Add Dispatcher implementation for CQRS pattern

Introduced a Dispatcher to manage command, query, and event handlers in a thread-safe manner utilizing read-write mutexes. This includes handler registration and dispatching logic, error handling for unregistered handlers, and support for concurrent operations. Added comprehensive tests for handler registration, dispatching, and error scenarios.

.gitea/workflows/ci-basic.yml

@@ -0,0 +1,50 @@
+name: Go CI/CD
+run-name: ${{ github.actor }} is running CI/CD basic
+
+on:
+  push:
+    branches-ignore:
+      - main
+      - release/**
+      - develop
+  pull_request:
+    branches-ignore:
+      - main
+      - release/**
+      - develop
+
+jobs:
+  go-ci:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Setup go
+        uses: actions/setup-go@v5
+        with:
+          go-version: '1.24'
+
+      - name: Download dependencies
+        shell: bash
+        run: |
+          go mod tidy -x
+
+      - name: Run tests
+        shell: bash
+        run: |
+          go test -json > test-report.out
+          go test -coverprofile=coverage.out
+
+      - name: SonarQube Analysis
+        uses: SonarSource/sonarqube-scan-action@v5
+        env:
+          SONAR_TOKEN: ${{ secrets.SONAR_TOKEN }}
+          SONAR_HOST_URL: ${{ vars.SONAR_HOST_URL }}
+
+      - name: Build binary
+        shell: bash
+        run: |
+          go build ./...

.gitea/workflows/ci-protected.yml

@@ -0,0 +1,50 @@
+name: Go CI/CD
+run-name: ${{ github.actor }} is running CI/CD protected
+
+on:
+  push:
+    branches:
+      - main
+      - release/**
+      - develop
+  pull_request:
+    branches:
+      - main
+      - release/**
+      - develop
+
+jobs:
+  go-ci:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Setup go
+        uses: actions/setup-go@v5
+        with:
+          go-version: '1.24'
+
+      - name: Download dependencies
+        shell: bash
+        run: |
+          go mod tidy -x
+
+      - name: Run tests
+        shell: bash
+        run: |
+          go test -json > test-report.out
+          go test -coverprofile=coverage.out
+
+      - name: SonarQube Analysis
+        uses: SonarSource/sonarqube-scan-action@v5
+        env:
+          SONAR_TOKEN: ${{ secrets.SONAR_TOKEN }}
+          SONAR_HOST_URL: ${{ vars.SONAR_HOST_URL }}
+
+      - name: Build binary
+        shell: bash
+        run: |
+          go build ./...

.gitea/workflows/ci-tag.yml

@@ -0,0 +1,43 @@
+name: Go CI/CD
+run-name: ${{ github.actor }} is running CI/CD Tag
+
+on:
+  push:
+    tags:
+      - '*'
+
+jobs:
+  go-ci:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Setup go
+        uses: actions/setup-go@v5
+        with:
+          go-version: '1.24'
+
+      - name: Download dependencies
+        shell: bash
+        run: |
+          go mod tidy -x
+
+      - name: Run tests
+        shell: bash
+        run: |
+          go test -json > test-report.out
+          go test -coverprofile=coverage.out
+
+      - name: SonarQube Analysis
+        uses: SonarSource/sonarqube-scan-action@v5
+        env:
+          SONAR_TOKEN: ${{ secrets.SONAR_TOKEN }}
+          SONAR_HOST_URL: ${{ vars.SONAR_HOST_URL }}
+
+      - name: Build binary
+        shell: bash
+        run: |
+          go build ./...

