BillingData: Extract GetData() from PaymentBillingData into GetSelection()

Elwig/Helpers/Billing/BillingData.cs

@@ -145,5 +145,36 @@ namespace Elwig.Helpers.Billing {
             }
             return dict;
         }
+
+        protected static Dictionary<string, JsonValue> GetSelection(JsonObject data, IEnumerable<string> attributeVariants) {
+            Dictionary<string, JsonValue> dict;
+            if (data["default"] is JsonValue def) {
+                dict = attributeVariants.ToDictionary(e => e, _ => def);
+            } else {
+                dict = [];
+            }
+
+            var variants = data.Where(p => !p.Key.StartsWith('/') && p.Key.Length == 2);
+            var attributes = data.Where(p => p.Key.StartsWith('/'));
+            var others = data.Where(p => !p.Key.StartsWith('/') && p.Key.Length > 2 && p.Key != "default");
+            foreach (var (idx, v) in variants) {
+                var curve = v?.AsValue() ?? throw new InvalidOperationException();
+                foreach (var i in attributeVariants.Where(e => e.StartsWith(idx[..^1]))) {
+                    dict[i] = curve;
+                }
+            }
+            foreach (var (idx, v) in attributes) {
+                var curve = v?.AsValue() ?? throw new InvalidOperationException();
+                foreach (var i in attributeVariants.Where(e => e[2..] == idx[1..])) {
+                    dict[i] = curve;
+                }
+            }
+            foreach (var (idx, v) in others) {
+                var curve = v?.AsValue() ?? throw new InvalidOperationException();
+                dict[idx.Replace("/", "")] = curve;
+            }
+
+            return dict;
+        }
     }
 }