defmodule Chaperon do
  @moduledoc """
  Chaperon is a HTTP service load & performance testing tool.
  """

  use Application
  require Logger
  alias Chaperon.Util

  # See http://elixir-lang.org/docs/stable/elixir/Application.html
  # for more information on OTP Applications
  def start(_type, _args) do
    HTTPoison.start()
    Chaperon.Supervisor.start_link()
  end

  @spec connect_to_master(atom) :: :ok | {:error, any}
  def connect_to_master(node_name) do
    if Node.connect(node_name) do
      :ok
    else
      {:error, "Connecting to Chaperon master node failed: #{node_name}"}
    end
  end

  @version Mix.Project.config()[:version]
  def version do
    @version
  end

  @doc """
  Connect the current node to a Chaperon cluster without taking on any work
  (not running any load test Session tasks).

  Useful if you want to connect to a running cluster for inspecting running load
  tests and kicking off new ones without performing any load testing work on the
  connecting node.
  """
  @spec connect_to_master_without_work(atom) :: :ok | {:error, any}
  def connect_to_master_without_work(node_name) do
    if Node.connect(node_name) do
      # wait a bit because of node connection delays
      Process.sleep(500)

      :ok = Chaperon.Master.ignore_node_as_worker(node())
    else
      {:error, "Connecting to Chaperon master node failed: #{node_name}"}
    end
  end

  @doc """
  Runs a given load_test module's scenarios concurrently, outputting metrics
  at the end.

  - `lt_mod` LoadTest module to be executed
  - `options` List of options to be used. Valid values are:
      - `:print_results` If set to `true`, will print all action results.
      - `:export` Can be set to any module implementing the `Chaperon.Exporter` behaviour.
        Defaults to `Chaperon.Export.CSV`. When using `Chaperon.Export.S3` it defaults to the CSV export format.
        You can use another export format by wrapping it in a tuple, like so: `{Chaperon.Export.S3, Chaperon.Export.JSON}`
      - `:output` Can be set to a file path
      - `:tag` Can be set to be used when using the default export filename.
        Allows adding a custom 'tag' string as a prefix to the generated result
        output filename.
      - `:metrics` Filtering options for metrics
          Valid filters:
            - (metric) -> boolean
            - [metric_type]
  ## Example

      alias Chaperon.Export.JSON

      # Prints results & outputs metrics in CSV (default) format at the end
      Chaperon.run_load_test MyLoadTest, print_results: true

      # Doesn't print results & outputs metrics in JSON format at the end
      Chaperon.run_load_test MyLoadTest, export: JSON

      # Outputs metrics in CSV format to metrics.csv file
      Chaperon.run_load_test MyLoadTest, output: "metrics.csv"

      # Outputs metrics in JSON format to metrics.json file
      Chaperon.run_load_test MyLoadTest, export: JSON, output: "metrics.json"

      # Outputs metrics in CCSV format to "results/<date>/MyLoadTest/master-<timestamp>.csv"
      Chaperon.run_load_test MyLoadTest, tag: "master"

      # Outputs metrics in JSON format to "results/<date>/MyLoadTest/master-<timestamp>.json"
      Chaperon.run_load_test MyLoadTest, export: JSON, tag: "master"

      # Tracks only calls in MyScenario (can take any function that returns `true` or `false`)
      Chaperon.run_load_test MyLoadTest, tag: "master", metrics: fn
        {:call, {MyScenario, _}} ->
          true
        _ ->
          false
      end

      # You can also just pass a list of metric types/names:
      Chaperon.run_load_test MyLoadTest metrics: [
        :run_scenario,
        :call,
        :post,
        :my_custom_metric
      ]
  """
  def run_load_test(lt_mod, options \\ []) do
    timeout = Chaperon.LoadTest.timeout(lt_mod)

    config =
      options
      |> Keyword.get(:config, %{})
      |> Map.put(:metrics, Chaperon.Scenario.Metrics.config(options))

    results =
      Chaperon.LoadTest
      |> Task.async(:run, [lt_mod, config])
      |> Task.await(timeout)

    duration_s = results.duration_ms / 1_000
    duration_min = Float.round(results.duration_ms / 60_000, 2)
    lt_name = Chaperon.LoadTest.name(lt_mod)

    Logger.info(
      "#{lt_name} finished in #{results.duration_ms} ms (#{duration_s} s / #{duration_min} min)"
    )

    if results.timed_out > 0 do
      succeeded = Enum.count(results.sessions)

