scripts: policy-endpoints: add move and follow options

If 'move' is set to true, endpoints will be moved to the new target when the
metadata 'target.node' key is present. If 'follow' is set to true, endpoints
will be moved to the newly changed default device automatically.

src/config/config.lua.d/10-endpoint-support.lua

@@ -8,6 +8,11 @@ endpoint_support.sessions = {
   ["video"] = {},
 }
 
+endpoint_support.policy = {
+  move = true,   -- moves endpoints when metadata target.node changes
+  follow = true  -- moves endpoints to the default device when it has changed
+}
+
 function endpoint_support.enable()
   -- Session item factories, building blocks for the session management graph
   -- Do not disable these unless you really know what you are doing
@@ -27,5 +32,5 @@ function endpoint_support.enable()
   load_script("create-endpoint.lua")
 
   -- Link endpoints to each other to make media flow in the graph
-  load_script("policy-endpoint.lua")
+  load_script("policy-endpoint.lua", endpoint_support.policy)
 end

src/scripts/policy-endpoint.lua

@@ -5,6 +5,13 @@
 --
 -- SPDX-License-Identifier: MIT
 
+-- Receive script arguments from config.lua
+local config = ...
+
+-- ensure config.move and config.follow are not nil
+config.move = config.move or false
+config.follow = config.follow or false
+
 target_class_assoc = {
   ["Stream/Input/Audio"] = "Audio/Source",
   ["Stream/Output/Audio"] = "Audio/Sink",
@@ -22,8 +29,137 @@ default_endpoint_key = {
   ["output"] = "default.session.endpoint.source",
 }
 
+metadata_key_target_class_assoc = {
+  ["default.session.endpoint.sink"] = {
+    ["audio"] = "Stream/Output/Audio",
+    ["video"] = "Stream/Output/Video",
+  },
+  ["default.session.endpoint.source"] = {
+    ["audio"] = "Stream/Input/Audio",
+    ["video"] = "Stream/Input/Video",
+  },
+}
+
+default_endpoint_target = {
+  ["Stream/Input/Audio"] = nil,
+  ["Stream/Output/Audio"] = nil
+}
+
+-- Endpoint Ids not linked to its node.target prop
+auto_linked_endpoints = {}
+
+function createLink (ep, target)
+  if ep:get_n_streams() > 0 and target:get_n_streams() > 0 then
+    local ep_id = ep['bound-id']
+    local target_id = target['bound-id']
+    local ep_is_output = (ep.direction == "output")
+    local props = {
+      ['endpoint-link.output.endpoint'] = (ep_is_output and ep_id) or target_id,
+      ['endpoint-link.output.stream'] = -1,
+      ['endpoint-link.input.endpoint'] = (ep_is_output and target_id) or ep_id,
+      ['endpoint-link.input.stream'] = -1,
+    }
+    ep:create_link (props)
+  end
+end
+
+function isEndpointLinkedWith (session, ep, target)
+  local ep_id = ep["bound_id"]
+  local target_id = target["bound_id"]
+  for link in session:iterate_links() do
+    local out_ep, _, in_ep, _ = link:get_linked_object_ids()
+    if (out_ep == ep_id and in_ep == target_id) or
+        (out_ep == target_id and in_ep == ep_id) then
+      return true
+    end
+  end
+  return false
+end
+
+function moveEndpoint (session, ep, target)
+  local ep_id = ep['bound-id']
+  local ep_is_output = (ep.direction == "output")
+  local total_links = 0
+  local moving = false
+
+  -- return if already moved
+  if isEndpointLinkedWith(session, ep, target) then
+    return
+  end
+
+  -- destroy all previous links
+  for link in session:iterate_links() do
+    local out_ep, _, in_ep, _ = link:get_linked_object_ids()
+    if (ep_is_output and out_ep == ep_id) or
+        (not ep_is_output and in_ep == ep_id) then
+      local curr_target = nil
+      total_links = total_links + 1
+      -- create new link when all previous links were destroyed
+      link:connect ("pw-proxy-destroyed", function (l)
+        total_links = total_links - 1
+        if total_links == 0 then
+          createLink (ep, target)
+        end
+      end)
+      link:request_destroy ()
+      moving = true
+    end
+  end
+
+  -- create link if never linked
+  if not moving then
+    createLink (ep, target)
+  end
+end
+
+function moveEndpointFromNodeId (ep_node_id, target_node_id)
+  for session in om_session:iterate() do
+    local ep = session:lookup_endpoint (Interest {
+        type = "endpoint",
+        Constraint { "node.id", "=", tostring(ep_node_id), type = "pw" }
+    })
+    if ep then
+      local target = session:lookup_endpoint (Interest {
+          type = "endpoint",
+          Constraint { "node.id", "=", tostring(target_node_id), type = "pw" }
+      })
+      if target then
+        moveEndpoint (session, ep, target)
+        break
+      end
+    end
+  end
+end
+
+function reevaluateAutoLinkedEndpoints (ep_media_class, target_id)
+  -- make sure the target Id has changed
+  if default_endpoint_target[ep_media_class] == target_id then
+    return
+  end
+  default_endpoint_target[ep_media_class] = target_id
+
+  -- move auto linked endpoints to the new target
+  for session in om_session:iterate_filtered (Interest { type = "session" } ) do
+    local target = session:lookup_endpoint (Interest {
+        type = "endpoint",
+        Constraint { "bound-id", "=", target_id, type = "gobject" }
+    })
+    if target then
+      for ep in session:iterate_endpoints (Interest{
+          type = "endpoint",
+          Constraint { "media-class", "=", ep_media_class, type = "gobject" },
+      } ) do
+        if auto_linked_endpoints[ep["bound-id"]] == true then
+          moveEndpoint (session, ep, target)
+        end
+      end
+    end
+  end
+end
+
 function findTarget (session, ep)
   local target = nil
+  local auto_linked = false
 
