From 20730e5f1a442e766416951cb88a73d49709e9a7 Mon Sep 17 00:00:00 2001
From: John Firebaugh <john.firebaugh@gmail.com>
Date: Fri, 1 Feb 2013 17:24:16 -0500
Subject: [PATCH] Entity#mergeTags

---
 js/id/graph/entity.js     | 14 ++++++++++++++
 test/spec/graph/entity.js | 27 +++++++++++++++++++++++++++
 2 files changed, 41 insertions(+)

diff --git a/js/id/graph/entity.js b/js/id/graph/entity.js
index f91bb89d9..ae612c268 100644
--- a/js/id/graph/entity.js
+++ b/js/id/graph/entity.js
@@ -66,6 +66,20 @@ iD.Entity.prototype = {
         return iD.Entity(this, attrs, {_updated: true});
     },
 
+    mergeTags: function(tags) {
+        var merged = _.clone(this.tags);
+        for (var k in tags) {
+            var t1 = merged[k],
+                t2 = tags[k];
+            if (t1 && t1 !== t2) {
+                merged[k] = t1 + "; " + t2;
+            } else {
+                merged[k] = t2;
+            }
+        }
+        return this.update({tags: merged});
+    },
+
     created: function() {
         return this._updated && this.osmId().charAt(0) === '-';
     },
diff --git a/test/spec/graph/entity.js b/test/spec/graph/entity.js
index a573f4c8c..088ab5516 100644
--- a/test/spec/graph/entity.js
+++ b/test/spec/graph/entity.js
@@ -69,6 +69,33 @@ describe('iD.Entity', function () {
         });
     });
 
+    describe("#mergeTags", function () {
+        it("returns a new Entity", function () {
+            var a = iD.Entity(),
+                b = a.mergeTags({});
+            expect(b instanceof iD.Entity).to.be.true;
+            expect(a).not.to.equal(b);
+        });
+
+        it("merges tags", function () {
+            var a = iD.Entity({tags: {a: 'a'}}),
+                b = a.mergeTags({b: 'b'});
+            expect(b.tags).to.eql({a: 'a', b: 'b'});
+        });
+
+        it("combines non-conflicting tags", function () {
+            var a = iD.Entity({tags: {a: 'a'}}),
+                b = a.mergeTags({a: 'a'});
+            expect(b.tags).to.eql({a: 'a'});
+        });
+
+        it("combines conflicting tags with semicolons", function () {
+            var a = iD.Entity({tags: {a: 'a'}}),
+                b = a.mergeTags({a: 'b'});
+            expect(b.tags).to.eql({a: 'a; b'});
+        });
+    });
+
     describe("#osmId", function () {
         it("returns an OSM ID as a string", function () {
             expect(iD.Entity({id: 'w1234'}).osmId()).to.eql('1234');