flow improvements (#52)

* flow improvements

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

flow/flow.go

@@ -1,17 +1,59 @@
 // Package flow is an interface used for saga pattern microservice workflow
 package flow
 
+import (
+	"context"
+	"errors"
+)
+
+var (
+	ErrStepNotExists = errors.New("step not exists")
+)
+
+// Step represents dedicated workflow step
 type Step interface {
+	// ID returns step id
+	ID() string
 	// Endpoint returns rpc endpoint service_name.service_method or broker topic
 	Endpoint() string
+	// Execute step run
+	Execute(ctx context.Context, req interface{}, opts ...ExecuteOption) error
+	// Requires returns dependent steps
+	Requires() []string
+	// Options returns step options
+	Options() StepOptions
+	// Require add required steps
+	Require(steps ...Step) error
+	// String
+	String() string
 }
 
+// Workflow contains all steps to execute
 type Workflow interface {
+	// ID returns id of the workflow
+	ID() string
+	// Steps returns steps slice where parallel steps returned on the same level
 	Steps() [][]Step
-	Stop() error
+	// Execute workflow with args, return execution id and error
+	Execute(ctx context.Context, req interface{}, opts ...ExecuteOption) (string, error)
+	// RemoveSteps remove steps from workflow
+	RemoveSteps(ctx context.Context, steps ...Step) error
+	// AppendSteps append steps to workflow
+	AppendSteps(ctx context.Context, steps ...Step) error
 }
 
+// Flow the base interface to interact with workflows
 type Flow interface {
-	Start(Workflow) error
-	Stop(Workflow)
+	// Options returns options
+	Options() Options
+	// Init initialize
+	Init(...Option) error
+	// WorkflowCreate creates new workflow with specific id and steps
+	WorkflowCreate(ctx context.Context, id string, steps ...Step) (Workflow, error)
+	// WorkflowSave saves workflow
+	WorkflowSave(ctx context.Context, w Workflow) error
+	// WorkflowLoad loads workflow with specific id
+	WorkflowLoad(ctx context.Context, id string) (Workflow, error)
+	// WorkflowList lists all workflows
+	WorkflowList(ctx context.Context) ([]Workflow, error)
 }