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DataAccessorBasedStore.ts
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DataAccessorBasedStore.ts
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import arrayifyStream from 'arrayify-stream';
import { DataFactory } from 'n3';
import type { NamedNode, Quad, Term } from 'rdf-js';
import { v4 as uuid } from 'uuid';
import type { AuxiliaryStrategy } from '../http/auxiliary/AuxiliaryStrategy';
import { BasicRepresentation } from '../http/representation/BasicRepresentation';
import type { Patch } from '../http/representation/Patch';
import type { Representation } from '../http/representation/Representation';
import type { RepresentationMetadata } from '../http/representation/RepresentationMetadata';
import type { ResourceIdentifier } from '../http/representation/ResourceIdentifier';
import { getLoggerFor } from '../logging/LogUtil';
import { INTERNAL_QUADS } from '../util/ContentTypes';
import { BadRequestHttpError } from '../util/errors/BadRequestHttpError';
import { ConflictHttpError } from '../util/errors/ConflictHttpError';
import { createErrorMessage } from '../util/errors/ErrorUtil';
import { ForbiddenHttpError } from '../util/errors/ForbiddenHttpError';
import { MethodNotAllowedHttpError } from '../util/errors/MethodNotAllowedHttpError';
import { NotFoundHttpError } from '../util/errors/NotFoundHttpError';
import { NotImplementedHttpError } from '../util/errors/NotImplementedHttpError';
import { PreconditionFailedHttpError } from '../util/errors/PreconditionFailedHttpError';
import type { IdentifierStrategy } from '../util/identifiers/IdentifierStrategy';
import {
ensureTrailingSlash,
isContainerIdentifier,
isContainerPath,
trimTrailingSlashes,
toCanonicalUriPath,
} from '../util/PathUtil';
import { parseQuads } from '../util/QuadUtil';
import { addResourceMetadata, updateModifiedDate } from '../util/ResourceUtil';
import {
CONTENT_TYPE,
DC,
SOLID_HTTP,
LDP,
POSIX,
PIM,
RDF,
XSD,
SOLID_META,
PREFERRED_PREFIX_TERM,
} from '../util/Vocabularies';
import type { DataAccessor } from './accessors/DataAccessor';
import type { Conditions } from './Conditions';
import type { ResourceStore } from './ResourceStore';
/**
* ResourceStore which uses a DataAccessor for backend access.
*
* The DataAccessor interface provides elementary store operations such as read and write.
* This DataAccessorBasedStore uses those elementary store operations
* to implement the more high-level ResourceStore contact, abstracting all common functionality
* such that new stores can be added by implementing the more simple DataAccessor contract.
* DataAccessorBasedStore thereby provides behaviours for reuse across different stores, such as:
* * Converting container metadata to data
* * Converting slug to URI
* * Checking if addResource target is a container
* * Checking if no containment triples are written to a container
* * etc.
*
* Currently "metadata" is seen as something that is not directly accessible.
* That means that a consumer can't write directly to the metadata of a resource, only indirectly through headers.
* (Except for containers where data and metadata overlap).
*
* The one thing this store does not take care of (yet?) are containment triples for containers
*
* Work has been done to minimize the number of required calls to the DataAccessor,
* but the main disadvantage is that sometimes multiple calls are required where a specific store might only need one.
