Refactoring query extraction from cookie into extender methods

BTCPayServer/Extensions/ControllerBaseExtensions.cs

@@ -0,0 +1,87 @@
+using System;
+using Microsoft.AspNetCore.Mvc;
+using Newtonsoft.Json;
+
+namespace BTCPayServer
+{
+    public static class ControllerBaseExtensions
+    {
+        public static void InvoicesQuery(this ControllerBase ctrl, ref string searchTerm, ref int? timezoneOffset)
+        {
+            ListCookiePreference.Parse(ctrl, "InvoicesQuery", ref searchTerm, ref timezoneOffset);
+        }
+        public static void PaymentRequestsQuery(this ControllerBase ctrl, ref string searchTerm, ref int? timezoneOffset)
+        {
+            ListCookiePreference.Parse(ctrl, "PaymentRequestsQuery", ref searchTerm, ref timezoneOffset);
+        }
+    }
+
+    // Classes here remember users preferences on certain pages and store them in unified blob cookie "UserPreferCookie"
+    class ListCookiePreference
+    {
+        internal static void Parse(ControllerBase ctrl, string propName,
+            ref string searchTerm, ref int? timezoneOffset)
+        {
+            var prop = typeof(UserPrefsCookie).GetProperty(propName);
+            var prefCookie = parsePrefCookie(ctrl);
+
+            // If the user enter an empty searchTerm, then the variable will be null and not empty string
+            // but we want searchTerm to be null only if the user is browsing the page via some link
+            // NOT if the user entered some empty search
+            searchTerm = searchTerm is string ? searchTerm :
+                         ctrl.Request.Query.ContainsKey(nameof(searchTerm)) ? string.Empty :
+                         null;
+            if (searchTerm is null)
+            {
+                var section = prop.GetValue(prefCookie) as ListQueryDataHolder;
+                if (section != null && !String.IsNullOrEmpty(section.SearchTerm))
+                {
+                    searchTerm = section.SearchTerm;
+                    timezoneOffset = section.TimezoneOffset ?? 0;
+                }
+            }
+            else
+            {
+                prop.SetValue(prefCookie, new ListQueryDataHolder(searchTerm, timezoneOffset));
+                ctrl.Response.Cookies.Append(nameof(UserPrefsCookie), JsonConvert.SerializeObject(prefCookie));
+            }
+        }
+
+        private static UserPrefsCookie parsePrefCookie(ControllerBase ctrl)
+        {
+            var prefCookie = new UserPrefsCookie();
+            ctrl.Request.Cookies.TryGetValue(nameof(UserPrefsCookie), out var strPrefCookie);
+            if (!String.IsNullOrEmpty(strPrefCookie))
+            {
+                try
+                {
+                    prefCookie = JsonConvert.DeserializeObject<UserPrefsCookie>(strPrefCookie);
+                }
+                catch { /* ignore cookie deserialization failures */ }
+            }
+
+            return prefCookie;
+        }
+
+        class UserPrefsCookie
+        {
+            public ListQueryDataHolder InvoicesQuery { get; set; }
+
+            public ListQueryDataHolder PaymentRequestsQuery { get; set; }
+        }
+
+        class ListQueryDataHolder
+        {
+            public ListQueryDataHolder() { }
+
+            public ListQueryDataHolder(string searchTerm, int? timezoneOffset)
+            {
+                SearchTerm = searchTerm;
+                TimezoneOffset = timezoneOffset;
+            }
+
+            public int? TimezoneOffset { get; set; }
+            public string SearchTerm { get; set; }
+        }
+    }
+}