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import json
import os

from flask import url_for


def configure_manifest_files(app):
    """
    Loads the manifest file and register the `url_for_asset_` template tag.

    :param app:
    :return:
    """
    manifest = {}

    def parse_manifest_json():
        try:
            manifest_file = os.path.join(os.path.dirname(__file__), os.pardir, 'static/dist/manifest.json')
            with open(manifest_file) as file:
                manifest.update(json.load(file))

                for source, target in manifest.copy().items():
                    manifest[source] = os.path.join("dist", target)
        except Exception:  # noqa pylint: disable=broad-except
            print("Please make sure to build the frontend in static/ directory and restart the server")

    def get_asset_url(filename):
        if app.debug:
            parse_manifest_json()
        return url_for('static', filename=manifest.get(filename, ''))

    parse_manifest_json()

    @app.context_processor
    def get_url_for_asset():  # pylint: disable=unused-variable
        """
        Template tag to return the asset URL.
        WebPack renders the assets after minification and modification
        under the static/dist folder.
        This template tag reads the asset name in manifest.json and returns
        the appropriate file.
        """
        return dict(url_for_asset=get_asset_url)
