core: add migration service

packages/hydrooj/src/service/migration.ts

@@ -0,0 +1,52 @@
+/* eslint-disable no-await-in-loop */
+import { Logger } from '@hydrooj/utils';
+import { Context, Service } from '../context';
+import * as system from '../model/system';
+
+export type MigrationScript = null | (() => Promise<boolean | void>);
+const logger = new Logger('migration');
+
+declare module '../context' {
+    interface Context {
+        migration: MigrationService;
+    }
+}
+
+export default class MigrationService extends Service {
+    private channels: Record<string, MigrationScript[]> = {};
+
+    constructor(ctx: Context) {
+        super(ctx, 'migration', true);
+    }
+
+    async registerChannel(name: string, s: MigrationScript[]) {
+        this.channels[name] = s;
+    }
+
+    async doUpgrade() {
+        for (const channel in this.channels) {
+            const name = `db.ver${channel === 'hydrooj' ? '' : `-${channel}`}`;
+            let dbVer = system.get(name) ?? 0;
+            const scripts = this.channels[channel];
+            const isFresh = !dbVer;
+            const expected = scripts.length;
+            if (isFresh) {
+                await scripts[0]?.();
+                await system.set(name, expected);
+                continue;
+            }
+            while (dbVer < expected) {
+                const func = scripts[dbVer];
+                if (typeof func !== 'function') {
+                    dbVer++;
+                    continue;
+                }
+                logger.info('Upgrading database [%s]: from %d to %d', channel, dbVer, expected);
+                const result = await func();
+                if (!result) break;
+                dbVer++;
+                await system.set(name, dbVer);
+            }
+        }
+    }
+}