Flamel

This package is a bag of helper functions. Some might be questionable but they are what they are so use them as you will.

Installation

In your mix.exs:

def deps do
  [
    {:flamel, "~> 1.10.0"}
  ]
end

or mainline the latest:

def deps do
  [
    {:flamel, github: "themusicman/flamel", branch: "main"}
  ]
end

Examples

Utility

try_and_return can be used with a function that throws and exception when you want to use that function in a with statement.

Flamel.try_and_return(fn -> :ok end) == :ok

Flamel.try_and_return(fn -> raise "error" end, {:ok, :default_value}) == {:ok, :default_value}

wrap function assists with wrapping a value in a tuple.

Flamel.wrap(:ok, []) == {:ok, []}

Flamel.wrap(:error, "error") == {:error, "error"}

There other wrap helper functions that can come in handy when working with LiveView, Genservers and the like that use wrap/2 under the hood. These functions are great for use when piping.

import Flamel.Wrap

ok(["apple", "pear"]) == {:ok, ["apple", "pear"]}

socket
|> assign(:user, user)
|> ok()

socket
|> assign(:user, user)
|> noreply()

The ok/1, noreply/1 helper functions were inspired by this tweet.

unwrap_* functions assists with handling functions that return a value wrapped in a tuple.

Flamel.unwrap_ok!({:ok, []}) == []

Flamel.unwrap_ok_or_nil({:error, "boom!"}) == nil

Context

Ability to create a context that can be used to build function pipelines

alias Flamel.Context

context =
  %Context{}
  |> assign_user(user)
  |> authorize()
  |> perform_action()

if context.assigns[:action_performed?] do
  # something you are allowed to do
end

def assign_user?(%Context{} = context, user) do
  Context.assign(context, :user, user)
end

def authorize(%Context{assigns: %{user: %{type: :admin}} = context) do
  context
end

def authorize(%Context{} = context) do
  Context.halt!(context, "Not permitted")
end

def perform_action(%Context{halt?: true}) do
  # do nothing
  context
end

def perform_action(%Context{assigns: %{user: user}} = context) do
  # Do something
  Context.assign(context, %{action_performed_by: user, action_performed?: true})
end

You don't have to use %Flamel.Context{} because Flamel.Context uses protocols. You can implement the Flamel.Contextable protocol for your own data type. Look at the interals of Flamel.Retryable.Exponential and Flamel.Retryable.Linear for an example.

Chain (experimental)

A chain allows you to apply a sequence of functions to a value. If the function applied reutrns an {:ok, value} tuple then the value is updated but if the function returns an {:error, reason, value} tuple then the reason is set on the chain and no further functions will be applied to the value.

def add_one(value) do
  {:ok, value + 1}
end

def minus_one_if_greater_than_one(value) when value > 1 do
  {:ok, value - 1}
end

def minus_one_if_greater_than_one(value) do
  {:ok, value}
end

1
|> Chain.new()
|> Chain.apply(&add_one/1)
|> Chain.apply(&minus_one_if_greater_than_one/1)
|> Chain.to_tuple() == {:ok, 1}

Chains can also be applied to an Enumerable:

def add_one(value) do
  {:ok, value + 1}
end

Enum.map([1, 2, 3], Chain.curry(fn chain ->
  chain
  |> Chain.apply(&add_one/1)
  |> Chain.to_value()
end) == [2, 3, 4]

Retryable (experimental)

Retryable functions that retry based on different strategies. Right now Linear and Exponential are the only 2 implemented but you can implement your own since the retry strategy uses two protocols (Flamel.Contextable and Flamel.Retryable.Strategy).

strategy = %Flamel.Retryable.Linear{} # or Flamel.Retryable.linear()
Flamel.Retryable.try(strategy, fn strategy -> {:ok, "success", strategy} end)
{:ok, "success", strategy}

You can also assign values to the strategy since it implements Flamel.Contextable.

strategy = %Flamel.Retryable.Exponential{} # or Flamel.Retryable.exponential()
import Flamel.Context

Flamel.Retryable.try(strategy, fn strategy ->
  case make_http_request(url, payload) do
    {:ok, result} ->
      {:ok, result, strategy}

