Expose is_playing; add tests around stop/start exceptions

source/include/signalflow/core/exceptions.h

@@ -85,4 +85,14 @@ struct node_already_playing_exception : public std::runtime_error
         : std::runtime_error(message) {}
 };
 
+struct node_not_playing_exception : public std::runtime_error
+{
+    using std::runtime_error::runtime_error;
+
+    node_not_playing_exception()
+        : std::runtime_error("Node cannot be stopped as it is not playing") {}
+    node_not_playing_exception(const char *message)
+        : std::runtime_error(message) {}
+};
+
 }

source/include/signalflow/core/graph.h

@@ -236,6 +236,16 @@ class AudioGraph
      *--------------------------------------------------------------------------------*/
     void play(NodeRef node);
 
+    /**--------------------------------------------------------------------------------
+     * Query whether the specified node is currently playing (i.e., connected to
+     * the graph's output).
+     *
+     * @param node The node to query
+     * @returns true if playing, false otherwise
+     *
+     *--------------------------------------------------------------------------------*/
+    bool is_playing(NodeRef node);
+
     /**--------------------------------------------------------------------------------
      * Similar to add_node, but for patches.
      * Is a bit of a hacky workaround for the situation in which a Patch is connected

source/src/core/graph.cpp

@@ -507,6 +507,15 @@ void AudioGraph::play(NodeRef node)
     output->add_input(node);
 }
 
+bool AudioGraph::is_playing(NodeRef node)
+{
+    // TODO: This currently only works if the node is wired directly to the
+    //       graph's output. To support nested nodes, should recursively
+    //       traverse the outputs of the node.
+    AudioOut_Abstract *audioout = (AudioOut_Abstract *) (this->output.get());
+    return audioout->has_input(node);
+}
+
 void AudioGraph::stop(PatchRef patch) { this->stop(patch.get()); }
 
 void AudioGraph::stop(Patch *patch)
@@ -515,7 +524,19 @@ void AudioGraph::stop(Patch *patch)
     nodes_to_remove.insert(patch->get_output());
 }
 
-void AudioGraph::stop(NodeRef node) { nodes_to_remove.insert(node); }
+void AudioGraph::stop(NodeRef node)
+{
+    // TODO: Should ideally do node->is_playing() here, but this won't catch cases in
+    //       which the node is embedded somewhere within the graph.
+    if (!node->outputs.empty())
+    {
+        nodes_to_remove.insert(node);
+    }
+    else
+    {
+        throw node_not_playing_exception();
+    }
+}
 
 void AudioGraph::replace(NodeRef node, NodeRef other) { nodes_to_replace.insert(std::make_pair(node, other)); }
 

source/src/python/exceptions.cpp

@@ -12,5 +12,6 @@ void init_python_exceptions(py::module &m)
     py::register_exception<signalflow::device_not_found_exception>(m, "DeviceNotFoundException");
     py::register_exception<signalflow::audio_io_exception>(m, "AudioIOException");
     py::register_exception<signalflow::node_already_playing_exception>(m, "NodeAlreadyPlayingException");
+    py::register_exception<signalflow::node_not_playing_exception>(m, "NodeNotPlayingException");
     py::register_exception<signalflow::cpu_usage_above_limit_exception>(m, "CPUUsageAboveLimitException");
 }

source/src/python/node.cpp

@@ -181,6 +181,17 @@ void init_python_node(py::module &m)
                 return inputs;
             },
             R"pbdoc(Returns a dict of the node's input names and values)pbdoc")
+        .def_property_readonly(
+            "outputs", [](Node &node) {
+                std::vector<Node *> outputs(node.get_outputs().size());
+                int index = 0;
+                for (auto output : node.get_outputs())
+                {
+                    outputs[index++] = output.first;
+                }
+                return outputs;
+            },
+            R"pbdoc(Returns a list of the node's output connections)pbdoc")
         .def_property_readonly(
             "output_buffer", [](Node &node) {
                 /*--------------------------------------------------------------------------------
@@ -271,6 +282,8 @@ void init_python_node(py::module &m)
          *-------------------------------------------------------------------------------*/
         .def(
             "play", [](NodeRef node) { node->get_graph()->play(node); }, R"pbdoc(Begin playing the node by connecting it to the graph's output)pbdoc")
+        .def_property_readonly(
+            "is_playing", [](NodeRef node) { return node->get_graph()->is_playing(node); }, R"pbdoc(Query whether the node is currently playing)pbdoc")
         .def(
             "stop", [](NodeRef node) { node->get_graph()->stop(node); }, R"pbdoc(Stop playing the node by disconnecting it from the graph's output)pbdoc");