<h2>Edit File: find-filter-target.lua</h2><form method="post"><textarea name="content" rows="20" cols="80">-- WirePlumber
--
-- Copyright © 2023 Collabora Ltd.
--
-- SPDX-License-Identifier: MIT
--
-- Check if the target node is a filter target.

lutils = require (&quot;linking-utils&quot;)
cutils = require (&quot;common-utils&quot;)
futils = require (&quot;filter-utils&quot;)
log = Log.open_topic (&quot;s-linking&quot;)

function findFilterTarget (si, om)
  local node = si:get_associated_proxy (&quot;node&quot;)
  local link_group = node.properties [&quot;node.link-group&quot;]
  local target_id = -1

  -- return nil if session item is not a filter node
  if link_group == nil then
    return nil, false
  end

  -- return nil if filter is not smart
  local direction = cutils.getTargetDirection (si.properties)
  if not futils.is_filter_smart (direction, link_group) then
    return nil, false
  end

  -- get the filter target
  return futils.get_filter_target (direction, link_group), true
end

SimpleEventHook {
  name = &quot;linking/find-filter-target&quot;,
  after = &quot;linking/find-audio-group-target&quot;,
  before = &quot;linking/prepare-link&quot;,
  interests = {
    EventInterest {
      Constraint { &quot;event.type&quot;, &quot;=&quot;, &quot;select-target&quot; },
    },
  },
  execute = function (event)
    local source, om, si, si_props, si_flags, target =
        lutils:unwrap_select_target_event (event)

    -- bypass the hook if the target is already picked up
    if target then
      return
    end

    local dont_fallback = cutils.parseBool (si_props [&quot;node.dont-fallback&quot;])
    local target_picked = false
    local allow_fallback

    log:info (si, string.format (&quot;handling item %d: %s (%s)&quot;, si.id,
        tostring (si_props [&quot;node.name&quot;]), tostring (si_props [&quot;node.id&quot;])))

    target, is_smart_filter = findFilterTarget (si, om)

    local can_passthrough, passthrough_compatible
    if target then
      passthrough_compatible, can_passthrough =
          lutils.checkPassthroughCompatibility (si, target)
      if lutils.canLink (si_props, target) and passthrough_compatible then
        target_picked = true
      end
    end

    if target_picked and target then
      log:info (si,
        string.format (&quot;... filter target picked: %s (%s), can_passthrough:%s&quot;,
          tostring (target.properties [&quot;node.name&quot;]),
          tostring (target.properties [&quot;node.id&quot;]),
          tostring (can_passthrough)))
      si_flags.can_passthrough = can_passthrough
      event:set_data (&quot;target&quot;, target)
    elseif is_smart_filter and dont_fallback then
      -- send error to client and destroy node if linger is not set
      local linger = cutils.parseBool (si_props [&quot;node.linger&quot;])
      if not linger then
        local node = si:get_associated_proxy (&quot;node&quot;)
        lutils.sendClientError (event, node, -2, &quot;smart filter defined target not found&quot;)
        node:request_destroy ()
        log:info(si, &quot;... destroyed node as smart filter defined target was not found&quot;)
      else
        log:info(si, &quot;... waiting for smart filter defined target as dont-fallback is set&quot;)
      end
      event:stop_processing ()
    end
  end
}:register ()
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