Add example

examples/stateful/main.go

@@ -0,0 +1,88 @@
+package main
+
+import (
+	"fmt"
+	"github.com/hovsep/fmesh"
+	"github.com/hovsep/fmesh/component"
+	"github.com/hovsep/fmesh/port"
+	"github.com/hovsep/fmesh/signal"
+	"os"
+)
+
+// This example shows that components can have external state (internal state is in experimental phase and will be added in further versions of f-mesh)
+func main() {
+	starter := component.New("starter").
+		WithInputs("i1").
+		WithOutputs("o1").
+		WithActivationFunc(func(inputs *port.Collection, outputs *port.Collection) error {
+			return port.ForwardSignals(inputs.ByName("i1"), outputs.ByName("o1"))
+		})
+
+	layer1 := component.New("layer 1").
+		WithDescription("This dummy bypass layer is needed to continue executing, so we will demonstrate that counter is called multiple times").
+		WithInputs("i1").
+		WithOutputs("o1").
+		WithActivationFunc(func(inputs *port.Collection, outputs *port.Collection) error {
+			return port.ForwardSignals(inputs.ByName("i1"), outputs.ByName("o1"))
+		})
+
+	layer2 := component.New("layer 2").
+		WithDescription("This dummy bypass layer is needed to continue executing, so we will demonstrate that counter is called multiple times").
+		WithInputs("i1").
+		WithOutputs("o1").
+		WithActivationFunc(func(inputs *port.Collection, outputs *port.Collection) error {
+			return port.ForwardSignals(inputs.ByName("i1"), outputs.ByName("o1"))
+		})
+
+	layer3 := component.New("layer 3").
+		WithDescription("This dummy bypass layer is needed to continue executing, so we will demonstrate that counter is called multiple times").
+		WithInputs("i1").
+		WithOutputs("o1").
+		WithActivationFunc(func(inputs *port.Collection, outputs *port.Collection) error {
+			return port.ForwardSignals(inputs.ByName("i1"), outputs.ByName("o1"))
+		})
+
+	//This variable is not part of f-mesh and just mutated from activation function
+	counterExternalState := 0
+
+	counter := component.New("counter").
+		WithDescription("Stateful counter").
+		WithInputs("i1").
+		WithOutputs("o1").WithActivationFunc(func(inputs *port.Collection, outputs *port.Collection) error {
+		for _, _ = range inputs.ByName("i1").AllSignalsOrNil() {
+			counterExternalState++
+		}
+
+		//Latest state is always kept on o1
+		outputs.ByName("o1").Clear().PutSignals(signal.New(counterExternalState))
+		return nil
+	})
+
+	// Chain: starter->layer1->layer2->layer3
+	starter.OutputByName("o1").PipeTo(layer1.InputByName("i1"))
+	layer1.OutputByName("o1").PipeTo(layer2.InputByName("i1"))
+	layer2.OutputByName("o1").PipeTo(layer3.InputByName("i1"))
+
+	// Layers 1-3 are also reporting to the counter
+	layer1.OutputByName("o1").PipeTo(counter.InputByName("i1"))
+	layer2.OutputByName("o1").PipeTo(counter.InputByName("i1"))
+	layer3.OutputByName("o1").PipeTo(counter.InputByName("i1"))
+
+	fm := fmesh.New("stateful").WithComponents(starter, layer1, layer2, layer3, counter)
+
+	//Init data (4 heterogeneous signals, value does not matter)
+	starter.InputByName("i1").PutSignals(signal.NewGroup(1, "a", 0, nil).SignalsOrNil()...)
+
+	//Run the mesh
+	_, err := fm.Run()
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+
+	count := fm.Components().ByName("counter").OutputByName("o1").FirstSignalPayloadOrDefault(0)
+
+	//Expected: 12 (4 signals repeated 3 times (on each layer))
+	fmt.Printf("Count: %d", count)
+
+}