feat: Create conditions based on input headers

.componentsignore

@@ -1,5 +1,6 @@
 [
   "Adapter",
+  "BasicConditions",
   "BasicRepresentation",
   "Error",
   "EventEmitter",

config/ldp/handler/components/request-parser.json

@@ -11,6 +11,7 @@
       },
       "args_preferenceParser": { "@type": "AcceptPreferenceParser" },
       "args_metadataParser": { "@id": "urn:solid-server:default:MetadataParser" },
+      "args_conditionsParser": { "@type": "BasicConditionsParser" },
       "args_bodyParser": {
         "@type": "WaterfallHandler",
         "handlers": [

src/index.ts

@@ -83,6 +83,10 @@ export * from './ldp/auxiliary/RoutingAuxiliaryStrategy';
 export * from './ldp/auxiliary/SuffixAuxiliaryIdentifierStrategy';
 export * from './ldp/auxiliary/Validator';
 
+// LDP/HTTP/Conditions
+export * from './ldp/http/conditions/BasicConditionsParser';
+export * from './ldp/http/conditions/ConditionsParser';
+
 // LDP/HTTP/Metadata
 export * from './ldp/http/metadata/ConstantMetadataWriter';
 export * from './ldp/http/metadata/ContentTypeParser';
@@ -258,6 +262,7 @@ export * from './storage/routing/RouterRule';
 // Storage
 export * from './storage/AtomicResourceStore';
 export * from './storage/BaseResourceStore';
+export * from './storage/BasicConditions';
 export * from './storage/Conditions';
 export * from './storage/DataAccessorBasedStore';
 export * from './storage/IndexRepresentationStore';

src/ldp/http/BasicRequestParser.ts

@@ -3,6 +3,7 @@ import { InternalServerError } from '../../util/errors/InternalServerError';
 import type { Operation } from '../operations/Operation';
 import { RepresentationMetadata } from '../representation/RepresentationMetadata';
 import type { BodyParser } from './BodyParser';
+import type { ConditionsParser } from './conditions/ConditionsParser';
 import type { MetadataParser } from './metadata/MetadataParser';
 import type { PreferenceParser } from './PreferenceParser';
 import { RequestParser } from './RequestParser';
@@ -15,17 +16,20 @@ export interface BasicRequestParserArgs {
   targetExtractor: TargetExtractor;
   preferenceParser: PreferenceParser;
   metadataParser: MetadataParser;
+  conditionsParser: ConditionsParser;
   bodyParser: BodyParser;
 }
 
 /**
  * Creates an {@link Operation} from an incoming {@link HttpRequest} by aggregating the results
- * of a {@link TargetExtractor}, {@link PreferenceParser}, {@link MetadataParser}, and {@link BodyParser}.
+ * of a {@link TargetExtractor}, {@link PreferenceParser}, {@link MetadataParser},
+ * {@link ConditionsParser} and {@link BodyParser}.
  */
 export class BasicRequestParser extends RequestParser {
   private readonly targetExtractor!: TargetExtractor;
   private readonly preferenceParser!: PreferenceParser;
   private readonly metadataParser!: MetadataParser;
+  private readonly conditionsParser!: ConditionsParser;
   private readonly bodyParser!: BodyParser;
 
   public constructor(args: BasicRequestParserArgs) {
@@ -42,8 +46,9 @@ export class BasicRequestParser extends RequestParser {
     const preferences = await this.preferenceParser.handleSafe({ request });
     const metadata = new RepresentationMetadata(target);
     await this.metadataParser.handleSafe({ request, metadata });
+    const conditions = await this.conditionsParser.handleSafe(request);
     const body = await this.bodyParser.handleSafe({ request, metadata });
 
-    return { method, target, preferences, body };
+    return { method, target, preferences, conditions, body };
   }
 }

