Day 17

Input

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

textarea = Kino.Input.textarea("Input:")

Common

defmodule Common do
  def parse_input(raw_input) do
    [x1, x2, y1, y2] =
      ~r/target area\: x=([-0-9]+)\.\.([-0-9]+), y=([-0-9]+)\.\.([-0-9]+)/
      |> Regex.run(raw_input, capture: :all_but_first)
      |> Enum.map(&String.to_integer/1)

    %TargetArea{x1: x1, x2: x2, y1: y1, y2: y2}
  end
end

defmodule Velocity do
  defstruct [:x, :y]

  def new(x, y), do: %__MODULE__{x: x, y: y}

  def drag(%__MODULE__{x: x, y: y}) when x < 0, do: %__MODULE__{x: x + 1, y: y - 1}
  def drag(%__MODULE__{x: x, y: y}) when x > 0, do: %__MODULE__{x: x - 1, y: y - 1}
  def drag(%__MODULE__{x: x, y: y}), do: %__MODULE__{x: x, y: y - 1}
end

defmodule Probe do
  defstruct [:x, :y, :velocity]

  def new(velocity) do
    %__MODULE__{x: 0, y: 0, velocity: velocity}
  end

  def step(%__MODULE__{x: x, y: y, velocity: velocity}) do
    x = x + velocity.x
    y = y + velocity.y
    velocity = Velocity.drag(velocity)

    %__MODULE__{x: x, y: y, velocity: velocity}
  end

  def in_target_area?(%__MODULE__{} = probe, %TargetArea{} = target_area) do
    probe.x in target_area.x1..target_area.x2 and
      probe.y in target_area.y1..target_area.y2
  end

  def under_target_area?(%__MODULE__{} = probe, %TargetArea{} = target_area) do
    probe.y < target_area.y1 and probe.y < target_area.y2
  end
end

defmodule TargetArea do
  defstruct [:x1, :x2, :y1, :y2]

  def distance_x(%__MODULE__{x1: x1, x2: x2}), do: min(abs(x1), abs(x2))
end

raw_input = Kino.Input.read(textarea)
input = Common.parse_input(raw_input)

Part 1

defmodule Part1 do
  def run(target_area) do
    IO.inspect(target_area)

    distance_x = TargetArea.distance_x(target_area) |> IO.inspect(label: :distance_x)
    velocity_x = floor(:math.sqrt(distance_x * 2)) |> IO.inspect(label: :velocity_x)
    max_y = 

  end
end

Part1.run(input)

Part 2

defmodule Part2 do
  def run(input) do
  end
end

Part2.run(input)