feat: add link generation support (short/sentence links) + wordlist

src/services/linkService.ts

@@ -0,0 +1,137 @@
+import { Link } from '../entities/Link';
+import { User } from '../entities/User';
+import { AppDataSource } from '../data-source';
+import { getEnvString } from '../tools/jwt';
+
+export type IdResponse = {
+	id: number;
+	exists: boolean;
+};
+
+export class LinkService {
+	dataSource = AppDataSource;
+	linkRepo = this.dataSource.getRepository(Link);
+
+	// Retrieve config to check whether subdomains are allowed
+	useSubdomains: boolean = getEnvString('useSubdomains', true) === 'true';
+
+	/**
+	 * Simply insert a new link entity anonymously.
+	 *
+	 * @param      {Link}     link    The link to insert
+	 */
+	async addAnonymous(link: Link): Promise<IdResponse> {
+		let result: IdResponse = { id: -1, exists: false };
+
+		// Sanity check: don't allow for adding links
+		// with subdomains if server has it disabled.
+		if (link.subdomain && !this.useSubdomains) link.subdomain = null;
+
+		// Check if entry can be inserted.
+		if (await this.canInsert(link)) {
+			await this.linkRepo.insert(link);
+
+			// Then get new link's ID
+			const insertedLink: Link[] = await this.linkRepo.findBy({
+				shortUri: link.shortUri,
+				 fullUrl: link.fullUrl
+			});
+
+			// Return appropriate id (or error)
+			if (insertedLink.length !== 1) {
+				result.id = -2;
+				result.exists = false;				
+			} else {
+				result.id = insertedLink[0].id;
+				result.exists = true;
+			}
+		}
+
+		return result;
+	}
+
+	/**
+	 * Adds a new link entity, and links it with passed user.
+	 * 
+	 * USE ONLY FOR AUTHENTICATED USERS. For unauthenticated users
+	 * use addAnonymous() instead. Returns IdResponse, containing
+	 * exists field indicating if an existing field has been found,
+	 * and if so, what is it's id. If exists is false, ID of the
+	 * newly created entity gets returned.
+	 * 
+	 * Errors: an error ocurred if ID is negative.
+	 * 
+	 * This can be:
+	 * 
+	 * - -1 - link can't be inserted (because an entry with shortUri or shortUri+subdomain combo exist),
+	 * 
+	 * - -2 - no conflicting entry exists but transaction failed anyway.
+	 * 
+	 * @param      {Link}                 link    The link
+	 * @param      {User}                 user    The user
+	 * @return     {Promise<IdResponse>}  Dictionary containing link ID and whether it already existed, or was just inserted
+	 */
+	async addIfNew(link: Link, user: User): Promise<IdResponse> {
+
+		let result: IdResponse = { id: -1, exists: false };
+
+		// If no conflicts are found,
+		// proceed with creating a new link entry.
+		if (await this.canInsert(link)) {
+			// Commit a transaction
+			this.dataSource.transaction(async (t) => {
+				link.author = user;
+				user.links.push(link);
+				t.insert(Link, link);
+				t.save(user);
+			});
+
+			// Then get new link's ID
+			const insertedLink: Link[] = await this.linkRepo.findBy({
+				shortUri: link.shortUri,
+				 fullUrl: link.fullUrl
+			});
+
+			// Return appropriate id (or error)
+			if (insertedLink.length !== 1) {
+				result.id = -2;
+				result.exists = false;				
+			} else {
+				result.id = insertedLink[0].id;
+				result.exists = true;
+			}
+
+		}
+
+		return result;
+	}
+
+	async canInsert(link: Link): Promise<boolean> {
+		let shortUriExists: boolean = true
+
+		// If both subdomains are enabled, and user 
+		// provided a subdomain, find if a record exists 
+		// that either has the exact shortUri 
+		// or shortUri and subdomain combo.
+		// If any of these turns out to be true, the request 
+		// must be invalidated and we can't proceed 
+		// with creation of a new link.
+		if (this.useSubdomains && link.subdomain)
+		{
+			shortUriExists = await this.linkRepo.existsBy({
+				shortUri: link.shortUri,
+				subdomain: link.subdomain
+			});
+		}
+		// If custom subdomains are disabled, fallback to
+		// checking only by the URIs - thus discarding
+		// any possible subdomains.
+		else
+		{
+			shortUriExists = await this.linkRepo.existsBy({ shortUri: link.shortUri });
+		}
+
+		return !shortUriExists;
+	}
+
+}