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Useful config wrapper for Elixir
defmodule Config do
@moduledoc """
This module handles fetching values from the config with some additional niceties
"""
@doc """
Fetches a value from the config, or from the environment if {:system, "VAR"}
is provided.
An optional default value can be provided if desired.
## Example
iex> {test_var, expected_value} = System.get_env |> Enum.take(1) |> List.first
...> Application.put_env(:myapp, :test_var, {:system, test_var})
...> ^expected_value = #{__MODULE__}.get(:myapp, :test_var)
...> :ok
:ok
iex> Application.put_env(:myapp, :test_var2, 1)
...> 1 = #{__MODULE__}.get(:myapp, :test_var2)
1
iex> :default = #{__MODULE__}.get(:myapp, :missing_var, :default)
:default
"""
@spec get(atom, atom, term | nil) :: term
def get(app, key, default \\ nil) when is_atom(app) and is_atom(key) do
case Application.get_env(app, key) do
{:system, env_var} ->
case System.get_env(env_var) do
nil -> default
val -> val
end
{:system, env_var, preconfigured_default} ->
case System.get_env(env_var) do
nil -> preconfigured_default
val -> val
end
nil ->
default
val ->
val
end
end
@doc """
Same as get/3, but returns the result as an integer.
If the value cannot be converted to an integer, the
default is returned instead.
"""
@spec get_integer(atom(), atom(), integer()) :: integer
def get_integer(app, key, default \\ nil) do
case get(app, key, nil) do
nil -> default
n when is_integer(n) -> n
n ->
case Integer.parse(n) do
{i, _} -> i
:error -> default
end
end
end
@doc """
Fetches a value from the config, or from the environment if {:system, "VAR"}
is provided.
If the environment variable is not set and no preconfigured default is provided
it will raise an ArgumentError
"""
@spec get!(atom, atom) :: term | no_return
def get!(app, key) when is_atom(app) and is_atom(key) do
case Application.fetch_env!(app, key) do
{:system, env_var} ->
case System.get_env(env_var) do
nil -> raise ArgumentError, message: "Environment variable #{env_var} not set"
value -> value
end
{:system, env_var, preconfigured_default} ->
case System.get_env(env_var) do
nil -> preconfigured_default
value -> value
end
val ->
val
end
end
end
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