Consolidate [NpmDownloads] into one service (#3318)

This moves the four npm download services into a single class, in line with #3174, and other service implementations we've written in the last couple months. 

1. Change the suffixes from **/m** to **/month** for consistency.
2. Add tests of one of the intervals besides total.
3. Rewrite mocked service tests as unit tests.
4. Use (and work with) the `intervalMap` pattern that I think @calebcartwright started us using.

services/npm/npm-downloads.service.js

@@ -10,95 +10,92 @@ const pointResponseSchema = Joi.object({
   downloads: nonNegativeInteger,
 }).required()
 
-// https://github.com/npm/registry/blob/master/docs/download-counts.md#output-1
-const rangeResponseSchema = Joi.object({
-  downloads: Joi.array()
-    .items(pointResponseSchema)
-    .required(),
-}).required()
-
-function DownloadsForInterval(interval) {
-  const { base, messageSuffix = '', query, isRange = false, name } = {
-    week: {
-      base: 'npm/dw',
-      messageSuffix: '/w',
-      query: 'point/last-week',
-      name: 'NpmDownloadsWeek',
-    },
-    month: {
-      base: 'npm/dm',
-      messageSuffix: '/m',
-      query: 'point/last-month',
-      name: 'NpmDownloadsMonth',
-    },
-    year: {
-      base: 'npm/dy',
-      messageSuffix: '/y',
-      query: 'point/last-year',
-      name: 'NpmDownloadsYear',
-    },
-    total: {
-      base: 'npm/dt',
-      query: 'range/1000-01-01:3000-01-01',
-      isRange: true,
-      name: 'NpmDownloadsTotal',
-    },
-  }[interval]
-
-  const schema = isRange ? rangeResponseSchema : pointResponseSchema
-
-  // This hits an entirely different API from the rest of the NPM services, so
-  // it does not use NpmBase.
-  return class NpmDownloads extends BaseJsonService {
-    static get name() {
-      return name
-    }
-
-    static get category() {
-      return 'downloads'
-    }
-
-    static get route() {
-      return {
-        base,
-        pattern: ':scope(@.+)?/:packageName',
-      }
-    }
-
-    static get examples() {
-      return [
-        {
-          title: 'npm',
-          pattern: ':packageName',
-          namedParams: { packageName: 'localeval' },
-          staticPreview: this.render({ downloads: 30000 }),
-          keywords: ['node'],
-        },
-      ]
-    }
-
-    static render({ downloads }) {
-      return {
-        message: `${metric(downloads)}${messageSuffix}`,
-        color: downloads > 0 ? 'brightgreen' : 'red',
-      }
-    }
-
-    async handle({ scope, packageName }) {
-      const slug = scope ? `${scope}/${packageName}` : packageName
-      let { downloads } = await this._requestJson({
-        schema,
-        url: `https://api.npmjs.org/downloads/${query}/${slug}`,
-        errorMessages: { 404: 'package not found or too new' },
-      })
-      if (isRange) {
-        downloads = downloads
-          .map(item => item.downloads)
-          .reduce((accum, current) => accum + current)
-      }
-      return this.constructor.render({ downloads })
-    }
-  }
+const intervalMap = {
+  dw: {
+    query: 'point/last-week',
+    schema: pointResponseSchema,
+    transform: json => json.downloads,
+    messageSuffix: '/week',
+  },
+  dm: {
+    query: 'point/last-month',
+    schema: pointResponseSchema,
+    transform: json => json.downloads,
+    messageSuffix: '/month',
+  },
+  dy: {
+    query: 'point/last-year',
+    schema: pointResponseSchema,
+    transform: json => json.downloads,
+    messageSuffix: '/year',
+  },
+  dt: {
+    query: 'range/1000-01-01:3000-01-01',
+    // https://github.com/npm/registry/blob/master/docs/download-counts.md#output-1
+    schema: Joi.object({
+      downloads: Joi.array()
+        .items(pointResponseSchema)
+        .required(),
+    }).required(),
+    transform: json =>
+      json.downloads
+        .map(item => item.downloads)
+        .reduce((accum, current) => accum + current),
+    messageSuffix: '',
+  },
 }
 