src/ldp/http/conditions/BasicConditionsParser.ts

@@ -0,0 +1,63 @@
+import { getLoggerFor } from '../../../logging/LogUtil';
+import type { HttpRequest } from '../../../server/HttpRequest';
+import type { BasicConditionsOptions } from '../../../storage/BasicConditions';
+import { BasicConditions } from '../../../storage/BasicConditions';
+import type { Conditions } from '../../../storage/Conditions';
+import { ConditionsParser } from './ConditionsParser';
+
+/**
+ * Creates a Conditions object based on the the following headers:
+ *  - If-Modified-Since
+ *  - If-Unmodified-Since
+ *  - If-Match
+ *  - If-None-Match
+ *
+ * Implementation based on RFC7232
+ */
+export class BasicConditionsParser extends ConditionsParser {
+  protected readonly logger = getLoggerFor(this);
+
+  public async handle(request: HttpRequest): Promise<Conditions | undefined> {
+    const options: BasicConditionsOptions = {
+      matchesETag: this.parseTagHeader(request, 'if-match'),
+      notMatchesETag: this.parseTagHeader(request, 'if-none-match'),
+    };
+
+    // A recipient MUST ignore If-Modified-Since if the request contains an If-None-Match header field
+    // A recipient MUST ignore the If-Modified-Since header field ... if the request method is neither GET nor HEAD.
+    if (!options.notMatchesETag && (request.method === 'GET' || request.method === 'HEAD')) {
+      options.modifiedSince = this.parseDateHeader(request, 'if-modified-since');
+    }
+
+    // A recipient MUST ignore If-Unmodified-Since if the request contains an If-Match header field
+    if (!options.matchesETag) {
+      options.unmodifiedSince = this.parseDateHeader(request, 'if-unmodified-since');
+    }
+
+    // Only return a Conditions object if there is at least one condition; undefined otherwise
+    this.logger.debug(`Found the following conditions: ${JSON.stringify(options)}`);
+    if (Object.values(options).some((val): boolean => typeof val !== 'undefined')) {
+      return new BasicConditions(options);
+    }
+  }
+
+  /**
+   * Converts a request header containing a datetime string to an actual Date object.
+   * Undefined if there is no value for the given header name.
+   */
+  private parseDateHeader(request: HttpRequest, header: 'if-modified-since' | 'if-unmodified-since'): Date | undefined {
+    const headerVal = request.headers[header];
+    if (headerVal) {
+      const timestamp = Date.parse(headerVal);
+      return Number.isNaN(timestamp) ? undefined : new Date(timestamp);
+    }
+  }
+
+  /**
+   * Converts a request header containing ETags to an array of ETags.
+   * Undefined if there is no value for the given header name.
+   */
+  private parseTagHeader(request: HttpRequest, header: 'if-match' | 'if-none-match'): string[] | undefined {
+    return request.headers[header]?.trim().split(/\s*,\s*/u);
+  }
+}

src/ldp/http/conditions/ConditionsParser.ts

@@ -0,0 +1,8 @@
+import type { HttpRequest } from '../../../server/HttpRequest';
+import type { Conditions } from '../../../storage/Conditions';
+import { AsyncHandler } from '../../../util/handlers/AsyncHandler';
+
+/**
+ * Creates a Conditions object based on the input HttpRequest.
+ */
+export abstract class ConditionsParser extends AsyncHandler<HttpRequest, Conditions | undefined> {}

src/ldp/operations/DeleteOperationHandler.ts

@@ -24,7 +24,7 @@ export class DeleteOperationHandler extends OperationHandler {
   }
 
   public async handle(input: Operation): Promise<ResponseDescription> {
-    await this.store.deleteResource(input.target);
+    await this.store.deleteResource(input.target, input.conditions);
     return new ResetResponseDescription();
   }
 }

src/ldp/operations/GetOperationHandler.ts

@@ -24,7 +24,7 @@ export class GetOperationHandler extends OperationHandler {
   }
 
   public async handle(input: Operation): Promise<ResponseDescription> {
-    const body = await this.store.getRepresentation(input.target, input.preferences);
+    const body = await this.store.getRepresentation(input.target, input.preferences, input.conditions);
 
     input.authorization?.addMetadata(body.metadata);
 

src/ldp/operations/HeadOperationHandler.ts

@@ -24,7 +24,7 @@ export class HeadOperationHandler extends OperationHandler {
   }
 
   public async handle(input: Operation): Promise<ResponseDescription> {
-    const body = await this.store.getRepresentation(input.target, input.preferences);
+    const body = await this.store.getRepresentation(input.target, input.preferences, input.conditions);
 
     // Close the Readable as we will not return it.
     body.data.destroy();

src/ldp/operations/Operation.ts

@@ -1,4 +1,5 @@
 import type { Authorization } from '../../authorization/Authorization';
+import type { Conditions } from '../../storage/Conditions';
 import type { Representation } from '../representation/Representation';
 import type { RepresentationPreferences } from '../representation/RepresentationPreferences';
 import type { ResourceIdentifier } from '../representation/ResourceIdentifier';
@@ -19,6 +20,10 @@ export interface Operation {
    * Representation preferences of the response. Will be empty if there are none.
    */
   preferences: RepresentationPreferences;
+  /**
+   * Conditions the resource must fulfill for a valid operation.
+   */
+  conditions?: Conditions;
   /**
    * This value will be set if the Operation was authorized by an Authorizer.
    */

src/ldp/operations/PatchOperationHandler.ts

@@ -36,7 +36,7 @@ export class PatchOperationHandler extends OperationHandler {
       this.logger.warn('No Content-Type header specified on PATCH request');
       throw new BadRequestHttpError('No Content-Type header specified on PATCH request');
     }
-    await this.store.modifyResource(input.target, input.body as Patch);
+    await this.store.modifyResource(input.target, input.body as Patch, input.conditions);
     return new ResetResponseDescription();
   }
 }

src/ldp/operations/PostOperationHandler.ts

@@ -35,7 +35,7 @@ export class PostOperationHandler extends OperationHandler {
       this.logger.warn('No Content-Type header specified on POST request');
       throw new BadRequestHttpError('No Content-Type header specified on POST request');
     }
-    const identifier = await this.store.addResource(input.target, input.body);
+    const identifier = await this.store.addResource(input.target, input.body, input.conditions);
     return new CreatedResponseDescription(identifier);
   }
 }