*/
export class DataAccessorBasedStore implements ResourceStore {
protected readonly logger = getLoggerFor(this);
private readonly accessor: DataAccessor;
private readonly identifierStrategy: IdentifierStrategy;
private readonly auxiliaryStrategy: AuxiliaryStrategy;
public constructor(accessor: DataAccessor, identifierStrategy: IdentifierStrategy,
auxiliaryStrategy: AuxiliaryStrategy) {
this.accessor = accessor;
this.identifierStrategy = identifierStrategy;
this.auxiliaryStrategy = auxiliaryStrategy;
}
public async hasResource(identifier: ResourceIdentifier): Promise<boolean> {
try {
this.validateIdentifier(identifier);
await this.accessor.getMetadata(identifier);
return true;
} catch (error: unknown) {
if (NotFoundHttpError.isInstance(error)) {
return false;
}
throw error;
}
}
public async getRepresentation(identifier: ResourceIdentifier): Promise<Representation> {
this.validateIdentifier(identifier);
// In the future we want to use getNormalizedMetadata and redirect in case the identifier differs
const metadata = await this.accessor.getMetadata(identifier);
let representation: Representation;
// Potentially add auxiliary related metadata
// Solid, §4.3: "Clients can discover auxiliary resources associated with a subject resource by making an HTTP HEAD
// or GET request on the target URL, and checking the HTTP Link header with the rel parameter"
// https://solid.github.io/specification/protocol#auxiliary-resources
await this.auxiliaryStrategy.addMetadata(metadata);
if (isContainerPath(metadata.identifier.value)) {
// Add containment triples of non-auxiliary resources
for await (const child of this.accessor.getChildren(identifier)) {
if (!this.auxiliaryStrategy.isAuxiliaryIdentifier({ path: child.identifier.value })) {
metadata.addQuads(child.quads());
metadata.add(LDP.terms.contains, child.identifier as NamedNode, SOLID_META.terms.ResponseMetadata);
}
}
// Generate a container representation from the metadata
// All triples should be in the same graph for the data representation
const data = metadata.quads().map((triple): Quad => {
if (triple.graph.termType === 'DefaultGraph') {
return triple;
}
return DataFactory.quad(triple.subject, triple.predicate, triple.object);
});
metadata.addQuad(DC.terms.namespace, PREFERRED_PREFIX_TERM, 'dc', SOLID_META.terms.ResponseMetadata);
metadata.addQuad(LDP.terms.namespace, PREFERRED_PREFIX_TERM, 'ldp', SOLID_META.terms.ResponseMetadata);
metadata.addQuad(POSIX.terms.namespace, PREFERRED_PREFIX_TERM, 'posix', SOLID_META.terms.ResponseMetadata);
metadata.addQuad(XSD.terms.namespace, PREFERRED_PREFIX_TERM, 'xsd', SOLID_META.terms.ResponseMetadata);
representation = new BasicRepresentation(data, metadata, INTERNAL_QUADS);
} else {
// Retrieve a document representation from the accessor
representation = new BasicRepresentation(await this.accessor.getData(identifier), metadata);
}
return representation;
}
public async addResource(container: ResourceIdentifier, representation: Representation, conditions?: Conditions):
Promise<ResourceIdentifier> {
this.validateIdentifier(container);
const parentMetadata = await this.getSafeNormalizedMetadata(container);
// Solid, §5.3: "When a POST method request targets a resource without an existing representation,
// the server MUST respond with the 404 status code."
// https://solid.github.io/specification/protocol#writing-resources
if (!parentMetadata) {
throw new NotFoundHttpError();
}
// Not using `container` since `getSafeNormalizedMetadata` might return metadata for a different identifier.
// Solid, §5: "Servers MUST respond with the 405 status code to requests using HTTP methods
// that are not supported by the target resource."
// https://solid.github.io/specification/protocol#reading-writing-resources
if (!isContainerPath(parentMetadata.identifier.value)) {
throw new MethodNotAllowedHttpError('The given path is not a container.');
}
this.validateConditions(conditions, parentMetadata);
// Solid, §5.1: "Servers MAY allow clients to suggest the URI of a resource created through POST,
// using the HTTP Slug header as defined in [RFC5023].
// Clients who want the server to assign a URI of a resource, MUST use the POST request."
// https://solid.github.io/specification/protocol#resource-type-heuristics
const newID = await this.createSafeUri(container, representation.metadata);
const isContainer = isContainerIdentifier(newID);
// Ensure the representation is supported by the accessor
// Containers are not checked because uploaded representations are treated as metadata
if (!isContainer) {
await this.accessor.canHandle(representation);
}
// Write the data. New containers should never be made for a POST request.
await this.writeData(newID, representation, isContainer, false, false);
return newID;
}
public async setRepresentation(identifier: ResourceIdentifier, representation: Representation,
conditions?: Conditions): Promise<ResourceIdentifier[]> {
this.validateIdentifier(identifier);
// Check if the resource already exists
const oldMetadata = await this.getSafeNormalizedMetadata(identifier);
// Might want to redirect in the future.
