refactoring

Resolve #7779

packages/backend/src/misc/cafy-id.ts

@@ -0,0 +1,32 @@
+import { Context } from 'cafy';
+
+export class ID<Maybe = string> extends Context<string | (Maybe extends {} ? string : Maybe)> {
+	public readonly name = 'ID';
+
+	constructor(optional = false, nullable = false) {
+		super(optional, nullable);
+
+		this.push((v: any) => {
+			if (typeof v !== 'string') {
+				return new Error('must-be-an-id');
+			}
+			return true;
+		});
+	}
+
+	public getType() {
+		return super.getType('String');
+	}
+
+	public makeOptional(): ID<undefined> {
+		return new ID(true, false);
+	}
+
+	public makeNullable(): ID<null> {
+		return new ID(false, true);
+	}
+
+	public makeOptionalNullable(): ID<undefined | null> {
+		return new ID(true, true);
+	}
+}