feat: Add contains function to IdentifierStrategy

src/util/identifiers/BaseIdentifierStrategy.ts

@@ -1,12 +1,16 @@
+import { URL } from 'url';
 import type { ResourceIdentifier } from '../../http/representation/ResourceIdentifier';
 import { InternalServerError } from '../errors/InternalServerError';
-import { ensureTrailingSlash } from '../PathUtil';
+import { ensureTrailingSlash, isContainerIdentifier } from '../PathUtil';
 import type { IdentifierStrategy } from './IdentifierStrategy';
 
 /**
  * Provides a default implementation for `getParentContainer`
  * which checks if the identifier is supported and not a root container.
  * If not, the last part before the first relevant slash will be removed to find the parent.
+ *
+ * Provides a default implementation for `contains`
+ * which does standard slash-semantics based string comparison.
  */
 export abstract class BaseIdentifierStrategy implements IdentifierStrategy {
   public abstract supportsIdentifier(identifier: ResourceIdentifier): boolean;
@@ -27,4 +31,22 @@ export abstract class BaseIdentifierStrategy implements IdentifierStrategy {
   }
 
   public abstract isRootContainer(identifier: ResourceIdentifier): boolean;
+
+  public contains(container: ResourceIdentifier, identifier: ResourceIdentifier, transitive: boolean): boolean {
+    if (!isContainerIdentifier(container)) {
+      return false;
+    }
+
+    if (!identifier.path.startsWith(container.path)) {
+      return false;
+    }
+
+    if (transitive) {
+      return true;
+    }
+
+    const tail = identifier.path.slice(container.path.length);
+    // If there is at least one `/` followed by a char this is not a direct parent container
+    return !/\/./u.test(tail);
+  }
 }

src/util/identifiers/IdentifierStrategy.ts

@@ -23,4 +23,14 @@ export interface IdentifierStrategy {
    * This does not check if this identifier actually exists.
    */
   isRootContainer: (identifier: ResourceIdentifier) => boolean;
+
+  /**
+   * Checks if the given container would contain the given identifier.
+   * This does not check that either of these identifiers actually exist.
+   * This is similar to calling {@link getParentContainer} on an identifier
+   * and comparing the result.
+   *
+   * If `transitive` is `false` this only checks if `container` is the direct parent container of `identifier`.
+   */
+  contains: (container: ResourceIdentifier, identifier: ResourceIdentifier, transitive: boolean) => boolean;
 }

test/unit/util/identifiers/BaseIdentifierStrategy.test.ts

@@ -14,9 +14,10 @@ class DummyStrategy extends BaseIdentifierStrategy {
 describe('A BaseIdentifierStrategy', (): void => {
   const strategy = new DummyStrategy();
 
+  describe('getParentContainer', (): void => {
     it('returns the parent identifier.', async(): Promise<void> => {
-    expect(strategy.getParentContainer({ path: 'http://test.com/foo/bar' })).toEqual({ path: 'http://test.com/foo/' });
-    expect(strategy.getParentContainer({ path: 'http://test.com/foo/bar/' })).toEqual({ path: 'http://test.com/foo/' });
+      expect(strategy.getParentContainer({ path: 'http://example.com/foo/bar' })).toEqual({ path: 'http://example.com/foo/' });
+      expect(strategy.getParentContainer({ path: 'http://example.com/foo/bar/' })).toEqual({ path: 'http://example.com/foo/' });
     });
 
     it('errors when attempting to get the parent of an unsupported identifier.', async(): Promise<void> => {
@@ -27,7 +28,31 @@ describe('A BaseIdentifierStrategy', (): void => {
     });
 
     it('errors when attempting to get the parent of a root container.', async(): Promise<void> => {
-    expect((): any => strategy.getParentContainer({ path: 'http://test.com/root' }))
-      .toThrow('Cannot obtain the parent of http://test.com/root because it is a root container.');
+      expect((): any => strategy.getParentContainer({ path: 'http://example.com/root' }))
+        .toThrow('Cannot obtain the parent of http://example.com/root because it is a root container.');
+    });
+  });
+
+  describe('contains', (): void => {
+    it('returns false if container parameter is not a container identifier.', async(): Promise<void> => {
+      expect(strategy.contains({ path: 'http://example.com' }, { path: 'http://example.com/foo' }, false)).toBe(false);
+    });
+
+    it('returns false if container parameter is longer.', async(): Promise<void> => {
+      expect(strategy.contains({ path: 'http://example.com/foo/' }, { path: 'http://example.com' }, false)).toBe(false);
+    });
+
+    it('returns false if container parameter is not the direct container.', async(): Promise<void> => {
+      expect(strategy.contains({ path: 'http://example.com/' }, { path: 'http://example.com/foo/bar' }, false)).toBe(false);
+    });
+
+    it('returns true if the container parameter is the direct container.', async(): Promise<void> => {
+      expect(strategy.contains({ path: 'http://example.com/' }, { path: 'http://example.com/foo/' }, false)).toBe(true);
+      expect(strategy.contains({ path: 'http://example.com/' }, { path: 'http://example.com/foo' }, false)).toBe(true);
+    });
+
+    it('returns true for transtive calls if container parameter is a grandparent.', async(): Promise<void> => {
+      expect(strategy.contains({ path: 'http://example.com/' }, { path: 'http://example.com/foo/bar' }, true)).toBe(true);
+    });
   });
 });