[EnterpriseSearch] engines list proxy endpoint (#148352)

## Summary

Added a proxy endpoint to list engines from enterprise search.

x-pack/plugins/enterprise_search/common/types/engines.ts

@@ -0,0 +1,20 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+export interface EnterpriseSearchEnginesResponse {
+  meta: {
+    from: number;
+    size: number;
+    total: number;
+  };
+  results: EnterpriseSearchEngine[];
+}
+
+export interface EnterpriseSearchEngine {
+  name: string;
+  indices: string[];
+}

x-pack/plugins/enterprise_search/server/routes/enterprise_search/engines.test.ts

@@ -0,0 +1,174 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+import { mockDependencies, mockRequestHandler, MockRouter } from '../../__mocks__';
+
+import { registerEnginesRoutes } from './engines';
+
+describe('engines routes', () => {
+  describe('GET /internal/enterprise_search/engines', () => {
+    let mockRouter: MockRouter;
+
+    beforeEach(() => {
+      jest.clearAllMocks();
+      mockRouter = new MockRouter({
+        method: 'get',
+        path: '/internal/enterprise_search/engines',
+      });
+
+      registerEnginesRoutes({
+        ...mockDependencies,
+        router: mockRouter.router,
+      });
+    });
+
+    it('creates a request to enterprise search', () => {
+      expect(mockRequestHandler.createRequest).toHaveBeenCalledWith({
+        path: '/api/engines',
+      });
+    });
+
+    it('validates query parameters', () => {
+      const request = { query: { from: 20, size: 20 } };
+
+      mockRouter.shouldValidate(request);
+    });
+
+    it('fails validation with invalid from parameter', () => {
+      const request = { query: { from: -10 } };
+
+      mockRouter.shouldThrow(request);
+    });
+
+    it('fails validation with invalid size parameter', () => {
+      const request = { query: { size: 0 } };
+
+      mockRouter.shouldThrow(request);
+    });
+  });
+
+  describe('GET /internal/enterprise_search/engines/{engine_name}', () => {
+    let mockRouter: MockRouter;
+
+    beforeEach(() => {
+      jest.clearAllMocks();
+      mockRouter = new MockRouter({
+        method: 'get',
+        path: '/internal/enterprise_search/engines/{engine_name}',
+      });
+
+      registerEnginesRoutes({
+        ...mockDependencies,
+        router: mockRouter.router,
+      });
+    });
+
+    it('creates a request to enterprise search', () => {
+      expect(mockRequestHandler.createRequest).toHaveBeenCalledWith({
+        path: '/api/engines/:engine_name',
+      });
+    });
+
+    it('validates correctly with engine_name', () => {
+      const request = { params: { engine_name: 'some-engine' } };
+
+      mockRouter.shouldValidate(request);
+    });
+
+    it('fails validation without name', () => {
+      const request = { params: {} };
+
+      mockRouter.shouldThrow(request);
+    });
+  });
+
+  describe('PUT /internal/enterprise_search/engines/{engine_name}', () => {
+    let mockRouter: MockRouter;
+
+    beforeEach(() => {
+      jest.clearAllMocks();
+      mockRouter = new MockRouter({
+        method: 'put',
+        path: '/internal/enterprise_search/engines/{engine_name}',
+      });
+
+      registerEnginesRoutes({
+        ...mockDependencies,
+        router: mockRouter.router,
+      });
+    });
+
+    it('creates a request to enterprise search', () => {
+      expect(mockRequestHandler.createRequest).toHaveBeenCalledWith({
+        path: '/api/engines/:engine_name',
+      });
+    });
+
+    it('validates correctly with engine_name', () => {
+      const request = {
+        params: { engine_name: 'some-engine' },
+        body: {
+          indices: ['search-unit-test'],
+        },
+      };
+
+      mockRouter.shouldValidate(request);
+    });
+
+    it('fails validation without name', () => {
+      const request = { params: {} };
+
+      mockRouter.shouldThrow(request);
+    });
+
+    it('fails validation without indices', () => {
+      const request = {
+        params: { engine_name: 'some-engine' },
+        body: {
+          name: 'some-engine',
+        },
+      };
+
+      mockRouter.shouldThrow(request);
+    });
+  });
+
+  describe('DELETE /internal/enterprise_search/engines/{engine_name}', () => {
+    let mockRouter: MockRouter;
+
+    beforeEach(() => {
+      jest.clearAllMocks();
+      mockRouter = new MockRouter({
+        method: 'delete',
+        path: '/internal/enterprise_search/engines/{engine_name}',
+      });
+
+      registerEnginesRoutes({
+        ...mockDependencies,
+        router: mockRouter.router,
+      });
+    });
+
+    it('creates a request to enterprise search', () => {
+      expect(mockRequestHandler.createRequest).toHaveBeenCalledWith({
+        path: '/api/engines/:engine_name',
+      });
+    });
+
+    it('validates correctly with engine_name', () => {
+      const request = { params: { engine_name: 'some-engine' } };
+
+      mockRouter.shouldValidate(request);
+    });
+
+    it('fails validation without name', () => {
+      const request = { params: {} };
+
+      mockRouter.shouldThrow(request);
+    });
+  });
+});

