// Package listusersessions implements the trusted internal read use case for
// listing all sessions of one user.
package listusersessions

import (
	"context"
	"fmt"

	"galaxy/authsession/internal/ports"
	"galaxy/authsession/internal/service/shared"
)

// Input describes one trusted internal list-user-sessions request.
type Input struct {
	// UserID identifies the owner whose sessions should be listed.
	UserID string
}

// Result describes one trusted internal list-user-sessions response.
type Result struct {
	// Sessions stores the frozen internal read-model DTO slice.
	Sessions []shared.Session
}

// Service executes the trusted internal list-user-sessions use case.
type Service struct {
	sessionStore ports.SessionStore
}

// New returns a list-user-sessions service wired to sessionStore.
func New(sessionStore ports.SessionStore) (*Service, error) {
	if sessionStore == nil {
		return nil, fmt.Errorf("listusersessions: session store must not be nil")
	}

	return &Service{sessionStore: sessionStore}, nil
}

// Execute loads all source-of-truth sessions for one user and projects them
// into the frozen internal read DTO shape.
func (s *Service) Execute(ctx context.Context, input Input) (Result, error) {
	userID, err := shared.ParseUserID(input.UserID)
	if err != nil {
		return Result{}, err
	}

	records, err := s.sessionStore.ListByUserID(ctx, userID)
	if err != nil {
		return Result{}, shared.ServiceUnavailable(err)
	}

	sessions, err := shared.ToSessions(records)
	if err != nil {
		return Result{}, shared.InternalError(err)
	}

	return Result{Sessions: sessions}, nil
}