feat: serve message fetches from the cache

Signed-off-by: Sebastian Krupinski <krupinski01@gmail.com>

lib/Providers/CachedService.php

@@ -173,14 +173,33 @@ class CachedService extends ServiceBase
 
     public function entityFetchBulk(EntityIdentifierInterface ...$identifiers): array
     {
-        // served from the cache in 5.2c
-        return $this->live()->entityFetchBulk(...$identifiers);
+        return iterator_to_array($this->entityFetchStream(...$identifiers), true);
     }
 
+    /**
+     * Fetch messages from the cache; messages that are not cached are fetched from the
+     * server and cached, mailboxes never harmonized are read from the server.
+     */
     public function entityFetchStream(EntityIdentifierInterface ...$identifiers): Generator
     {
-        // served from the cache in 5.2c
-        return $this->live()->entityFetchStream(...$identifiers);
+        $byMailbox = [];
+        foreach ($identifiers as $identifier) {
+            if ($identifier->provider() !== $this->provider() || (string) $identifier->service() !== $this->serviceId()) {
+                throw new \InvalidArgumentException('Entity identifier does not belong to this service: ' . $identifier);
+            }
+            $byMailbox[(string) $identifier->collection()][] = (int) $identifier->entity();
+        }
+
+        foreach ($byMailbox as $mailbox => $uids) {
+            $uidValidity = $this->mailboxStore->state($this->serviceId(), (string) $mailbox)['uidValidity'];
+            $entities = $uidValidity === null
+                ? $this->liveMail()->entityFetch((string) $mailbox, ...$uids)
+                : $this->hydrate((string) $mailbox, (int) $uidValidity, $uids);
+
+            foreach ($entities as $entity) {
+                yield $entity->urn() => $entity;
+            }
+        }
     }
 
     /**
@@ -289,6 +308,9 @@ class CachedService extends ServiceBase
                     $missing[] = $uid;
                     continue;
                 }
+                if ($entity->getProperties()->getIncompleteSections() !== []) {
+                    $this->completeSections($mailbox, $uidValidity, $entity);
+                }
                 $entities[$uid] = $entity;
             }
 
@@ -307,6 +329,31 @@ class CachedService extends ServiceBase
         }
     }
 
+    /**
+     * Fetch the full content of sections cut off at ingest and store the completed message.
+     *
+     * Content is immutable, so the meta document and change sequence are untouched. A
+     * failure leaves the cut off text in place; it is tried again on the next read.
+     */
+    private function completeSections(string $mailbox, int $uidValidity, EntityResource $entity): void
+    {
+        $properties = $entity->getProperties();
+        $uid = (int) $entity->identifier();
+
+        try {
+            $sections = $this->liveMail()->messageSections($mailbox, $uid, ...$properties->getIncompleteSections());
+            if ($sections === []) {
+                return;
+            }
+            foreach ($sections as $partId => $content) {
+                $properties->completeSection((string) $partId, $content);
+            }
+            $this->fileStore->write($this->tenantId(), $this->serviceId(), $mailbox, $uidValidity, $uid, $entity->toCacheContent());
+        } catch (\Throwable) {
+            // keep the cut off text; retried on the next read
+        }
+    }
+
     /**
      * An entity from its meta document and message.json; null when the content is missing or outdated.
      */