   Log.trace(session, "Searching link target for " .. ep['bound-id'] ..
                      " (name:'" .. ep['name'] ..
@@ -53,6 +189,9 @@ function findTarget (session, ep)
       if candidate_ep['direction'] == direction and
          candidate_ep['media-class'] == media_class
       then
+        -- we consider auto linked any target that is not in node.target prop
+        auto_linked = true
+
         -- honor default endpoint, if present
         if metadata then
           local key = default_endpoint_key[direction]
@@ -75,7 +214,7 @@ function findTarget (session, ep)
     end
   end
 
-  return target
+  return target, auto_linked
 end
 
 function handleEndpoint (session, ep)
@@ -96,17 +235,10 @@ function handleEndpoint (session, ep)
   end
 
   -- if not, find a suitable target and link
-  local target = findTarget (session, ep)
+  local target, auto_linked = findTarget (session, ep)
   if target then
-    local ep_is_output = (ep.direction == "output")
-    local target_id = target['bound-id']
-    local props = {
-      ['endpoint-link.output.endpoint'] = (ep_is_output and ep_id) or target_id,
-      ['endpoint-link.output.stream'] = -1,
-      ['endpoint-link.input.endpoint'] = (ep_is_output and target_id) or ep_id,
-      ['endpoint-link.input.stream'] = -1,
-    }
-    ep:create_link (props)
+    createLink (ep, target)
+    auto_linked_endpoints[ep_id] = auto_linked
   end
 end
 
@@ -118,9 +250,9 @@ function handleLink (link)
 end
 
 om_metadata = ObjectManager { Interest { type = "metadata" } }
-om = ObjectManager { Interest { type = "session" } }
+om_session = ObjectManager { Interest { type = "session" } }
 
-om:connect("object-added", function (om, session)
+om_session:connect("object-added", function (om, session)
   session:connect('endpoints-changed', function (session)
     for ep in session:iterate_endpoints() do
       handleEndpoint(session, ep)
@@ -134,5 +266,25 @@ om:connect("object-added", function (om, session)
   end)
 end)
 
+om_metadata:connect("object-added", function (om, metadata)
+  metadata:connect("changed", function (m, subject, key, t, value)
+    if config.move and key == "target.node" then
+      moveEndpointFromNodeId (subject, tonumber (value))
+    elseif config.follow and string.find(key, "default.session.endpoint") then
+      local session = om_session:lookup (Interest {
+          type = "session",
+          Constraint { "bound-id", "=", subject, type = "gobject" }
+      })
+      if session then
+        local target_class =
+            metadata_key_target_class_assoc[key][session.properties["session.name"]]
+        if target_class then
+          reevaluateAutoLinkedEndpoints (target_class, tonumber (value))
+        end
+      end
+    end
+  end)
+end)
+
 om_metadata:activate()
-om:activate()
+om_session:activate()