# This implements SDD dependencies


subroutine(sddvalue_as_string(node val), ());

#
# clear_value_cache()
#
# Purpose: This clears the cache of a value, so it will need to be recomputed on next use.
#
# Parameters val: the value show cache to clear
#

subroutine(clear_value_cache(node val), (

  if (val?{"cached_value"}) then (
    delete_node(val{"cached_value"});
  );

)); # clear_value_cache()



#
# announce_sdd_parameter_change()
#
# Purpose: This announces the change of a parameter of an SDD.  It causes all dependends' cached values to be cleared,
#          so they will be recomputed when next needed.
#

subroutine(announce_sdd_parameter_change(node providersdd, string providervalname), (

#  echo("announce_sdd_parameter_change; providersd=" . providersdd . "; providervalname=" . providervalname);

  # If there are any dependencies of this SDD...
  node parameter = providersdd{providervalname};
  if (parameter?{"dependencies"}) then (

    node dependencies = parameter{"dependencies"};

    # ...then remove them from cache
    node dependency;
    foreach dependency (dependencies) (

      node dependentsdd = @dependency{"dependentsdd"};
      string dependentvalname = @dependency{"dependentvalname"};
      node val = @dependentsdd{dependentvalname};

      # Clear the cache for this value (forcing it to be recomputed next time it's used)
#echo("val: " . val);
#echo("val: " . node_as_string(val));
#      if (val ne "NULL") then
      if (val ne "NULL") then (
        clear_value_cache(val);
#echo("Cleared value cache for val=" . sddvalue_as_string(val));

      # If this is an "add" operation, follow it down to its parameters, in case those need to be recomputed also
      # This is a narrow implementation; it probably needs to follow all examples like this; but for now I'm just
      # trying to get <span> to work in <td>. - GMF 2011-03-29

      # Look for subnodes which appear to be sdd values, and clear their caches.  Without this, if we have an sddadd which
      # is the xmin of a dependent SDD, it may have a cached value even though its subvalues have changed; we need to clear
      # the caches of all subvalues when clearing the SDD's cache in this case.
#if (false) then (
node subval;
#echo("val: " . node_as_string(val));
#echo("START");
foreach subval val (
#  echo("subval: " . subval);
#echo("subval: " . node_as_string(subval));
#echo("@subval: " . node_as_string(@subval));
#  echo("subval type: " . @(@subval){"type"});
#echo("node_type: " . node_type(subval));
#echo("?subval: " . node_exists(subval));
  if (node_type(subval) eq "node") then (
#echo("subval: " . node_as_string(@subval));
#echo("subval{type}: " . @(@subval){"type"});
    if ((@subval)?{"type"}) then (
      clear_value_cache(@subval);
#echo("subval: " . node_as_string(@subval));
    );
  );
);
#echo("DONE");
#);

#if (@val{"type"} eq "add") then (
##echo("ADD");
#        node value1 = @val{"value1"};
#	node value2 = @val{"value2"};
#clear_value_cache(value1);
#clear_value_cache(value2);
#);
); # if val
      # Propagate changes to any dependents of the dependent value
      announce_sdd_parameter_change(dependentsdd, dependentvalname);

    ); # foreach dependency

  ); # if dependencies

)); # announce_sdd_parameter_change()



#
# register_sdd_dependency()
#
# Purpose: This registers a dependency of a value in one SDD on a value in another SDD
#
# Parameters: dependentsdd: the SDD whose value is dependent
#             dependentvalname: the name of the dependent value
#             providersdd: the SDD who provides the value to the dependent
#             providervalname: the name of the value which provides to dependent
#

subroutine(register_sdd_dependency(node dependentsdd, string dependentvalname, node providersdd, string providervalname), (

  string dependencyname = (dependentsdd + 0) . "_" . dependentvalname;

  # Remember in the dependent SDD, that this value depends on the provider value
  set_node_type(providersdd{providervalname}{"dependencies"}{dependencyname}{"dependentsdd"}, "node");
  @providersdd{providervalname}{"dependencies"}{dependencyname}{"dependentsdd"} = dependentsdd;
  @providersdd{providervalname}{"dependencies"}{dependencyname}{"dependentvalname"} = dependentvalname;

)); # register_dependency_value_on_sdd_parameter()