feat: added readBuildstamp (#20)

Author: oljekechoro

README.md

@@ -88,3 +88,20 @@ Output in `some/path/stamp.json`:
 	"date": "2020-09-04T19:53:03.790Z"
 }
 ```
+### readBuildstamp(path)
+Safely parses and returns buildstamp by given path. Returns `undefined` on error.
+```javascript
+import { readBuildstamp } from 'buildstamp'
+
+const stamp = getBuildstamp('some/path')
+/*
+{
+  git: {
+    commitId: 'fc6e78b11ef4c7db1c8b89fa6b0d9b3ad4ad481d',
+    repoName: 'qiwi/buildstamp.git'
+  },
+  docker: { imageTag: 'foo', bar: 'bar' },
+  date: '2020-08-27T20:47:41.958Z'
+}
+*/
+```

src/main/ts/getter.ts

@@ -0,0 +1,11 @@
+import { readFileToString } from './utils'
+import { TStamp } from './interfaces'
+
+export const readBuildstamp = (stampPath: string): TStamp | undefined => {
+  try {
+    return JSON.parse(readFileToString(stampPath))
+  } catch (e) {
+    console.error('Buildstamp reading error:', e.message)
+  }
+  return undefined
+}

src/main/ts/index.ts

@@ -2,3 +2,4 @@ import { execute } from './executor'
 
 export * from './interfaces'
 export { execute }
+export { readBuildstamp } from './getter'

src/test/ts/getter.ts

@@ -0,0 +1,35 @@
+import { readBuildstamp, TStamp } from '../../main/ts'
+import * as utils from '../../main/ts/utils'
+
+const stamp: TStamp = {
+  git: {
+    commitId: 'foo',
+    repoName: 'bar',
+    repoUrl: 'baz',
+  },
+  date: 0,
+  docker: {
+    imageTag: 'bat',
+  },
+}
+
+describe('readBuildstamp', () => {
+  it('reads and parses file', () => {
+    jest.spyOn(utils, 'readFileToString')
+      .mockImplementation(() => JSON.stringify(stamp))
+    expect(readBuildstamp('some/path')).toEqual(stamp)
+  })
+
+  it('logs an error', () => {
+    jest.spyOn(utils, 'readFileToString')
+      .mockImplementation(() => {
+        throw new Error('foo')
+      })
+    const errorSpy = jest.spyOn(console, 'error')
+      .mockImplementation(() => { /* noop */ })
+    expect(readBuildstamp('some/path')).toBeUndefined()
+    expect(errorSpy).toHaveBeenCalled()
+  })
+
+  afterAll(jest.resetAllMocks)
+})