// See #480
// Solid, §3.1: "If two URIs differ only in the trailing slash, and the server has associated a resource with
// one of them, then the other URI MUST NOT correspond to another resource. Instead, the server MAY respond to
// requests for the latter URI with a 301 redirect to the former."
// https://solid.github.io/specification/protocol#uri-slash-semantics
if (oldMetadata && oldMetadata.identifier.value !== identifier.path) {
throw new ConflictHttpError(`${identifier.path} conflicts with existing path ${oldMetadata.identifier.value}`);
}
// Solid, §3.1: "Paths ending with a slash denote a container resource."
// https://solid.github.io/specification/protocol#uri-slash-semantics
const isContainer = isContainerIdentifier(identifier);
if (!isContainer && this.isContainerType(representation.metadata)) {
throw new BadRequestHttpError('Containers should have a `/` at the end of their path, resources should not.');
}
// Ensure the representation is supported by the accessor
// Containers are not checked because uploaded representations are treated as metadata
if (!isContainer) {
await this.accessor.canHandle(representation);
}
this.validateConditions(conditions, oldMetadata);
// Potentially have to create containers if it didn't exist yet
return this.writeData(identifier, representation, isContainer, !oldMetadata, Boolean(oldMetadata));
}
public async modifyResource(identifier: ResourceIdentifier, patch: Patch,
conditions?: Conditions): Promise<ResourceIdentifier[]> {
if (conditions) {
let metadata: RepresentationMetadata | undefined;
try {
metadata = await this.accessor.getMetadata(identifier);
} catch (error: unknown) {
if (!NotFoundHttpError.isInstance(error)) {
throw error;
}
}
this.validateConditions(conditions, metadata);
}
throw new NotImplementedHttpError('Patches are not supported by the default store.');
}
public async deleteResource(identifier: ResourceIdentifier, conditions?: Conditions): Promise<ResourceIdentifier[]> {
this.validateIdentifier(identifier);
const metadata = await this.accessor.getMetadata(identifier);
// Solid, §5.4: "When a DELETE request targets storage’s root container or its associated ACL resource,
// the server MUST respond with the 405 status code."
// https://solid.github.io/specification/protocol#deleting-resources
if (this.isRootStorage(metadata)) {
throw new MethodNotAllowedHttpError('Cannot delete a root storage container.');
}
if (this.auxiliaryStrategy.isAuxiliaryIdentifier(identifier) &&
this.auxiliaryStrategy.isRequiredInRoot(identifier)) {
const subjectIdentifier = this.auxiliaryStrategy.getSubjectIdentifier(identifier);
const parentMetadata = await this.accessor.getMetadata(subjectIdentifier);
if (this.isRootStorage(parentMetadata)) {
throw new MethodNotAllowedHttpError(`Cannot delete ${identifier.path} from a root storage container.`);
}
}
// Solid, §5.4: "When a DELETE request is made to a container, the server MUST delete the container
// if it contains no resources. If the container contains resources,
// the server MUST respond with the 409 status code and response body describing the error."
// https://solid.github.io/specification/protocol#deleting-resources
// Auxiliary resources are not counted when deleting a container since they will also be deleted.
if (isContainerIdentifier(identifier) && await this.hasProperChildren(identifier)) {
throw new ConflictHttpError('Can only delete empty containers.');
}
this.validateConditions(conditions, metadata);
// Solid, §5.4: "When a contained resource is deleted,
// the server MUST also delete the associated auxiliary resources"
// https://solid.github.io/specification/protocol#deleting-resources
const deleted = [ identifier ];
if (!this.auxiliaryStrategy.isAuxiliaryIdentifier(identifier)) {
const auxiliaries = this.auxiliaryStrategy.getAuxiliaryIdentifiers(identifier);
deleted.push(...await this.safelyDeleteAuxiliaryResources(auxiliaries));
}
if (!this.identifierStrategy.isRootContainer(identifier)) {
const container = this.identifierStrategy.getParentContainer(identifier);
deleted.push(container);
// Update modified date of parent
await this.updateContainerModifiedDate(container);
}
await this.accessor.deleteResource(identifier);
return deleted;
}
/**
* Verify if the given identifier matches the stored base.
