Added enpoint for fetching application implementing a strategy

`/api/client/applications?strategyName=foo` now returns list of
apps implementing that strategy!

docs/api/metrics-api.md

@@ -178,6 +178,14 @@ a link to follow for more datails.
 }
 ```
 
+#### Query Params
+You can also specify the query param: _strategyName_, which will return all applications 
+implementing the given strategy.
+
+`GET  http://unleash.host.com/api/client/applications?strategyName=someStrategyName`
+
+
+
 
 ### Application Details
 

lib/db/app.js

@@ -0,0 +1,67 @@
+'use strict';
+
+const express = require('express');
+const favicon = require('serve-favicon');
+const bodyParser = require('body-parser');
+const cookieParser = require('cookie-parser');
+const validator = require('express-validator');
+const responseTime = require('response-time');
+const log4js = require('log4js');
+const logger = require('./logger');
+const routes = require('./routes');
+const path = require('path');
+const errorHandler = require('errorhandler');
+
+const { REQUEST_TIME } = require('./events');
+
+module.exports = function (config) {
+    const app = express();
+
+    const baseUriPath  = config.baseUriPath || '';
+    const publicFolder = config.publicFolder;
+
+    app.set('trust proxy');
+    app.set('port', config.port);
+    app.locals.baseUriPath = baseUriPath;
+    app.use(cookieParser());
+
+    if (publicFolder) {
+        app.use(favicon(path.join(publicFolder, 'favicon.ico')));
+    }
+
+    app.use(responseTime((req, res, time) => {
+        const timingInfo = { path: req.path, method: req.method, statusCode: res.statusCode, time };
+        config.eventBus.emit(REQUEST_TIME, timingInfo);
+    }));
+
+    app.use(validator([]));
+
+    if (publicFolder) {
+        app.use(baseUriPath, express.static(publicFolder));
+    }
+
+    app.use(bodyParser.json({ strict: false }));
+
+    if (config.enableRequestLogger) {
+        app.use(log4js.connectLogger(logger, {
+            format: ':status :method :url :response-timems',
+            level: 'auto', // 3XX=WARN, 4xx/5xx=ERROR
+        }));
+    }
+
+    // Setup API routes
+    const apiRouter = express.Router(); // eslint-disable-line new-cap
+    routes.createAPI(apiRouter, config);
+    app.use(`${baseUriPath}/api/`, apiRouter);
+
+    // Setup deprecated routes
+    const router = express.Router(); // eslint-disable-line new-cap
+    routes.createLegacy(router, config);
+    app.use(baseUriPath, router);
+
+    if (process.env.NODE_ENV !== 'production') {
+        app.use(errorHandler());
+    }
+
+    return app;
+};

lib/db/client-strategy-store.js

@@ -56,7 +56,30 @@ class ClientStrategyStore {
             .where('app_name', appName)
             .from(TABLE)
             .map((row) => row.strategies)
-            .then(arr => arr[0])
+            .then(arr => arr[0]);
+    }
+
+    /**
+     * Could also be done in SQL:
+     * (not sure if it is faster though)
+     *
+     * SELECT app_name from (
+     *   SELECT app_name, json_array_elements(strategies)::text as strategyName from client_strategies
+     *   ) as foo
+     * WHERE foo.strategyName = '"other"';
+     */
+    getAppsForStrategy (strategyName) {
+        return this.getAll()
+            .then(apps => apps
+                .filter(app => app.strategies.includes(strategyName))
+                .map(app => app.appName));
+    }
+
+    getApplications () {
+        return this.db
+            .select('app_name')
+            .from(TABLE)
+            .map((row) => row.app_name);
     }
 };
 

lib/routes/metrics.js

@@ -100,9 +100,18 @@ module.exports = function (app, config) {
     });
 
     app.get('/client/applications/', (req, res) => {
-        clientInstanceStore.getApplications()
+        const strategyName = req.query.strategyName;
+        let appsPromise;
+
+        if (strategyName) {
+            appsPromise = clientStrategyStore.getAppsForStrategy(strategyName);
+        } else {
+            appsPromise = clientStrategyStore.getApplications();
+        }
+
+        appsPromise
             .then(apps => {
-                const applications = apps.map(({ appName }) => ({
+                const applications = apps.map(appName => ({
                     appName,
                     links: {
                         appDetails: `/api/client/applications/${appName}`,

test/e2e/metrics-api.test.js

@@ -92,7 +92,7 @@ test.serial('should get list of applications', async t => {
         .expect('Content-Type', /json/)
         .expect((res) => {
             t.true(res.status === 200);
-            t.true(res.body.applications.length === 2);
+            t.true(res.body.applications.length === 1);
         })
         .then(destroy);
 });

test/unit/routes/fixtures/fake-client-strategy-store.js

@@ -1,6 +1,14 @@
 'use strict';
 
-module.exports = () => ({
-    insert: () => Promise.resolve(),
-    getAll: () => Promise.resolve([])
-});
+module.exports = () => {
+    const _instances = [];
+
+    return {
+        insert: () => {
+            _instances.push();
+            return Promise.resolve();
+        },
+        getAll: () => Promise.resolve(_instances),
+        getApplications: () => Promise.resolve([]),
+    };
+};