.gitignore

@@ -0,0 +1,64 @@
+# Binaries for programs and plugins
+bin
+*.exe
+*.dll
+*.so
+*.dylib
+*.test
+
+# Output of the 'go tool cover' command
+*.out
+coverage.xml
+test-report.xml
+
+# Directory for Go modules
+/vendor/
+
+# Go workspace file
+go.work
+go.work.sum
+
+# Editor configs
+*.swp
+*.swo
+*.bak
+*.tmp
+*.log
+*.viminfo
+*.un~
+Session.vim
+
+# JetBrains Rider specific
+.idea/
+*.iml
+.idea/**/workspace.xml
+.idea/**/tasks.xml
+.idea/**/shelf/
+
+# Sublime Text specific
+*.sublime-workspace
+*.sublime-project
+
+# VSCode specific
+.vscode/
+.vscode/settings.json
+.vscode/tasks.json
+.vscode/launch.json
+
+# Emacs specific
+*~
+\#*\#
+.#*
+
+# MacOS specific
+.DS_Store
+.AppleDouble
+.LSOverride
+
+# Node modules (in case of tools/scripts)
+node_modules/
+
+# Python virtual environments (for dev tools/scripts)
+venv/
+*.pyc
+__pycache__/

dispatcher.go

@@ -0,0 +1,206 @@
+package stonecqrs
+
+import (
+	"context"
+	"fmt"
+	"sync"
+
+	"gitstormr.dev/stone-utils/stoneerror"
+)
+
+// errCommandHandlerNotFound indicates a missing command handler error.
+// errQueryHandlerNotFound indicates a missing query handler error.
+// errEventHandlerNotFound indicates a missing event handler error.
+var (
+	errCommandHandlerNotFound = stoneerror.New(
+		1001, "command handler not found",
+	)
+	errQueryHandlerNotFound = stoneerror.New(1002, "query handler not found")
+	errEventHandlerNotFound = stoneerror.New(1003, "event handler not found")
+)
+
+// Command represents an action or operation to be handled by a dispatcher.
+type Command interface{}
+
+// Query represents a marker interface used to identify query types.
+type Query interface{}
+
+// Event represents a domain event within the application architecture.
+type Event interface{}
+
+// CommandHandler defines an interface for handling commands in a CQRS pattern.
+// Implementations should process commands and return resulting events or errors.
+// Handle processes the given command and returns any resulting events or error.
+type CommandHandler interface {
+	Handle(ctx context.Context, cmd Command) ([]Event, error)
+}
+
+// QueryHandler defines an interface for handling queries within a context.
+type QueryHandler interface {
+	Handle(ctx context.Context, query Query) (interface{}, error)
+}
+
+// EventHandler is an interface for handling specific types of events.
+// It defines a single method Handle to process an Event with a context.
+// Handle returns an error if the event handling fails.
+type EventHandler interface {
+	Handle(ctx context.Context, event Event) error
+}
+
+// Dispatcher is responsible for managing and dispatching handlers.
+// It supports command, query, and event handlers concurrently.
+// Commands, queries, and events are identified by their type names.
+// Uses a read-write mutex to ensure thread-safe operations.
+type Dispatcher struct {
+	commandHandlers map[string]CommandHandler
+	queryHandlers   map[string]QueryHandler
+	eventHandlers   map[string][]EventHandler
+	mutex           sync.RWMutex
+}
+
+// NewDispatcher creates and returns a new instance of Dispatcher.
+func NewDispatcher() *Dispatcher {
+	return &Dispatcher{
+		commandHandlers: make(map[string]CommandHandler),
+		queryHandlers:   make(map[string]QueryHandler),
+		eventHandlers:   make(map[string][]EventHandler),
+	}
+}
+
+// RegisterCommandHandler registers a handler for a specific command type.
+func (d *Dispatcher) RegisterCommandHandler(
+	cmd Command, handler CommandHandler,
+) {
+	d.mutex.Lock()
+	defer d.mutex.Unlock()
+	d.commandHandlers[typeName(cmd)] = handler
+}
+
+// RegisterQueryHandler registers a handler for the specified query type.
