policy-endpint: add support for stream audio nodes without media.role

If a stream audio node does not have the 'media.role' property set, the policy
will asign the 'Default' media role name to it. In addition to this, if the
'Default' endpoint can not be found, the policy will link the stream audio node
with the lowest priority endpoint.

Video nodes will always be handled by policy-node.lua, and they will never be
handled by policy-endpoint-client.lua

This allows users to assign a particular endpoint for streams that don't have
the 'media.role' property set.

src/scripts/policy-endpoint-client.lua

@@ -39,6 +39,7 @@ end
 
 function findRole(role, tmc)
   if role and not config.roles[role] then
+    -- find the role with matching alias
     for r, p in pairs(config.roles) do
       -- default media class can be overridden in the role config data
       mc = p["media.class"] or "Audio/Sink"
@@ -50,11 +51,24 @@ function findRole(role, tmc)
         end
       end
     end
+
+    -- otherwise get the lowest priority role
+    local lowest_priority_p = nil
+    local lowest_priority_r = nil
+    for r, p in pairs(config.roles) do
+      mc = p["media.class"] or "Audio/Sink"
+      if tmc == mc and (lowest_priority_p == nil or
+          p.priority < lowest_priority_p.priority) then
+        lowest_priority_p = p
+        lowest_priority_r = r
+      end
+    end
+    return lowest_priority_r
   end
   return role
 end
 
-function findTargetEndpoint (node, media_class)
+function findTargetEndpoint (node, media_class, role)
   local target_class_assoc = {
     ["Stream/Input/Audio"] = "Audio/Source",
     ["Stream/Output/Audio"] = "Audio/Sink",
@@ -71,7 +85,7 @@ function findTargetEndpoint (node, media_class)
   end
 
   -- find highest priority endpoint by role
-  media_role = findRole(node.properties["media.role"], target_media_class)
+  media_role = findRole(role, target_media_class)
   for si_target_ep in endpoints_om:iterate {
     Constraint { "role", "=", media_role, type = "pw-global" },
     Constraint { "media.class", "=", target_media_class, type = "pw-global" },
@@ -140,8 +154,7 @@ function checkLinkable (si)
   end
 
   -- Determine if we can handle item by this policy
-  local media_role = node.properties["media.role"]
-  if endpoints_om:get_n_objects () == 0 or media_role == nil then
+  if endpoints_om:get_n_objects () == 0 then
     Log.debug (si, "item won't be handled by this policy")
     return false
   end
@@ -156,12 +169,12 @@ function handleLinkable (si)
 
   local node = si:get_associated_proxy ("node")
   local media_class = node.properties["media.class"] or ""
-  local media_role = node.properties["media.role"] or ""
+  local media_role = node.properties["media.role"] or "Default"
   Log.info (si, "handling item " .. tostring(node.properties["node.name"]) ..
       " with role " .. media_role)
 
   -- find proper target endpoint
-  local si_target_ep = findTargetEndpoint (node, media_class)
+  local si_target_ep = findTargetEndpoint (node, media_class, media_role)
   if not si_target_ep then
     Log.info (si, "... target endpoint not found")
     return
@@ -223,7 +236,7 @@ endpoints_om = ObjectManager { Interest { type = "SiEndpoint" }}
 linkables_om = ObjectManager { Interest { type = "SiLinkable",
   -- only handle si-audio-adapter and si-node
   Constraint {
-    "item.factory.name", "c", "si-audio-adapter", "si-node", type = "pw-global" },
+    "item.factory.name", "=", "si-audio-adapter", type = "pw-global" },
   }
 }
 links_om = ObjectManager { Interest { type = "SiLink",

src/scripts/policy-node.lua

@@ -517,8 +517,8 @@ function checkLinkable(si)
   end
 
   -- Determine if we can handle item by this policy
-  local media_role = si_props["media.role"]
-  if endpoints_om:get_n_objects () > 0 and media_role ~= nil then
+  if endpoints_om:get_n_objects () > 0 and
+      si_props["item.factory.name"] == "si-audio-adapter" then
     return false
   end