src/ldp/operations/PutOperationHandler.ts

@@ -35,7 +35,7 @@ export class PutOperationHandler extends OperationHandler {
       this.logger.warn('No Content-Type header specified on PUT request');
       throw new BadRequestHttpError('No Content-Type header specified on PUT request');
     }
-    await this.store.setRepresentation(input.target, input.body);
+    await this.store.setRepresentation(input.target, input.body, input.conditions);
     return new ResetResponseDescription();
   }
 }

src/storage/BasicConditions.ts

@@ -0,0 +1,69 @@
+import type { RepresentationMetadata } from '../ldp/representation/RepresentationMetadata';
+import { DC } from '../util/Vocabularies';
+import { getETag } from './Conditions';
+import type { Conditions } from './Conditions';
+
+export interface BasicConditionsOptions {
+  matchesETag?: string[];
+  notMatchesETag?: string[];
+  modifiedSince?: Date;
+  unmodifiedSince?: Date;
+}
+
+/**
+ * Stores all the relevant Conditions values and matches them based on RFC7232.
+ */
+export class BasicConditions implements Conditions {
+  public readonly matchesETag?: string[];
+  public readonly notMatchesETag?: string[];
+  public readonly modifiedSince?: Date;
+  public readonly unmodifiedSince?: Date;
+
+  public constructor(options: BasicConditionsOptions) {
+    this.matchesETag = options.matchesETag;
+    this.notMatchesETag = options.notMatchesETag;
+    this.modifiedSince = options.modifiedSince;
+    this.unmodifiedSince = options.unmodifiedSince;
+  }
+
+  public matchesMetadata(metadata?: RepresentationMetadata): boolean {
+    if (!metadata) {
+      // RFC7232: ...If-Match... If the field-value is "*", the condition is false if the origin server
+      // does not have a current representation for the target resource.
+      return !this.matchesETag?.includes('*');
+    }
+
+    const modified = metadata.get(DC.terms.modified);
+    const modifiedDate = modified ? new Date(modified.value) : undefined;
+    const etag = getETag(metadata);
+    return this.matches(etag, modifiedDate);
+  }
+
+  public matches(eTag?: string, lastModified?: Date): boolean {
+    // RFC7232: ...If-None-Match... If the field-value is "*", the condition is false if the origin server
+    // has a current representation for the target resource.
+    if (this.notMatchesETag?.includes('*')) {
+      return false;
+    }
+
+    if (eTag) {
+      if (this.matchesETag && !this.matchesETag.includes(eTag) && !this.matchesETag.includes('*')) {
+        return false;
+      }
+      if (this.notMatchesETag?.includes(eTag)) {
+        return false;
+      }
+    }
+
+    if (lastModified) {
+      if (this.modifiedSince && lastModified < this.modifiedSince) {
+        return false;
+      }
+      if (this.unmodifiedSince && lastModified > this.unmodifiedSince) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+}

src/storage/Conditions.ts

@@ -24,11 +24,13 @@ export interface Conditions {
 
   /**
    * Checks validity based on the given metadata.
-   * @param metadata - Metadata of the representation.
+   * @param metadata - Metadata of the representation. Undefined if the resource does not exist.
    */
-  matchesMetadata: (metadata: RepresentationMetadata) => boolean;
+  matchesMetadata: (metadata?: RepresentationMetadata) => boolean;
   /**
    * Checks validity based on the given ETag and/or date.
+   * This function assumes the resource being checked exists.
+   * If not, the `matchesMetadata` function should be used.
    * @param eTag - Condition based on ETag.
    * @param lastModified - Condition based on last modified date.
    */

test/integration/RequestParser.test.ts

@@ -2,19 +2,24 @@ import { Readable } from 'stream';
 import arrayifyStream from 'arrayify-stream';
 import { AcceptPreferenceParser } from '../../src/ldp/http/AcceptPreferenceParser';
 import { BasicRequestParser } from '../../src/ldp/http/BasicRequestParser';
+import { BasicConditionsParser } from '../../src/ldp/http/conditions/BasicConditionsParser';
 import { ContentTypeParser } from '../../src/ldp/http/metadata/ContentTypeParser';
 import { OriginalUrlExtractor } from '../../src/ldp/http/OriginalUrlExtractor';
 import { RawBodyParser } from '../../src/ldp/http/RawBodyParser';
 import { RepresentationMetadata } from '../../src/ldp/representation/RepresentationMetadata';
 import type { HttpRequest } from '../../src/server/HttpRequest';
+import { BasicConditions } from '../../src/storage/BasicConditions';
 import { guardedStreamFrom } from '../../src/util/StreamUtil';
 