    {:error, status, reason} ->
      {:error, reason, assign(strategy, :http_status, status)}
  end
end)

{:ok, "success", strategy}

There is a Flamel.Retryable.Http strategy but it currently just implements the Exponential strategy. The intent is to change the retry interval based on the HTTP status but this is not implemented yet. PRs are welcome. ;)

Delayed Task (experimental)

Executes an Task.async with a delay.

task =
  Flamel.Task.delay(
    interval_in_milliseconds,
    fn ->
      do_something()
    end
  )

result = Task.await(task)

Module

Detect if a module implements a behaviour.

Flamel.Module.implements?(MyApp.Sender, MyApp.Worker) == true

Predicates

Flamel.blank?(%{}) == true

# present is the opposite of blank?
Flamel.present?(%{}) == false

Conversions

Flamel.to_boolean("Y") == true

Flamel.to_integer(nil) == ""

Flamel.to_integer(1) == 1

Flamel.to_float(nil) == 0.0

Flamel.to_float(1) == 1.0

Flamel.to_string(nil) == ""

DateTime

Flamel.Moment.to_datetime("2000-10-31T01:30:00.000-05:00") == ~U[2000-10-31 06:30:00.000Z]

Flamel.Moment.to_datetime(~N[2019-10-31 23:00:07]) == ~N[2019-10-31 23:00:07]

Flamel.Moment.to_date(~D[2000-10-31]) == ~D[2000-10-31]

Flamel.Moment.to_date("2000-10-31") == ~D[2000-10-31]

Flamel.Moment.to_iso8601(~U[2000-10-31 06:30:00.000Z]) == "2000-10-31T06:30:00.000Z"

Flamel.Moment.to_iso8601(~D[2019-10-31]) == "2019-10-31"

All of the to_* functions are implemented using Protocols. So you can implement you own behavior for types that do not already have implementations.

Current Time Mocking

In your application code you will need to use Flamel.Moment.CurrentTime:

now = Flamel.Moment.CurrentTime.utc_now()

Then if you want to mock the current time you can call Flamel.Moment.CurrentTime.time_travel in your test:

now = DateTime.utc_now() |> DateTime.add(3600, :second)

Flamel.Moment.CurrentTime.time_travel(now) do
  # inside here the current time is mocked to the value you pass to time_travel
  assert Flamel.Moment.CurrentTime.utc_now() == now
end

# outside the block we are back to unmocked time

IMPORTANT: This mocking only applies to the process that Flamel.Moment.CurrentTime.time_travel is called in

Number

Flamel.Number.clamp(-10, 0) == 0

Flamel.Number.clamp(10, 0) == 10

Flamel.Number.clamp(10, 0, 5) == 5

Maps/Structs

Flamel.Map.atomize_keys(%{"first_name" => "Thomas", "dob" => "07/01/1981"}) == %{first_name: "Thomas", dob: "07/01/1981"}

map =
  Flamel.Map.assign(
    %{assigns: %{hobbies: ["playing"]}},
    :assigns,
    set: [name: "Osa"],
    push: [hobbies: ["soccer", "coloring"]]
  )

get_in(map, [:assigns, :hobbies]) == ["soccer", "coloring", "playing"]
get_in(map, [:assigns, :name]) == "Osa"

Flamel.Map.Indifferent.get(%{test: "value"}, "test") == "value"

Flamel.Map.Indifferent.get(%{test: "value"}, :test) == "value"

Flamel.Map.Safely.get(%Person{name: "Todd"}, &String.upcase(&1.name)) == "TODD"

Flamel.Map.Safely.get(%{name: "Todd"}, &String.upcase(&1.bad_field), "N/A") == "N/A"

Flamel.Map.put_if_present(%{name: "Todd"}, :name, nil) == %{name: "Todd"}

Flamel.Map.put_if_present(%{name: "Todd"}, :name, "Bob") == %{name: "Bob"}

Documentation can be generated with ExDoc and published on HexDocs. Once published, the docs can be found at https://hexdocs.pm/flamel.