Merge edges with same destination

lib/mosaik/graph/vertex.rb

@@ -10,12 +10,12 @@ class Vertex
 
       def initialize(id, attributes = {})
         @id = id
-        @edges = Hash.new { |h, k| h[k] = [] }
+        @edges = Hash.new { |h, k| h[k] = Edge.new }
         @attributes = attributes
       end
 
       def add_edge(to, **attributes)
-        edges[to] << Edge.new(attributes)
+        edges[to].attributes.merge!(attributes)
       end
 
       def remove_edge(id)

spec/mosaik/graph/graph_spec.rb

@@ -24,25 +24,38 @@
       graph.add_directed_edge("vertex1", "vertex2")
 
       expect(graph.find_vertex("vertex1").edges.keys).to eq ["vertex2"]
+      expect(graph.find_vertex("vertex2").edges).to be_empty
     end
 
-    it "adds a directed edge with attributes" do
+    it "sets the attributes" do
       graph.add_vertex("vertex1")
       graph.add_vertex("vertex2")
       graph.add_directed_edge("vertex1", "vertex2", key: "value")
 
-      expect(graph.find_vertex("vertex1").edges.keys).to eq ["vertex2"]
-      expect(graph.find_vertex("vertex1").edges["vertex2"].first.attributes).to eq key: "value"
+      expect(graph.find_vertex("vertex1").edges["vertex2"].attributes).to eq key: "value"
     end
 
-    it "adds a directed edge twice" do
-      graph.add_vertex("vertex1")
-      graph.add_vertex("vertex2")
-      graph.add_directed_edge("vertex1", "vertex2")
-      graph.add_directed_edge("vertex1", "vertex2")
+    context "when the edge already exists" do
+      it "does not add a directed edge multiple times" do
+        graph.add_vertex("vertex1")
+        graph.add_vertex("vertex2")
+        graph.add_directed_edge("vertex1", "vertex2")
+        graph.add_directed_edge("vertex1", "vertex2")
+        graph.add_directed_edge("vertex1", "vertex2")
 
-      expect(graph.find_vertex("vertex1").edges.keys).to eq ["vertex2"]
-      expect(graph.find_vertex("vertex1").edges["vertex2"].size).to eq 2
+        expect(graph.find_vertex("vertex1").edges.keys).to eq ["vertex2"]
+        expect(graph.find_vertex("vertex2").edges.keys).to be_empty
+      end
+
+      it "merges the attributes" do
+        graph.add_vertex("vertex1")
+        graph.add_vertex("vertex2")
+        graph.add_directed_edge("vertex1", "vertex2", key: "value")
+        graph.add_directed_edge("vertex1", "vertex2", value: "key")
+        graph.add_directed_edge("vertex1", "vertex2", key: "key")
+
+        expect(graph.find_vertex("vertex1").edges["vertex2"].attributes).to eq key: "key", value: "key"
+      end
     end
   end
 
@@ -53,25 +66,39 @@
       graph.add_undirected_edge("vertex1", "vertex2")
 
       expect(graph.find_vertex("vertex1").edges.keys).to eq ["vertex2"]
+      expect(graph.find_vertex("vertex2").edges.keys).to eq ["vertex1"]
     end
 
-    it "adds an undirected edge with attributes" do
+    it "sets the attributes" do
       graph.add_vertex("vertex1")
       graph.add_vertex("vertex2")
       graph.add_undirected_edge("vertex1", "vertex2", key: "value")
 
-      expect(graph.find_vertex("vertex1").edges.keys).to eq ["vertex2"]
-      expect(graph.find_vertex("vertex1").edges["vertex2"].first.attributes).to eq key: "value"
+      expect(graph.find_vertex("vertex1").edges["vertex2"].attributes).to eq key: "value"
+      expect(graph.find_vertex("vertex2").edges["vertex1"].attributes).to eq key: "value"
     end
 
-    it "adds an undirected edge twice" do
-      graph.add_vertex("vertex1")
-      graph.add_vertex("vertex2")
-      graph.add_undirected_edge("vertex1", "vertex2")
-      graph.add_undirected_edge("vertex1", "vertex2")
+    context "when the edge already exists" do
+      it "adds an undirected edge multiple times" do
+        graph.add_vertex("vertex1")
+        graph.add_vertex("vertex2")
+        graph.add_undirected_edge("vertex1", "vertex2")
+        graph.add_undirected_edge("vertex1", "vertex2")
 
-      expect(graph.find_vertex("vertex1").edges.keys).to eq ["vertex2"]
-      expect(graph.find_vertex("vertex1").edges["vertex2"].size).to eq 2
+        expect(graph.find_vertex("vertex1").edges.keys).to eq ["vertex2"]
+        expect(graph.find_vertex("vertex2").edges.keys).to eq ["vertex1"]
+      end
+
+      it "merges the attributes" do
+        graph.add_vertex("vertex1")
+        graph.add_vertex("vertex2")
+        graph.add_undirected_edge("vertex1", "vertex2", key: "value")
+        graph.add_undirected_edge("vertex1", "vertex2", value: "key")
+        graph.add_undirected_edge("vertex1", "vertex2", key: "key")
+
+        expect(graph.find_vertex("vertex1").edges["vertex2"].attributes).to eq key: "key", value: "key"
+        expect(graph.find_vertex("vertex2").edges["vertex1"].attributes).to eq key: "key", value: "key"
+      end
     end
   end
 

spec/mosaik/graph/vertex_spec.rb

@@ -16,19 +16,28 @@
       expect(vertex.edges.keys).to eq ["child"]
     end
 
-    it "adds an edge with attributes" do
+    it "sets the attributes" do
       vertex.add_edge("child", key: "value")
 
-      expect(vertex.edges.keys).to eq ["child"]
-      expect(vertex.edges["child"].first.attributes).to eq key: "value"
+      expect(vertex.edges["child"].attributes).to eq key: "value"
     end
 
-    it "adds an edge twice" do
-      vertex.add_edge("child")
-      vertex.add_edge("child")
+    context "when the edge already exists" do
+      it "does not add an edge multiple times" do
+        vertex.add_edge("child")
+        vertex.add_edge("child")
+        vertex.add_edge("child")
 
-      expect(vertex.edges.keys).to eq ["child"]
-      expect(vertex.edges["child"].size).to eq 2
+        expect(vertex.edges.keys).to eq ["child"]
+      end
+
+      it "merges the attributes" do
+        vertex.add_edge("child", key: "value")
+        vertex.add_edge("child", value: "key")
+        vertex.add_edge("child", key: "key")
+
+        expect(vertex.edges["child"].attributes).to eq key: "key", value: "key"
+      end
     end
   end
 end