Add Change.apply method for object modification

CHANGES.md

@@ -2,6 +2,7 @@
 
 ## CURRENT
 
+- Add Change.apply method for modifying objects
 - Update bunyan to 0.23.1
 - #143 Preserve raw Buffer value in Control objects
 - Test code coverage with node-istanbul

lib/change.js

@@ -1,6 +1,6 @@
 // Copyright 2011 Mark Cavage, Inc.  All rights reserved.
 
-var assert = require('assert');
+var assert = require('assert-plus');
 
 var Attribute = require('./attribute');
 var Protocol = require('./protocol');
@@ -111,6 +111,68 @@ Change.compare = function (a, b) {
   return Attribute.compare(a.modification, b.modification);
 };
 
+/**
+ * Apply a Change to properties of an object.
+ *
+ * @param {Object} change the change to apply.
+ * @param {Object} obj the object to apply it to.
+ * @param {Boolean} scalar convert single-item arrays to scalars. Default: false
+ */
+Change.apply = function apply(change, obj, scalar) {
+  assert.string(change.operation);
+  assert.string(change.modification.type);
+  assert.ok(Array.isArray(change.modification.vals));
+  assert.object(obj);
+
+  var type = change.modification.type;
+  var vals = change.modification.vals;
+  var data = obj[type];
+  if (data !== undefined) {
+    if (!Array.isArray(data)) {
+      data = [data];
+    }
+  } else {
+    data = [];
+  }
+  switch (change.operation) {
+  case 'replace':
+    if (vals.length === 0) {
+      // replace empty is a delete
+      delete obj[type];
+      return obj;
+    } else {
+      data = vals;
+    }
+    break;
+  case 'add':
+    // add only new unique entries
+    var newValues = vals.filter(function (entry) {
+      return (data.indexOf(entry) === -1);
+    });
+    data = data.concat(newValues);
+    break;
+  case 'delete':
+    data = data.filter(function (entry) {
+      return (vals.indexOf(entry) === -1);
+    });
+    if (data.length === 0) {
+      // Erase the attribute if empty
+      delete obj[type];
+      return obj;
+    }
+    break;
+  default:
+    break;
+  }
+  if (scalar && data.length === 1) {
+    // store single-value outputs as scalars, if requested
+    obj[type] = data[0];
+  } else {
+    obj[type] = data;
+  }
+  return obj;
+};
+
 
 Change.prototype.parse = function (ber) {
   assert.ok(ber);

test/change.test.js

@@ -114,3 +114,129 @@ test('parse', function (t) {
 
   t.end();
 });
+
+
+test('apply - replace', function (t) {
+  var res;
+  var single = new Change({
+    operation: 'replace',
+    modification: {
+      type: 'cn',
+      vals: ['new']
+    }
+  });
+  var twin = new Change({
+    operation: 'replace',
+      modification: {
+        type: 'cn',
+        vals: ['new', 'two']
+      }
+  });
+
+  // plain
+  res = Change.apply(single, { cn: ['old'] });
+  t.ok(res.cn);
+  t.equal(res.cn.length, 1);
+  t.equal(res.cn[0], 'new');
+
+  // multiple
+  res = Change.apply(single, { cn: ['old', 'also'] });
+  t.ok(res.cn);
+  t.equal(res.cn.length, 1);
+  t.equal(res.cn[0], 'new');
+
+  //absent
+  res = Change.apply(single, { dn: ['otherjunk'] });
+  t.ok(res.cn);
+  t.equal(res.cn.length, 1);
+  t.equal(res.cn[0], 'new');
+
+  // scalar formatting "success"
+  res = Change.apply(single, { cn: 'old' }, true);
+  t.ok(res.cn);
+  t.equal(res.cn, 'new');
+
+  // scalar formatting "failure"
+  res = Change.apply(twin, { cn: 'old' }, true);
+  t.ok(res.cn);
+  t.equal(res.cn.length, 2);
+  t.equal(res.cn[0], 'new');
+  t.equal(res.cn[1], 'two');
+
+  t.end();
+});
+
+
+test('apply - add', function (t) {
+  var res;
+  var single = new Change({
+    operation: 'add',
+    modification: {
+      type: 'cn',
+      vals: ['new']
+    }
+  });
+
+  // plain
+  res = Change.apply(single, { cn: ['old'] });
+  t.deepEqual(res.cn, ['old', 'new']);
+
+  // multiple
+  res = Change.apply(single, { cn: ['old', 'also'] });
+  t.deepEqual(res.cn, ['old', 'also', 'new']);
+
+  //absent
+  res = Change.apply(single, { dn: ['otherjunk'] });
+  t.deepEqual(res.cn, ['new']);
+
+  // scalar formatting "success"
+  res = Change.apply(single, { }, true);
+  t.equal(res.cn, 'new');
+
+  // scalar formatting "failure"
+  res = Change.apply(single, { cn: 'old' }, true);
+  t.deepEqual(res.cn, ['old', 'new']);
+
+  // duplicate add
+  res = Change.apply(single, { cn: 'new' });
+  t.deepEqual(res.cn, ['new']);
+
+  t.end();
+});
+
+
+test('apply - delete', function (t) {
+  var res;
+  var single = new Change({
+    operation: 'delete',
+    modification: {
+      type: 'cn',
+      vals: ['old']
+    }
+  });
+
+  // plain
+  res = Change.apply(single, { cn: ['old', 'new'] });
+  t.deepEqual(res.cn, ['new']);
+
+  // empty
+  res = Change.apply(single, { cn: ['old'] });
+  t.equal(res.cn, undefined);
+  t.ok(Object.keys(res).indexOf('cn') === -1);
+
+  // scalar formatting "success"
+  res = Change.apply(single, { cn: ['old', 'one'] }, true);
+  t.equal(res.cn, 'one');
+
+  // scalar formatting "failure"
+  res = Change.apply(single, { cn: ['old', 'several', 'items'] }, true);
+  t.deepEqual(res.cn, ['several', 'items']);
+
+
+  //absent
+  res = Change.apply(single, { dn: ['otherjunk'] });
+  t.ok(res);
+  t.equal(res.cn, undefined);
+
+  t.end();
+});