Add authenticated content editing

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

internal/service/content.go

@@ -0,0 +1,73 @@
+package service
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"github.com/example/cms/internal/domain"
+	"github.com/example/cms/internal/repository"
+	"regexp"
+	"strings"
+	"time"
+)
+
+type IContentService interface {
+	List(context.Context, int, int) ([]domain.Content, error)
+	Get(context.Context, string) (domain.Content, error)
+	Update(context.Context, domain.Content, domain.Session) (domain.Content, error)
+}
+type ContentService struct {
+	repo repository.IContentRepository
+	auth *AuthService
+}
+
+func NewContentService(r repository.IContentRepository, a *AuthService) *ContentService {
+	return &ContentService{repo: r, auth: a}
+}
+func (s *ContentService) List(ctx context.Context, limit, offset int) ([]domain.Content, error) {
+	if limit < 1 {
+		limit = 20
+	}
+	if limit > 100 {
+		limit = 100
+	}
+	if offset < 0 {
+		offset = 0
+	}
+	return s.repo.List(ctx, limit, offset)
+}
+func (s *ContentService) Get(ctx context.Context, slug string) (domain.Content, error) {
+	if !validSlug(slug) {
+		return domain.Content{}, errors.New("invalid slug")
+	}
+	return s.repo.FindBySlug(ctx, slug)
+}
+func (s *ContentService) Update(ctx context.Context, c domain.Content, session domain.Session) (domain.Content, error) {
+	if s.auth == nil || !s.auth.CanEdit(ctx, session) {
+		return domain.Content{}, errors.New("forbidden")
+	}
+	if !validSlug(c.Slug) || strings.TrimSpace(c.Title) == "" || strings.TrimSpace(c.Body) == "" {
+		return domain.Content{}, errors.New("invalid content")
+	}
+	old, err := s.repo.FindBySlug(ctx, c.Slug)
+	if err != nil {
+		return domain.Content{}, err
+	}
+	c.ID = old.ID
+	c.CreatedAt = old.CreatedAt
+	c.CreatedBy = old.CreatedBy
+	c.UpdatedAt = time.Now()
+	if session.UserID != nil {
+		c.UpdatedBy = *session.UserID
+	}
+	snapshot, _ := json.Marshal(c)
+	h := domain.ContentHistory{ContentID: c.ID, Operation: "updated", CreatedAt: c.UpdatedAt, Snapshot: string(snapshot), ActorID: session.UserID, ActorAdminID: session.AdminID}
+	if err = s.repo.Update(ctx, c, h); err != nil {
+		return domain.Content{}, err
+	}
+	return c, nil
+}
+
+var slugRE = regexp.MustCompile(`^[a-z0-9]+(?:-[a-z0-9]+)*$`)
+
+func validSlug(s string) bool { return len(s) <= 200 && slugRE.MatchString(s) }