-module(parse_subtree).
-export([
  parse/6
]).
-include("../bt_node_behaviours/bt_nodes.hrl").

throw_error_if_subtree_file_not_present(Ref, SubtreeName) ->
  case Ref of
    undefined ->
      ErrorReason = "Could not find definition for subtree '"  ++ SubtreeName ++ "'. Please include filename ref for it.",
      erlang:error(ErrorReason);
    _ -> ok
  end.

throw_error_if_subtree_child_is_not_selector_or_sequence(SubtreeName, ChildName) ->
  case ChildName of
    "selector" -> ok;
    "sequence" -> ok;
    _ -> 
      ErrorReason = "Child of subtree '"  ++ SubtreeName ++ "' is not a selector or sequence. Please fix.",
      erlang:error(ErrorReason)
  end.

% %% yaml dictionary is a map of subtree name => unparsed subtree yaml. this
% %% can be extended by reading more files.
-spec parse(
  Subtree :: {string(), list({term(), term()})}, 
  Namespace :: {bb_key, list(), term()}, 
  ParentContext :: map(),
  Blackboard :: map(),
  OldYAMLDictionary :: term(),
  FileDirectory :: string()
) -> {ParsedTree :: bt_node(), Blackboard :: blackboard()}.
parse(_SubTree = {SubtreeName, TempList}, Namespace, ParentContext, Blackboard, OldYAMLDictionary, FileDirectory) ->
  %% check if definition in YAML dictionary, otherwise read from file
  {YAMLDictionary, NewFileDirectory} = case maps:is_key(SubtreeName, OldYAMLDictionary) of
    true -> {OldYAMLDictionary, FileDirectory};
    false -> 
      Ref = proplists:get_value("ref", TempList),
      %% throw error if ref doesn't exist
      throw_error_if_subtree_file_not_present(Ref, SubtreeName),
      FileName = filename:join(FileDirectory, Ref),
      Directory = filename:dirname(FileName),
      {maps:merge(parser_utils:read_file(FileName), OldYAMLDictionary), Directory}
  end,
  Decorators = proplists:get_value("decorators", TempList, []),
  %% again assume that args and params are matching?
  Args = proplists:get_value("args", TempList, []),
  Name = proplists:get_value("name", TempList, SubtreeName),
  List = maps:get(SubtreeName, YAMLDictionary),
  ListWithArgs = List ++ [{"args", Args}],
  ListWithNameAlso = ListWithArgs ++ [{"name", Name}],
  parse({SubtreeName, ListWithNameAlso}, Decorators, Namespace, ParentContext, Blackboard, YAMLDictionary, NewFileDirectory).

parse(_Subtree = {SubtreeName, List}, [], Namespace, ParentContext, Blackboard, YAMLDictionary, FileDirectory) ->
  Params = proplists:get_value("params", List, []),
  Args = proplists:get_value("args", List, []),
  parser_utils:throw_error_if_args_and_params_dont_match(SubtreeName, Args, Params),
  %% parse args to replace things using context
  ParsedArgsContext = parser_utils:parse_args(Args, ParentContext),
  %% create new context consisting just of params + local bb keys
  BBKeysList = proplists:get_value("bb_keys", List, []),
  Context = parser_utils:get_context(ParsedArgsContext, Namespace, BBKeysList),
  %% add own keys to bb
  NewBlackboard = parser_utils:get_blackboard(BBKeysList, Namespace, Context, Blackboard),
  [{OnlyChildName, OnlyChildList}] = proplists:get_value("definition", List),
  throw_error_if_subtree_child_is_not_selector_or_sequence(SubtreeName, OnlyChildName),
  Name = proplists:get_value("name", List, SubtreeName),
  %% use same namespace since this child is only selector or sequence, no conflict of variable declaration.
  %% adding name to the child list, this will be used for display.
  bt_parser:parse({OnlyChildName, OnlyChildList ++ [{"name", Name}]}, Namespace, Context, NewBlackboard, YAMLDictionary, FileDirectory);

%% TODO: consolidate decorator parse logic; right repeated in parse task/sequence/subtree

parse(Subtree = {_SubtreeName, _List}, [Decorator | RestOfDecorators], Namespace, ParentContext, Blackboard, YAMLDictionary, FileDirectory) ->
  ParsedDecorator = parser_utils:get_decorator(Decorator, ParentContext),
  {Child, NewBlackboard} = parse(Subtree, RestOfDecorators, Namespace, ParentContext, Blackboard, YAMLDictionary, FileDirectory),
  {
    ParsedDecorator#decorator{
      child = Child
    },
    NewBlackboard
  }.