feat: authsession service

authsession/internal/service/getsession/service.go

@@ -0,0 +1,65 @@
+// Package getsession implements the trusted internal read use case for one
+// device session.
+package getsession
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"galaxy/authsession/internal/ports"
+	"galaxy/authsession/internal/service/shared"
+)
+
+// Input describes one trusted internal get-session request.
+type Input struct {
+	// DeviceSessionID identifies the session that should be read.
+	DeviceSessionID string
+}
+
+// Result describes one trusted internal get-session response.
+type Result struct {
+	// Session stores the frozen internal read-model DTO.
+	Session shared.Session
+}
+
+// Service executes the trusted internal get-session use case against the
+// configured ports.
+type Service struct {
+	sessionStore ports.SessionStore
+}
+
+// New returns a get-session service wired to sessionStore.
+func New(sessionStore ports.SessionStore) (*Service, error) {
+	if sessionStore == nil {
+		return nil, fmt.Errorf("getsession: session store must not be nil")
+	}
+
+	return &Service{sessionStore: sessionStore}, nil
+}
+
+// Execute loads one source-of-truth session and projects it into the frozen
+// internal read DTO shape.
+func (s *Service) Execute(ctx context.Context, input Input) (Result, error) {
+	deviceSessionID, err := shared.ParseDeviceSessionID(input.DeviceSessionID)
+	if err != nil {
+		return Result{}, err
+	}
+
+	record, err := s.sessionStore.Get(ctx, deviceSessionID)
+	if err != nil {
+		switch {
+		case errors.Is(err, ports.ErrNotFound):
+			return Result{}, shared.SessionNotFound()
+		default:
+			return Result{}, shared.ServiceUnavailable(err)
+		}
+	}
+
+	session, err := shared.ToSession(record)
+	if err != nil {
+		return Result{}, shared.InternalError(err)
+	}
+
+	return Result{Session: session}, nil
+}