text: # Copyright 2022 The Brax Authors.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
  """Components.
  
  In Braxlines Composer, each environment is built reusing
  components defined in this folder. This faciliates reusability,
  procedural generation, and randomizability of Brax environments.
  """
  import copy
  import importlib
  from typing import Any, Dict
  
  DEFAULT_REGISTER_COMPONENTS = ('ant', 'ground', 'halfcheetah', 'singleton',
                                 'pro_ant', 'octopus', 'humanoid')
  
  COMPONENT_MAPPING = {}
  
  
  def list_components():
    return sorted(COMPONENT_MAPPING)
  
  
  def exists(component: str):
    return component in COMPONENT_MAPPING
  
  
  def register_component(component: str,
                         component_specs: Any = None,
                         load_path: str = None,
                         override: bool = False):
    """Register component library."""
    global COMPONENT_MAPPING
    if not override and component in COMPONENT_MAPPING:
      return COMPONENT_MAPPING[component]
    if component_specs is None:
      if not load_path:
        if '.' not in component:
          load_path = f'brax.experimental.composer.components.{component}'
        else:
          load_path = component
      component_lib = importlib.import_module(load_path)
    COMPONENT_MAPPING[component] = component_lib
    return component_lib
  
  
  def register_default_components():
    """Register all default components."""
    for component in DEFAULT_REGISTER_COMPONENTS:
      register_component(component)
  
  
  def load_component(component: str,
                     component_specs: Dict[str, Any] = None,
                     component_params: Dict[str, Any] = None,
                     **override_specs) -> Dict[str, Any]:
    """Load component config information."""
    if isinstance(component, str):
      # if string, load a library under composer/components
      component_lib = register_component(
          component=component, component_specs=component_specs)
      specs_fn = component_lib.get_specs
    else:
      # else, assume it's a custom get_specs()
      specs_fn = component
    default_specs = specs_fn(**(component_params or {}))
    default_specs = copy.deepcopy(default_specs)
    default_specs.update(override_specs)
    return default_specs
  