changes to service interface and addition of example services

lib/index.ts

@@ -12,6 +12,8 @@ export * from './fetch/NativeFetch';
 export * from './init/AppRunner';
 
 export * from './service/IService';
+export * from './service/ServiceEmpty';
+export * from './service/ServiceAggregation';
 
 export * from './service-registry/ServiceRegistry';
 export * from './service-registry/ServiceRegistryHardcodedTestOnly';

lib/service-registry/ServiceRegistryHardcodedTestOnly.ts

@@ -14,7 +14,8 @@ export class ServiceRegistryHardcodedTestOnly implements ServiceRegistry {
   public async initializeServices(): Promise<void> {
     await Promise.all(
       this.services.map(
-        async(aggregatorService): Promise<void> => aggregatorService.initialize(),
+        async(aggregatorService): Promise<void> => new Promise<void>((resolve): void =>
+          aggregatorService.subscribeInitialized(resolve)),
       ),
     );
   }
@@ -46,7 +47,7 @@ export class ServiceRegistryHardcodedTestOnly implements ServiceRegistry {
   public get descriptions(): string[] {
     const result = [];
     for (const service of this.services) {
-      result.push(service.description);
+      result.push(service.description.toString());
     }
     return result;
   }

lib/service/ServiceAggregation.ts

@@ -0,0 +1,70 @@
+import { StreamParser, StreamWriter } from 'n3';
+import { v4 } from 'uuid';
+import type { IFetch } from '../fetch/IFetch';
+import type { IPod } from '../pod/IPod';
+import { AsyncConstructor } from '../core/AsyncConstructor';
+import type { IService, Operation, OperationResult, OperationTestResult, ServiceDescription } from './IService';
+
+export class ServiceAggregation extends AsyncConstructor implements IService {
+  public fetch: IFetch;
+  public pod: IPod;
+  private podLocation: string | undefined;
+
+  public constructor(args: ServiceAggregationArgs) {
+    super(args);
+    this.fetch = args.fetch;
+    this.pod = args.pod;
+  }
+
+  protected async initialize(args: ServiceAggregationArgs): Promise<void> {
+    this.podLocation = await args.pod.newServiceLocation(this.description);
+  }
+
+  public async test(operation: Operation): Promise<OperationTestResult> {
+    if (operation.operation !== 'Aggregation') {
+      throw new Error('Not an aggregation operation');
+    }
+    return {
+      aggregatorService: this,
+      operation,
+      runnable: true,
+    };
+  }
+
+  public async run(operation: Operation): Promise<OperationResult> {
+    const resultLocation = `${this.podLocation}/${v4()}.ttl`;
+
+    const streamWriter = new StreamWriter();
+    for (const source of operation.sources) {
+      const streamParser = new StreamParser();
+      // eslint-disable-next-line ts/no-unsafe-argument
+      (await this.fetch.fetch(source)).body?.pipeThrough(streamParser as any);
+      streamParser.pipe(streamWriter);
+    }
+
+    await this.fetch.fetch(resultLocation, {
+      method: 'PUT',
+      body: streamWriter,
+      headers: {
+        'Content-Type': 'text/turtle', // eslint-disable-line ts/naming-convention
+      },
+    });
+
+    return {
+      aggregatorService: this,
+      operation,
+      resultLocation,
+    };
+  }
+
+  public get description(): ServiceDescription {
+    return {
+      toString: (): string => 'Aggregation',
+    };
+  }
+}
+
+export type ServiceAggregationArgs = {
+  fetch: IFetch;
+  pod: IPod;
+};

lib/service/ServiceEmpty.ts

@@ -0,0 +1,51 @@
+import { AsyncConstructor } from '../core/AsyncConstructor';
+import type { IPod } from '../pod/IPod';
+import type { IFetch } from '../fetch/IFetch';
+import type { IService, Operation, OperationResult, OperationTestResult, ServiceDescription } from './IService';
+import type { ServiceAggregationArgs } from './ServiceAggregation';
+
+export class ServiceEmpty extends AsyncConstructor implements IService {
+  private podLocation: string | undefined;
+  public fetch: IFetch;
+  public pod: IPod;
+
+  public constructor(args: ServiceAggregationArgs) {
+    super(args);
+    this.fetch = args.fetch;
+    this.pod = args.pod;
+  }
+
+  protected async initialize(args: ServiceAggregationArgs): Promise<void> {
+    this.podLocation = await args.pod.newServiceLocation(this.description);
+  }
+
+  public async test(operation: Operation): Promise<OperationTestResult> {
+    if (operation.operation !== 'Empty') {
+      throw new Error('Not a Empty operation');
+    }
+    return {
+      aggregatorService: this,
+      operation,
+      runnable: true,
+    };
+  }
+
+  public async run(operation: Operation): Promise<OperationResult> {
+    return {
+      aggregatorService: this,
+      operation,
+      resultLocation: '',
+    };
+  }
+
+  public get description(): ServiceDescription {
+    return {
+      toString: (): string => 'Empty',
+    };
+  }
+}
+
+export type ServiceEmptyArgs = {
+  fetch: IFetch;
+  pod: IPod;
+};