How to implement complexed custom sort?

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6

And I’ve kind of came up with some way: implementing a custom sort Protocol may do.

defprotocol ChessSorter do
  @spec asc(any, any) :: boolean
  def asc(_, _)
end

defmodule Coordinate do
  defstruct [:x, :y]

  defimpl ChessSorter, for: __MODULE__ do
    def asc(%{x: x1, y: y1}, %{x: x2, y: y2}) when x1 == x2, do: y1 <= y2
    def asc(%{x: x1}, %{x: x2}), x1 <= x2
  end
end

defmodule Piece do
  defstruct [:type]

  defimpl ChessSorter, for: __MODULE__ do
    @types %{
      Pawn => 1,
      Knight => 2,
      Bishop => 3,
      Rook => 4,
      Queen => 5,
      King => 6,
    }

    def asc(%{type: t1}, %{tpe: t2}), do: @types[t1] <= @types[t2]
  end
end

defmodule Fighter
  defstruct [ :owner, :piece, :position ]

  defimpl ChessSorter, for: __MODULE__ do
    def asc(
          %{owner: o1, piece: p2, position: pos1},
          %{owner: o2, piece: p2, position: pos2}
        )
        when o1 == o2 and p1 == p2,
        do: ChessSorter.asc(pos1, pos2)

    def asc(%{owner: o1, piece: p2}, %{owner: o2, piece: p2}) when o1 == o2,
      do: ChessSorter.asc(p1, p2)

    def asc(%{owner: :opponent}, %{owner: :player}), do: false
    def asc(%{owner: :player}, %{owner: :opponent}), do: true
  end
end

And then : fighters |> Enum.sort(&ChessSorter.asc/2). So this recursively does sorting down to basic Kernel.<= s.

But I am afraid this may be veery slow. :disappointed: Is it?