-module.exports = ['week', 'month', 'year', 'total'].map(DownloadsForInterval)
+// This hits an entirely different API from the rest of the NPM services, so
+// it does not use NpmBase.
+module.exports = class NpmDownloads extends BaseJsonService {
+  static get category() {
+    return 'downloads'
+  }
+
+  static get route() {
+    return {
+      base: 'npm',
+      pattern: ':interval(dw|dm|dy|dt)/:scope(@.+)?/:packageName',
+    }
+  }
+
+  static get examples() {
+    return [
+      {
+        title: 'npm',
+        namedParams: { interval: 'dw', packageName: 'localeval' },
+        staticPreview: this.render({ interval: 'dw', downloadCount: 30000 }),
+        keywords: ['node'],
+      },
+    ]
+  }
+
+  // For testing.
+  static get _intervalMap() {
+    return intervalMap
+  }
+
+  static render({ interval, downloadCount }) {
+    const { messageSuffix } = intervalMap[interval]
+
+    return {
+      message: `${metric(downloadCount)}${messageSuffix}`,
+      color: downloadCount > 0 ? 'brightgreen' : 'red',
+    }
+  }
+
+  async handle({ interval, scope, packageName }) {
+    const { query, schema, transform } = intervalMap[interval]
+
+    const slug = scope ? `${scope}/${packageName}` : packageName
+    const json = await this._requestJson({
+      schema,
+      url: `https://api.npmjs.org/downloads/${query}/${slug}`,
+      errorMessages: { 404: 'package not found or too new' },
+    })
+
+    const downloadCount = transform(json)
+
+    return this.constructor.render({ interval, downloadCount })
+  }
+}

services/npm/npm-downloads.spec.js

@@ -0,0 +1,25 @@
+'use strict'
+
+const { test, given } = require('sazerac')
+const NpmDownloads = require('./npm-downloads.service')
+
+describe('NpmDownloads', function() {
+  test(NpmDownloads._intervalMap.dt.transform, () => {
+    given({
+      downloads: [
+        { downloads: 2, day: '2018-01-01' },
+        { downloads: 3, day: '2018-01-02' },
+      ],
+    }).expect(5)
+  })
+
+  test(NpmDownloads.render, () => {
+    given({
+      interval: 'dt',
+      downloadCount: 0,
+    }).expect({
+      message: '0',
+      color: 'red',
+    })
+  })
+})

services/npm/npm-downloads.tester.js

@@ -1,14 +1,19 @@
 'use strict'
 
-const { ServiceTester } = require('../tester')
-const { isMetric } = require('../test-validators')
+const { isMetricOverTimePeriod, isMetric } = require('../test-validators')
+const t = (module.exports = require('../tester').createServiceTester())
 
-const t = new ServiceTester({
-  id: 'NpmDownloads',
-  title: 'NpmDownloads',
-  pathPrefix: '/npm',
-})
-module.exports = t
+t.create('weekly downloads of left-pad')
+  .get('/dw/left-pad.json')
+  .expectBadge({
+    label: 'downloads',
+    message: isMetricOverTimePeriod,
+    color: 'brightgreen',
+  })
+
+t.create('weekly downloads of @cycle/core')
+  .get('/dw/@cycle/core.json')
+  .expectBadge({ label: 'downloads', message: isMetricOverTimePeriod })
 
 t.create('total downloads of left-pad')
   .get('/dt/left-pad.json')
@@ -22,32 +27,7 @@ t.create('total downloads of @cycle/core')
   .get('/dt/@cycle/core.json')
   .expectBadge({ label: 'downloads', message: isMetric })
 
-t.create('total downloads of package with zero downloads')
-  .get('/dt/package-no-downloads.json')
-  .intercept(nock =>
-    nock('https://api.npmjs.org')
-      .get('/downloads/range/1000-01-01:3000-01-01/package-no-downloads')
-      .reply(200, {
-        downloads: [{ downloads: 0, day: '2018-01-01' }],
-      })
-  )
-  .expectBadge({ label: 'downloads', message: '0', color: 'red' })
-
-t.create('exact total downloads value')
-  .get('/dt/exact-value.json')
-  .intercept(nock =>
-    nock('https://api.npmjs.org')
-      .get('/downloads/range/1000-01-01:3000-01-01/exact-value')
-      .reply(200, {
-        downloads: [
-          { downloads: 2, day: '2018-01-01' },
-          { downloads: 3, day: '2018-01-02' },
-        ],
-      })
-  )
-  .expectBadge({ label: 'downloads', message: '5' })
-
-t.create('total downloads of unknown package')
+t.create('downloads of unknown package')
   .get('/dt/npm-api-does-not-have-this-package.json')
   .expectBadge({
     label: 'downloads',