add initial implementation of auth gateway with models, routes, and session management

containers/auth-gateway/auth_gateway/services/resolver.py

@@ -0,0 +1,63 @@
+from dataclasses import dataclass
+from urllib.parse import urlsplit
+
+from auth_gateway.models.applications import ApplicationModel
+from auth_gateway.models.routes import AppRoutesModel, RoutePolicyBindingModel
+from auth_gateway.models.runtime import RuntimeConfig
+
+
+@dataclass
+class RequestContext:
+    host: str
+    path: str
+    application: ApplicationModel
+    route: RoutePolicyBindingModel | None
+    policy_name: str
+
+
+def normalize_host(raw_host: str) -> str:
+    return raw_host.split(":", 1)[0].strip().lower()
+
+
+def normalize_path(raw_uri: str) -> str:
+    parsed = urlsplit(raw_uri or "/")
+    path = parsed.path or "/"
+    return path if path.startswith("/") else f"/{path}"
+
+
+def resolve_application(runtime_config: RuntimeConfig, host: str) -> ApplicationModel | None:
+    normalized_host = normalize_host(host)
+    for application in runtime_config.applications.values():
+        if normalized_host in {candidate.lower() for candidate in application.hosts}:
+            return application
+    return None
+
+
+def resolve_route(runtime_config: RuntimeConfig, application_id: str, path: str) -> tuple[RoutePolicyBindingModel | None, str | None]:
+    app_routes: AppRoutesModel | None = runtime_config.routes_by_app.get(application_id)
+    if not app_routes:
+        return None, None
+
+    normalized_path = normalize_path(path)
+    sorted_routes = sorted(app_routes.routes, key=lambda route: len(route.path_prefix), reverse=True)
+    for route in sorted_routes:
+        route_prefix = normalize_path(route.path_prefix)
+        if normalized_path.startswith(route_prefix):
+            return route, route.policy
+    return None, app_routes.default_policy
+
+
+def resolve_request_context(runtime_config: RuntimeConfig, host: str, path: str) -> RequestContext | None:
+    application = resolve_application(runtime_config, host)
+    if not application:
+        return None
+    route, policy_name = resolve_route(runtime_config, application.id, path)
+    if not policy_name:
+        return None
+    return RequestContext(
+        host=normalize_host(host),
+        path=normalize_path(path),
+        application=application,
+        route=route,
+        policy_name=policy_name,
+    )