defmodule TalkJS do
  @external_resource "./README.md"
  @moduledoc """
  #{File.read!(@external_resource) |> String.split("---", parts: 2) |> List.last()}
  """

  @typedoc "TalkJS config"
  @type t :: %__MODULE__{
          api_key: binary(),
          app_id: binary(),
          base_url: binary(),
          http_client: term
        }

  defstruct [
    :api_key,
    :app_id,
    base_url: "https://api.talkjs.com/v1/",
    http_client: TalkJS.HTTPClient.HTTPC
  ]

  @doc """
  Create a new TalkJS client

  Options for the TalkJS client:application
    * `:api_key` - the API key provided by TalkJS (YOUR_SECRET_KEY)
    * `:app_id` - the app id provided by TalkJS (YOUR_APP_ID)
    * `:base_url` - the base URL for the API (default: "https://api.talkjs.com/v1/")
    * `:http_client` - the HTTP client to use (default: TalkJS.HTTPClient.HTTPC).
      Must adhere to `TalkJS.HTTPClient` behaviour

  Example usage:

  ```elixir
    client = TalkJS.new(api_key: "...", app_id: "...")
  ```
  """
  @spec new(opts :: Keyword.t()) :: TalkJS.t()
  def new(opts) do
    client = struct!(__MODULE__, opts)
    client.http_client.init()

    validate!(opts, :api_key)
    validate!(opts, :app_id)

    client
  end

  defp validate!(opts, key) do
    case Keyword.fetch(opts, key) do
      {:ok, _} -> :ok
      :error -> raise ArgumentError, "missing required option: #{key}"
    end
  end

  @doc """
  Perform a request to TalkJS

  Example usage:

  ```elixir
    client = TalkJS.new(api_key: "...", app_id: "...")

    TalkJS.request(:get, "$app_id/users/#id", client, %{})
  ```
  """
  @spec request(
          method :: :get | :delete | :post | :put,
          path :: String.t(),
          client :: TalkJS.t(),
          params :: map(),
          opts :: Keyword.t()
        ) ::
          {:ok, term()} | {:error, term()}
  def request(method, path, client, params, opts \\ [])

  def request(method, path, client, _params, opts) when method in [:get, :delete] do
    url = URI.parse(client.base_url <> path) |> URI.to_string()

    headers = build_headers(client)

    do_request(client, method, url, headers, "", opts)
  end

  def request(method, path, client, params, opts) when method in [:post, :put] do
    url = client.base_url <> path

    headers = build_headers(client)

    body = (params || %{}) |> Jason.encode!(params)

    do_request(client, method, url, headers, body, opts)
  end

  defp do_request(client, method, url, headers, body, opts) do
    http_opts = opts[:http_opts] || []

    case client.http_client.request(method, url, headers, body, http_opts) do
      {:ok, %{status: status} = resp} when status >= 200 and status < 300 ->
        decoded_body = Jason.decode!(resp.body)

        {:ok, decoded_body}

      {:ok, resp} ->
        # IO.inspect(resp)
        decoded_body = Jason.decode!(resp.body)
        {:error, decoded_body}

      {:error, error} ->
        {:error, error}
    end
  end

  defp build_headers(client) do
    [
      {"authorization", "Bearer #{client.api_key}"}
    ]
  end
end