added support for registering custom tasks

Signed-off-by: hughneale <mail@hughneale.com>

Author: hughneale

model/task.go

@@ -18,8 +18,92 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"sync"
 )
 
+// TaskConstructor is a function that creates a new instance of a task type
+type TaskConstructor func() Task
+
+// TaskRegistry manages the registration of task types for JSON unmarshaling
+type TaskRegistry struct {
+	mu           sync.RWMutex
+	constructors map[string]TaskConstructor
+}
+
+// NewTaskRegistry creates a new task registry
+func NewTaskRegistry() *TaskRegistry {
+	return &TaskRegistry{
+		constructors: make(map[string]TaskConstructor),
+	}
+}
+
+// RegisterTask registers a custom task type with a constructor function
+func (r *TaskRegistry) RegisterTask(taskType string, constructor TaskConstructor) error {
+
+	if len(taskType) == 0 {
+		return fmt.Errorf("task type cannot be empty")
+	}
+
+	if constructor == nil {
+		return fmt.Errorf("constructor function cannot be nil")
+	}
+
+	r.mu.Lock()
+	defer r.mu.Unlock()
+
+	if _, exists := r.constructors[taskType]; exists {
+		return fmt.Errorf("task type '%s' is already registered", taskType)
+	}
+
+	r.constructors[taskType] = constructor
+	return nil
+}
+
+// GetConstructor returns the constructor function for a given task type
+func (r *TaskRegistry) GetConstructor(taskType string) (TaskConstructor, bool) {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+	constructor, exists := r.constructors[taskType]
+	return constructor, exists
+}
+
+// UnregisterTask removes a task type from the registry (mainly for testing)
+func (r *TaskRegistry) UnregisterTask(taskType string) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	delete(r.constructors, taskType)
+}
+
+// ListRegisteredTypes returns all registered task types
+func (r *TaskRegistry) ListRegisteredTypes() []string {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+
+	types := make([]string, 0, len(r.constructors))
+	for taskType := range r.constructors {
+		types = append(types, taskType)
+	}
+	return types
+}
+
+// Global task registry instance
+var defaultRegistry = NewTaskRegistry()
+
+// RegisterTask registers a custom task type with the global registry
+func RegisterTask(taskType string, constructor TaskConstructor) error {
+	return defaultRegistry.RegisterTask(taskType, constructor)
+}
+
+// GetTaskConstructor returns the constructor function for a given task type from the global registry
+func GetTaskConstructor(taskType string) (TaskConstructor, bool) {
+	return defaultRegistry.GetConstructor(taskType)
+}
+
+// ListRegisteredTaskTypes returns all registered task types from the global registry
+func ListRegisteredTaskTypes() []string {
+	return defaultRegistry.ListRegisteredTypes()
+}
+
 type TaskBase struct {
 	// A runtime expression, if any, used to determine whether or not the task should be run.
 	If *RuntimeExpression `json:"if,omitempty" validate:"omitempty"`
@@ -118,23 +202,34 @@ func (tl *TaskList) UnmarshalJSON(data []byte) error {
 	return nil
 }
 
-var taskTypeRegistry = map[string]func() Task{
-	"call_http":     func() Task { return &CallHTTP{} },
-	"call_openapi":  func() Task { return &CallOpenAPI{} },
-	"call_grpc":     func() Task { return &CallGRPC{} },
-	"call_asyncapi": func() Task { return &CallAsyncAPI{} },
-	"call":          func() Task { return &CallFunction{} },
-	"do":            func() Task { return &DoTask{} },
-	"fork":          func() Task { return &ForkTask{} },
-	"emit":          func() Task { return &EmitTask{} },
-	"for":           func() Task { return &ForTask{} },
-	"listen":        func() Task { return &ListenTask{} },
-	"raise":         func() Task { return &RaiseTask{} },
-	"run":           func() Task { return &RunTask{} },
-	"set":           func() Task { return &SetTask{} },
-	"switch":        func() Task { return &SwitchTask{} },
-	"try":           func() Task { return &TryTask{} },
-	"wait":          func() Task { return &WaitTask{} },
+// Initialize built-in task types with the registry
+func init() {
+
+	// Register all built-in task types
+	builtInTasks := map[string]TaskConstructor{
+		"call_http":     func() Task { return &CallHTTP{} },
+		"call_openapi":  func() Task { return &CallOpenAPI{} },
+		"call_grpc":     func() Task { return &CallGRPC{} },
+		"call_asyncapi": func() Task { return &CallAsyncAPI{} },
+		"call":          func() Task { return &CallFunction{} },
+		"do":            func() Task { return &DoTask{} },
+		"fork":          func() Task { return &ForkTask{} },
+		"emit":          func() Task { return &EmitTask{} },
+		"for":           func() Task { return &ForTask{} },
+		"listen":        func() Task { return &ListenTask{} },
+		"raise":         func() Task { return &RaiseTask{} },
+		"run":           func() Task { return &RunTask{} },
+		"set":           func() Task { return &SetTask{} },
+		"switch":        func() Task { return &SwitchTask{} },
+		"try":           func() Task { return &TryTask{} },
+		"wait":          func() Task { return &WaitTask{} },
+	}
+
+	for taskType, constructor := range builtInTasks {
+		if err := defaultRegistry.RegisterTask(taskType, constructor); err != nil {
+			panic(fmt.Sprintf("failed to register built-in task type '%s': %v", taskType, err))
+		}
+	}
 }
 
 func unmarshalTask(key string, taskRaw json.RawMessage) (Task, error) {
@@ -150,27 +245,32 @@ func unmarshalTask(key string, taskRaw json.RawMessage) (Task, error) {
 	if callValue, hasCall := taskType["call"].(string); hasCall {
 		// Form composite key and check if it's in the registry
 		registryKey := fmt.Sprintf("call_%s", callValue)
-		if constructor, exists := taskTypeRegistry[registryKey]; exists {
+		if constructor, exists := defaultRegistry.GetConstructor(registryKey); exists {
 			task = constructor()
 		} else {
 			// Default to CallFunction for unrecognized call values
-			task = &CallFunction{}
+			if constructor, exists := defaultRegistry.GetConstructor("call"); exists {
+				task = constructor()
+			}
 		}
 	} else if _, hasFor := taskType["for"]; hasFor {
 		// Handle special case "for" that also has "do"
-		task = taskTypeRegistry["for"]()
+		if constructor, exists := defaultRegistry.GetConstructor("for"); exists {
+			task = constructor()
+		}
 	} else {
 		// Handle everything else (e.g., "do", "fork")
 		for typeKey := range taskType {
-			if constructor, exists := taskTypeRegistry[typeKey]; exists {
+			if constructor, exists := defaultRegistry.GetConstructor(typeKey); exists {
 				task = constructor()
 				break
 			}
 		}
 	}
 
 	if task == nil {
-		return nil, fmt.Errorf("unknown task type for key '%s'", key)
+		return nil, fmt.Errorf("unknown task type for key '%s'. Available types: %v",
+			key, defaultRegistry.ListRegisteredTypes())
 	}
 
 	// Populate the task with raw data