 describe('A BasicRequestParser with simple input parsers', (): void => {
   const targetExtractor = new OriginalUrlExtractor();
   const preferenceParser = new AcceptPreferenceParser();
   const metadataParser = new ContentTypeParser();
+  const conditionsParser = new BasicConditionsParser();
   const bodyParser = new RawBodyParser();
-  const requestParser = new BasicRequestParser({ targetExtractor, preferenceParser, metadataParser, bodyParser });
+  const requestParser = new BasicRequestParser(
+    { targetExtractor, preferenceParser, metadataParser, conditionsParser, bodyParser },
+  );
 
   it('can parse an incoming request.', async(): Promise<void> => {
     const request = guardedStreamFrom([ '<http://test.com/s> <http://test.com/p> <http://test.com/o>.' ]) as HttpRequest;
@@ -24,6 +29,8 @@ describe('A BasicRequestParser with simple input parsers', (): void => {
       accept: 'text/turtle; q=0.8',
       'accept-language': 'en-gb, en;q=0.5',
       'content-type': 'text/turtle',
+      'if-unmodified-since': 'Wed, 21 Oct 2015 07:28:00 UTC',
+      'if-none-match': '12345',
       'transfer-encoding': 'chunked',
       host: 'test.com',
     };
@@ -36,6 +43,10 @@ describe('A BasicRequestParser with simple input parsers', (): void => {
         type: { 'text/turtle': 0.8 },
         language: { 'en-gb': 1, en: 0.5 },
       },
+      conditions: new BasicConditions({
+        unmodifiedSince: new Date('2015-10-21T07:28:00.000Z'),
+        notMatchesETag: [ '12345' ],
+      }),
       body: {
         data: expect.any(Readable),
         binary: true,

test/unit/ldp/http/BasicRequestParser.test.ts

@@ -1,5 +1,6 @@
 import { BasicRequestParser } from '../../../../src/ldp/http/BasicRequestParser';
 import type { BodyParser } from '../../../../src/ldp/http/BodyParser';
+import type { ConditionsParser } from '../../../../src/ldp/http/conditions/ConditionsParser';
 import type { MetadataParser } from '../../../../src/ldp/http/metadata/MetadataParser';
 import type { PreferenceParser } from '../../../../src/ldp/http/PreferenceParser';
 import type { TargetExtractor } from '../../../../src/ldp/http/TargetExtractor';
@@ -10,6 +11,7 @@ describe('A BasicRequestParser', (): void => {
   let targetExtractor: TargetExtractor;
   let preferenceParser: PreferenceParser;
   let metadataParser: MetadataParser;
+  let conditionsParser: ConditionsParser;
   let bodyParser: BodyParser;
   let requestParser: BasicRequestParser;
 
@@ -17,8 +19,11 @@ describe('A BasicRequestParser', (): void => {
     targetExtractor = new StaticAsyncHandler(true, 'target' as any);
     preferenceParser = new StaticAsyncHandler(true, 'preference' as any);
     metadataParser = new StaticAsyncHandler(true, undefined);
+    conditionsParser = new StaticAsyncHandler(true, 'conditions' as any);
     bodyParser = new StaticAsyncHandler(true, 'body' as any);
-    requestParser = new BasicRequestParser({ targetExtractor, preferenceParser, metadataParser, bodyParser });
+    requestParser = new BasicRequestParser(
+      { targetExtractor, preferenceParser, metadataParser, conditionsParser, bodyParser },
+    );
   });
 
   it('can handle any input.', async(): Promise<void> => {
@@ -36,6 +41,7 @@ describe('A BasicRequestParser', (): void => {
       method: 'GET',
       target: 'target',
       preferences: 'preference',
+      conditions: 'conditions',
       body: { data: 'body', metadata: new RepresentationMetadata('target') },
     });
   });

