app/services/data/normalizer/hydraNormalizer.ts

import {AnyJson, ApiResponse, HydraMetadata} from '~/types/data'
import UrlUtils from '~/services/utils/urlUtils'
import {METADATA_TYPE} from '~/types/enum/data'
import models from "~/models/models";
import ApiResource from "~/models/ApiResource";
import {isArray} from "lodash";

/**
 * Normalisation et dé-normalisation du format de données Hydra
 */
class HydraNormalizer {

  /**
   * Normalize the given entity into an Hydra formatted content.
   * @param entity
   */
  public static normalizeEntity(entity: ApiResource): AnyJson {
    const iriEncodedFields = HydraNormalizer.getIriEncodedFields(entity)

    for (const field in iriEncodedFields) {
      const value = entity[field]
      const targetEntity = iriEncodedFields[field].entity

      if (isArray(value)) {
        entity[field] = value.map((id: number) => {
          return UrlUtils.makeIRI(targetEntity, id)
        })
      } else {
        entity[field] = UrlUtils.makeIRI(targetEntity, value)
      }
    }

    return entity.$toJson()
  }

  /**
   * Parse une réponse Hydra et retourne un objet ApiResponse
   *
   * @param {AnyJson} data
   * @param model
   * @return {AnyJson} réponse parsée
   */
  public static denormalize(data: AnyJson, model?: typeof ApiResource): ApiResponse {
    return {
      data: HydraNormalizer.getData(data, model),
      metadata: HydraNormalizer.getMetadata(data)
    }
  }

  protected static getData(hydraData: AnyJson, model?: typeof ApiResource): AnyJson {
    if (hydraData['@type'] === 'hydra:Collection') {
      let members = hydraData['hydra:member']
      let results = []

      for (let item of members) {
        results.push(HydraNormalizer.denormalizeItem(item, model))
      }

      return results
    } else {
      return HydraNormalizer.denormalizeItem(hydraData, model)
    }
  }

  /**
   * Dénormalise un item d'une réponse hydra
   *
   * @param item
   * @param model
   * @protected
   */
  protected static denormalizeItem(item: AnyJson, model?: typeof ApiResource): AnyJson {

    if (!model) {
      const {entity, id} = HydraNormalizer.parseIRI(item['@id'])
      if (!id) {
        throw Error('De-normalization error : Could not determine the model of the entity')
      }
      model = models[entity]
    }

    const instance = new model(item)

    const iriEncodedFields = HydraNormalizer.getIriEncodedFields(instance)

    for (const field in iriEncodedFields) {
      const value = instance[field]
      const targetEntity = iriEncodedFields[field].entity

      if (isArray(value)) {
        instance[field] = value.map((iri: string) => {
          return HydraNormalizer.getIdFromIri(iri, targetEntity)
        })
      } else {
        instance[field] = HydraNormalizer.getIdFromIri(value, targetEntity)
      }
    }

    return instance
  }

  /**
   * Génère les métadonnées d'un item ou d'une collection
   *
   * @param data
   * @protected
   */
  protected static getMetadata(data: AnyJson): HydraMetadata {
    if (data['@type'] !== 'hydra:Collection') {
      // A single item, no metadata
      return { type: METADATA_TYPE.ITEM }
    }

    const metadata: HydraMetadata = {
      totalItems: data['hydra:totalItems']
    }

    if (data['hydra:view']) {
      /**
       * Extract the page number from the IRIs in the hydra:view section
       */
      const extractPageNumber = (pos: string, default_: number | undefined=undefined): number | undefined => {
        const iri = data['hydra:view']['hydra:' + pos]
        if (!iri) {
          return default_
        }
        return UrlUtils.getParameter(
            data['hydra:view']['hydra:' + pos],
            'page',
            default_
        ) as number | undefined
      }

      // TODO: utile d'ajouter la page en cours?
      metadata.firstPage = extractPageNumber('first', 1)
      metadata.lastPage = extractPageNumber('last', 1)
      metadata.nextPage = extractPageNumber('next')
      metadata.previousPage = extractPageNumber('previous')
    }

    metadata.type = METADATA_TYPE.COLLECTION

    return metadata
  }

  /**
   * Parse the given IRI
   * @param iri
   * @protected
   */
  protected static parseIRI(iri: string) {
    const rx = /\/api\/(\w+)\/(\d+)/
    const match = rx.exec(iri)
    if (!match) {
      throw Error('could not parse the IRI : ' + iri)
    }

    return {
      entity: match[1],
      id: parseInt(match[2])
    }
  }

  /**
   * Get the array of the entity's fields marked as IRIEncoded
   * @see models/decorators.ts
   *
   * @param entity
   * @protected
   */
  protected static getIriEncodedFields(entity: ApiResource): Record<string, ApiResource> {
    const prototype = Object.getPrototypeOf(entity)
    return prototype.constructor.relations
  }

  /**
   * Retrieve the entitie's id from the given IRI
   * Throws an error if the IRI does not match the expected entity
   *
   * @param iri
   * @param expectedEntity
   * @protected
   */
  protected static getIdFromIri(iri: string, expectedEntity: string): number {
    const { entity, id } = HydraNormalizer.parseIRI(iri)
    if (entity !== expectedEntity) {
      throw Error("IRI entity does not match the field's target entity (" + entity + ' != ' + expectedEntity + ")")
    }
    return id
  }
}

export default HydraNormalizer