Added fetcher factory

updates_notifier/__init__.py

+from .entry import Entry

updates_notifier/fetchers/__init__.py

 from .project_fetcher import ProjectFetcher
+from .utils import create_fetchers_from_dict

updates_notifier/fetchers/utils.py

+from typing import Any, Dict, List, Type
+
+from .atom_rss_fetcher import AtomRSSFetcher
+from .gitea_fetcher import GiteaFetcher
+from .github_fetcher import GithubFetcher
+from .gitlab_fetcher import GitLabFetcher
+from .project_fetcher import ProjectFetcher
+
+_TYPE_ATOM_RSS = "atom_rss"
+_TYPE_GITEA = "gitea"
+_TYPE_GITHUB = "github"
+_TYPE_GITLAB = "gitlab"
+
+
+class FactoryError(RuntimeError):
+    pass
+
+
+class FactoryParamError(FactoryError):
+    def __init__(self, param_name: str, expected_type: Type, given_type: Type):
+        self.message = (
+            f"Invalid type for parameter {param_name}, wanted {expected_type.__name__}"
+            f", but got {given_type.__name__}"
+        )
+        self.repr = (
+            f"<{type(self).__name__} param_name={param_name}"
+            f"expected_type={expected_type.__name__} given_type={given_type.__name__}>"
+        )
+
+    def __str__(self) -> str:
+        return self.message
+
+    def __repr__(self) -> str:
+        return self.repr
+
+
+def _assert_param_type_is(param_name: str, value: Any, expected_type: Type) -> None:
+    if not isinstance(value, expected_type):
+        raise FactoryParamError(param_name, expected_type, type(value).__name__)
+
+
+def create_fetcher(
+    fetcher_type: str, feed_id: int, name: str, **kwargs
+) -> ProjectFetcher:
+    if not isinstance(fetcher_type, str):
+        raise FactoryError(
+            f"Fetcher type must be a str, got {type(fetcher_type).__name__}"
+        )
+
+    _assert_param_type_is("feed_id", feed_id, int)
+    _assert_param_type_is("name", name, str)
+
+    if fetcher_type == _TYPE_ATOM_RSS:
+        url = kwargs.get("url")
+        _assert_param_type_is("url", url, str)
+
+        return AtomRSSFetcher(feed_id, name, url)
+
+    if fetcher_type == _TYPE_GITEA:
+        gitea_host = kwargs.get("host")
+        _assert_param_type_is("host", gitea_host, str)
+
+        repository = kwargs.get("repository")
+        _assert_param_type_is("repository", repository, str)
+
+        return GiteaFetcher(feed_id, name, gitea_host, repository)
+
+    if fetcher_type == _TYPE_GITHUB:
+        repository = kwargs.get("repository")
+        _assert_param_type_is("repository", repository, str)
+
+        return GithubFetcher(feed_id, name, repository)
+
+    if fetcher_type == _TYPE_GITLAB:
+        gitlab_host = kwargs.get("host")
+        _assert_param_type_is("host", gitlab_host, str)
+
+        repository = kwargs.get("repository")
+        _assert_param_type_is("repository", repository, str)
+
+        return GitLabFetcher(feed_id, name, gitlab_host, repository)
+
+    raise FactoryError(f"Invalid fetcher type '{fetcher_type}'")
+
+
+def create_fetchers_from_dict(feeds_params: List[Any]) -> List[ProjectFetcher]:
+    assert isinstance(feeds_params, list)
+
+    fetchers: List[ProjectFetcher] = []
+
+    for idx, params in enumerate(feeds_params):
+        try:
+            fetchers.append(create_fetcher(**params))
+        except FactoryError as err:
+            raise RuntimeError(
+                "Could not load fetcher at index %s: %s", idx, str(err)
+            ) from err
+
+    return fetchers