fix(topology): validate time and list missions

topology_api/routes/snapshot.py

@@ -1,12 +1,36 @@
 # topology_api/routes/snapshot.py
+from datetime import datetime
+
 from flask import Blueprint, request, jsonify
 from topology_api.queries.snapshot_queries import (
-    resolve_snapshot_time, fetch_snapshot, fetch_layout,
+    resolve_snapshot_time, fetch_snapshot, fetch_layout, fetch_missions,
 )
 
 snapshot_bp = Blueprint("snapshot", __name__)
 
 
+def _parse_iso_timestamp(value):
+    if value is None:
+        return None
+    try:
+        parsed = datetime.fromisoformat(value.replace("Z", "+00:00"))
+    except ValueError:
+        return None
+    if parsed.tzinfo is None:
+        return None
+    return parsed.isoformat()
+
+
+@snapshot_bp.route("/api/v1/bases/<base_code>/missions")
+def get_missions(base_code):
+    if base_code != "guanghan":
+        return jsonify({
+            "error": "base_not_found",
+            "message": f"Base '{base_code}' not found.",
+        }), 404
+    return jsonify({"missions": fetch_missions(base_code)})
+
+
 @snapshot_bp.route("/api/v1/bases/<base_code>/snapshot")
 def get_snapshot(base_code):
     if base_code != "guanghan":
@@ -17,10 +41,19 @@ def get_snapshot(base_code):
 
     requested_mission = request.args.get("mission")
     requested_at = request.args.get("at")
+    normalized_at = _parse_iso_timestamp(requested_at)
+
+    if requested_at is not None and normalized_at is None:
+        return jsonify({
+            "error": "invalid_time",
+            "message": (
+                "Parameter 'at' must be an ISO 8601 timestamp with a timezone."
+            ),
+        }), 400
 
     snapshot_at, anchor_source = resolve_snapshot_time(
         requested_mission=requested_mission,
-        requested_at=requested_at,
+        requested_at=normalized_at,
     )
 
     if anchor_source == "mission_not_found":