1 files changed, 97 insertions, 0 deletions
diff --git a/src/common/remote/activitypub/resolver.ts b/src/common/remote/activitypub/resolver.ts
new file mode 100644
index 0000000000..50ac1b0b19
--- /dev/null
+++ b/src/common/remote/activitypub/resolver.ts
@@ -0,0 +1,97 @@
+import RemoteUserObject from '../../../models/remote-user-object';
+import { IObject } from './type';
+const request = require('request-promise-native');
+
+type IResult = {
+  resolver: Resolver;
+  object: IObject;
+};
+
+async function resolveUnrequestedOne(this: Resolver, value) {
+	if (typeof value !== 'string') {
+		return { resolver: this, object: value };
+	}
+
+	const resolver = new Resolver(this.requesting);
+
+	resolver.requesting.add(value);
+
+	const object = await request({
+		url: value,
+		headers: {
+			Accept: 'application/activity+json, application/ld+json'
+		},
+		json: true
+	});
+
+	if (object === null || (
+		Array.isArray(object['@context']) ?
+			!object['@context'].includes('https://www.w3.org/ns/activitystreams') :
+			object['@context'] !== 'https://www.w3.org/ns/activitystreams'
+	)) {
+		throw new Error;
+	}
+
+	return { resolver, object };
+}
+
+async function resolveCollection(this: Resolver, value) {
+	if (Array.isArray(value)) {
+		return value;
+	}
+
+	const resolved = typeof value === 'string' ?
+		await resolveUnrequestedOne.call(this, value) :
+		value;
+
+	switch (resolved.type) {
+	case 'Collection':
+		return resolved.items;
+
+	case 'OrderedCollection':
+		return resolved.orderedItems;
+
+	default:
+		return [resolved];
+	}
+}
+
+export default class Resolver {
+	requesting: Set<string>;
+
+	constructor(iterable?: Iterable<string>) {
+		this.requesting = new Set(iterable);
+	}
+
+	async resolve(value): Promise<Promise<IResult>[]> {
+		const collection = await resolveCollection.call(this, value);
+
+		return collection
+			.filter(element => !this.requesting.has(element))
+			.map(resolveUnrequestedOne.bind(this));
+	}
+
+	resolveOne(value) {
+		if (this.requesting.has(value)) {
+			throw new Error;
+		}
+
+		return resolveUnrequestedOne.call(this, value);
+	}
+
+	async resolveRemoteUserObjects(value) {
+		const collection = await resolveCollection.call(this, value);
+
+		return collection.filter(element => !this.requesting.has(element)).map(element => {
+			if (typeof element === 'string') {
+				const object = RemoteUserObject.findOne({ uri: element });
+
+				if (object !== null) {
+					return object;
+				}
+			}
+
+			return resolveUnrequestedOne.call(this, element);
+		});
+	}
+}