Add save method

lib/index.js

@@ -9,5 +9,6 @@ module.exports = {
     parse: require('./parse'),
     assign: require('./assign'),
     load: require('./load'),
-    stringify: require('./stringify')
+    stringify: require('./stringify'),
+    save: require('./save')
 };

lib/save.js

@@ -0,0 +1,27 @@
+'use strict';
+
+const fs = require('fs');
+const promisify = require('es6-promisify');
+const stringify = require('./stringify');
+
+const writeFile = promisify(fs.writeFile);
+
+/**
+ * Save normalized declaration to target format
+ *
+ * @param   {String}    filename    Filename for save declaration
+ * @param   {BemCell[]} cells       Normalized declaraions
+ * @param   {Object}    [opts]      Addtional options
+ * @param   {String}    [opts.format='v2'] The desired format
+ * @param   {String}    [opts.exportType='cjs'] The desired type for export
+ * @returns {Promise.<void>}
+ */
+module.exports = (filename, cells, opts) => {
+    const defaults = {
+        format: 'v2',
+        exportType: 'cjs'
+    };
+    const data = stringify(cells, Object.assign({}, defaults, opts));
+
+    return writeFile(data);
+}

package.json

@@ -37,7 +37,9 @@
     "eslint-config-pedant": "^0.8.0",
     "jscs": "^3.0.3",
     "matcha": "^0.7.0",
-    "nyc": "^10.0.0"
+    "nyc": "^10.0.0",
+    "proxyquire": "^1.7.10",
+    "sinon": "^1.17.7"
   },
   "scripts": {
     "lint": "eslint . && jscs .",

test/save.test.js

@@ -0,0 +1,51 @@
+const test = require('ava');
+const sinon = require('sinon');
+const proxyquire = require('proxyquire');
+
+test.beforeEach(t => {
+    const stringifyStub = sinon.stub();
+    const writeFileStub = (a, cb) => setTimeout(cb(), 10);
+
+    t.context = {
+        stringifyStub: stringifyStub,
+        writeFileStub: writeFileStub,
+        save: proxyquire('../lib/save', {
+            './stringify': stringifyStub,
+            fs: { writeFile: writeFileStub }
+        })
+    }
+});
+
+test('method save should be returns Promise', t => {
+    const promise = t.context.save();
+
+    t.truthy(promise.then, 'not a Promise')
+    t.notThrows(promise);
+});
+
+test('method save should be save file in cjs by default', t => {
+    const save = t.context.save;
+    const stringifyStub = t.context.stringifyStub;
+
+    save('decl-test.js');
+
+    t.truthy(stringifyStub.calledWith(undefined, { format: 'v2', exportType: 'cjs' }));
+});
+
+test('method save should be save file in custom format', t => {
+    const save = t.context.save;
+    const stringifyStub = t.context.stringifyStub;
+
+    save('decl-test.js', null, { format: 'v5' });
+
+    t.truthy(stringifyStub.calledWith(null, { format: 'v5', exportType: 'cjs' }));
+});
+
+test('method save should be save file in custom type', t => {
+    const save = t.context.save;
+    const stringifyStub = t.context.stringifyStub;
+
+    save('decl-test.js', null, { exportType: 'txt' });
+
+    t.truthy(stringifyStub.calledWith(null, { format: 'v2', exportType: 'txt' }));
+});