defmodule Cartographer.Board do
  defstruct(
    tiles: %{},
    height: nil,
    width: nil
  )

  def new_board(height, width) do
    %__MODULE__{
      height: height,
      width: width,
    }
  end

  def in_bounds(%__MODULE__{:height => height, :width => width}, x, y) do
    x >= 0 and x < width and y >= 0 and y < height
  end

  def coordinate_range(center_x, center_y, range) do
    for x <- (center_x - range)..(center_x + range), y <- (center_y - range)..(center_y + range), do: {x, y}
  end

  def height(board), do: board.height
  def width(board), do: board.width

  def get(board), do: board

  def get(board, x, y) do
    Map.get(board.tiles, {x, y})
  end

  def get(board, center_x, center_y, range) do
    coordinate_range(center_x, center_y, range)
    |> Enum.filter(fn({x, y}) -> in_bounds(board, x, y) end)
    |> Enum.reduce(%{}, &(Map.put(&2, &1, Map.get(board.tiles, &1))))
  end

  def set(board, x, y, data) do
    in_bounds(board, x, y)
    |> _set(board, x, y, data)
  end

  defp _set(_in_bounds = true, board, x, y, data) do
    tiles = board.tiles
    |> Map.put({x, y}, data)

    board
    |> Map.put(:tiles, tiles)
  end

  defp _set(_not_in_bounds, board, _x, _y, _data), do: board

  def neighbors(board, center_x, center_y) do
    coordinate_range(center_x, center_y, 1)
    |> List.delete({center_x, center_y})
    |> Enum.filter(fn({x, y}) -> in_bounds(board, x, y) end)
    |> Enum.reduce(%{}, &(Map.put(&2, &1, Map.get(board.tiles, &1))))
  end
end