+func (d *Dispatcher) RegisterQueryHandler(query Query, handler QueryHandler) {
+	d.mutex.Lock()
+	defer d.mutex.Unlock()
+	d.queryHandlers[typeName(query)] = handler
+}
+
+// RegisterEventHandler registers a handler for a specific type of event.
+func (d *Dispatcher) RegisterEventHandler(event Event, handler EventHandler) {
+	d.mutex.Lock()
+	defer d.mutex.Unlock()
+	name := typeName(event)
+	d.eventHandlers[name] = append(d.eventHandlers[name], handler)
+}
+
+// DispatchCommand processes a Command and dispatches the resulting Events.
+// Returns the generated Events or an error if command handling fails.
+func (d *Dispatcher) DispatchCommand(ctx context.Context, cmd Command) (
+	[]Event, error,
+) {
+	handler, err := d.getCommandHandler(cmd)
+	if err != nil {
+		return nil, err
+	}
+
+	events, err := handler.Handle(ctx, cmd)
+	if err != nil {
+		return nil, err
+	}
+
+	if len(events) > 0 {
+		if err = d.DispatchEvents(ctx, events...); err != nil {
+			return events, stoneerror.Wrap(
+				err, 1004, "failed to dispatch generated events",
+			)
+		}
+	}
+
+	return events, nil
+}
+
+// DispatchQuery dispatches a query to its corresponding handler.
+// It retrieves the query handler and invokes its Handle method.
+// Returns the result of the query handler or an error if not found.
+func (d *Dispatcher) DispatchQuery(
+	ctx context.Context, query Query,
+) (interface{}, error) {
+	handler, err := d.getQueryHandler(query)
+	if err != nil {
+		return nil, err
+	}
+	return handler.Handle(ctx, query)
+}
+
+// DispatchEvents dispatches multiple events to their registered handlers.
+// It processes each event sequentially and stops on the first error.
+// Returns an error if any event fails to dispatch.
+func (d *Dispatcher) DispatchEvents(
+	ctx context.Context, events ...Event,
+) error {
+	for _, event := range events {
+		if err := d.DispatchEvent(ctx, event); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// DispatchEvent dispatches an event to all registered event handlers.
+// It returns an error if any handler fails to process the event.
+func (d *Dispatcher) DispatchEvent(ctx context.Context, event Event) error {
+	handlers, err := d.getEventHandlers(event)
+	if err != nil {
+		return err
+	}
+
+	for _, handler := range handlers {
+		if err = handler.Handle(ctx, event); err != nil {
+			return stoneerror.Wrap(err, 1005, "event handling failed")
+		}
+	}
+
+	return nil
+}
+
+// getCommandHandler retrieves the CommandHandler for the given Command.
+// Returns an error if no handler is found.
+func (d *Dispatcher) getCommandHandler(cmd Command) (CommandHandler, error) {
+	d.mutex.RLock()
+	defer d.mutex.RUnlock()
+
+	handler, exists := d.commandHandlers[typeName(cmd)]
+	if !exists {
+		return nil, errCommandHandlerNotFound
+	}
+	return handler, nil
+}
+
+// getQueryHandler retrieves the handler for a specific query type.
+// It returns an error if the handler is not found.
+func (d *Dispatcher) getQueryHandler(query Query) (QueryHandler, error) {
+	d.mutex.RLock()
+	defer d.mutex.RUnlock()
+
+	handler, exists := d.queryHandlers[typeName(query)]
+	if !exists {
+		return nil, errQueryHandlerNotFound
+	}
+	return handler, nil
+}
+
+// getEventHandlers retrieves all handlers for a specific event type.
+// Returns an error if no handlers are registered for the event type.
+func (d *Dispatcher) getEventHandlers(event Event) ([]EventHandler, error) {
+	d.mutex.RLock()
+	defer d.mutex.RUnlock()
+
+	handlers, exists := d.eventHandlers[typeName(event)]
+	if !exists {
+		return nil, errEventHandlerNotFound
+	}
+	return handlers, nil
+}
+
+// typeName returns the name of the type of the given interface value.
+func typeName(v interface{}) string {
+	return fmt.Sprintf("%T", v)
+}

