Initial commit: stateful OpenStack API laboratory simulator.

Ship Keystone auth, multi-service handlers (Yoga→Dalmatian), Compose/Helm
packaging, API contract packs, and pytest/Pulumi coverage labs.

app/openstack/paging.py

@@ -0,0 +1,46 @@
+"""OpenStack-style limit/marker pagination helpers."""
+
+from __future__ import annotations
+
+from typing import Any, Callable
+
+from starlette.requests import Request
+
+
+def parse_limit(request: Request, *, default: int = 0, maximum: int = 1000) -> int:
+    raw = request.query_params.get("limit")
+    if raw is None or raw == "":
+        return default
+    try:
+        value = int(raw)
+    except ValueError:
+        return default
+    if value <= 0:
+        return default
+    return min(value, maximum)
+
+
+def paginate_rows(
+    rows: list[Any],
+    request: Request,
+    *,
+    id_attr: Callable[[Any], str],
+    default_limit: int = 0,
+) -> tuple[list[Any], list[dict[str, str]]]:
+    """Slice rows by marker/limit. Returns (page, link dicts for next)."""
+
+    marker = request.query_params.get("marker")
+    limit = parse_limit(request, default=default_limit)
+    start = 0
+    if marker:
+        for index, row in enumerate(rows):
+            if id_attr(row) == marker:
+                start = index + 1
+                break
+    page = rows[start:]
+    links: list[dict[str, str]] = []
+    if limit > 0 and len(page) > limit:
+        page = page[:limit]
+        last = page[-1]
+        links.append({"rel": "next", "href": f"?marker={id_attr(last)}&limit={limit}"})
+    return page, links