refactor: usecase structure

backend/internal/domain/domain.go

@@ -0,0 +1,16 @@
+// Package domain contains common values used accross the whole domain implementation.
+package domain
+
+import "errors"
+
+var (
+	// ErrNotFound is a sentinel error value returned when an entity is not found.
+	ErrNotFound = errors.New("not found")
+
+	// ErrForbidden is a sentinel error value returned when an operation is forbidden.
+	ErrForbidden = errors.New("forbidden")
+
+	// ErrInvalidCharacter is a sentinel error value returned when an operation targets a character and that
+	// character does not exist or is otherwise invalid.
+	ErrInvalidCharacter = errors.New("invlid character")
+)

backend/internal/domain/ports/repository/repository.go

@@ -0,0 +1,35 @@
+// Package repository defines the port interface for a session repository to
+// abstract persistence access for a session.
+package repository
+
+import (
+	"context"
+	"errors"
+
+	"github.com/halimath/fate-core-remote-table/backend/internal/domain/session"
+)
+
+// NoSave is a sentinel value returned to signal, that a repository must not be
+// saved in the datastore.
+var NoSave = errors.New("no save")
+
+// UnitOfWork defines a function type that defines the interface for callback
+// functions that perform some atomic unit of work on a [session.Session].
+// ctx is used to define deadlines and additional context values. exists signals
+// whether the s exists in the datastore. s contains the current values for the
+// session.
+//
+// The function returns a session.Session to update the datastore with if the
+// returned error is nil. If the error is the sentinal value NoSave, then no
+// insert/update is exectued and the returned session is ignored. Any other
+// non-nil error value causes no update and is propagated to any caller.
+type UnitOfWork func(ctx context.Context, exists bool, s session.Session) (session.Session, error)
+
+// Port defines the port interface for repository implementations
+// managing a session.
+type Port interface {
+	// Perform executes uow. It first tries to load the session.Session identified
+	// by id and passes that information to uow. It returns an error returned
+	// from uow or from the underlying datastore.
+	Perform(ctx context.Context, id string, uow UnitOfWork) error
+}

backend/internal/domain/ports/repository/repositorymock/repositorymock.go

@@ -0,0 +1,28 @@
+package repositorymock
+
+import (
+	"context"
+	"errors"
+
+	"github.com/halimath/fate-core-remote-table/backend/internal/domain/ports/repository"
+	"github.com/halimath/fate-core-remote-table/backend/internal/domain/session"
+)
+
+type Mock struct {
+	S session.Session
+}
+
+func (r *Mock) Perform(ctx context.Context, id string, uow repository.UnitOfWork) error {
+	s, err := uow(ctx, r.S.ID == id, r.S)
+	if errors.Is(err, repository.NoSave) {
+		return nil
+	}
+
+	if err != nil {
+		return err
+	}
+
+	r.S = s
+
+	return nil
+}