import sys
from importlib.abc import MetaPathFinder, Loader
from importlib.machinery import ModuleSpec

import graphql_server.flask


class GrapheneFileUploadImportHook(MetaPathFinder, Loader):
    """
    Since we can't modify `graphene_file_upload` lib directly and
    it's still trying to import from `flask_graphql` (since not maintained),
    we can achieve this by manipulating Python's module import system
    to intercept and redirect imports from `flask_graphql` to `graphql_server.flask`.
    This method is a bit hacky but works well for this issue.

    Import this module before importing `graphene_file_upload`.
    """
    def find_spec(self, fullname, path, target=None):
        if fullname == 'flask_graphql':
            return ModuleSpec(fullname, self, is_package=False)

    def create_module(self, spec):
        # Since flask_graphql doesn't exist, we're going to redirect it to graphql_server.flask
        return sys.modules.setdefault(spec.name, sys.modules['graphql_server.flask'])

    def exec_module(self, module):
        # No module execution needed as we're aliasing to an existing module
        pass


# Add the custom import hook to the beginning of the meta path finder list
sys.meta_path.insert(0, GrapheneFileUploadImportHook())