Add YouTube cache table

src/database/metadata_cache.js

@@ -0,0 +1,69 @@
+import { createMySQLDuplicateKeyUpdate } from '../util/on-duplicate-key-update';
+const Switches = require('../switches');
+
+const Media = require('cytube-mediaquery/lib/media');
+
+// TODO: these fullname-vs-shortcode hacks really need to be abolished
+function mediaquery2cytube(type) {
+    switch (type) {
+        case 'youtube':
+            return 'yt';
+        default:
+            throw new Error(`mediaquery2cytube: no mapping for ${type}`);
+    }
+}
+
+function cytube2mediaquery(type) {
+    switch (type) {
+        case 'yt':
+            return 'youtube';
+        default:
+            throw new Error(`cytube2mediaquery: no mapping for ${type}`);
+    }
+}
+
+class MetadataCacheDB {
+    constructor(db) {
+        this.db = db;
+    }
+
+    async put(media) {
+        if (!Switches.isActive('ytCache')) return;
+
+        media = new Media(media);
+        media.type = mediaquery2cytube(media.type);
+        return this.db.runTransaction(async tx => {
+            let insert = tx.table('media_metadata_cache')
+                .insert({
+                    id: media.id,
+                    type: media.type,
+                    metadata: JSON.stringify(media)
+                });
+            let update = tx.raw(createMySQLDuplicateKeyUpdate(
+                ['metadata']
+            ));
+
+            return tx.raw(insert.toString() + update.toString());
+        });
+    }
+
+    async get(id, type) {
+        if (!Switches.isActive('ytCache')) return null;
+
+        return this.db.runTransaction(async tx => {
+            let row = await tx.table('media_metadata_cache')
+                .where({ id, type })
+                .first();
+
+            if (row === undefined || row === null) {
+                return null;
+            }
+
+            let metadata = JSON.parse(row.metadata);
+            metadata.type = cytube2mediaquery(metadata.type);
+            return new Media(metadata);
+        });
+    }
+}
+
+export { MetadataCacheDB };

src/database/tables.js

@@ -142,4 +142,17 @@ export async function initTables() {
         t.timestamps(/* useTimestamps */ true, /* defaultToNow */ true);
         t.index('created_at');
     });
+
+    await ensureTable('media_metadata_cache', t => {
+        // The types of id and type are chosen for compatibility
+        // with the existing channel_libraries table.
+        // TODO in the future schema, revisit the ID layout for different media types.
+        t.string('id', 255).notNullable();
+        t.string('type', 2).notNullable();
+        t.text('metadata').notNullable();
+        t.timestamps(/* useTimestamps */ true, /* defaultToNow */ true);
+
+        t.primary(['type', 'id']);
+        t.index('updated_at');
+    });
 }