feat(document datasource): add document datasource

arango-document-datasource.js

@@ -0,0 +1,82 @@
+const { DataSource } = require('apollo-datasource');
+const DataLoader = require('dataloader');
+const { aql } = require('arangojs');
+
+/**
+ * An ArangoDb implementation of the Apollo DataSource.
+ *
+ * This DataSource is solely for resolving Arando Documents by their Id.
+ * Requests are batched and cached per request.
+ *
+ * @class ArangoDocumentDataSource
+ * @extends {DataSource}
+ */
+class ArangoDocumentDataSource extends DataSource {
+  /**
+   * Creates an instance of ArangoDocumentDataSource.
+   * @param {Database} db
+   * @memberof ArangoDocumentDataSource
+   */
+  constructor(db) {
+    super();
+    this.db = db;
+  }
+
+  /**
+   * Initializes the DataSource. Called at the beginning of each request.
+   *
+   * @memberof ArangoDocumentDataSource
+   */
+  initialize() {
+    this.dataloader = new DataLoader(keys => this.loadKeys(keys));
+  }
+
+  /**
+   * Gets a Document by its _id
+   *
+   * @param {string} id The _id to query for
+   * @returns {any} The corresponding Document
+   * @memberof ArangoDocumentDataSource
+   */
+  async get(id) {
+    return this.dataloader.load(id);
+  }
+
+  /**
+   * Gets several Documents at once by their _id
+   *
+   * @param {string[]} ids The _ids to query for
+   * @returns {any[]} The corresponding Documents. In the order their Ids were specified in the ids array
+   * @memberof ArangoDocumentDataSource
+   */
+  async getMany(ids) {
+    return this.dataloader.loadMany(ids);
+  }
+
+  /**
+   * Queries the database for the given keys.
+   *
+   * @param {string[]} keys The keys to qeury for
+   * @private
+   * @returns {*[]} The corresponding Documents. In the order their Ids were specified in the ids array
+   * @memberof ArangoDocumentDataSource
+   */
+  async loadKeys(keys) {
+    const cursor = await this.db.query(aql`RETURN DOCUMENT(${keys})`);
+    const nodes = await cursor.all();
+
+    return keys.map(key => {
+      const node = nodes.find(node => node._id === key);
+
+      if (node) {
+        node.id = node._id;
+      }
+
+      return node;
+    });
+  }
+}
+
+module.exports = {
+  ArangoDocumentDataSource: ArangoDocumentDataSource
+};

arango-document-datasource.test.js

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+const { ArangoDocumentDataSource } = require('.');
+
+describe('ArangDocumentDataSource', () => {
+  test('it batches key loads', async () => {
+    const results = [{ _id: '123' }, { _id: '456' }];
+    const db = createDb(results);
+    const datasource = new ArangoDocumentDataSource(db);
+    datasource.initialize();
+
+    const docs = await Promise.all([
+      datasource.get('123'),
+      datasource.get('456')
+    ]);
+
+    expect(docs).toEqual(results);
+    expect(db.query).toHaveBeenCalledTimes(1);
+  });
+
+  test('it caches key loads', async () => {
+    const results = [{ _id: '123' }];
+    const db = createDb(results);
+    const datasource = new ArangoDocumentDataSource(db);
+    datasource.initialize();
+
+    for (let i = 0; i < 3; i++) {
+      const doc = await datasource.get('123');
+      expect(db.query).toHaveBeenCalledTimes(1);
+      expect(doc).toEqual(results[0]);
+    }
+  });
+
+  test('it returns docs for several keys', async () => {
+    const results = [{ _id: '123' }, { _id: '456' }];
+    const db = createDb(results);
+    const datasource = new ArangoDocumentDataSource(db);
+    datasource.initialize();
+
+    const docs = await datasource.getMany(['456', '123']);
+
+    expect(docs).toEqual(results.reverse());
+    expect(db.query).toHaveBeenCalledTimes(1);
+  });
+});
+
+function createDb(queryResults) {
+  return {
+    query: jest.fn().mockResolvedValue({
+      all: () => queryResults
+    })
+  };
+}

index.js

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+module.exports = {
+  ...require('./arango-datasource'),
+  ...require('./arango-document-datasource')
+};