x-pack/plugins/enterprise_search/server/routes/enterprise_search/engines.ts

@@ -0,0 +1,67 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+import { schema } from '@kbn/config-schema';
+
+import { RouteDependencies } from '../../plugin';
+
+export function registerEnginesRoutes({
+  router,
+  enterpriseSearchRequestHandler,
+}: RouteDependencies) {
+  router.get(
+    {
+      path: '/internal/enterprise_search/engines',
+      validate: {
+        query: schema.object({
+          from: schema.number({ defaultValue: 0, min: 0 }),
+          size: schema.number({ defaultValue: 10, min: 1 }),
+        }),
+      },
+    },
+    enterpriseSearchRequestHandler.createRequest({ path: '/api/engines' })
+  );
+
+  router.get(
+    {
+      path: '/internal/enterprise_search/engines/{engine_name}',
+      validate: {
+        params: schema.object({
+          engine_name: schema.string(),
+        }),
+      },
+    },
+    enterpriseSearchRequestHandler.createRequest({ path: '/api/engines/:engine_name' })
+  );
+
+  router.put(
+    {
+      path: '/internal/enterprise_search/engines/{engine_name}',
+      validate: {
+        params: schema.object({
+          engine_name: schema.string(),
+        }),
+        body: schema.object({
+          name: schema.maybe(schema.string()),
+          indices: schema.arrayOf(schema.string()),
+        }),
+      },
+    },
+    enterpriseSearchRequestHandler.createRequest({ path: '/api/engines/:engine_name' })
+  );
+
+  router.delete(
+    {
+      path: '/internal/enterprise_search/engines/{engine_name}',
+      validate: {
+        params: schema.object({
+          engine_name: schema.string(),
+        }),
+      },
+    },
+    enterpriseSearchRequestHandler.createRequest({ path: '/api/engines/:engine_name' })
+  );
+}

x-pack/plugins/enterprise_search/server/routes/enterprise_search/index.ts

@@ -8,6 +8,7 @@
 import { RouteDependencies } from '../../plugin';
 
 import { registerDocumentRoute } from './documents';
+import { registerEnginesRoutes } from './engines';
 import { registerIndexRoutes } from './indices';
 import { registerMappingRoute } from './mapping';
 import { registerSearchRoute } from './search';
@@ -17,4 +18,5 @@ export const registerEnterpriseSearchRoutes = (dependencies: RouteDependencies)
   registerMappingRoute(dependencies);
   registerSearchRoute(dependencies);
   registerDocumentRoute(dependencies);
+  registerEnginesRoutes(dependencies);
 };