feat: purge the site cache after SEO writes

- every write that records history (admin, MCP, batch, import, undo,
  automatic) queues the framework's site-cache purge (kind seo, slug the
  address or * for settings and robots.txt) after its commit, once per
  transaction; a rolled-back write never purges
- the record-deleted cleanup and the address tracking of saves outside the
  admin run in lagoon transactions, so their history purges as well

classes/generate.go

@@ -7,6 +7,7 @@ import (
 
 	"git.golem15.com/golem15/sm-seo-plugin/models"
 	"git.golem15.com/golem15/summercms/modules/conga"
+	"git.golem15.com/golem15/summercms/modules/lagoon"
 	"git.golem15.com/golem15/summercms/modules/pact"
 	"gorm.io/gorm"
 )
@@ -193,7 +194,9 @@ func (s *Service) RecordDeleted(ctx context.Context, ev *pact.RecordDeleted) err
 		return err
 	}
 	ctx = WithVia(ctx, models.ViaAuto)
-	return db.Transaction(func(tx *gorm.DB) error {
+	// A lagoon transaction, so the history it records purges the site
+	// cache after the commit.
+	return lagoon.Transaction(ctx, db, func(ctx context.Context, tx *gorm.DB) error {
 		entries, err := LoadEntries(tx, typ.Content.Model, ev.ID)
 		if err != nil || len(entries) == 0 {
 			return err

classes/history.go

@@ -7,10 +7,13 @@ import (
 	"fmt"
 	"reflect"
 	"strings"
+	"sync"
 	"time"
 
 	"git.golem15.com/golem15/sm-seo-plugin/models"
 	"git.golem15.com/golem15/summercms/modules/bouncer"
+	"git.golem15.com/golem15/summercms/modules/cooler"
+	"git.golem15.com/golem15/summercms/modules/lagoon"
 	"git.golem15.com/golem15/summercms/modules/pact"
 	"git.golem15.com/golem15/summercms/modules/phrasebook"
 	"gorm.io/gorm"
@@ -232,10 +235,82 @@ func (s *Service) Record(ctx context.Context, db *gorm.DB, changes ...Change) er
 		if err := db.Create(&row).Error; err != nil {
 			return err
 		}
+		s.purgeAfterCommit(ctx, db, purgeSlug(c))
 	}
 	return nil
 }
 
+// SiteCacheKind is the purge kind of SEO writes (P33-19).
+const SiteCacheKind = "seo"
+
+// purgeAfterCommit queues the rendered site's cache purge once the write
+// db belongs to commits (P33-19, D-97): every SEO write that records
+// history (admin, MCP, batch, import, undo, automatic) refreshes the
+// layer's cached resolve answers and pages. A transaction purges once,
+// however many rows it records; a rolled-back write never purges. Without
+// a configured purger (site_cache.purge_url) it does nothing.
+func (s *Service) purgeAfterCommit(ctx context.Context, db *gorm.DB, slug string) {
+	if s == nil || s.app == nil {
+		return
+	}
+	p := cooler.SiteCacheFromApp(s.app)
+	if p == nil {
+		return
+	}
+	var pool gorm.ConnPool
+	if db != nil && db.Statement != nil {
+		if _, inTx := db.Statement.ConnPool.(gorm.TxCommitter); inTx {
+			pool = db.Statement.ConnPool
+		}
+	}
+	if pool != nil {
+		purgeMu.Lock()
+		if purging == nil || len(purging) > maxPendingPurges {
+			// Rolled-back transactions leave their key behind; the map is
+			// reset rather than grow.
+			purging = map[gorm.ConnPool]bool{}
+		}
+		if purging[pool] {
+			purgeMu.Unlock()
+			return
+		}
+		purging[pool] = true
+		purgeMu.Unlock()
+		lagoon.AfterCommit(ctx, db, func(context.Context, *gorm.DB) {
+			purgeMu.Lock()
+			delete(purging, pool)
+			purgeMu.Unlock()
+		})
+	}
+	cooler.PurgeSiteCacheAfterCommit(ctx, db, p, SiteCacheKind, slug)
+}
+
+// maxPendingPurges caps the transactions purgeAfterCommit remembers.
+const maxPendingPurges = 1024
+
+// purging holds the open transactions whose site-cache purge is queued, so
+// each purges once whichever Service instance records in it.
+var (
+	purgeMu sync.Mutex
+	purging map[gorm.ConnPool]bool
+)
+
+// purgeSlug is the purge's slug: "*" for the settings and robots.txt,
+// else the changed object's address.
+func purgeSlug(c Change) string {
+	if c.Kind == models.SubjectSettings || c.Kind == models.SubjectRobots {
+		return "*"
+	}
+	for _, values := range []map[string]any{c.After, c.Before} {
+		for _, key := range []string{"url", "source"} {
+			if v, ok := values[key].(string); ok && strings.TrimSpace(v) != "" {
+				return v
+			}
+		}
+	}
+	return "*"
+}
+
 // translator returns the application translator, nil when none.
 func (s *Service) translator() *phrasebook.Translator {
 	if s == nil || s.app == nil {