vitessce/src/loaders/JsonLoader.js

Vitessce app and React component library

import Ajv from 'ajv';
import { FileType } from '../app/constants';
import AbstractTwoStepLoader from './AbstractTwoStepLoader';
import { LoaderValidationError, AbstractLoaderError } from './errors/index';
import LoaderResult from './LoaderResult';

import cellsSchema from '../schemas/cells.schema.json';
import moleculesSchema from '../schemas/molecules.schema.json';
import neighborhoodsSchema from '../schemas/neighborhoods.schema.json';
import rasterSchema from '../schemas/raster.schema.json';
import cellSetsSchema from '../schemas/cell-sets.schema.json';

const fileTypeToSchema = {
  [FileType.CELLS_JSON]: cellsSchema,
  [FileType.MOLECULES_JSON]: moleculesSchema,
  [FileType.NEIGHBORHOODS_JSON]: neighborhoodsSchema,
  [FileType.RASTER_JSON]: rasterSchema,
  [FileType.CELL_SETS_JSON]: cellSetsSchema,
};

export default class JsonLoader extends AbstractTwoStepLoader {
  constructor(dataSource, params) {
    super(dataSource, params);

    const { fileType } = params;
    this.schema = fileTypeToSchema[fileType];
  }

  load() {
    const {
      url, type, fileType,
    } = this;
    if (this.data) {
      return this.data;
    }
    this.data = this.dataSource.data
      .then((data) => {
        if (data instanceof AbstractLoaderError) {
          return Promise.reject(data);
        }
        const [valid, reason] = this.validate(data);
        if (valid) {
          return Promise.resolve(new LoaderResult(data, url));
        }
        return Promise.reject(new LoaderValidationError(type, fileType, url, reason));
      });
    return this.data;
  }

  validate(data) {
    const { schema, fileType } = this;
    if (!schema) {
      throw Error(`No schema for ${fileType}`);
    }
    const validate = new Ajv().compile(schema);
    const valid = validate(data);
    let failureReason;
    if (!valid) {
      failureReason = validate.errors;
    }
    return [valid, failureReason];
  }
}