zoeys.computer/lib/zoeyscomputer_web/plugs/discord_handler.ex

defmodule ZoeyscomputerWeb.DiscordHandler do
  require Logger
  alias ExAws.S3
  import Plug.Conn
  import Mogrify

  def init(opts), do: opts

  @discord_patterns [
    ~r/^Mozilla\/5\.0 \(compatible; Discordbot\//,
    # Discord's specific Mac client pattern
    ~r/^Mozilla\/5\.0 \(Macintosh; Intel Mac OS X [0-9_.]+; rv:[0-9.]+\) Gecko\/20100101 Firefox\/[0-9.]+$/
  ]

  def call(%{path_info: ["images", _id | _]} = conn, _opts) do
    user_agent = List.first(get_req_header(conn, "user-agent"))
    Logger.metadata()[:request_id]

    Logger.info("Processing image request:\n user_agent: #{user_agent}")

    Logger.info("Is discord request: #{is_discord_request?(user_agent)}")

    cond do
      is_discord_request?(user_agent) -> handle_discord(conn)
      true -> conn
    end
  end

  def call(conn, _opts), do: conn

  defp is_discord_request?(nil), do: false

  defp is_discord_request?(user_agent) do
    Enum.any?(@discord_patterns, fn pattern ->
      Regex.match?(pattern, user_agent)
    end)
  end

  defp handle_discord(%{path_info: ["images", id]} = conn) do
    case download_from_s3("imgs", id) do
      {:ok, image_binary, content_type} ->
        conn
        |> put_resp_content_type(content_type)
        # Optional: Add caching
        |> put_resp_header("cache-control", "public, max-age=86400")
        |> send_resp(200, image_binary)
        |> halt()

      {:error, reason} ->
        IO.inspect(reason)

        conn
        |> put_resp_content_type("text/plain")
        |> send_resp(500, "Failed to retrieve image")
        |> halt()
    end
  end

  defp download_from_s3(bucket, key) do
    case S3.get_object(bucket, "uploads/#{key}.png") |> ExAws.request() do
      {:ok, %{body: image_binary}} ->
        local_path = "/tmp/#{key}.png"
        File.write!(local_path, image_binary)

        image = open(local_path) |> format("webp") |> save()

        {:ok, file_binary} = File.read(image.path)

        {:ok, file_binary, "image/webp"}

      error ->
        error
    end
  end
end