ammocpr/lib/ammoprices/scraping/retailers/natchez.ex

defmodule Ammoprices.Scraping.Retailers.Natchez do
  @moduledoc false
  @behaviour Ammoprices.Scraping.Scraper

  alias Ammoprices.Scraping.HttpClient
  alias Ammoprices.Scraping.TextDetector

  @slug_to_caliber %{
    "9mm-luger" => "9mm Luger",
    "45-acp" => "45 Auto",
    "380-acp" => "380 Auto",
    "40-sw" => "40 S&W",
    "38-special" => "38 Spl",
    "357-magnum" => "357 Mag",
    "10mm-auto" => "10mm Auto",
    "223-rem" => "223 Rem",
    "556-nato" => "5.56mm",
    "308-win" => "308 Win",
    "762x39" => "7.62x39mm",
    "30-06" => "30-06 Sprg",
    "300-blackout" => "300 Blk",
    "65-creedmoor" => "6.5 Creedmoor",
    "22-lr" => "22 LR",
    "22-wmr" => "22 WMR",
    "17-hmr" => "17 HMR",
    "12-gauge" => "12 Gauge",
    "16-gauge" => "16 Gauge",
    "20-gauge" => "20 Gauge"
  }

  @impl true
  def retailer_slug, do: "natchez"

  @impl true
  def category_url(_caliber), do: nil

  @impl true
  def parse_products(_), do: []

  @impl true
  def fetch(retailer, caliber) do
    case build_query(caliber.slug) do
      nil ->
        {:ok, []}

      query ->
        url = retailer.base_url <> "/graphql"

        case HttpClient.post_json(url, %{query: query}, [{"store", "default"}]) do
          {:ok, %{status: 200, body: body}} -> {:ok, parse_graphql_response(body)}
          {:ok, %{status: s}} -> {:error, "HTTP #{s}"}
          {:error, reason} -> {:error, reason}
        end
    end
  end

  def build_query(slug) do
    case Map.get(@slug_to_caliber, slug) do
      nil ->
        nil

      caliber_value ->
        escaped = escape_gql_string(caliber_value)

        """
        {
          products(
            search: "#{escaped}"
            filter: { caliber: { eq: "#{escaped}" } }
            pageSize: 48
            currentPage: 1
          ) {
            items {
              name sku url_key stock_status brand grain rounds case_material
              price_range { minimum_price { final_price { value } } }
            }
            total_count
            page_info { total_pages }
          }
        }
        """
    end
  end

  defp escape_gql_string(str) do
    str
    |> String.replace("\\", "\\\\")
    |> String.replace("\"", "\\\"")
    |> String.replace("\n", "\\n")
  end

  def parse_graphql_response(%{"data" => %{"products" => %{"items" => items}}}) do
    items
    |> Enum.map(&parse_item/1)
    |> Enum.reject(&is_nil/1)
  end

  def parse_graphql_response(_), do: []

  defp parse_item(item) do
    case extract_price(item) do
      {:ok, price_cents} ->
        round_count = parse_integer(item["rounds"])
        ppr = if round_count && round_count > 0, do: round(price_cents / round_count)
        name = item["name"]

        %{
          title: name,
          url: "/#{item["url_key"]}.html",
          brand: item["brand"],
          price_cents: price_cents,
          price_per_round_cents: ppr,
          grain_weight: parse_integer(item["grain"]),
          round_count: round_count,
          casing: parse_casing(item["case_material"]),
          subsonic: TextDetector.detect_subsonic(name),
          in_stock: item["stock_status"] == "IN_STOCK"
        }

      :error ->
        nil
    end
  end

  defp extract_price(%{"price_range" => %{"minimum_price" => %{"final_price" => %{"value" => value}}}}) do
    {:ok,
     value
     |> String.to_float()
     |> Kernel.*(100)
     |> round()}
  end

  defp extract_price(_), do: :error

  defp parse_integer(nil), do: nil

  defp parse_integer(str) when is_binary(str) do
    case Integer.parse(str) do
      {n, _} -> n
      :error -> nil
    end
  end

  defp parse_integer(_), do: nil

  defp parse_casing(nil), do: nil
  defp parse_casing(material), do: String.downcase(material)
end