package lighthouse

import (
	"context"

	"git.golem15.com/golem15/summercms/modules/bouncer"
)

// User is the identity a realtime driver needs: the id and display name.
type User struct {
	ID   uint
	Name *string
}

// UserLookup loads a user by id. found is false when no such user exists.
type UserLookup func(ctx context.Context, id uint) (user User, found bool, err error)

// SetUserLookup installs the application's user lookup.
func (s *Service) SetUserLookup(fn UserLookup) {
	if s == nil {
		return
	}
	s.mu.Lock()
	s.lookup = fn
	s.mu.Unlock()
}

// User loads user id through the installed lookup. Without a lookup it
// returns User{ID: id} with a nil Name and found true.
func (s *Service) User(ctx context.Context, id uint) (User, bool, error) {
	if s == nil {
		return User{ID: id}, true, nil
	}
	s.mu.RLock()
	fn := s.lookup
	s.mu.RUnlock()
	if fn == nil {
		return User{ID: id}, true, nil
	}
	return fn(ctx, id)
}

// Actor is who caused a broadcast. It marshals as {"user_id":…,"name":…}.
type Actor struct {
	UserID *uint   `json:"user_id"`
	Name   *string `json:"name"`
}

// SystemActor is the actor of writes made without a signed-in user:
// {"user_id":null,"name":"System"}.
func SystemActor() Actor {
	name := "System"
	return Actor{Name: &name}
}

// Actor returns the actor of the request in ctx. No principal, or a
// backend-admin principal, gives SystemActor: the WinterCMS frontend user is
// empty in backend requests. Otherwise it is the principal's id and the
// looked-up name (nil when the lookup fails or finds nothing).
func (s *Service) Actor(ctx context.Context) Actor {
	p, ok := bouncer.User(ctx)
	if !ok || p == nil || p.Backend {
		return SystemActor()
	}
	id := p.ID
	a := Actor{UserID: &id}
	if u, found, err := s.User(ctx, id); err == nil && found {
		a.Name = u.Name
	}
	return a
}