aphora

# Copyright 2019 Schicksal
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#   http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

defmodule Aphora.Config do
  @moduledoc """
  This module provides a simple interface to the `config.exs` file, by providing a `default` variable fallback.
  """

  @default [
    datacenter: 0,
    worker: 0,
    epoch: 1_546_300_800_000
  ]

  @typedoc """
  This can be any non-negative integer within the span of `0..31` and represents the `t:datacenter/0` in which the `t:worker/0` resides in.
  """
  @typedoc since: "0.1.0"
  @type datacenter() :: non_neg_integer()

  @doc """
  Returns the set unique `t:datacenter/0` identifier from the config, or otherwise the `default` value `0`.  

  ## Examples

      iex> Aphora.Config.datacenter()
      0
  """
  @doc since: "0.1.0"
  @spec get_datacenter() :: datacenter()
  def get_datacenter, do: Application.get_env(:aphora, :datacenter) || @default[:datacenter]

  @typedoc """
  This can be any non-negative integer within the span of `0..1_023` and represents the unique `t:worker/0` within a `t:datacenter/0`.  

  *A `t:worker/0` should **never** be assigned twice with the same ID within the same `t:datacenter/0`.*
  """
  @typedoc since: "0.1.0"
  @type worker() :: non_neg_integer()

  @doc """
  Returns the set unique `t:worker/0` identifier from the config, or otherwise the `default` value `0`.  

  ## Examples

      iex> Aphora.Config.worker()
      0
  """
  @doc since: "0.1.0"
  @spec get_worker() :: worker()
  def get_worker, do: Application.get_env(:aphora, :worker) || @default[:worker]

  @typedoc """
  This can be any non-negative integer and represents the `t:epoch/0` with which the `t:Aphora.Worker.timestamp/0` is generated.

  *`t:epoch/0` should **never** be changed after deploying IDs to prevent duplicates.*
  """
  @typedoc since: "0.1.0"
  @type epoch() :: non_neg_integer()

  @doc """
  Returns the set unique `t:epoch/0` identifier from the config, or otherwise the `default` value `1_546_300_800_000`.  

  ## Examples

      iex> Aphora.Config.epoch()
      1546300800000000
  """
  @doc since: "0.1.0"
  @spec get_epoch() :: epoch()
  def get_epoch, do: Application.get_env(:aphora, :epoch) || @default[:epoch]
end