defmodule Phoenix do
  @moduledoc """
  This is the documentation for the Phoenix project.

  To get started, see our [overview guides](overview.md).
  """
  use Application

  @doc false
  def start(_type, _args) do
    # Warm up caches
    _ = Phoenix.Template.engines()
    _ = Phoenix.Template.format_encoder("index.html")
    warn_on_missing_json_library()

    # Configure proper system flags from Phoenix only
    if stacktrace_depth = Application.get_env(:phoenix, :stacktrace_depth) do
      :erlang.system_flag(:backtrace_depth, stacktrace_depth)
    end

    if filter = Application.get_env(:phoenix, :filter_parameters) do
      Application.put_env(:phoenix, :filter_parameters, Phoenix.Logger.compile_filter(filter))
    end

    if Application.fetch_env!(:phoenix, :logger) do
      Phoenix.Logger.install()
    end

    children = [
      # Code reloading must be serial across all Phoenix apps
      Phoenix.CodeReloader.Server,
      {DynamicSupervisor, name: Phoenix.Transports.LongPoll.Supervisor, strategy: :one_for_one}
    ]

    Supervisor.start_link(children, strategy: :one_for_one, name: Phoenix.Supervisor)
  end

  @doc """
  Returns the configured JSON encoding library for Phoenix.

  To customize the JSON library, including the following
  in your `config/config.exs`:

      config :phoenix, :json_library, AlternativeJsonLibrary

  The configured module is required to provide three functions:

  - **`decode!/1`** — decodes a JSON binary, raising on invalid input
  - **`encode!/1`** — encodes a term to a JSON binary, raising on encoding errors
  - **`encode_to_iodata!/1`** — encodes a term to JSON as iodata, raising on
  encoding errors.

  These correspond to the single-argument, raising variants of
  the functions provided by Elixir's built-in `JSON` module. A conforming
  `:json_library` module does not need to implement any other functions
  `JSON` has, that are not defined above.
  """
  def json_library do
    Application.get_env(:phoenix, :json_library, Jason)
  end

  @doc """
  Returns the `:plug_init_mode` that controls when plugs are
  initialized.

  We recommend to set it to `:runtime` in development for
  compilation time improvements. It must be `:compile` in
  production (the default).

  This option is passed as the `:init_mode` to `Plug.Builder.compile/3`.
  """
  def plug_init_mode do
    Application.get_env(:phoenix, :plug_init_mode, :compile)
  end

  defp warn_on_missing_json_library do
    configured_lib = Application.get_env(:phoenix, :json_library)

    if configured_lib && not Code.ensure_loaded?(configured_lib) do
      IO.warn("""
      found #{inspect(configured_lib)} in your application configuration
      for Phoenix JSON encoding, but module #{inspect(configured_lib)} is not available.
      Ensure #{inspect(configured_lib)} is listed as a dependency in mix.exs.
      """)
    end
  end
end