Fixes #1933 - GraphQL Connection API

packages/fhir-router/src/graphql.test.ts

@@ -942,4 +942,38 @@ describe('GraphQL', () => {
     expect(check3.extension).toHaveLength(1);
     expect(check3.extension[0]).toMatchObject(p3.extension?.[1] as Extension);
   });
+
+  test('Connection API', async () => {
+    const request: FhirRequest = {
+      method: 'POST',
+      pathname: '/fhir/R4/$graphql',
+      query: {},
+      params: {},
+      body: {
+        query: `
+      {
+        PatientConnection(name: "Smith") {
+          count offset pageSize
+          edges {
+            mode, score, resource { id name { given } }
+          }
+          first previous next last
+        }
+      }
+    `,
+      },
+    };
+
+    const res = await graphqlHandler(request, repo);
+    expect(res[0]).toMatchObject(allOk);
+
+    const data = (res?.[1] as any).data;
+    expect(data.PatientConnection).toBeDefined();
+    expect(data.PatientConnection).toMatchObject({
+      count: 1,
+      offset: 0,
+      pageSize: 20,
+      edges: [{ resource: { name: [{ given: ['Alice'] }] } }],
+    });
+  });
 });

packages/fhir-router/src/graphql.ts

@@ -3,6 +3,7 @@ import {
   badRequest,
   buildTypeName,
   capitalize,
+  DEFAULT_SEARCH_COUNT,
   evalFhirPathTyped,
   Filter,
   forbidden,
@@ -111,6 +112,19 @@ interface GraphQLContext {
   dataLoader: DataLoader<Reference, Resource>;
 }
 
+interface ConnectionResponse {
+  count?: number;
+  offset?: number;
+  pageSize?: number;
+  edges?: ConnectionEdge[];
+}
+
+interface ConnectionEdge {
+  mode?: string;
+  score?: number;
+  resource?: Resource;
+}
+
 /**
  * Handles FHIR GraphQL requests.
  *
@@ -208,6 +222,14 @@ function buildRootSchema(): GraphQLSchema {
       args: buildSearchArgs(resourceType),
       resolve: resolveBySearch,
     };
+
+    // FHIR GraphQL Connection API
+    fields[resourceType + 'Connection'] = {
+      // type: new GraphQLList(graphQLType),
+      type: buildConnectionType(resourceType, graphQLType),
+      args: buildSearchArgs(resourceType),
+      resolve: resolveByConnectionApi,
+    };
   }
 
   return new GraphQLSchema({
@@ -495,6 +517,33 @@ function getPropertyType(elementDefinition: ElementDefinition, typeName: string)
   return graphqlType;
 }
 
+function buildConnectionType(resourceType: ResourceType, resourceGraphQLType: GraphQLOutputType): GraphQLOutputType {
+  return new GraphQLObjectType({
+    name: resourceType + 'Connection',
+    fields: {
+      count: { type: GraphQLInt },
+      offset: { type: GraphQLInt },
+      pageSize: { type: GraphQLInt },
+      first: { type: GraphQLString },
+      previous: { type: GraphQLString },
+      next: { type: GraphQLString },
+      last: { type: GraphQLString },
+      edges: {
+        type: new GraphQLList(
+          new GraphQLObjectType({
+            name: resourceType + 'ConnectionEdge',
+            fields: {
+              mode: { type: GraphQLString },
+              score: { type: GraphQLFloat },
+              resource: { type: resourceGraphQLType },
+            },
+          })
+        ),
+      },
+    },
+  });
+}
+
 /**
  * GraphQL data loader for search requests.
  * The field name should always end with "List" (i.e., "Patient" search uses "PatientList").
@@ -513,12 +562,48 @@ async function resolveBySearch(
   info: GraphQLResolveInfo
 ): Promise<Resource[] | undefined> {
   const fieldName = info.fieldName;
-  const resourceType = fieldName.substring(0, fieldName.length - 4) as ResourceType; // Remove "List"
+  const resourceType = fieldName.substring(0, fieldName.length - 'List'.length) as ResourceType;
   const searchRequest = parseSearchArgs(resourceType, source, args);
   const bundle = await ctx.repo.search(searchRequest);
   return bundle.entry?.map((e) => e.resource as Resource);
 }
 
+/**
+ * GraphQL data loader for search requests.
+ * The field name should always end with "List" (i.e., "Patient" search uses "PatientList").
+ * The search args should be FHIR search parameters.
+ * @param source The source/root.  This should always be null for our top level readers.
+ * @param args The GraphQL search arguments.
+ * @param ctx The GraphQL context.
+ * @param info The GraphQL resolve info.  This includes the schema, and additional field details.
+ * @returns Promise to read the resoures for the query.
+ * @implements {GraphQLFieldResolver}
+ */
+async function resolveByConnectionApi(
+  source: any,
+  args: Record<string, string>,
+  ctx: GraphQLContext,
+  info: GraphQLResolveInfo
+): Promise<ConnectionResponse | undefined> {
+  const fieldName = info.fieldName;
+  const resourceType = fieldName.substring(0, fieldName.length - 'Connection'.length) as ResourceType;
+  const searchRequest = parseSearchArgs(resourceType, source, args);
+  if (isFieldRequested(info, 'count')) {
+    searchRequest.total = 'accurate';
+  }
+  const bundle = await ctx.repo.search(searchRequest);
+  return {
+    count: bundle.total,
+    offset: searchRequest.offset || 0,
+    pageSize: searchRequest.count || DEFAULT_SEARCH_COUNT,
+    edges: bundle.entry?.map((e) => ({
+      mode: e.search?.mode,
+      score: e.search?.score,
+      resource: e.resource as Resource,
+    })),
+  };
+}
+
 /**
  * GraphQL data loader for ID requests.
  * The field name should always by the resource type.
@@ -693,6 +778,20 @@ function getDepth(path: ReadonlyArray<string | number>): number {
   return path.filter((p) => p === 'selections').length;
 }
 
+/**
+ * Returns true if the field is requested in the GraphQL query.
+ * @param info The GraphQL resolve info.  This includes the field name.
+ * @param fieldName The field name to check.
+ * @returns True if the field is requested in the GraphQL query.
+ */
+function isFieldRequested(info: GraphQLResolveInfo, fieldName: string): boolean {
+  return info.fieldNodes.some((fieldNode) =>
+    fieldNode.selectionSet?.selections.some((selection) => {
+      return selection.kind === 'Field' && selection.name.value === fieldName;
+    })
+  );
+}
+
 /**
  * Returns an OperationOutcome for GraphQL errors.
  * @param errors Array of GraphQL errors.