defmodule Timber.Integrations.ExAwsHTTPClient do
  @moduledoc """
  [ExAWS](https://github.com/CargoSense/ex_aws) is an excellent library for interfacing with the
  AWS API. The Timber `ExAWSHTTPClient` adds structured logging to the HTTP requests being
  sent to the AWS API. This gives you valuable insight into AWS communication from your application.
  We use is internally at Timber.

  **By default**, this library will only log destructive requests (`POST`, `PUT`, `DELETE`,
  and `PATCH`). `GET` requests can be turned via configuration (see below).

  ## Installation

  ```elixir
  config :ex_aws,
    http_client: Timber.Integrations.ExAwsHTTPClient
  ```

  ## Configuration

  ```elixir
  config :timber, Timber.Integrations.ExAWSHTTPClient,
    http_methods_to_log: [:post, :put, :delete, :patch],
    capture_bodies: false
  ```

  * `http_methods_to_log` - (default: `[:post, :put, :delete, :patch]`). Only log requests whose method
    is included in the list. Use `:all` to log all methods.
  * `capture_bodies` - (default: `false`). When enabled, The first 2048 characters of the body will
    be included in the metadata of the log. It is recommended to enable this for debug purposes
    only as it can get excessive. You can also lower the size via
    `config :timber, :http_body_size_limit, 2048`.


  ## Only log specific services

  ExAws offers the ability to configure on a per service basis:

  ```elixir
  config :ex_aws, :lambda,
    http_client: Timber.Integrations.ExAwsHTTPClient
  ```

  Alternatively you can exclude services in the same way:

  ```elixir
  config :ex_aws,
    http_client: Timber.Integrations.ExAwsHTTPClient

  # Fallback to the defualt, non-logging HTTP client
  config :ex_aws, :lambda,
    http_client: ExAws.Request.Hackney
  ```
  """

  alias Timber.Events.HTTPRequestEvent
  alias Timber.Events.HTTPResponseEvent

  require Logger

  # Set a timeout slightly over the general AWS timeout. This ensures that we receive
  # the timeout event from AWS before we receive it internally, preventing orphaned requests.
  @default_opts [recv_timeout: 62_000]
  @default_service_name "aws"
  @http_methods_to_log_default [:patch, :post, :put, :delete]

  def request(method, url, body \\ "", headers \\ [], http_opts \\ []) do
    opts =
      :ex_aws
      |> Application.get_env(:hackney_opts, @default_opts)
      |> Keyword.merge(http_opts)
      |> Keyword.put(:with_body, true)

    service_name =
      case String.split(url, ".", parts: 2) do
        [prefix, _suffix] ->
          String.replace(prefix, "https://", "")

        _else ->
          @default_service_name
      end

    timer = Timber.start_timer()
    should_log = should_log_method?(method, http_methods_to_log())

    log_request(should_log, service_name, method, url, body, headers)

    case :hackney.request(method, url, headers, body, opts) do
      {:ok, status, headers} ->
        log_response(should_log, service_name, status, headers, timer)
        {:ok, %{status_code: status, headers: headers}}

      {:ok, status, headers, body} ->
        log_response(should_log, service_name, status, headers, timer, body: body)
        {:ok, %{status_code: status, headers: headers, body: body}}

      {:error, reason} ->
        # Errors are not logged because they should be handled. It is up
        # to the caller to log these properly.
        {:error, %{reason: reason}}
    end
  end

  defp should_log_method?(_method, :all),
    do: true

  defp should_log_method?(method, allowed_methods) do
    Enum.member?(allowed_methods, method)
  end

  defp log_request(false, _service_name, _method, _url, _body, _headers),
    do: nil

  defp log_request(true, service_name, method, url, body, headers) do
    Logger.debug(fn ->
      body = if capture_bodies?(), do: body, else: nil

      event =
        HTTPRequestEvent.new(
          direction: "outgoing",
          method: method,
          url: url,
          body: body,
          headers: headers,
          service_name: service_name
        )

      message = HTTPRequestEvent.message(event)
      {message, event: event}
    end)
  end

  defp log_response(should_log, service_name, status, headers, timer, opts \\ [])

  defp log_response(false, _service_name, _status, _headers, _timer, _opts),
    do: nil

  defp log_response(true, service_name, status, headers, timer, opts) do
    Logger.debug(fn ->
      time_ms = Timber.duration_ms(timer)
      body = Keyword.get(opts, :body)
      body = if capture_bodies?(), do: body, else: nil

      event =
        HTTPResponseEvent.new(
          direction: "incoming",
          body: body,
          status: status,
          headers: headers,
          service_name: service_name,
          time_ms: time_ms
        )

      message = HTTPResponseEvent.message(event)
      {message, event: event}
    end)
  end

  #
  # Config
  #

  defp config, do: Elixir.Application.get_env(:timber, __MODULE__, [])
  defp capture_bodies?, do: Keyword.get(config(), :capture_bodies, false)

  defp http_methods_to_log,
    do: Keyword.get(config(), :http_methods_to_log, @http_methods_to_log_default)
end