*/
protected validateIdentifier(identifier: ResourceIdentifier): void {
if (!this.identifierStrategy.supportsIdentifier(identifier)) {
throw new NotFoundHttpError();
}
}
/**
* Verify if the given metadata matches the conditions.
*/
protected validateConditions(conditions?: Conditions, metadata?: RepresentationMetadata): void {
// The 412 (Precondition Failed) status code indicates
// that one or more conditions given in the request header fields evaluated to false when tested on the server.
if (conditions && !conditions.matchesMetadata(metadata)) {
throw new PreconditionFailedHttpError();
}
}
/**
* Returns the metadata matching the identifier, ignoring the presence of a trailing slash or not.
*
* Solid, §3.1: "If two URIs differ only in the trailing slash,
* and the server has associated a resource with one of them,
* then the other URI MUST NOT correspond to another resource."
* https://solid.github.io/specification/protocol#uri-slash-semantics
*
* First the identifier gets requested and if no result is found
* the identifier with differing trailing slash is requested.
* @param identifier - Identifier that needs to be checked.
*/
protected async getNormalizedMetadata(identifier: ResourceIdentifier): Promise<RepresentationMetadata> {
const hasSlash = isContainerIdentifier(identifier);
try {
return await this.accessor.getMetadata(identifier);
} catch (error: unknown) {
if (NotFoundHttpError.isInstance(error)) {
const otherIdentifier =
{ path: hasSlash ? trimTrailingSlashes(identifier.path) : ensureTrailingSlash(identifier.path) };
// Only try to access other identifier if it is valid in the scope of the DataAccessor
this.validateIdentifier(otherIdentifier);
return this.accessor.getMetadata(otherIdentifier);
}
throw error;
}
}
/**
* Returns the result of `getNormalizedMetadata` or undefined if a 404 error is thrown.
*/
protected async getSafeNormalizedMetadata(identifier: ResourceIdentifier):
Promise<RepresentationMetadata | undefined> {
try {
return await this.getNormalizedMetadata(identifier);
} catch (error: unknown) {
if (!NotFoundHttpError.isInstance(error)) {
throw error;
}
}
}
/**
* Write the given resource to the DataAccessor. Metadata will be updated with necessary triples.
* In case of containers `handleContainerData` will be used to verify the data.
* @param identifier - Identifier of the resource.
* @param representation - Corresponding Representation.
* @param isContainer - Is the incoming resource a container?
* @param createContainers - Should parent containers (potentially) be created?
* @param exists - If the resource already exists.
*
* @returns Identifiers of resources that were possibly modified.
*/
protected async writeData(identifier: ResourceIdentifier, representation: Representation, isContainer: boolean,
createContainers: boolean, exists: boolean): Promise<ResourceIdentifier[]> {
// Make sure the metadata has the correct identifier and correct type quads
// Need to do this before handling container data to have the correct identifier
representation.metadata.identifier = DataFactory.namedNode(identifier.path);
addResourceMetadata(representation.metadata, isContainer);
// Validate container data
if (isContainer) {
await this.handleContainerData(representation);
}
// Validate auxiliary data
if (this.auxiliaryStrategy.isAuxiliaryIdentifier(identifier)) {
await this.auxiliaryStrategy.validate(representation);
}
// Add date modified metadata
updateModifiedDate(representation.metadata);
// Root container should not have a parent container
// Solid, §5.3: "Servers MUST create intermediate containers and include corresponding containment triples
// in container representations derived from the URI path component of PUT and PATCH requests."
// https://solid.github.io/specification/protocol#writing-resources
const modified = [];
if (!this.identifierStrategy.isRootContainer(identifier) && !exists) {
const container = this.identifierStrategy.getParentContainer(identifier);
if (!createContainers) {
modified.push(container);
} else {
const created = await this.createRecursiveContainers(container);
modified.push(...created.length === 0 ? [ container ] : created);
}
// Parent container is also modified
await this.updateContainerModifiedDate(container);
}
// Remove all generated metadata to prevent it from being stored permanently
this.removeResponseMetadata(representation.metadata);
await (isContainer ?
this.accessor.writeContainer(identifier, representation.metadata) :
this.accessor.writeDocument(identifier, representation.data, representation.metadata));
return [ ...modified, identifier ];
}
/**
* Verify if the incoming data for a container is valid (RDF and no containment triples).
