layr8

defmodule Layr8.Config do
  @moduledoc """
  Configuration for a Layr8 client.

  Fields can be supplied explicitly or resolved from environment variables:
  - `LAYR8_NODE_URL` — WebSocket URL of the cloud-node
  - `LAYR8_API_KEY`  — authentication key
  - `LAYR8_AGENT_DID` — agent DID (optional; ephemeral DID created on connect if absent)

  HTTP(S) URLs are automatically normalized to WebSocket scheme:
  - `https://` → `wss://`
  - `http://`  → `ws://`

  ## Example

      config = Layr8.Config.resolve!(%{node_url: "wss://node.example.com/plugin_socket/websocket", api_key: "secret"})
  """

  @enforce_keys [:node_url, :api_key]
  defstruct [:node_url, :api_key, agent_did: ""]

  @type t :: %__MODULE__{
          node_url: String.t(),
          api_key: String.t(),
          agent_did: String.t()
        }

  @doc """
  Resolves a config map or struct, filling missing fields from environment variables,
  normalizing the URL scheme, and validating required fields.

  Raises `Layr8.Error` if required fields are missing.
  """
  @spec resolve!(map()) :: t()
  def resolve!(cfg \\ %{}) do
    node_url = Map.get(cfg, :node_url) || System.get_env("LAYR8_NODE_URL") || ""
    api_key = Map.get(cfg, :api_key) || System.get_env("LAYR8_API_KEY") || ""
    agent_did = Map.get(cfg, :agent_did) || System.get_env("LAYR8_AGENT_DID") || ""

    if node_url == "" do
      raise Layr8.Error,
        message: "node_url is required (set in config or LAYR8_NODE_URL env)"
    end

    normalized_url = normalize_url(node_url)

    if api_key == "" do
      raise Layr8.Error,
        message: "api_key is required (set in config or LAYR8_API_KEY env)"
    end

    %__MODULE__{
      node_url: normalized_url,
      api_key: api_key,
      agent_did: agent_did
    }
  end

  @doc """
  Derives the REST API base URL from a WebSocket URL.

      iex> Layr8.Config.rest_url_from_websocket("wss://node.example.com/plugin_socket/websocket")
      "https://node.example.com"

      iex> Layr8.Config.rest_url_from_websocket("ws://localhost:4000/plugin_socket/websocket")
      "http://localhost:4000"
  """
  @spec rest_url_from_websocket(String.t()) :: String.t()
  def rest_url_from_websocket(ws_url) do
    uri = URI.parse(ws_url)

    scheme =
      case uri.scheme do
        "wss" -> "https"
        _ -> "http"
      end

    host_part =
      if uri.port && uri.port not in [80, 443] do
        "#{uri.host}:#{uri.port}"
      else
        uri.host
      end

    "#{scheme}://#{host_part}"
  end

  @doc false
  @spec normalize_url(String.t()) :: String.t()
  def normalize_url(url) do
    cond do
      String.starts_with?(url, "https://") ->
        "wss://" <> String.slice(url, String.length("https://")..-1//1)

      String.starts_with?(url, "http://") ->
        "ws://" <> String.slice(url, String.length("http://")..-1//1)

      true ->
        url
    end
  end
end