Add function to retrieve and cache vector files

package.json

@@ -35,8 +35,14 @@
     }
   },
   "dependencies": {
+    "@types/geojson": "^7946.0.7",
+    "@types/lru-cache": "^5.1.0",
+    "@types/topojson-client": "^3.0.0",
+    "@types/topojson-specification": "^1.0.1",
     "lodash": "^4.17.15",
-    "semver": "7.3.2"
+    "lru-cache": "^6.0.0",
+    "semver": "7.3.2",
+    "topojson-client": "^3.1.0"
   },
   "devDependencies": {
     "@babel/cli": "^7.6.4",

src/ems_client.ts

@@ -20,10 +20,12 @@
 import _ from 'lodash';
 import { TMSService } from './tms_service';
 import { EMSFormatType, FileLayer } from './file_layer';
+import { FeatureCollection } from 'geojson';
 import semver from 'semver';
 import { format as formatUrl, parse as parseUrl, UrlObject } from 'url';
 import { toAbsoluteUrl } from './utils';
 import { ParsedUrlQueryInput } from 'querystring';
+import LRUCache from 'lru-cache';
 
 const DEFAULT_EMS_VERSION = '7.12';
 
@@ -110,6 +112,7 @@ type BaseClientConfig = {
   landingPageUrl?: string;
   fetchFunction: Function;
   proxyPath?: string;
+  cacheSize?: number;
 };
 
 type DeprecatedClientConfig = BaseClientConfig & {
@@ -216,6 +219,7 @@ export class EMSClient {
   private readonly _emsLandingPageUrl: string;
   private readonly _language: string;
   private readonly _proxyPath: string;
+  private readonly _cache: LRUCache<string, FeatureCollection>;
 
   /**
    * these methods are assigned outside the constructor
@@ -253,6 +257,9 @@ export class EMSClient {
 
     this._fetchFunction = config.fetchFunction;
     this._proxyPath = config.proxyPath || '';
+    this._cache = new LRUCache<string, FeatureCollection>({
+      max: config.cacheSize || 10,
+    });
 
     this._invalidateSettings();
   }
@@ -275,9 +282,9 @@ export class EMSClient {
   /**
    * this internal method is overridden by the tests to simulate custom manifest.
    */
-  async getManifest<T>(manifestUrl: string): Promise<T> {
+  async getManifest<T>(endpointUrl: string): Promise<T> {
     try {
-      const url = extendUrl(manifestUrl, { query: this._queryParams });
+      const url = extendUrl(endpointUrl, { query: this._queryParams });
       const result = await this._fetchWithTimeout(url);
       return result ? await result.json() : null;
     } catch (e) {
@@ -287,7 +294,7 @@ export class EMSClient {
       if (!(e instanceof Error)) {
         e = new Error(e.data || `status ${e.statusText || e.status}`);
       }
-      throw new Error(`Unable to retrieve manifest from ${manifestUrl}: ${e.message}`);
+      throw new Error(`Unable to retrieve data from ${endpointUrl}: ${e.message}`);
     }
   }
 
@@ -329,6 +336,15 @@ export class EMSClient {
     return await this._loadTMSServices();
   }
 
+  cacheGeoJson(layerId: string, geoJson: FeatureCollection): void {
+    this._cache.set(layerId, geoJson);
+    return;
+  }
+
+  getCachedGeoJson(layerId: string) {
+    return this._cache.get(layerId);
+  }
+
   getTileApiUrl(): string {
     return this._tileApiUrl;
   }
@@ -406,6 +422,7 @@ export class EMSClient {
   }
 
   private _invalidateSettings(): void {
+    this._cache.reset();
     this._getMainCatalog = _.once(
       async (): Promise<EmsCatalogManifest> => {
         // Preserve manifestServiceUrl parameter for backwards compatibility with EMS v7.2

src/file_layer.ts

@@ -25,6 +25,8 @@ import {
   FileLayerConfig,
 } from './ems_client';
 import { AbstractEmsService } from './ems_service';
+import { FeatureCollection } from 'geojson';
+import * as topojson from 'topojson-client';
 
 export enum EMSFormatType {
   geojson = 'geojson',
@@ -42,6 +44,34 @@ export class FileLayer extends AbstractEmsService {
     this._config = config;
   }
 
