spaceapi-server/spaceapi_server/template/__init__.py

import json

import jinja2


# The Jinja2 environment
__ENV = None


def _env_init(force: bool = False):
    """
    Initialize the Jinja2 environment.
    :param force: If true, force reload the environment.
    """
    global __ENV
    if __ENV is None or force:
        # Use json.dumps as finalizer in order to preserve complex data structures
        __ENV = jinja2.Environment(finalize=json.dumps)
    return __ENV


def render(template: str):
    """
    Render the given string as a Jinja2 template.
    :param template: The template string to render.
    """
    # Make sure the Jinja2 environment is initialized
    env = _env_init()
    # Create a Jinja2 template from the input string
    t = env.from_string(template)
    decoder = json.JSONDecoder()
    # Render the template and turn the JSON dump back into complex data structures
    # Only parse the first JSON object in the string, ignore the rest
    obj, i = decoder.raw_decode(t.render())
    return obj


def render_traverse(obj):
    """
    Walk through a complex, JSON-serializable data structure, and pass
    string objects through the Jinja2 templating engine.
    :param obj: The object to traverse.
    """
    if isinstance(obj, list):
        # list -> recurse into each item
        for i in range(len(obj)):
            obj[i] = render_traverse(obj[i])
        return obj
    elif isinstance(obj, dict):
        # dict -> recurse into the value of each (key, value)
        for k, v in obj.items():
            obj[k] = render_traverse(obj[k])
        return obj
    elif isinstance(obj, str):
        # str -> template
        return render(obj)
    else:
        # anything else -> return as-is
        return obj