Add new way to set from transitions

* Add function `Machinist.from/2` that expects a state
  and a block of `to` statements

README.md

@@ -15,7 +15,7 @@ You can install `machinist` by adding it to your list of dependencies in `mix.e
 ```elixir
 def deps do
  [
- {:machinist, "~> 0.3.0"}
+ {:machinist, "~> 0.4.0"}
  ]
 end
 ```
@@ -77,6 +77,28 @@ iex> Door.transit(door_opened, event: "lock")
 {:error, :not_allowed}
 ```
 
+### Group transitions with repeated `from` state
+
+In the example above we could group the `from :unlocked` definitions like this:
+
+```elixir
+# ...
+transitions do
+ from :locked, to: :unlocked, event: "unlock"
+ from :unlocked do
+ to :locked, event: "lock"
+ to :opened, event: "open"
+ end
+ from :opened, to: :closed, event: "close"
+ from :closed, to: :opened, event: "open"
+ from :closed, to: :locked, event: "lock"
+end
+# ...
+```
+
+This is an option to help us organize and increase the readability when having
+a large number of transition definitions
+
 ### Setting different attribute name that holds the state
 
 By default `machinist` expects the struct being updated holds a `state` attribute, if you hold state in a different attribute, just pass the name as an atom, as follows:

lib/machinist.ex

@@ -51,6 +51,26 @@ defmodule Machinist do
  iex> Door.transit(door_opened, event: "lock")
  iex> {:error, :not_allowed}
 
+ ### Group transitions of many repeated `from` state
+
+ In the example above we also could group the `from :unlocked` definitions:
+
+ # ...
+ transitions do
+ from :locked, to: :unlocked, event: "unlock"
+ from :unlocked do
+ to :locked, event: "lock"
+ to :opened, event: "open"
+ end
+ from :opened, to: :closed, event: "close"
+ from :closed, to: :opened, event: "open"
+ from :closed, to: :locked, event: "lock"
+ end
+ # ...
+
+ This is an option to help us organize and increase the readability when having
+ a large number of transition definitions
+
  ### Setting different attribute name that holds the state
 
  By default `machinist` expects the struct being updated holds a `state` attribute,
@@ -346,7 +366,27 @@ defmodule Machinist do
 
  from _state, to: :expired, event: "enrollment_expired"
  """
+ defmacro from(state, do: {_, _, to_statements}) do
+ define_transitions(state, to_statements)
+ end
+
  defmacro from(state, to: new_state, event: event) do
+ define_transition(state, to: new_state, event: event)
+ end
+
+ @doc false
+ defp define_transitions(_state, []), do: []
+
+ @doc false
+ defp define_transitions(state, [{:to, _line, [new_state, [event: event]]} | transitions]) do
+ [
+ define_transition(state, to: new_state, event: event)
+ | define_transitions(state, transitions)
+ ]
+ end
+
+ @doc false
+ defp define_transition(state, to: new_state, event: event) do
  quote do
  @impl true
  def transit(%@__struct__{@__attr__ => unquote(state)} = resource, event: unquote(event)) do

mix.exs

@@ -1,13 +1,13 @@
 defmodule Machinist.MixProject do
  use Mix.Project
 
- @version "0.3.0"
+ @version "0.4.0"
  @repo_url "https://github.com/norbajunior/machinist"
 
  def project do
  [
  app: :machinist,
- version: "0.3.0",
+ version: @version,
  elixir: "~> 1.6",
  start_permanent: Mix.env() == :prod,
  deps: deps(),

test/machinist_test.exs

@@ -131,8 +131,12 @@ defmodule MachinistTest do
  transitions do
  from(:new, to: :registered, event: "register")
  from(:registered, to: :interview_scheduled, event: "schedule_interview")
- from(:interview_scheduled, to: :approved, event: "approve_interview")
- from(:interview_scheduled, to: :repproved, event: "reprove_interview")
+
+ from :interview_scheduled do
+ to(:approved, event: "approve_interview")
+ to(:repproved, event: "reprove_interview")
+ end
+
  from(:approved, to: :enrolled, event: "enroll")
  from(_state, to: :application_expired, event: "application_expired")
  end
@@ -152,4 +156,29 @@ defmodule MachinistTest do
  Example5.transit(%Example5{state: :approved}, event: "application_expired")
  end
  end
+
+ describe "a example with passing a block of transitions to from" do
+ defmodule Example6 do
+ defstruct state: :test
+
+ use Machinist
+
+ transitions do
+ from(:test, to: :test1, event: "test1")
+
+ from :test1 do
+ to(:test2, event: "test2")
+ to(:test3, event: "test3")
+ to(:test4, event: "test4")
+ end
+ end
+ end
+
+ test "all transitions" do
+ assert {:ok, example} = Example6.transit(%Example6{}, event: "test1")
+ assert {:ok, %Example6{state: :test2}} = Example6.transit(example, event: "test2")
+ assert {:ok, %Example6{state: :test3}} = Example6.transit(example, event: "test3")
+ assert {:ok, %Example6{state: :test4}} = Example6.transit(example, event: "test4")
+ end
+ end
 end