test/unit/ldp/http/conditions/BasicConditionsParser.test.ts

@@ -0,0 +1,60 @@
+import { BasicConditionsParser } from '../../../../../src/ldp/http/conditions/BasicConditionsParser';
+import type { HttpRequest } from '../../../../../src/server/HttpRequest';
+
+describe('A BasicConditionsParser', (): void => {
+  const dateString = 'Wed, 21 Oct 2015 07:28:00 UTC';
+  const date = new Date('2015-10-21T07:28:00.000Z');
+  let request: HttpRequest;
+  const parser = new BasicConditionsParser();
+
+  beforeEach(async(): Promise<void> => {
+    request = { headers: {}, method: 'GET' } as HttpRequest;
+  });
+
+  it('returns undefined if there are no relevant headers.', async(): Promise<void> => {
+    await expect(parser.handleSafe(request)).resolves.toBeUndefined();
+  });
+
+  it('parses the if-modified-since header.', async(): Promise<void> => {
+    request.headers['if-modified-since'] = dateString;
+    await expect(parser.handleSafe(request)).resolves.toEqual({ modifiedSince: date });
+  });
+
+  it('parses the if-unmodified-since header.', async(): Promise<void> => {
+    request.headers['if-unmodified-since'] = dateString;
+    await expect(parser.handleSafe(request)).resolves.toEqual({ unmodifiedSince: date });
+  });
+
+  it('parses the if-match header.', async(): Promise<void> => {
+    request.headers['if-match'] = '"1234567", "abcdefg"';
+    await expect(parser.handleSafe(request)).resolves.toEqual({ matchesETag: [ '"1234567"', '"abcdefg"' ]});
+  });
+
+  it('parses the if-none-match header.', async(): Promise<void> => {
+    request.headers['if-none-match'] = '*';
+    await expect(parser.handleSafe(request)).resolves.toEqual({ notMatchesETag: [ '*' ]});
+  });
+
+  it('does not parse the if-modified-since header if there is an if-none-match header.', async(): Promise<void> => {
+    request.headers['if-modified-since'] = dateString;
+    request.headers['if-none-match'] = '*';
+    await expect(parser.handleSafe(request)).resolves.toEqual({ notMatchesETag: [ '*' ]});
+  });
+
+  it('only parses the if-modified-since header for GET and HEAD requests.', async(): Promise<void> => {
+    request.headers['if-modified-since'] = dateString;
+    request.method = 'PUT';
+    await expect(parser.handleSafe(request)).resolves.toBeUndefined();
+  });
+
+  it('does not parse the if-unmodified-since header if there is an if-match header.', async(): Promise<void> => {
+    request.headers['if-unmodified-since'] = dateString;
+    request.headers['if-match'] = '*';
+    await expect(parser.handleSafe(request)).resolves.toEqual({ matchesETag: [ '*' ]});
+  });
+
+  it('ignores invalid dates.', async(): Promise<void> => {
+    request.headers['if-modified-since'] = 'notADate';
+    await expect(parser.handleSafe(request)).resolves.toBeUndefined();
+  });
+});

test/unit/ldp/operations/DeleteOperationHandler.test.ts

@@ -1,9 +1,11 @@
 import { DeleteOperationHandler } from '../../../../src/ldp/operations/DeleteOperationHandler';
 import type { Operation } from '../../../../src/ldp/operations/Operation';
+import { BasicConditions } from '../../../../src/storage/BasicConditions';
 import type { ResourceStore } from '../../../../src/storage/ResourceStore';
 import { NotImplementedHttpError } from '../../../../src/util/errors/NotImplementedHttpError';
 
 describe('A DeleteOperationHandler', (): void => {
+  const conditions = new BasicConditions({});
   const store = {} as unknown as ResourceStore;
   const handler = new DeleteOperationHandler(store);
   beforeEach(async(): Promise<void> => {
@@ -16,9 +18,9 @@ describe('A DeleteOperationHandler', (): void => {
   });
 
   it('deletes the resource from the store and returns the correct response.', async(): Promise<void> => {
-    const result = await handler.handle({ target: { path: 'url' }} as Operation);
+    const result = await handler.handle({ target: { path: 'url' }, conditions } as Operation);
     expect(store.deleteResource).toHaveBeenCalledTimes(1);
-    expect(store.deleteResource).toHaveBeenLastCalledWith({ path: 'url' });
+    expect(store.deleteResource).toHaveBeenLastCalledWith({ path: 'url' }, conditions);
     expect(result.statusCode).toBe(205);
     expect(result.metadata).toBeUndefined();
     expect(result.data).toBeUndefined();

test/unit/ldp/operations/GetOperationHandler.test.ts

@@ -2,15 +2,24 @@ import type { Authorization } from '../../../../src/authorization/Authorization'
 import { GetOperationHandler } from '../../../../src/ldp/operations/GetOperationHandler';
 import type { Operation } from '../../../../src/ldp/operations/Operation';
 import type { Representation } from '../../../../src/ldp/representation/Representation';
+import { BasicConditions } from '../../../../src/storage/BasicConditions';
 import type { ResourceStore } from '../../../../src/storage/ResourceStore';
 import { NotImplementedHttpError } from '../../../../src/util/errors/NotImplementedHttpError';
 
 describe('A GetOperationHandler', (): void => {
-  const store = {
+  const conditions = new BasicConditions({});
-    getRepresentation: async(): Promise<Representation> =>
+  const preferences = {};
-      ({ binary: false, data: 'data', metadata: 'metadata' } as any),
+  let store: ResourceStore;
+  let handler: GetOperationHandler;
+
+  beforeEach(async(): Promise<void> => {
+    store = {
+      getRepresentation: jest.fn(async(): Promise<Representation> =>
+        ({ binary: false, data: 'data', metadata: 'metadata' } as any)),
     } as unknown as ResourceStore;
-  const handler = new GetOperationHandler(store);
+
+    handler = new GetOperationHandler(store);
+  });
 
   it('only supports GET operations.', async(): Promise<void> => {
     await expect(handler.canHandle({ method: 'GET' } as Operation)).resolves.toBeUndefined();
@@ -18,16 +27,22 @@ describe('A GetOperationHandler', (): void => {
   });
 