* Adds the container data to its metadata afterwards.
*
* @param representation - Container representation.
*/
protected async handleContainerData(representation: Representation): Promise<void> {
let quads: Quad[];
try {
// No need to parse the data if it already contains internal/quads
if (representation.metadata.contentType === INTERNAL_QUADS) {
quads = await arrayifyStream(representation.data);
} else {
const { contentType, identifier } = representation.metadata;
quads = await parseQuads(representation.data, { format: contentType, baseIRI: identifier.value });
}
} catch (error: unknown) {
throw new BadRequestHttpError(`Can only create containers with RDF data. ${createErrorMessage(error)}`,
{ cause: error });
}
// Solid, §5.3: "Servers MUST NOT allow HTTP POST, PUT and PATCH to update a container’s containment triples;
// if the server receives such a request, it MUST respond with a 409 status code."
// https://solid.github.io/specification/protocol#writing-resources
if (quads.some((quad): boolean => quad.predicate.value === LDP.contains)) {
throw new ConflictHttpError('Container bodies are not allowed to have containment triples.');
}
// Input content type doesn't matter anymore
representation.metadata.removeAll(CONTENT_TYPE);
// Container data is stored in the metadata
representation.metadata.addQuads(quads);
}
/**
* Removes all generated data from metadata to prevent it from being stored permanently.
*/
protected removeResponseMetadata(metadata: RepresentationMetadata): void {
metadata.removeQuads(
metadata.quads(null, null, null, SOLID_META.terms.ResponseMetadata),
);
}
/**
* Updates the last modified date of the given container
*/
protected async updateContainerModifiedDate(container: ResourceIdentifier): Promise<void> {
const parentMetadata = await this.accessor.getMetadata(container);
updateModifiedDate(parentMetadata);
this.removeResponseMetadata(parentMetadata);
await this.accessor.writeContainer(container, parentMetadata);
}
/**
* Generates a new URI for a resource in the given container, potentially using the given slug.
*
* Solid, §5.3: "Servers MUST allow creating new resources with a POST request to URI path ending `/`.
* Servers MUST create a resource with URI path ending `/{id}` in container `/`.
* Servers MUST create a container with URI path ending `/{id}/` in container `/` for requests
* including the HTTP Link header with rel="type" targeting a valid LDP container type."
* https://solid.github.io/specification/protocol#writing-resources
*
* @param container - Parent container of the new URI.
* @param isContainer - Does the new URI represent a container?
* @param slug - Slug to use for the new URI.
*/
protected createURI(container: ResourceIdentifier, isContainer: boolean, slug?: string): ResourceIdentifier {
this.validateSlug(isContainer, slug);
const base = ensureTrailingSlash(container.path);
const name = (slug && this.cleanSlug(slug)) ?? uuid();
const suffix = isContainer ? '/' : '';
return { path: `${base}${name}${suffix}` };
}
/**
* Validates if the slug and headers are valid.
* Errors if slug exists, ends on slash, but ContainerType Link header is NOT present
* @param isContainer - Is the slug supposed to represent a container?
* @param slug - Is the requested slug (if any).
*/
protected validateSlug(isContainer: boolean, slug?: string): void {
if (slug && isContainerPath(slug) && !isContainer) {
throw new BadRequestHttpError('Only slugs used to create containers can end with a `/`.');
}
}
/**
* Clean http Slug to be compatible with the server. Makes sure there are no unwanted characters
* e.g.: cleanslug('&%26') returns '%26%26'
* @param slug - the slug to clean
*/
protected cleanSlug(slug: string): string {
if (/\/[^/]/u.test(slug)) {
throw new BadRequestHttpError('Slugs should not contain slashes');
}
return toCanonicalUriPath(trimTrailingSlashes(slug));
}
/**
* Generate a valid URI to store a new Resource in the given container.
* URI will be based on the slug header if there is one and is guaranteed to not exist yet.
*
* @param container - Identifier of the target container.
* @param metadata - Metadata of the new resource.
