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

Normal usage

No further setup needed

With FlowRuns

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, ?string $flowType = null, ?string $flowId = null, ?Carbon $clearOlderThan = null): int;
}

⚡ Example Implementation

1.1. With FlowRuns (Recomended)

If you want you can use the FlowRuns which would allow multiple FlowEngines running at the same time. The default state for every run is always 'start'.

Important: Follow the steps inside setup first for this to work!

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

1.2. Without FlowRuns (e.g. Chat)

If you only want to use one flow at a time.

class Chat extends Model implements FlowSubject
{
    use HasFlow;

    protected $casts = [
        'context' => 'array',
        'cooldown_until' => 'datetime',
        'active' => 'boolean'
    ];

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

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

    public function getStateKey(): string
    {
        return $this->state_key;
    }

    public function setStateKey(string $state): void
    {
        $this->state_key = $state;
    }

    public function getContext(): array
    {
        return $this->context ?? [];
    }

    public function setContext(array $context): void
    {
        $this->context = $context;
    }

    public function getCooldown(): ?Carbon
    {
        return $this->cooldown_until;
    }

    public function setCooldown(Carbon $until): void
    {
        $this->cooldown_until = $until;
    }

    public function persist(): void
    {
        $this->save();
    }
}

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

app(ChatFlow::class)->run($chat, $message);

or

//With use HasFlow;
$chat->runFlow($message);

or

//With use HasFlowRuns;
$chat->runFlow(ChatFlow::class, $message, $force);
//With use HasFlowRuns and 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()->owner.
$chat->startFlow(ChatFlow::class)->subject()->owner;

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');

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();

⚠️ 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.