Add Discord-hosted preview caching (C11)

media-scrape/src/store.ts

@@ -114,6 +114,7 @@ export interface MediaRow {
     preview_bytes: number | null;
     file_path: string | null;
     download_error: string | null;
+    preview_error: string | null;
     created_at: string;
 }
 
@@ -145,6 +146,7 @@ CREATE TABLE IF NOT EXISTS media (
     preview_bytes INTEGER,
     file_path TEXT,
     download_error TEXT,
+    preview_error TEXT,
     created_at TEXT NOT NULL
 );
 
@@ -178,6 +180,7 @@ export class ScrapeStore {
         if (!names.has("source")) this.db.exec("ALTER TABLE media ADD COLUMN source TEXT");
         if (!names.has("file_path")) this.db.exec("ALTER TABLE media ADD COLUMN file_path TEXT");
         if (!names.has("download_error")) this.db.exec("ALTER TABLE media ADD COLUMN download_error TEXT");
+        if (!names.has("preview_error")) this.db.exec("ALTER TABLE media ADD COLUMN preview_error TEXT");
     }
 
     close(): void {
@@ -291,6 +294,25 @@ export class ScrapeStore {
         this.db.prepare("UPDATE media SET download_error = ? WHERE id = ?").run(error.slice(0, 200), id);
     }
 
+    /** Image and GIF rows that still need a cached preview. */
+    pendingPreviews(limit = 5000): MediaRow[] {
+        return this.db
+            .prepare(
+                "SELECT * FROM media WHERE (kind = 'image' OR kind = 'gif') AND preview_hash IS NULL AND preview_error IS NULL ORDER BY id LIMIT ?"
+            )
+            .all(limit) as unknown as MediaRow[];
+    }
+
+    markPreview(id: number, preview: { hash: string; bytes: number }): void {
+        this.db
+            .prepare("UPDATE media SET preview_hash = ?, preview_bytes = ?, preview_error = NULL WHERE id = ?")
+            .run(preview.hash, preview.bytes, id);
+    }
+
+    markPreviewError(id: number, error: string): void {
+        this.db.prepare("UPDATE media SET preview_error = ? WHERE id = ?").run(error.slice(0, 200), id);
+    }
+
     getMedia(id: number): MediaRow | null {
         const row = this.db.prepare("SELECT * FROM media WHERE id = ?").get(id) as unknown as
             | MediaRow