refactor: add helper method to add query param

Author: gurza

src/CompaniesHouse/UriBuilders/SearchCompanyUriBuilder.cs

@@ -13,10 +13,7 @@ protected override string BuildQuery(SearchCompanyRequest request)
     {
         var queryBuilder = new StringBuilder(base.BuildQuery(request));
 
-        if (!string.IsNullOrWhiteSpace(request.Restrictions))
-        {
-            queryBuilder.Append($"&restrictions={Uri.EscapeDataString(request.Restrictions)}");
-        }
+        AppendParameterIfValid(queryBuilder, "restrictions", request.Restrictions, value => !string.IsNullOrWhiteSpace(value));
 
         return queryBuilder.ToString();
     }

src/CompaniesHouse/UriBuilders/SearchUriBuilder.cs

@@ -25,17 +25,23 @@ protected virtual string BuildQuery(TSearch request)
         {
             var queryBuilder = new StringBuilder($"?q={Uri.EscapeDataString(request.Query)}");
 
-            if (request.ItemsPerPage.HasValue)
-            {
-                queryBuilder.Append($"&items_per_page={request.ItemsPerPage.Value}");
-            }
+            AppendParameterIfValid(queryBuilder, "items_per_page", request.ItemsPerPage, value => value.HasValue);
+            AppendParameterIfValid(queryBuilder, "start_index", request.StartIndex, value => value.HasValue);
+
+            return queryBuilder.ToString();
+        }
 
-            if (request.StartIndex.HasValue)
+        protected void AppendParameterIfValid<T>(StringBuilder builder, string parameterName, T parameterValue, Func<T, bool> isValid)
+        {
+            if (!isValid(parameterValue)) return;
+
+            var value = parameterValue switch
             {
-                queryBuilder.Append($"&start_index={request.StartIndex.Value}");
-            }
+                string s => Uri.EscapeDataString(s),
+                _ => parameterValue.ToString()
+            };
 
-            return queryBuilder.ToString();
+            builder.Append($"&{parameterName}={value}");
         }
     }
 }