FlowEngine

A simple, flexible state machine engine for Laravel to handle dynamic flows like chats, onboarding, workflows, and more.

🚀 Concept

FlowEngine allows you to define state-driven flows where each subject (e.g. a chat, user, or process) moves through states based on input.

Typical flow:

1. Receive input
2. Process current state
3. Transition to next state
4. Persist state + context
5. Stop execution
6. Resume later (via new input or cooldown)

Setup

1. Publish the migrations:

php artisan vendor:publish --tag="helvetitec.flowengine.migrations"

2. Run migrations:

php artisan migrate

🧱 Core Components

FlowEngine

The base class that handles execution:

abstract class FlowEngine
{
    abstract protected function doRun(mixed $input): void;

    final public function run(FlowSubject $subject, mixed $input): void;

    final protected function subject(): FlowSubject;
    
    final protected function cooldown(?Carbon $until): static;

    final protected function transition(string $nextState): static;

    final protected function set(string $key, mixed $value): static;

    final protected function get(string $key, mixed $default = null): mixed;

    final protected function pull(string $key, mixed $default = null, bool $persist = false): mixed;

    final protected function delete(string $key): static;

    final protected function stop(bool $persist = true): never;

    final protected function transitionAndStop(string $nextState): never;

    final protected function deactivate(): never;
}

FlowSubject

Any model that participates in a flow must implement:

interface FlowSubject
{
    public function getActive(): bool;
    public function setActive(bool $active): void;

    public function getStateKey(): string;
    public function setStateKey(string $state): void;

    public function getContext(): array;
    public function setContext(?array $context): void;

    public function getCooldown(): ?Carbon;
    public function setCooldown(?Carbon $until): void;

    public function persist(): void;
}

FlowRun

class FlowRun extends Model implements FlowSubject
{
    public function subject();

    public function getActive(): bool;

    public function setActive(bool $active): void;
    
    public function getStateKey(): string;

    public function setStateKey(string $state): void;

    public function getContext(): array;

    public function setContext(?array $context): void;

    public function getCooldown(): ?Carbon;

    public function setCooldown(?Carbon $until): void;

    public function persist(): void;

    public function resolveFlow(): FlowEngine;

    public function runFlow(mixed $input = null, bool $force = false): void;

    public function mergeContext(array $data): static;

    public static function clear(string $flowClass, ?Carbon $clearOlderThan = null, ?string $flowType = null, ?string $flowId = null): int;
}

⚡ Example Implementation

1. FlowRuns

FlowRuns allow multiple FlowEngines running at the same time. The default state for every run is always 'start'.

//Add to your Subject (e.g Chat)
use HasFlowRuns;

2. Flow

class ChatFlow extends FlowEngine
{
    protected function doRun(mixed $input): void
    {
        $state = $this->subject()->getStateKey();

        if(!($this->subject() instanceof Chat)){
            throw new LogicException("Subject is not instance of Chat!");
        }

        match ($state) {
            'start' => $this->start(),
            'waiting' => $this->handleAnswer($input),
            default => $this->start(),
        };
    }

    private function start(): void
    {
        ChatService::send($this->subject(), "Choose 1 or 2");

        $this->transition('waiting')
             ->set('options', [1,2]) //Sets the context for the flow
             ->stop();
    }

    private function handleAnswer($input): void
    {
        $options = $this->get('options');
        if(!in_array($input, $options)){
            ChatService::send($this->subject(), "Invalid input");
            $this->stop();
            return;
        }
        ChatService::send($this->subject(), "You chose: {$input}");

        $this->transition('done')
             ->delete('options')
             ->cooldown(now()->addMinutes(5))
             ->stop();
    }
}

3. Triggering the Flow

$chat->runFlow(ChatFlow::class, $message, $force);
//With merged context
$chat->startFlow(ChatFlow::class)->mergeContext(['some_context_to_start' => 'Hello World'])->runFlow("input");
//Update the context for all FlowRuns of the model at once.
$chat->broadcastContext(['context_for_all_runs' => true]);
//Returns the object related to the flow. In this case it would be $chat as well as it is the owner, but its powerful inside the FlowEngine as you can call subject()->getOwner().
$chat->startFlow(ChatFlow::class)->subject()->getOwner();
//Clears all flowruns older than a specific date with the selected flowclass
FlowRun::clear(ChatFlow::class, now()->subMonth());
//Clears all flowruns from a specific model
FlowRun::clear(ChatFlow::class, now()->subMonth(), Chat::class, 1);
//Clears all flowruns older than a specific date. Prefer to use the more specific ones!
FlowRun::clearAll(now()->subMonth());

You typically call this from:

• Controllers
• Jobs
• Event listeners
• Webhooks

🔁 Flow Lifecycle

Input → run() → doRun()
        ↓
   state logic
        ↓
 transition()
 set()
 cooldown()
        ↓
     stop()
        ↓
   persist()

🧩 Helper Methods

Transition state

Handles the transition between states.

$this->transition('next_state');

Store data in context

Stores and loads data from the context.

$this->set('key', 'value');

$value = $this->get('key');

Pull data from context and delete

$value = $this->pull('key');

Delete data from context

$this->delete('key');

Clear all data from context

$this->clear();

Cooldown

Adds a cooldown between this run and the next run.

$this->cooldown(now()->addMinutes(10));

Stop execution

Stops the execution of the current flow.

$this->stop(); //persists

or

$this->stop(persist: false); //does not persist

Transition and Stop

Sets the next state and stops.

$this->transitionAndStop('next_state');

Deactivate

Deactivates the flow and stops it.

$this->deactivate();

Pause flow

$this->pause(now()->addMinutes(5));

Reset Flow

$this->reset(now()->addHour());

⚠️ Important Rules

1. Always use run()

// ✅ Correct
app(MyFlow::class)->run($subject, $input);

// ❌ Wrong
$flow->doRun($input);

2. Always stop after sending output

$this->transition('next')
     ->stop();

3. Do not persist manually

Persistence is handled automatically by the engine.

4. Use state keys as strings

'start'
'waiting_for_input'
'completed'

5. Hints

Exceptions

The FlowEngine will throw a FlowEngineException if you call FlowEngine->run(). This exception has the following additional context for easier debugging: flow_engine_class Returns the class of the FlowEngine like ChatFlowExample.

flow_engine_context Returns the current context of the FlowSubject.

flow_engine_state Returns the current state of the FlowSubject.

input Returns the latest input of the run.

Enable/Disable flows

You can fully disable flows by setting the setActive/getActive methods to a custom field or use setActive in FlowRuns.

protected $fillable = [
    'flow_active'
];

protected $casts = [
    'flow_active' => 'boolean'
];

public function setActive(bool $active): void
{
    $this->flow_active = $active;
}

public function getActive(): bool
{
    return $this->flow_active;
}

6. 📄 AI Usage

AI was used to create this readme file and for smaller parts of the code to make it cleaner.