  :paper, :rock ->
    6

  x, x ->
    3

  _, _ ->
    0
end

input
|> Kino.Input.read()
|> String.split("\n", trim: true)
|> Enum.map(fn line ->
  [opponent, mine] = String.split(line, " ")
  opponent = opponent_map[opponent]
  mine = elf_map[mine]

  play_result.(mine, opponent) + choice_point[mine]
end)
|> Enum.sum()

Part 2

opponent_map = %{"A" => :rock, "B" => :paper, "C" => :scissor}
elf_map = %{"X" => :lose, "Y" => :draw, "Z" => :win}
result_point = %{win: 6, draw: 3, lose: 0}
choice_point = %{rock: 1, paper: 2, scissor: 3}

should_play = fn
  :win, :scissor ->
    :rock

  :win, :paper ->
    :scissor

  :win, :rock ->
    :paper

  :lose, :scissor ->
    :paper

  :lose, :paper ->
    :rock

  :lose, :rock ->
    :scissor

  :draw, x ->
    x
end

input
|> Kino.Input.read()
|> String.split("\n", trim: true)
|> Enum.map(fn line ->
  [opponent, mine] = String.split(line, " ")
  opponent = opponent_map[opponent]
  elf_result = elf_map[mine]
  mine = should_play.(elf_result, opponent)

  result_point[elf_result] + choice_point[mine]
end)
|> Enum.sum()