Initial commit

backend/internal/items/service.go

@@ -0,0 +1,147 @@
+package items
+
+import (
+	"context"
+	"strings"
+)
+
+// Field length limits enforced on input.
+const (
+	maxTitleLen       = 200
+	maxDescriptionLen = 2000
+)
+
+// Service holds the business rules for items. It depends only on the
+// Repository interface; main wires the Bun implementation in.
+type Service struct {
+	repo Repository
+}
+
+// NewService returns a Service over the given repository.
+func NewService(repo Repository) *Service {
+	return &Service{repo: repo}
+}
+
+// CreateInput is the request body for creating an item.
+type CreateInput struct {
+	Title       string `json:"title"`
+	Description string `json:"description"`
+	Status      Status `json:"status"`
+}
+
+// UpdateInput patches only provided fields (nil = leave untouched), which
+// is why every field is a pointer.
+type UpdateInput struct {
+	Title       *string `json:"title"`
+	Description *string `json:"description"`
+	Status      *Status `json:"status"`
+}
+
+// List validates the filter and delegates to the repository.
+func (s *Service) List(ctx context.Context, f Filter) ([]Item, error) {
+	f, err := normalizeFilter(f)
+	if err != nil {
+		return nil, err
+	}
+	return s.repo.List(ctx, f)
+}
+
+// Get returns one item.
+func (s *Service) Get(ctx context.Context, id int64) (Item, error) {
+	return s.repo.Get(ctx, id)
+}
+
+// Create validates input and stores a new item.
+func (s *Service) Create(ctx context.Context, in CreateInput) (Item, error) {
+	item := Item{
+		Title:       strings.TrimSpace(in.Title),
+		Description: strings.TrimSpace(in.Description),
+	}
+	if item.Title == "" {
+		return Item{}, &ValidationError{Field: "title", Reason: "required"}
+	}
+	if len(item.Title) > maxTitleLen {
+		return Item{}, &ValidationError{Field: "title", Reason: "must be at most 200 characters"}
+	}
+	if len(item.Description) > maxDescriptionLen {
+		return Item{}, &ValidationError{Field: "description", Reason: "must be at most 2000 characters"}
+	}
+
+	switch in.Status {
+	case "":
+		item.Status = StatusActive
+	case StatusActive, StatusArchived:
+		item.Status = in.Status
+	default:
+		return Item{}, &ValidationError{Field: "status", Reason: "must be active or archived"}
+	}
+
+	if err := s.repo.Create(ctx, &item); err != nil {
+		return Item{}, err
+	}
+	return item, nil
+}
+
+// Update applies a partial patch to an existing item.
+func (s *Service) Update(ctx context.Context, id int64, in UpdateInput) (Item, error) {
+	if in.Title == nil && in.Description == nil && in.Status == nil {
+		return Item{}, &ValidationError{Field: "body", Reason: "at least one field must be set"}
+	}
+
+	item, err := s.repo.Get(ctx, id)
+	if err != nil {
+		return Item{}, err
+	}
+
+	if in.Title != nil {
+		item.Title = strings.TrimSpace(*in.Title)
+		if item.Title == "" {
+			return Item{}, &ValidationError{Field: "title", Reason: "required"}
+		}
+		if len(item.Title) > maxTitleLen {
+			return Item{}, &ValidationError{Field: "title", Reason: "must be at most 200 characters"}
+		}
+	}
+	if in.Description != nil {
+		item.Description = strings.TrimSpace(*in.Description)
+		if len(item.Description) > maxDescriptionLen {
+			return Item{}, &ValidationError{Field: "description", Reason: "must be at most 2000 characters"}
+		}
+	}
+	if in.Status != nil {
+		if !in.Status.Valid() {
+			return Item{}, &ValidationError{Field: "status", Reason: "must be active or archived"}
+		}
+		item.Status = *in.Status
+	}
+
+	if err := s.repo.Update(ctx, &item); err != nil {
+		return Item{}, err
+	}
+	return item, nil
+}
+
+// Delete removes an item.
+func (s *Service) Delete(ctx context.Context, id int64) error {
+	return s.repo.Delete(ctx, id)
+}
+
+// normalizeFilter applies paging defaults and validates the status filter.
+func normalizeFilter(f Filter) (Filter, error) {
+	switch f.Status {
+	case "":
+	case StatusActive, StatusArchived:
+	default:
+		return Filter{}, &ValidationError{Field: "status", Reason: "must be active or archived"}
+	}
+	if f.Limit <= 0 {
+		f.Limit = DefaultLimit
+	}
+	if f.Limit > MaxLimit {
+		f.Limit = MaxLimit
+	}
+	if f.Offset < 0 {
+		f.Offset = 0
+	}
+	return f, nil
+}