- (feat) add concept of post processors

- (feat) add 'key as default value' post processor (closes #109)
- (chore) move clean functionality to a post processor
- (chore) move sort functionality to a post processor
- (refactor) get rid of leading underscore on protected properties/methods

tests/post-processors/purge-obsolete-keys.post-processor.spec.ts

@@ -0,0 +1,36 @@
+import { expect } from 'chai';
+
+import { PostProcessorInterface } from '../../src/post-processors/post-processor.interface';
+import { PurgeObsoleteKeysPostProcessor } from '../../src/post-processors/purge-obsolete-keys.post-processor';
+import { TranslationCollection } from '../../src/utils/translation.collection';
+
+describe('KeyAsDefaultValuePostProcessor', () => {
+
+	let processor: PostProcessorInterface;
+
+	beforeEach(() => {
+		processor = new PurgeObsoleteKeysPostProcessor();
+	});
+
+	it('should purge obsolete keys', () => {
+		const collection = new TranslationCollection({
+			'I am completely new': '',
+			'I already exist': '',
+			'I already exist but was not present in extract': ''
+		});
+		const extracted = new TranslationCollection({
+			'I am completely new': '',
+			'I already exist': ''
+		});
+		const existing = new TranslationCollection({
+			'I already exist': '',
+			'I already exist but was not present in extract': ''
+		});
+
+		expect(processor.process(collection, extracted, existing).values).to.deep.equal({
+			'I am completely new': '',
+			'I already exist': ''
+		});
+	});
+
+});