   it('returns the representation from the store with the correct response.', async(): Promise<void> => {
-    const result = await handler.handle({ target: { path: 'url' }} as Operation);
+    const result = await handler.handle({ target: { path: 'url' }, preferences, conditions } as Operation);
     expect(result.statusCode).toBe(200);
     expect(result.metadata).toBe('metadata');
     expect(result.data).toBe('data');
+    expect(store.getRepresentation).toHaveBeenCalledTimes(1);
+    expect(store.getRepresentation).toHaveBeenLastCalledWith({ path: 'url' }, preferences, conditions);
   });
 
   it('adds authorization metadata in case the operation is an AuthorizedOperation.', async(): Promise<void> => {
     const authorization: Authorization = { addMetadata: jest.fn() };
-    const result = await handler.handle({ target: { path: 'url' }, authorization } as Operation);
+    const result = await handler.handle(
+      { target: { path: 'url' }, preferences, conditions, authorization } as Operation,
+    );
     expect(result.statusCode).toBe(200);
+    expect(store.getRepresentation).toHaveBeenCalledTimes(1);
+    expect(store.getRepresentation).toHaveBeenLastCalledWith({ path: 'url' }, preferences, conditions);
     expect(authorization.addMetadata).toHaveBeenCalledTimes(1);
     expect(authorization.addMetadata).toHaveBeenLastCalledWith('metadata');
   });

test/unit/ldp/operations/HeadOperationHandler.test.ts

@@ -3,10 +3,13 @@ import type { Authorization } from '../../../../src/authorization/Authorization'
 import { HeadOperationHandler } from '../../../../src/ldp/operations/HeadOperationHandler';
 import type { Operation } from '../../../../src/ldp/operations/Operation';
 import type { Representation } from '../../../../src/ldp/representation/Representation';
+import { BasicConditions } from '../../../../src/storage/BasicConditions';
 import type { ResourceStore } from '../../../../src/storage/ResourceStore';
 import { NotImplementedHttpError } from '../../../../src/util/errors/NotImplementedHttpError';
 
 describe('A HeadOperationHandler', (): void => {
+  const conditions = new BasicConditions({});
+  const preferences = {};
   let store: ResourceStore;
   let handler: HeadOperationHandler;
   let data: Readable;
@@ -14,8 +17,8 @@ describe('A HeadOperationHandler', (): void => {
   beforeEach(async(): Promise<void> => {
     data = { destroy: jest.fn() } as any;
     store = {
-      getRepresentation: async(): Promise<Representation> =>
+      getRepresentation: jest.fn(async(): Promise<Representation> =>
-        ({ binary: false, data, metadata: 'metadata' } as any),
+        ({ binary: false, data, metadata: 'metadata' } as any)),
     } as any;
     handler = new HeadOperationHandler(store);
   });
@@ -27,17 +30,23 @@ describe('A HeadOperationHandler', (): void => {
   });
 
   it('returns the representation from the store with the correct response.', async(): Promise<void> => {
-    const result = await handler.handle({ target: { path: 'url' }} as Operation);
+    const result = await handler.handle({ target: { path: 'url' }, preferences, conditions } as Operation);
     expect(result.statusCode).toBe(200);
     expect(result.metadata).toBe('metadata');
     expect(result.data).toBeUndefined();
     expect(data.destroy).toHaveBeenCalledTimes(1);
+    expect(store.getRepresentation).toHaveBeenCalledTimes(1);
+    expect(store.getRepresentation).toHaveBeenLastCalledWith({ path: 'url' }, preferences, conditions);
   });
 
   it('adds authorization metadata in case the operation is an AuthorizedOperation.', async(): Promise<void> => {
     const authorization: Authorization = { addMetadata: jest.fn() };
-    const result = await handler.handle({ target: { path: 'url' }, authorization } as Operation);
+    const result = await handler.handle(
+      { target: { path: 'url' }, preferences, conditions, authorization } as Operation,
+    );
     expect(result.statusCode).toBe(200);
+    expect(store.getRepresentation).toHaveBeenCalledTimes(1);
+    expect(store.getRepresentation).toHaveBeenLastCalledWith({ path: 'url' }, preferences, conditions);
     expect(authorization.addMetadata).toHaveBeenCalledTimes(1);
     expect(authorization.addMetadata).toHaveBeenLastCalledWith('metadata');
   });

test/unit/ldp/operations/PatchOperationHandler.test.ts

@@ -1,11 +1,13 @@
 import type { Operation } from '../../../../src/ldp/operations/Operation';
 import { PatchOperationHandler } from '../../../../src/ldp/operations/PatchOperationHandler';
 import { RepresentationMetadata } from '../../../../src/ldp/representation/RepresentationMetadata';
+import { BasicConditions } from '../../../../src/storage/BasicConditions';
 import type { ResourceStore } from '../../../../src/storage/ResourceStore';
 import { BadRequestHttpError } from '../../../../src/util/errors/BadRequestHttpError';
 import { NotImplementedHttpError } from '../../../../src/util/errors/NotImplementedHttpError';
 
 describe('A PatchOperationHandler', (): void => {
+  const conditions = new BasicConditions({});
   const store = {} as unknown as ResourceStore;
   const handler = new PatchOperationHandler(store);
   beforeEach(async(): Promise<void> => {
@@ -25,9 +27,9 @@ describe('A PatchOperationHandler', (): void => {
 
