import type { Term } from 'rdf-js';
import { getLoggerFor } from '../../logging/LogUtil';
import type { ResourceStore } from '../../storage/ResourceStore';
import { BadRequestHttpError } from '../../util/errors/BadRequestHttpError';
import { InternalServerError } from '../../util/errors/InternalServerError';
import { NotImplementedHttpError } from '../../util/errors/NotImplementedHttpError';
import { find } from '../../util/IterableUtil';
import { AS, LDP, RDF, SOLID_AS } from '../../util/Vocabularies';
import { CreatedResponseDescription } from '../output/response/CreatedResponseDescription';
import type { ResponseDescription } from '../output/response/ResponseDescription';
import type { OperationHandlerInput } from './OperationHandler';
import { OperationHandler } from './OperationHandler';

/**
 * Handles POST {@link Operation}s.
 * Calls the addResource function from a {@link ResourceStore}.
 */
export class PostOperationHandler extends OperationHandler {
  protected readonly logger = getLoggerFor(this);

  private readonly store: ResourceStore;

  public constructor(store: ResourceStore) {
    super();
    this.store = store;
  }

  public async canHandle({ operation }: OperationHandlerInput): Promise<void> {
    if (operation.method !== 'POST') {
      throw new NotImplementedHttpError('This handler only supports POST operations');
    }
  }

  public async handle({ operation }: OperationHandlerInput): Promise<ResponseDescription> {
    const type = new Set(operation.body.metadata.getAll(RDF.terms.type).map((term: Term): string => term.value));
    const isContainerType = type.has(LDP.Container) || type.has(LDP.BasicContainer);
    // Solid, §2.1: "A Solid server MUST reject PUT, POST and PATCH requests
    // without the Content-Type header with a status code of 400."
    // https://solid.github.io/specification/protocol#http-server
    // An exception is made for LDP Containers as nothing is done with the body, so a Content-type is not required
    if (!operation.body.metadata.contentType && !isContainerType) {
      this.logger.warn('POST requests require the Content-Type header to be set');
      throw new BadRequestHttpError('POST requests require the Content-Type header to be set');
    }
    const changes = await this.store.addResource(operation.target, operation.body, operation.conditions);
    const createdIdentifier = find(changes.keys(), (identifier): boolean =>
      Boolean(changes.get(identifier)?.has(SOLID_AS.terms.Activity, AS.terms.Create)));
    if (!createdIdentifier) {
      throw new InternalServerError('Operation was successful but no created identifier was returned.');
    }
    return new CreatedResponseDescription(createdIdentifier);
  }
}