StateControl

This shard provides a flexible state machine implementation in Crystal programming language.

You can use any enum to describe different states and use the StateControl(T) class with that enum to create your own specific state machine class.

The StateControl(T) class allows you to manage transitions between states, track transition history, and monitor time spent in each state. By using this shard, you have the flexibility to define and use your own enums and state machine classes tailored to your specific needs.

Installation

  1. Add the dependency to your shard.yml:

    dependencies:
  state_control:
    github: dammer/state_control

  2. Run shards install

Usage

require "state_control"

# define an enum that describes states
enum TestStatus
  Yellow
  Red
  Green
  BlinkGreen
end

# define the state_control class
class TestStatusControl < StateControl(TestStatus)
  # enable state transitions history tracking (optional)
  include SaveHistory
  # set history size limit
  maximum_history_size 4

  # enable routes
  route_enable red: :yellow
  route_enable yellow: :green
  route_enable green: :blink_green
  route_enable blink_green: :red

  # кeyword `any` can be used to define multiple routes
  route_enable any: :yellow
  # this is the same as:
  # route_enable red: :yellow
  # route_enable green: :yellow
  # route_enable blinkgreen: :yellow

  # disable unnecessary routes
  route_disable green: :yellow
  route_disable blinkgreen: :yellow

  # draw routes table (optional, debug)
  inspect_routes
  # ┌────────────┬────────────┬────────────┬────────────┬────────────┐
  # │     ->     │   Yellow   │    Red     │   Green    │ BlinkGreen │
  # ├────────────┼────────────┼────────────┼────────────┼────────────┤
  # │   Yellow   │            │            │     X      │            │
  # ├────────────┼────────────┼────────────┼────────────┼────────────┤
  # │    Red     │     X      │            │            │            │
  # ├────────────┼────────────┼────────────┼────────────┼────────────┤
  # │   Green    │            │            │            │     X      │
  # ├────────────┼────────────┼────────────┼────────────┼────────────┤
  # │ BlinkGreen │            │     X      │            │            │
  # └────────────┴────────────┴────────────┴────────────┴────────────┘

  # permanent custom handler on success transition by the route (optional)
  protected def on_success(prev, current)
    # `super` call is required if `on_succes` defined for compatibility
    super
    # do something here
    puts "transited from: #{prev} to: #{current}"
    # or or something useful ;)
    # emit StateChangedEvent, prev, current
  end
end

# create a state_conrtol instance
state_control = Specs::TestStatusControl.new(:yellow)

# check the current state
state_control.state.yellow?   # => true
state_control.state           # => TestStatus::Yellow

# check if transite to a route is possible
state_control.can?(:red)      # => false
state_control.can?(:green)    # => true

# get all possible routes from the current state
state_control.possible_routes # => [TestStatus::Green]

# transition (bad)
state_control.go(:red)        # => false
state_control.state.red?      # => false

# transition (good)
state_control.go(:green)      # => true
state_control.state.green?    # => true

# check if no routes from current state
state_control.final_state?    # => false

# move through states
i = 0
while dest = state_control.possible_routes.first?
  sleep(i += 1)
  state_control.go(dest)
  break if state_control.state.green?
end

# inspect time line
state_control.inspect_timeline
# ┌───┬────────────┬────────────────────────────────┬────────────────────┐
# │ # │   State    │              Time              │       Spent        │
# ├───┼────────────┼────────────────────────────────┼────────────────────┤
# │ 0 │ BlinkGreen │ 2023-04-06T16:23:21.961333359Z │ 00:00:02.002182295 │
# ├───┼────────────┼────────────────────────────────┼────────────────────┤
# │ 1 │    Red     │ 2023-04-06T16:23:23.963515654Z │ 00:00:02.998190151 │
# ├───┼────────────┼────────────────────────────────┼────────────────────┤
# │ 2 │   Yellow   │ 2023-04-06T16:23:26.961705805Z │ 00:00:04.004193440 │
# ├───┼────────────┼────────────────────────────────┼────────────────────┤
# │ 3 │   Green    │ 2023-04-06T16:23:30.965899245Z │         ∞          │
# └───┴────────────┴────────────────────────────────┴────────────────────┘

# pass once block on success transition
var = false

def blink_green_success
  puts "current state Blink Green!"
end

state_control.go(:blink_green) do
  blink_green_success
  var = true
end

var # => true

# JSON::Serializable compatible
requie "json"

struct JsonTest
  include JSON::Serializable

  getter test_name : String
  getter state_control : TestStatusControl

  def initialize(@test_name, @state_control = TestStatusControl.new)
  end
end

# serialization
json_test = JsonTest.new("json_1")
json_test.state_control.go(:red) # => false
string = json_test.to_json
string.should eq %q<{"test_name":"json_1","state_control":"yellow"}>

# deserialization
json_test = JsonTest.from_json(string)
json_test.state_control.state.yellow?.should be_true

Development

During the development process, we follow best practices to ensure code quality and maintainability. Here are some guidelines:

We appreciate your contribution to the project and adherence to these development guidelines, which help us maintain high code quality and ensure a smooth development process.

Contributing

  1. Fork it (https://github.com/your-github-user/state_control/fork)
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create a new Pull Request

Acknowledgements

I would like to acknowledge the following sources and tools that have been instrumental in the creation of this project:

Contributors