// Package classes holds the SEO plugin's logic: the service every writer
// goes through, the entry store and the effective-SEO resolver.
package classes

import (
	"context"
	"errors"

	"git.golem15.com/golem15/summercms/modules/backpack"
	"git.golem15.com/golem15/summercms/modules/cabana"
	"git.golem15.com/golem15/summercms/modules/compass"
	"git.golem15.com/golem15/summercms/modules/signpost"
	"gorm.io/gorm"
)

// ErrNotBooted is returned when the service has no booted application.
var ErrNotBooted = errors.New("golem15.seo: app is not booted")

// Service is the plugin's single entry point for reads and writes of SEO
// data. The admin extension, the admin controllers, the listeners, the job
// and the API all call it, so every write goes through the same checks and
// history.
type Service struct {
	app *backpack.App
}

// NewService returns the service of a booted application. It needs the
// application's database; the signpost registry is optional (without it no
// content type takes part).
func NewService(app *backpack.App) (*Service, error) {
	if app == nil {
		return nil, ErrNotBooted
	}
	if db, ok := app.Lookup[*gorm.DB](); !ok || db == nil {
		return nil, errors.New("database is not configured")
	}
	return &Service{app: app}, nil
}

// App returns the booted application.
func (s *Service) App() *backpack.App {
	if s == nil {
		return nil
	}
	return s.app
}

// DB returns the write transaction carried by ctx (cabana.TxFromContext),
// else the application's database bound to ctx.
func (s *Service) DB(ctx context.Context) (*gorm.DB, error) {
	if tx, ok := cabana.TxFromContext(ctx); ok && tx != nil {
		return tx, nil
	}
	if s == nil || s.app == nil {
		return nil, ErrNotBooted
	}
	db, ok := s.app.Lookup[*gorm.DB]()
	if !ok || db == nil {
		return nil, errors.New("golem15.seo: database is not configured")
	}
	return db.WithContext(ctx), nil
}

// Registry returns the menu item type registry, nil when none is published.
func (s *Service) Registry() *signpost.Registry {
	if s == nil || s.app == nil {
		return nil
	}
	reg, _ := s.app.Lookup[*signpost.Registry]()
	return reg
}

// Config returns the application config, nil when there is none.
func (s *Service) Config() *compass.Config {
	if s == nil || s.app == nil {
		return nil
	}
	return s.app.Config
}