      Logger.warn(
        "#{lt_name} : #{results.timed_out} sessions timed out. #{succeeded} sessions succeeded."
      )
    end

    if options[:print_results] do
      print_results(results)
    end

    session =
      results
      |> Chaperon.LoadTest.merge_sessions()

    session =
      if session.config[:merge_scenario_sessions] do
        session
        |> Chaperon.Scenario.Metrics.add_histogram_metrics()
      else
        session
      end

    if options[:print_metrics] do
      print_metrics(session)
    end

    print_separator()

    {exporter, new_options} = options |> exporter

    {:ok, data} =
      exporter
      |> apply(:encode, [
        session,
        Keyword.merge(
          new_options,
          load_test: Util.shortened_module_name(lt_mod),
          duration: duration_s
        )
      ])

    case options |> output(lt_mod) do
      :remote ->
        {:remote, session, data}

      output ->
        Logger.info("Using result exporter #{inspect(exporter)} with options #{inspect(options)}")

        {:ok, _} =
          exporter
          |> apply(:write_output, [
            lt_mod,
            new_options,
            data,
            output
          ])

        session
    end
  end

  defp output(options, lt_mod) do
    options
    |> Keyword.get(:output, default_output_file(options, lt_mod))
  end

  def exporter(options) do
    case Keyword.get(options, :export, Chaperon.Export.CSV) do
      {exporter, nested_exporter} when exporter == Chaperon.Export.S3 ->
        options =
          options
          |> Keyword.put(:export, nested_exporter)

        Logger.info(
          "Chaperon.exporter | Using S3 exporter #{inspect(exporter)} with nested #{
            inspect(nested_exporter)
          }"
        )

        {Chaperon.Export.S3, options}

      exporter ->
        Logger.info("Chaperon.exporter | Using exporter #{inspect(exporter)}")
        {exporter, options |> Keyword.delete(:export)}
    end
  end

  # if output not defined by user, use default output format and file name
  defp default_output_file(options, lt_mod) do
    mod_name =
      lt_mod
      |> Chaperon.LoadTest.name()
      |> String.split(".")
      |> Enum.join("/")

    timestamp =
      DateTime.utc_now()
      |> DateTime.to_unix()

    dir = "results/#{Date.utc_today()}/#{mod_name}"

    case options[:tag] do
      nil -> "#{dir}/#{timestamp}"
      t -> "#{dir}/#{t}-#{timestamp}"
    end
  end

  def write_output_to_stdio(lt_mod, output) do
    IO.puts(output)
    print_separator()

    IO.inspect(
      %{
        scenarios: lt_mod.scenarios,
        default_config: Chaperon.LoadTest.default_config(lt_mod)
      },
      pretty: true
    )

    :ok
  end

  def write_output_to_file(lt_mod, runtime_config, output, path) do
    path
    |> Path.dirname()
    |> File.mkdir_p!()

    File.write!(path, output)

    config_file_path = path <> ".config.exs"

    File.write!(
      config_file_path,
      inspect(
        lt_mod
        |> Chaperon.LoadTest.default_config()
        |> DeepMerge.deep_merge(runtime_config),
        pretty: true,
        limit: :infinity,
        printable_limit: :infinity
      )
    )

    scenarios_file_path = path <> ".scenarios.exs"

    File.write!(
      scenarios_file_path,
      inspect(
        lt_mod.scenarios,
        pretty: true,
        limit: :infinity,
        printable_limit: :infinity
      )
    )

    {:ok, [path, config_file_path, scenarios_file_path]}
  end

  defp print_separator do
    IO.puts("")
    IO.puts(for _ <- 1..80, do: "=")
    IO.puts("")
  end

  defp print_metrics(session) do
    print_separator()
    Logger.info("Metrics:")

    for {k, v} <- session.metrics do
      k = inspect(k)
      delimiter = for _ <- 1..byte_size(k), do: "="
      IO.puts("#{delimiter}\n#{k}\n#{delimiter}")
      IO.inspect(v)
      IO.puts("")
    end
  end

  defp print_results(results) do
    print_separator()
    Logger.info("Results:")

    for session <- results.sessions do
      for {action, results} <- session.results do
        for res <- results |> List.wrap() |> List.flatten() do
          case res do
            {:async, name, results} when is_list(results) ->
              results
              |> Enum.each(&print_result(name, &1))

            {:async, name, res} ->
              Logger.info("~> #{name} -> #{res.status_code}")

            results when is_list(results) ->
              results
              |> Enum.each(&print_result(action, &1))

            res ->
              print_result(action, res)
          end
        end
      end
    end
  end

  defp print_result(action, %HTTPoison.Response{status_code: status_code}) do
    Logger.info("#{action} -> #{status_code}")
  end

  defp print_result(action, result) when is_binary(result) do
    Logger.info("#{action} -> #{result}")
  end
end