defmodule CobblemonUi.TierListScraper do
  @url "https://rankedboost.com/pokemon/tier-list/"
  @filename "pokemon_tier_list.json"

  def output_file do
    dir = System.get_env("CACHE_DIR", ".")
    Path.join(dir, @filename)
  end

  def run do
    with {:ok, html} <- fetch_page(),
         pokemon <- parse(html),
         :ok <- write_json(pokemon) do
      {:ok, pokemon}
    end
  end

  def fetch_page do
    case Req.get(@url) do
      {:ok, %Req.Response{status: 200, body: body}} -> {:ok, body}
      {:ok, %Req.Response{status: status}} -> {:error, {:http_error, status}}
      {:error, err} -> {:error, err}
    end
  end

  def parse(html) do
    html
    |> Floki.parse_document!()
    |> Floki.find(".pokemon-tier")
    |> Enum.map(&extract_pokemon/1)
  end

  defp extract_pokemon(node) do
    name =
      node
      |> Floki.find(".name")
      |> Floki.text()
      |> String.trim()

    tier =
      node
      |> Floki.find(".tier")
      |> Floki.text()
      |> String.trim()

    %{name: name, tier: tier}
  end

  def write_json(data) do
    json = Jason.encode!(data, pretty: true)
    File.write(output_file(), json)
  end

  # Returns a map of %{lowercase_name => tier} for fast lookup, or an empty map if unavailable.
  def load_tier_list do
    with {:ok, contents} <- File.read(output_file()),
         {:ok, entries} <- Jason.decode(contents) do
      Map.new(entries, fn %{"name" => name, "tier" => tier} ->
        {String.downcase(name), tier}
      end)
    else
      _ -> %{}
    end
  end
end