db: add versioned schema migration runner

src/db/migrations/index.ts

@@ -0,0 +1,66 @@
+import type { Database } from 'bun:sqlite';
+
+import { LEGACY_SCHEMA_BUNDLE_MIGRATION } from './001_legacy-schema-bundle.js';
+import type {
+  SchemaMigrationArgs,
+  SchemaMigrationDefinition,
+} from './types.js';
+
+const SCHEMA_MIGRATIONS_TABLE = 'schema_migrations';
+
+const ORDERED_SCHEMA_MIGRATIONS: readonly SchemaMigrationDefinition[] = [
+  LEGACY_SCHEMA_BUNDLE_MIGRATION,
+];
+
+function ensureSchemaMigrationsTable(database: Database): void {
+  database.exec(`
+    CREATE TABLE IF NOT EXISTS ${SCHEMA_MIGRATIONS_TABLE} (
+      version INTEGER PRIMARY KEY,
+      name TEXT NOT NULL,
+      applied_at TEXT NOT NULL DEFAULT (datetime('now'))
+    )
+  `);
+}
+
+function getAppliedSchemaVersions(database: Database): Set<number> {
+  const rows = database
+    .prepare(
+      `SELECT version
+         FROM ${SCHEMA_MIGRATIONS_TABLE}
+        ORDER BY version ASC`,
+    )
+    .all() as Array<{ version: number }>;
+  return new Set(rows.map((row) => row.version));
+}
+
+function recordAppliedSchemaMigration(
+  database: Database,
+  migration: SchemaMigrationDefinition,
+): void {
+  database
+    .prepare(
+      `INSERT INTO ${SCHEMA_MIGRATIONS_TABLE} (version, name)
+       VALUES (?, ?)`,
+    )
+    .run(migration.version, migration.name);
+}
+
+export function applyVersionedSchemaMigrations(
+  database: Database,
+  args: SchemaMigrationArgs,
+): void {
+  ensureSchemaMigrationsTable(database);
+  const appliedVersions = getAppliedSchemaVersions(database);
+
+  for (const migration of ORDERED_SCHEMA_MIGRATIONS) {
+    const alreadyApplied = appliedVersions.has(migration.version);
+    if (alreadyApplied && !migration.alwaysRun) {
+      continue;
+    }
+
+    migration.apply(database, args);
+    if (!alreadyApplied) {
+      recordAppliedSchemaMigration(database, migration);
+    }
+  }
+}