vega-lite/src/compile/data/geojson.ts

Vega-Lite is a concise high-level language for interactive visualization.

import {Transforms as VgTransform, Vector2} from 'vega';
import {isString} from 'vega-util';
import {GeoPositionChannel, LATITUDE, LATITUDE2, LONGITUDE, LONGITUDE2, SHAPE} from '../../channel.js';
import {getFieldOrDatumDef, isDatumDef, isFieldDef, isValueDef} from '../../channeldef.js';
import {GEOJSON} from '../../type.js';
import {duplicate, hash} from '../../util.js';
import {VgExprRef} from '../../vega.schema.js';
import {UnitModel} from '../unit.js';
import {DataFlowNode} from './dataflow.js';

export class GeoJSONNode extends DataFlowNode {
  public clone() {
    return new GeoJSONNode(null, duplicate(this.fields), this.geojson, this.signal);
  }

  public static parseAll(parent: DataFlowNode, model: UnitModel): DataFlowNode {
    if (model.component.projection && !model.component.projection.isFit) {
      return parent;
    }

    let geoJsonCounter = 0;

    for (const coordinates of [
      [LONGITUDE, LATITUDE],
      [LONGITUDE2, LATITUDE2],
    ] as Vector2<GeoPositionChannel>[]) {
      const pair = coordinates.map((channel) => {
        const def = getFieldOrDatumDef(model.encoding[channel]);
        return isFieldDef(def)
          ? def.field
          : isDatumDef(def)
            ? {expr: `${def.datum}`}
            : isValueDef(def)
              ? {expr: `${def['value']}`}
              : undefined;
      }) as [GeoPositionChannel, GeoPositionChannel];

      if (pair[0] || pair[1]) {
        parent = new GeoJSONNode(parent, pair, null, model.getName(`geojson_${geoJsonCounter++}`));
      }
    }

    if (model.channelHasField(SHAPE)) {
      const fieldDef = model.typedFieldDef(SHAPE);
      if (fieldDef.type === GEOJSON) {
        parent = new GeoJSONNode(parent, null, fieldDef.field, model.getName(`geojson_${geoJsonCounter++}`));
      }
    }

    return parent;
  }

  constructor(
    parent: DataFlowNode,
    private fields?: Vector2<string | VgExprRef>,
    private geojson?: string,
    private signal?: string,
  ) {
    super(parent);
  }

  public dependentFields() {
    const fields = (this.fields ?? []).filter(isString) as string[];
    return new Set([...(this.geojson ? [this.geojson] : []), ...fields]);
  }

  public producedFields() {
    return new Set<string>();
  }

  public hash() {
    return `GeoJSON ${this.geojson} ${this.signal} ${hash(this.fields)}`;
  }

  public assemble(): VgTransform[] {
    return [
      ...(this.geojson
        ? [
            {
              type: 'filter',
              expr: `isValid(datum["${this.geojson}"])`,
            } as const,
          ]
        : []),
      {
        type: 'geojson',
        ...(this.fields ? {fields: this.fields} : {}),
        ...(this.geojson ? {geojson: this.geojson} : {}),
        signal: this.signal,
      },
    ];
  }
}