   it('deletes the resource from the store and returns the correct response.', async(): Promise<void> => {
     const metadata = new RepresentationMetadata('text/turtle');
-    const result = await handler.handle({ target: { path: 'url' }, body: { metadata }} as Operation);
+    const result = await handler.handle({ target: { path: 'url' }, body: { metadata }, conditions } as Operation);
     expect(store.modifyResource).toHaveBeenCalledTimes(1);
-    expect(store.modifyResource).toHaveBeenLastCalledWith({ path: 'url' }, { metadata });
+    expect(store.modifyResource).toHaveBeenLastCalledWith({ path: 'url' }, { metadata }, conditions);
     expect(result.statusCode).toBe(205);
     expect(result.metadata).toBeUndefined();
     expect(result.data).toBeUndefined();

test/unit/ldp/operations/PostOperationHandler.test.ts

@@ -2,16 +2,23 @@ import type { Operation } from '../../../../src/ldp/operations/Operation';
 import { PostOperationHandler } from '../../../../src/ldp/operations/PostOperationHandler';
 import { RepresentationMetadata } from '../../../../src/ldp/representation/RepresentationMetadata';
 import type { ResourceIdentifier } from '../../../../src/ldp/representation/ResourceIdentifier';
+import { BasicConditions } from '../../../../src/storage/BasicConditions';
 import type { ResourceStore } from '../../../../src/storage/ResourceStore';
 import { BadRequestHttpError } from '../../../../src/util/errors/BadRequestHttpError';
 import { NotImplementedHttpError } from '../../../../src/util/errors/NotImplementedHttpError';
 import { SOLID_HTTP } from '../../../../src/util/Vocabularies';
 
 describe('A PostOperationHandler', (): void => {
-  const store = {
+  const conditions = new BasicConditions({});
-    addResource: async(): Promise<ResourceIdentifier> => ({ path: 'newPath' } as ResourceIdentifier),
+  let store: ResourceStore;
+  let handler: PostOperationHandler;
+
+  beforeEach(async(): Promise<void> => {
+    store = {
+      addResource: jest.fn(async(): Promise<ResourceIdentifier> => ({ path: 'newPath' } as ResourceIdentifier)),
     } as unknown as ResourceStore;
-  const handler = new PostOperationHandler(store);
+    handler = new PostOperationHandler(store);
+  });
 
   it('only supports POST operations.', async(): Promise<void> => {
     await expect(handler.canHandle({ method: 'POST', body: { }} as Operation))
@@ -28,10 +35,14 @@ describe('A PostOperationHandler', (): void => {
 
   it('adds the given representation to the store and returns the correct response.', async(): Promise<void> => {
     const metadata = new RepresentationMetadata('text/turtle');
-    const result = await handler.handle({ method: 'POST', body: { metadata }} as Operation);
+    const result = await handler.handle(
+      { method: 'POST', target: { path: 'url' }, body: { metadata }, conditions } as Operation,
+    );
     expect(result.statusCode).toBe(201);
     expect(result.metadata).toBeInstanceOf(RepresentationMetadata);
     expect(result.metadata?.get(SOLID_HTTP.location)?.value).toBe('newPath');
     expect(result.data).toBeUndefined();
+    expect(store.addResource).toHaveBeenCalledTimes(1);
+    expect(store.addResource).toHaveBeenLastCalledWith({ path: 'url' }, { metadata }, conditions);
   });
 });

test/unit/ldp/operations/PutOperationHandler.test.ts

@@ -1,11 +1,13 @@
 import type { Operation } from '../../../../src/ldp/operations/Operation';
 import { PutOperationHandler } from '../../../../src/ldp/operations/PutOperationHandler';
 import { RepresentationMetadata } from '../../../../src/ldp/representation/RepresentationMetadata';
+import { BasicConditions } from '../../../../src/storage/BasicConditions';
 import type { ResourceStore } from '../../../../src/storage/ResourceStore';
 import { BadRequestHttpError } from '../../../../src/util/errors/BadRequestHttpError';
 import { NotImplementedHttpError } from '../../../../src/util/errors/NotImplementedHttpError';
 
 describe('A PutOperationHandler', (): void => {
+  const conditions = new BasicConditions({});
   const store = {} as unknown as ResourceStore;
   const handler = new PutOperationHandler(store);
   beforeEach(async(): Promise<void> => {
@@ -26,9 +28,9 @@ describe('A PutOperationHandler', (): void => {
 
   it('sets the representation in the store and returns the correct response.', async(): Promise<void> => {
     const metadata = new RepresentationMetadata('text/turtle');
-    const result = await handler.handle({ target: { path: 'url' }, body: { metadata }} as Operation);
+    const result = await handler.handle({ target: { path: 'url' }, body: { metadata }, conditions } as Operation);
     expect(store.setRepresentation).toHaveBeenCalledTimes(1);
-    expect(store.setRepresentation).toHaveBeenLastCalledWith({ path: 'url' }, { metadata });
+    expect(store.setRepresentation).toHaveBeenLastCalledWith({ path: 'url' }, { metadata }, conditions);
     expect(result.statusCode).toBe(205);
     expect(result.metadata).toBeUndefined();
     expect(result.data).toBeUndefined();

