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Filename : policy-endpoint-client.lua
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-- WirePlumber
--
-- Copyright © 2021 Collabora Ltd.
--    @author Julian Bouzas <julian.bouzas@collabora.com>
--
-- SPDX-License-Identifier: MIT

-- Receive script arguments from config.lua
local config = ... or {}
config.roles = config.roles or {}

local self = {}
self.scanning = false
self.pending_rescan = false

function rescan ()
  for si in linkables_om:iterate() do
    handleLinkable (si)
  end
end

function scheduleRescan ()
  if self.scanning then
    self.pending_rescan = true
    return
  end

  self.scanning = true
  rescan ()
  self.scanning = false

  if self.pending_rescan then
    self.pending_rescan = false
    Core.sync(function ()
      scheduleRescan ()
    end)
  end
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"
      if (type(p.alias) == "table" and tmc == mc) then
        for i = 1, #(p.alias), 1 do
          if role == p.alias[i] then
            return r
          end
        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, role)
  local target_class_assoc = {
    ["Stream/Input/Audio"] = "Audio/Source",
    ["Stream/Output/Audio"] = "Audio/Sink",
    ["Stream/Input/Video"] = "Video/Source",
  }
  local media_role = nil
  local highest_priority = -1
  local target = nil

  -- get target media class
  local target_media_class = target_class_assoc[media_class]
  if not target_media_class then
    return nil
  end

  -- find highest priority endpoint by role
  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" },
  } do
    local priority = tonumber(si_target_ep.properties["priority"])
    if priority > highest_priority then
      highest_priority = priority
      target = si_target_ep
    end
  end

  return target
end

function createLink (si, si_target_ep)
  local out_item = nil
  local in_item = nil
  local si_props = si.properties
  local target_ep_props = si_target_ep.properties

  if si_props["item.node.direction"] == "output" then
    -- playback
    out_item = si
    in_item = si_target_ep
  else
    -- capture
    out_item = si_target_ep
    in_item = si
  end

  Log.info (string.format("link %s <-> %s",
      tostring(si_props["node.name"]),
      tostring(target_ep_props["name"])))

  -- create and configure link
  local si_link = SessionItem ( "si-standard-link" )
  if not si_link:configure {
    ["out.item"] = out_item,
    ["in.item"] = in_item,
    ["out.item.port.context"] = "output",
    ["in.item.port.context"] = "input",
    ["is.policy.endpoint.client.link"] = true,
    ["media.role"] = target_ep_props["role"],
    ["target.media.class"] = target_ep_props["media.class"],
    ["item.plugged.usec"] = si_props["item.plugged.usec"],
  } then
    Log.warning (si_link, "failed to configure si-standard-link")
    return
  end

  -- register
  si_link:register()
end

function checkLinkable (si)
  -- only handle session items that has a node associated proxy
  local node = si:get_associated_proxy ("node")
  if not node or not node.properties then
    return false
  end

  -- only handle stream session items
  local media_class = node.properties["media.class"]
  if not media_class or not string.find (media_class, "Stream") then
    return false
  end

  -- Determine if we can handle item by this policy
  if endpoints_om:get_n_objects () == 0 then
    Log.debug (si, "item won't be handled by this policy")
    return false
  end

  return true
end

function handleLinkable (si)
  if not checkLinkable (si) then
    return
  end

  local node = si:get_associated_proxy ("node")
  local media_class = node.properties["media.class"] 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, media_role)
  if not si_target_ep then
    Log.info (si, "... target endpoint not found")
    return
  end

  -- Check if item is linked to proper target, otherwise re-link
  for link in links_om:iterate() do
    local out_id = tonumber(link.properties["out.item.id"])
    local in_id = tonumber(link.properties["in.item.id"])
    if out_id == si.id or in_id == si.id then
      local is_out = out_id == si.id and true or false
      for peer_ep in endpoints_om:iterate() do
        if peer_ep.id == (is_out and in_id or out_id) then

          if peer_ep.id == si_target_ep.id then
            Log.info (si, "... already linked to proper target endpoint")
            return
          end

          -- remove old link if active, otherwise schedule rescan
          if ((link:get_active_features() & Feature.SessionItem.ACTIVE) ~= 0) then
            link:remove ()
            Log.info (si, "... moving to new target")
          else
            scheduleRescan ()
            Log.info (si, "... scheduled rescan")
            return
          end

        end
      end
    end
  end

  -- create new link
  createLink (si, si_target_ep)
end

function unhandleLinkable (si)
  if not checkLinkable (si) then
    return
  end

  local node = si:get_associated_proxy ("node")
  Log.info (si, "unhandling item " .. tostring(node.properties["node.name"]))

  -- remove any links associated with this item
  for silink in links_om:iterate() do
    local out_id = tonumber (silink.properties["out.item.id"])
    local in_id = tonumber (silink.properties["in.item.id"])
    if out_id == si.id or in_id == si.id then
      silink:remove ()
      Log.info (silink, "... link removed")
    end
  end
end

endpoints_om = ObjectManager { Interest { type = "SiEndpoint" }}
linkables_om = ObjectManager { Interest { type = "SiLinkable",
  -- only handle si-audio-adapter and si-node
  Constraint {
    "item.factory.name", "=", "si-audio-adapter", type = "pw-global" },
  Constraint {
    "active-features", "!", 0, type = "gobject" },
  }
}
links_om = ObjectManager { Interest { type = "SiLink",
  -- only handle links created by this policy
  Constraint { "is.policy.endpoint.client.link", "=", true, type = "pw-global" },
} }

linkables_om:connect("objects-changed", function (om)
  scheduleRescan ()
end)

linkables_om:connect("object-removed", function (om, si)
  unhandleLinkable (si)
end)

endpoints_om:activate()
linkables_om:activate()
links_om:activate()