package seo

import (
	"context"

	"git.golem15.com/golem15/sm-seo-plugin/classes"
	"git.golem15.com/golem15/summercms/modules/backpack"
	"git.golem15.com/golem15/summercms/modules/lagoon"
	"git.golem15.com/golem15/summercms/modules/pact"
	"gorm.io/gorm"
)

// listen subscribes to the framework's record events (D-92): a deleted
// record of a content type loses its SEO entries (kept in history), a
// created one gets its address snapshot, and an updated one whose address
// changed gets its 301 after commit (D-18), whoever wrote it: Journal's
// API, MCP, an import, or an admin form whose SEO tab the administrator
// does not see. Listener errors are logged by the bus and never fail the
// write that fired them.
func (p *Plugin) listen(app *backpack.App) {
	if app == nil || app.Events == nil {
		return
	}
	app.Events.Listen("golem15.seo", func(ctx context.Context, ev *pact.RecordDeleted) error {
		svc := p.Service()
		if svc == nil {
			return nil
		}
		return svc.RecordDeleted(ctx, ev)
	})
	app.Events.Listen("golem15.seo", func(ctx context.Context, ev *pact.RecordSaved) error {
		svc := p.Service()
		if svc == nil || ev == nil {
			return nil
		}
		if ev.Created {
			return svc.RecordCreated(ctx, ev)
		}
		return p.addressesAfterSave(ctx, svc, ev.Model, ev.ID)
	})
}

// addressesAfterSave re-describes a saved record of a content type in a
// transaction of its own and applies AddressChanged to every locale whose
// address differs from its entry's URL. After an admin save whose SEO tab
// already did this, nothing differs and nothing happens.
func (p *Plugin) addressesAfterSave(ctx context.Context, svc *classes.Service, model, id string) error {
	reg := svc.Registry()
	if reg == nil {
		return nil
	}
	typ, ok := reg.ContentTypeForModel(model)
	if !ok || typ.Content == nil {
		return nil
	}
	db, err := svc.DB(ctx)
	if err != nil {
		return err
	}
	// A lagoon transaction, so the history the 301 records purges the site
	// cache after the commit.
	return lagoon.Transaction(ctx, db, func(ctx context.Context, tx *gorm.DB) error {
		changes, err := svc.AddressChanges(ctx, tx, typ, id)
		if err != nil {
			return err
		}
		for _, change := range changes {
			if _, err := svc.AddressChanged(ctx, tx, change); err != nil {
				return err
			}
		}
		return nil
	})
}