chore: Fix possible EPG generate and cache race condition

Make sure only valid data is ever used to generate EPG XML files

Author: sparkison

app/Http/Controllers/EpgGenerateController.php

@@ -227,11 +227,10 @@ private function generate($playlist)
             }
 
             try {
-                // Try to use cached data first
-                // if ($cacheService->isCacheValid($epg)) {
-                // Do a quick check instead of fetching metadata and parsing
-                // If flagged as cached, use the cache
-                if ($epg->is_cached) {
+                // Try to use cached data first with proper validation
+                // CRITICAL: Check both is_cached flag AND that cache is actually valid
+                // This prevents race condition where cache is being regenerated
+                if ($epg->is_cached && $cacheService->isCacheValid($epg)) {
                     // Get all programmes from cache
                     $startDate = Carbon::now()->subDays(1)->format('Y-m-d');
                     $epgDays = config('dev.default_epg_days', 7);

app/Jobs/GenerateEpgCache.php

@@ -64,7 +64,8 @@ public function handle(EpgCacheService $cacheService): void
                 'processing_phase' => null,
             ]);
 
-            // Clear out any related EPG file caches
+            // Clear playlist EPG cache files AFTER new cache is generated
+            // This ensures users can still get cached EPG files during regeneration
             foreach ($epg->getAllPlaylists() as $playlist) {
                 EpgCacheService::clearPlaylistEpgCacheFile($playlist);
             }

app/Listeners/SyncListener.php

@@ -110,9 +110,15 @@ private function handleAutoMergeChannels(\App\Models\Playlist $playlist): void
     private function postProcessEpg(Epg $epg)
     {
         // Update status to Processing (so UI components will continue to refresh) and dispatch cache job
+        // IMPORTANT: Set is_cached to false to prevent race condition where users
+        // try to read the EPG cache (JSON files) while it's being regenerated
+        // Note: Playlist EPG cache files (XML) are NOT cleared here - they remain available
+        // for users until the new cache is generated, preventing fallback to slow XML reader
         // Note: processing_started_at and processing_phase will be set by GenerateEpgCache job
         $epg->update([
             'status' => Status::Processing,
+            'is_cached' => false,
+            'cache_meta' => null,
             'processing_started_at' => null,
             'processing_phase' => null,
         ]);

app/Services/EpgCacheService.php

@@ -55,6 +55,12 @@ private function getCacheFilePath(Epg $epg, string $filename): string
      */
     public function isCacheValid(Epg $epg): bool
     {
+        // CRITICAL: If EPG is currently being processed, cache is NOT valid
+        // This prevents race condition where we try to read a cache being regenerated
+        if ($epg->processing_phase === 'cache' || $epg->status === Status::Processing) {
+            return false;
+        }
+
         $metadataPath = $this->getCacheFilePath($epg, self::METADATA_FILE);
 
         if (!Storage::disk('local')->exists($metadataPath)) {