test/unit/storage/BasicConditions.test.ts

@@ -0,0 +1,78 @@
+import { RepresentationMetadata } from '../../../src/ldp/representation/RepresentationMetadata';
+import { BasicConditions } from '../../../src/storage/BasicConditions';
+import { getETag } from '../../../src/storage/Conditions';
+import { DC } from '../../../src/util/Vocabularies';
+
+describe('A BasicConditions', (): void => {
+  const now = new Date(2020, 10, 20);
+  const tomorrow = new Date(2020, 10, 21);
+  const yesterday = new Date(2020, 10, 19);
+  const eTags = [ '123456', 'abcdefg' ];
+
+  it('copies the input parameters.', async(): Promise<void> => {
+    const options = { matchesETag: eTags, notMatchesETag: eTags, modifiedSince: now, unmodifiedSince: now };
+    expect(new BasicConditions(options)).toMatchObject(options);
+  });
+
+  it('always returns false if notMatchesETag contains *.', async(): Promise<void> => {
+    const conditions = new BasicConditions({ notMatchesETag: [ '*' ]});
+    expect(conditions.matches()).toBe(false);
+  });
+
+  it('requires matchesETag to contain the provided ETag.', async(): Promise<void> => {
+    const conditions = new BasicConditions({ matchesETag: [ '1234' ]});
+    expect(conditions.matches('abcd')).toBe(false);
+    expect(conditions.matches('1234')).toBe(true);
+  });
+
+  it('supports all ETags if matchesETag contains *.', async(): Promise<void> => {
+    const conditions = new BasicConditions({ matchesETag: [ '*' ]});
+    expect(conditions.matches('abcd')).toBe(true);
+    expect(conditions.matches('1234')).toBe(true);
+  });
+
+  it('requires notMatchesETag to not contain the provided ETag.', async(): Promise<void> => {
+    const conditions = new BasicConditions({ notMatchesETag: [ '1234' ]});
+    expect(conditions.matches('1234')).toBe(false);
+    expect(conditions.matches('abcd')).toBe(true);
+  });
+
+  it('requires lastModified to be after modifiedSince.', async(): Promise<void> => {
+    const conditions = new BasicConditions({ modifiedSince: now });
+    expect(conditions.matches(undefined, yesterday)).toBe(false);
+    expect(conditions.matches(undefined, tomorrow)).toBe(true);
+  });
+
+  it('requires lastModified to be before unmodifiedSince.', async(): Promise<void> => {
+    const conditions = new BasicConditions({ unmodifiedSince: now });
+    expect(conditions.matches(undefined, tomorrow)).toBe(false);
+    expect(conditions.matches(undefined, yesterday)).toBe(true);
+  });
+
+  it('can match based on the last modified date in the metadata.', async(): Promise<void> => {
+    const metadata = new RepresentationMetadata({ [DC.modified]: now.toISOString() });
+    const conditions = new BasicConditions({
+      modifiedSince: yesterday,
+      unmodifiedSince: tomorrow,
+      matchesETag: [ getETag(metadata)! ],
+      notMatchesETag: [ '123456' ],
+    });
+    expect(conditions.matchesMetadata(metadata)).toBe(true);
+  });
+
+  it('matches if no date is found in the metadata.', async(): Promise<void> => {
+    const metadata = new RepresentationMetadata();
+    const conditions = new BasicConditions({
+      modifiedSince: yesterday,
+      unmodifiedSince: tomorrow,
+      matchesETag: [ getETag(metadata)! ],
+      notMatchesETag: [ '123456' ],
+    });
+    expect(conditions.matchesMetadata(metadata)).toBe(true);
+  });
+
+  it('checks if matchesETag contains * for resources that do not exist.', async(): Promise<void> => {
+    expect(new BasicConditions({ matchesETag: [ '*' ]}).matchesMetadata()).toBe(false);
+    expect(new BasicConditions({}).matchesMetadata()).toBe(true);
+  });
+});

test/unit/storage/Conditions.test.ts

@@ -0,0 +1,17 @@
+import { RepresentationMetadata } from '../../../src/ldp/representation/RepresentationMetadata';
+import { getETag } from '../../../src/storage/Conditions';
+import { DC } from '../../../src/util/Vocabularies';
+
+describe('Conditions', (): void => {
+  describe('#getETag', (): void => {
+    it('creates an ETag based on the date last modified.', async(): Promise<void> => {
+      const now = new Date();
+      const metadata = new RepresentationMetadata({ [DC.modified]: now.toISOString() });
+      expect(getETag(metadata)).toBe(`"${now.getTime()}"`);
+    });
+
+    it('returns undefined if no date was found.', async(): Promise<void> => {
+      expect(getETag(new RepresentationMetadata())).toBeUndefined();
+    });
+  });
+});