feat: Create PathBasedAuthorizer

src/authorization/PathBasedAuthorizer.ts

@@ -0,0 +1,52 @@
+import { NotImplementedHttpError } from '../util/errors/NotImplementedHttpError';
+import { ensureTrailingSlash, trimTrailingSlashes } from '../util/PathUtil';
+import type { Authorization } from './Authorization';
+import type { AuthorizerArgs } from './Authorizer';
+import { Authorizer } from './Authorizer';
+
+/**
+ * Redirects requests to specific authorizers based on their identifier.
+ * The keys in the input map will be converted to regular expressions.
+ * The regular expressions should all start with a slash
+ * and will be evaluated relative to the base URL.
+ *
+ * Will error if no match is found.
+ */
+export class PathBasedAuthorizer extends Authorizer {
+  private readonly baseUrl: string;
+  private readonly paths: Map<RegExp, Authorizer>;
+
+  public constructor(baseUrl: string, paths: Record<string, Authorizer>) {
+    super();
+    this.baseUrl = ensureTrailingSlash(baseUrl);
+    const entries = Object.entries(paths).map(([ key, val ]): [RegExp, Authorizer] => [ new RegExp(key, 'u'), val ]);
+    this.paths = new Map(entries);
+  }
+
+  public async canHandle(input: AuthorizerArgs): Promise<void> {
+    const authorizer = this.findAuthorizer(input.identifier.path);
+    await authorizer.canHandle(input);
+  }
+
+  public async handle(input: AuthorizerArgs): Promise<Authorization> {
+    const authorizer = this.findAuthorizer(input.identifier.path);
+    return authorizer.handle(input);
+  }
+
+  /**
+   * Find the authorizer corresponding to the given path.
+   * Errors if there is no match.
+   */
+  private findAuthorizer(path: string): Authorizer {
+    if (path.startsWith(this.baseUrl)) {
+      // We want to keep the leading slash
+      const relative = path.slice(trimTrailingSlashes(this.baseUrl).length);
+      for (const [ regex, authorizer ] of this.paths) {
+        if (regex.test(relative)) {
+          return authorizer;
+        }
+      }
+    }
+    throw new NotImplementedHttpError('No regex matches the given path.');
+  }
+}