defmodule AOC.Day8 do
  use AOC.Day, day: 8, debug: true

  def parse_input(lines) do
    Enum.map(lines, fn line ->
      line
      |> String.split("", trim: true)
      |> Enum.map(&String.to_integer/1)
    end)
  end

  def part1(rows) do
    rows = with_index(rows)

    cols = Enum.zip(rows) |> Enum.map(&Tuple.to_list/1)
    rrows = Enum.map(rows, &Enum.reverse/1)
    rcols = Enum.map(cols, &Enum.reverse/1)

    [rows, cols, rrows, rcols]
    |> Enum.map(&count_visible/1)
    |> Enum.reduce(&MapSet.union/2)
    |> Enum.count()
  end

  def part2(rows) do
    rows
  end

  def with_index(rows) do
    Enum.with_index(rows, fn row, y ->
      Enum.with_index(row, fn el, x ->
        %{height: el, x: x, y: y}
      end)
    end)
  end

  def count_visible(rows) do
    rows
    |> Enum.map(&count_visible_row/1)
    |> Enum.map(&elem(&1, 0))
    |> Enum.reduce(&MapSet.union/2)
  end

  def count_visible_row(row) do
    Enum.reduce(row, {MapSet.new(), -1}, fn
      %{height: h, x: x, y: y}, {trees, highest} when h > highest ->
        {MapSet.put(trees, {x, y}), h}

      _, acc ->
        acc
    end)
  end
end