dispatcher_test.go

@@ -0,0 +1,112 @@
+package stonecqrs
+
+import (
+	"context"
+	"fmt"
+	"testing"
+)
+
+type testCommand struct {
+	message string
+}
+
+type testQuery struct {
+	message string
+}
+
+type testEvent struct {
+	message string
+}
+
+type unknownEvent struct{}
+
+type testCommandHandler struct{}
+
+func (handler *testCommandHandler) Handle(
+	ctx context.Context, cmd Command,
+) ([]Event, error) {
+	fmt.Println(cmd)
+	return []Event{
+		testEvent{message: "test"},
+	}, nil
+}
+
+type testQueryHandler struct{}
+
+func (handler *testQueryHandler) Handle(
+	ctx context.Context, query Query,
+) (interface{}, error) {
+	fmt.Println(query)
+	return "test", nil
+}
+
+type testEventHandler struct{}
+
+func (handler *testEventHandler) Handle(
+	ctx context.Context, event Event,
+) error {
+	fmt.Println(event)
+	return nil
+}
+
+func Test_NewDispatcher(t *testing.T) {
+	d := NewDispatcher()
+	if d == nil {
+		t.Fatal("expected non-nil dispatcher")
+	}
+}
+
+func Test_Register(t *testing.T) {
+	d := NewDispatcher()
+	d.RegisterCommandHandler(testCommand{}, &testCommandHandler{})
+	d.RegisterQueryHandler(testQuery{}, &testQueryHandler{})
+	d.RegisterEventHandler(testEvent{}, &testEventHandler{})
+}
+
+func Test_DispatchCommandWithEvents(t *testing.T) {
+	d := NewDispatcher()
+	d.RegisterCommandHandler(testCommand{}, &testCommandHandler{})
+	d.RegisterQueryHandler(testQuery{}, &testQueryHandler{})
+	d.RegisterEventHandler(testEvent{}, &testEventHandler{})
+
+	_, err := d.DispatchCommand(context.Background(), testCommand{})
+
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func Test_DispatchQuery(t *testing.T) {
+	d := NewDispatcher()
+	d.RegisterQueryHandler(testQuery{}, &testQueryHandler{})
+
+	_, err := d.DispatchQuery(context.Background(), testQuery{})
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func Test_UnknownEvent(t *testing.T) {
+	d := NewDispatcher()
+	d.RegisterCommandHandler(testCommand{}, &testCommandHandler{})
+	d.RegisterQueryHandler(testQuery{}, &testQueryHandler{})
+	d.RegisterEventHandler(testEvent{}, &testEventHandler{})
+
+	_, err := d.DispatchCommand(context.Background(), unknownEvent{})
+
+	if err == nil {
+		t.Fatal("expected error")
+	}
+
+	err = d.DispatchEvent(context.Background(), unknownEvent{})
+
+	if err == nil {
+		t.Fatal("expected error")
+	}
+
+	err = d.DispatchEvent(context.Background(), unknownEvent{})
+
+	if err == nil {
+		t.Fatal("expected error")
+	}
+}

go.mod

@@ -0,0 +1,5 @@
+module gitstormr.dev/stone-utils/stonecqrs
+
+go 1.24
+
+require gitstormr.dev/stone-utils/stoneerror v1.0.0

go.sum

@@ -0,0 +1,2 @@
+gitstormr.dev/stone-utils/stoneerror v1.0.0 h1:EJpn4MZBeYifWlCoQBEGmGdEtNABjOrUzJmQSqcXqY0=
+gitstormr.dev/stone-utils/stoneerror v1.0.0/go.mod h1:Rs34Oz14ILsbkZ++Ov9PObTz7mRvyyvcCcML9AeyIyk=

sonar-project.properties

@@ -0,0 +1,10 @@
+sonar.projectKey=f33dd35c-308c-4f08-ace2-6449efc238e9
+sonar.projectName=stone-utils/stonecqrs
+sonar.language=go
+sonar.sources=.
+sonar.exclusions=**/*_test.go
+sonar.tests=.
+sonar.test.inclusions=**/*_test.go
+sonar.go.tests.reportPaths=test-report.out
+sonar.go.coverage.reportPaths=coverage.out
+sonar.qualitygate.wait=true