defmodule CobblemonUi.CobblemonFS.PartyStore do
  @moduledoc """
  Parses a player's party storage `.dat` file.

  Party layout:
    Root -> party -> slot0..slot5
  """

  alias CobblemonUi.CobblemonFS.{NBT, Pokemon}

  @party_slots 6

  @doc """
  Reads and parses a party `.dat` file at the given path.

  Returns `{:ok, [pokemon | nil]}` or `{:error, reason}`.
  """
  @spec parse(String.t()) :: {:ok, list(map() | nil)} | {:error, term()}
  def parse(path) do
    with {:ok, data} <- File.read(path),
         {:ok, {_name, root}} <- NBT.decode(data) do
      slots = for i <- 0..(@party_slots - 1), do: Pokemon.normalize(Map.get(root, "Slot#{i}"))
      {:ok, slots}
    else
      {:error, :enoent} -> {:error, :not_found}
      {:error, reason} -> {:error, {:corrupt_data, reason}}
    end
  end
end