*/
protected async createSafeUri(container: ResourceIdentifier, metadata: RepresentationMetadata):
Promise<ResourceIdentifier> {
// Get all values needed for naming the resource
const isContainer = this.isContainerType(metadata);
const slug = metadata.get(SOLID_HTTP.slug)?.value;
metadata.removeAll(SOLID_HTTP.slug);
let newID: ResourceIdentifier = this.createURI(container, isContainer, slug);
// Solid, §5.3: "When a POST method request with the Slug header targets an auxiliary resource,
// the server MUST respond with the 403 status code and response body describing the error."
// https://solid.github.io/specification/protocol#writing-resources
if (this.auxiliaryStrategy.isAuxiliaryIdentifier(newID)) {
throw new ForbiddenHttpError('Slug bodies that would result in an auxiliary resource are forbidden');
}
// Make sure we don't already have a resource with this exact name (or with differing trailing slash)
const withSlash = { path: ensureTrailingSlash(newID.path) };
const withoutSlash = { path: trimTrailingSlashes(newID.path) };
if (await this.hasResource(withSlash) || await this.hasResource(withoutSlash)) {
newID = this.createURI(container, isContainer);
}
return newID;
}
/**
* Checks if the given metadata represents a (potential) container,
* based on the metadata.
* @param metadata - Metadata of the (new) resource.
*/
protected isContainerType(metadata: RepresentationMetadata): boolean {
return this.hasContainerType(metadata.getAll(RDF.type));
}
/**
* Checks in a list of types if any of them match a Container type.
*/
protected hasContainerType(rdfTypes: Term[]): boolean {
return rdfTypes.some((type): boolean => type.value === LDP.Container || type.value === LDP.BasicContainer);
}
/**
* Verifies if this is the metadata of a root storage container.
*/
protected isRootStorage(metadata: RepresentationMetadata): boolean {
return metadata.getAll(RDF.type).some((term): boolean => term.value === PIM.Storage);
}
/**
* Checks if the given container has any non-auxiliary resources.
*/
protected async hasProperChildren(container: ResourceIdentifier): Promise<boolean> {
for await (const child of this.accessor.getChildren(container)) {
if (!this.auxiliaryStrategy.isAuxiliaryIdentifier({ path: child.identifier.value })) {
return true;
}
}
return false;
}
/**
* Deletes the given array of auxiliary identifiers.
* Does not throw an error if something goes wrong.
*/
protected async safelyDeleteAuxiliaryResources(identifiers: ResourceIdentifier[]): Promise<ResourceIdentifier[]> {
const deleted: ResourceIdentifier[] = [];
await Promise.all(identifiers.map(async(identifier): Promise<void> => {
try {
await this.accessor.deleteResource(identifier);
deleted.push(identifier);
} catch (error: unknown) {
if (!NotFoundHttpError.isInstance(error)) {
this.logger.error(`Error deleting auxiliary resource ${identifier.path}: ${createErrorMessage(error)}`);
}
}
}));
return deleted;
}
/**
* Create containers starting from the root until the given identifier corresponds to an existing container.
* Will throw errors if the identifier of the last existing "container" corresponds to an existing document.
* @param container - Identifier of the container which will need to exist.
*/
protected async createRecursiveContainers(container: ResourceIdentifier): Promise<ResourceIdentifier[]> {
// Verify whether the container already exists
try {
const metadata = await this.getNormalizedMetadata(container);
// See #480
// Solid, §3.1: "If two URIs differ only in the trailing slash, and the server has associated a resource with
// one of them, then the other URI MUST NOT correspond to another resource. Instead, the server MAY respond to
// requests for the latter URI with a 301 redirect to the former."
// https://solid.github.io/specification/protocol#uri-slash-semantics
if (!isContainerPath(metadata.identifier.value)) {
throw new ForbiddenHttpError(`Creating container ${container.path} conflicts with an existing resource.`);
}
return [];
} catch (error: unknown) {
if (!NotFoundHttpError.isInstance(error)) {
throw error;
}
}
// Create the container, starting with its parent
const ancestors = this.identifierStrategy.isRootContainer(container) ?
[] :
await this.createRecursiveContainers(this.identifierStrategy.getParentContainer(container));
await this.writeData(container, new BasicRepresentation([], container), true, false, false);
return [ ...ancestors, container ];
}
}