+  async getGeoJson(): Promise<FeatureCollection | undefined> {
+    const cachedGeoJson = this._emsClient.getCachedGeoJson(this.getId());
+    if (cachedGeoJson) {
+      return cachedGeoJson;
+    }
+
+    const format = this.getDefaultFormatType();
+    const fetchUrl = this.getDefaultFormatUrl();
+    // let fetchedJson;
+    let geojson;
+    const fetchedJson = await this._emsClient.getManifest(fetchUrl);
+    if (fetchedJson) {
+      if (format === 'geojson') {
+        geojson = (fetchedJson as unknown) as FeatureCollection;
+      } else if (format === 'topojson') {
+        const meta = this.getDefaultFormatMeta();
+        const featureCollectionPath = meta?.feature_collection_path ?? 'data';
+        // @ts-expect-error see https://github.com/DefinitelyTyped/DefinitelyTyped/pull/52156
+        geojson = topojson.feature(fetchedJson, featureCollectionPath) as FeatureCollection;
+      } else {
+        return;
+      }
+      this._emsClient.cacheGeoJson(this.getId(), geojson);
+      return geojson;
+    }
+    return;
+  }
+
   getFields(): FileLayerConfig['fields'] {
     return this._config.fields;
   }
@@ -96,7 +126,9 @@ export class FileLayer extends AbstractEmsService {
     return this._getFormatMeta(format);
   }
 
-  getFormatOfTypeMeta(type: EMSFormatTypeStrings): { [key: string]: string } | undefined {
+  getFormatOfTypeMeta(
+    type: EMSFormatTypeStrings
+  ): { [key: string]: string | undefined; feature_collection_path?: string } | undefined {
     const format = this._getFormatOfType(type);
     return this._getFormatMeta(format);
   }

test/__snapshots__/ems_client.test.ts.snap

@@ -0,0 +1,83 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`.getFileLayers[1] - getGeoJson defaults should convert topojson to geojson 1`] = `
+Object {
+  "features": Array [
+    Object {
+      "geometry": Object {
+        "coordinates": Array [
+          Array [
+            Array [
+              72.77144284428442,
+              62.593,
+            ],
+            Array [
+              50.625,
+              50.06444104410441,
+            ],
+            Array [
+              91.7565793579358,
+              35.46,
+            ],
+            Array [
+              93.867,
+              58.2621401140114,
+            ],
+            Array [
+              72.77144284428442,
+              62.593,
+            ],
+          ],
+        ],
+        "type": "Polygon",
+      },
+      "properties": Object {
+        "foo": "bar",
+      },
+      "type": "Feature",
+    },
+  ],
+  "type": "FeatureCollection",
+}
+`;
+
+exports[`.getFileLayers[1] - getGeoJson limited cache 1`] = `
+Object {
+  "features": Array [
+    Object {
+      "geometry": Object {
+        "coordinates": Array [
+          Array [
+            Array [
+              72.77144284428442,
+              62.593,
+            ],
+            Array [
+              50.625,
+              50.06444104410441,
+            ],
+            Array [
+              91.7565793579358,
+              35.46,
+            ],
+            Array [
+              93.867,
+              58.2621401140114,
+            ],
+            Array [
+              72.77144284428442,
+              62.593,
+            ],
+          ],
+        ],
+        "type": "Polygon",
+      },
+      "properties": Object {
+        "foo": "bar",
+      },
+      "type": "Feature",
+    },
+  ],
+  "type": "FeatureCollection",
+}
+`;