From 37a84ae8dffe7cff3e07ef8bc525879ed859ec66 Mon Sep 17 00:00:00 2001
From: Wojtek Turyn <wojciech.turyn@inforit.com>
Date: Thu, 15 Oct 2015 10:16:33 +0200
Subject: [PATCH] required() method

---
 lib/nconf/provider.js | 25 +++++++++++++++++++++++++
 test/nconf-test.js    | 11 +++++++++++
 2 files changed, 36 insertions(+)

diff --git a/lib/nconf/provider.js b/lib/nconf/provider.js
index d35b820..5e39e38 100644
--- a/lib/nconf/provider.js
+++ b/lib/nconf/provider.js
@@ -287,6 +287,31 @@ Provider.prototype.set = function (key, value, callback) {
   return this._execute('set', 2, key, value, callback);
 };
 
+
+//
+// ### function required (keys)
+// #### @keys {array} List of keys
+// Throws an error if any of `keys` has no value, otherwise returns `true`
+Provider.prototype.required = function (keys) {
+  if (!Array.isArray(keys)) {
+    throw new Error('Incorrect parameter, array expected');
+  }
+
+  var missing = [];
+  keys.forEach(function(key) {
+    if (typeof this.get(key) === 'undefined') {
+      missing.push(key);
+    }
+  }, this);
+
+  if (missing.length) {
+    throw new Error('Missing required keys: ' + missing.join(', '));
+  } else {
+    return true;
+  }
+
+};
+
 //
 // ### function reset (callback)
 // #### @callback {function} **Optional** Continuation to respond to when complete.
diff --git a/test/nconf-test.js b/test/nconf-test.js
index f0fce79..89bfab9 100644
--- a/test/nconf-test.js
+++ b/test/nconf-test.js
@@ -24,6 +24,7 @@ vows.describe('nconf').addBatch({
       assert.isFunction(nconf.load);
       assert.isFunction(nconf.save);
       assert.isFunction(nconf.reset);
+      assert.isFunction(nconf.required);
     },
     "the use() method": {
       "should instaniate the correct store": function () {
@@ -41,6 +42,16 @@ vows.describe('nconf').addBatch({
         data = JSON.parse(data.toString());
         assert.equal(nconf.version, data.version);
       }
+    },
+    "the required() method": {
+      "should throw error with missing keys": function() {
+        nconf.set('foo:bar:bazz', 'buzz');
+        assert.throws(nconf.required.bind(null, ['missingkey', 'foo:bar:bazz']), Error);
+      },
+      "should return true if all required keys exist": function() {
+        nconf.set('foo:bar:bazz', 'buzz');
+        assert.isTrue(nconf.required(['foo:bar:bazz']));
+      }
     }
   }
 }).addBatch({