Pastafari

Pastafari is a library for building simple finite state machines in Ruby.

Installation

Add this line to your application's Gemfile:

gem 'pastafari'

And then execute:

$ bundle

Or install it yourself as:

$ gem install pastafari

Usage

# Define an FSM with the Pastafari FSM DSL:
fsm = Pastafari::FSM.build do
  # Set the order of operations with #transition.
  # :before runs the current state's transition functions before processing the input.
  # :after runs the transition function after input processing.
  transition :after # :after is the default value

  # Set the initial state:
  initial_state :first_state
  # If #initial_state isn't called, the first state defined by the DSL will be
  # assumed to be the initial FSM state.

  state :first_state do
    # Define the input processing function:
    process { |i| puts i }

    # If this state can transition into another state, define the transition
    # conditions:
    transition_to(:second_state).when { |i| i == 1 }
    # The transition function is a predicate - it should return a truthy or falsey
    # value. If the function returns a truthy value, the FSM will transition into
    # the new state.

    # You can define as many transitions as you'd like:
    transition_to(:third_state).when { |i| i == 2 }
    # If a transition references a state that isn't defined, Pastafari will
    # raise an error.    
  end

  state :second_state do
    # The processing function MUST be called; if it isn't, Pastafari will
    # raise an error.
    process { |i| puts i / 2 }
  end

  state :third_state do
    process { |i| puts i / 3 }

    # Transition functions are optional.
  end
end

# Run the FSM with #run. Pass in an array, or a value that can be converted to an
# Array with #Array.
fsm.run([1, 2, 3]) # => should print 1, 1, 1

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/pastafari. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The gem is available as open source under the terms of the MIT License.