gross json preprocessor abuse time

1 files changed, 124 insertions, 29 deletions

diff --git a/discord/json.hpp b/discord/json.hpp
index 3f78391..40f078f 100644
--- a/discord/json.hpp
+++ b/discord/json.hpp
@@ -1,45 +1,140 @@
 #pragma once
 #include <nlohmann/json.hpp>
+#include <optional>
 
-#define JS_D(k, t)         \
-    do {                   \
-        j.at(k).get_to(t); \
+namespace detail { // more or less because idk what to name this stuff
+template<typename T>
+struct is_optional : ::std::false_type {};
+
+template<typename T>
+struct is_optional<::std::optional<T>> : ::std::true_type {};
+
+template<typename T>
+inline void json_direct(const ::nlohmann::json &j, const char *key, T &val) {
+    if constexpr (is_optional<T>::value)
+        val = j.at(key).get<T::value_type>();
+    else
+        j.at(key).get_to(val);
+}
+
+template<typename T>
+inline void json_optional(const ::nlohmann::json &j, const char *key, T &val) {
+    if constexpr (is_optional<T>::value) {
+        if (j.contains(key))
+            val = j.at(key).get<T::value_type>();
+        else
+            val = ::std::nullopt;
+    } else {
+        if (j.contains(key))
+            j.at(key).get_to(val);
+    }
+}
+
+template<typename T>
+inline void json_nullable(const ::nlohmann::json &j, const char *key, T &val) {
+    if constexpr (is_optional<T>::value) {
+        const auto &at = j.at(key);
+        if (!at.is_null())
+            val = at.get<T::value_type>();
+        else
+            val = std::nullopt;
+    } else {
+        const auto &at = j.at(key);
+        if (!at.is_null())
+            at.get_to(val);
+    }
+}
+
+template<typename T>
+inline void json_optional_nullable(const ::nlohmann::json &j, const char *key, T &val) {
+    if constexpr (is_optional<T>::value) {
+        if (j.contains(key)) {
+            const auto &at = j.at(key);
+            if (!at.is_null())
+                val = at.get<T::value_type>();
+            else
+                val = std::nullopt;
+        } else {
+            val = std::nullopt;
+        }
+    } else {
+        if (j.contains(key)) {
+            const auto &at = j.at(key);
+            if (!at.is_null())
+                at.get_to(val);
+        }
+    }
+}
+
+template<typename T>
+inline void json_update_optional_nullable(const ::nlohmann::json &j, const char *key, T &val) {
+    if constexpr (is_optional<T>::value) {
+        if (j.contains(key)) {
+            const auto &at = j.at(key);
+            if (!at.is_null())
+                val = at.get<T::value_type>();
+            else
+                val = std::nullopt;
+        }
+    } else {
+        if (j.contains(key)) {
+            const auto &at = j.at(key);
+            if (!at.is_null())
+                at.get_to(val);
+            else
+                val = T();
+        }
+    }
+}
+
+template<typename T, typename U>
+inline void json_update_optional_nullable_default(const ::nlohmann::json &j, const char *key, T &val, const U &fallback) {
+    if constexpr (is_optional<T>::value) {
+        if (j.contains(key)) {
+            const auto &at = j.at(key);
+            if (at.is_null())
+                val = fallback;
+            else
+                val = at.get<T::value_type>();
+        }
+    } else {
+        if (j.contains(key)) {
+            const auto &at = j.at(key);
+            if (at.is_null())
+                val = fallback;
+            else
+                at.get_to(val);
+        }
+    }
+}
+} // namespace detail
+
+#define JS_D(k, t)                    \
+    do {                              \
+        detail::json_direct(j, k, t); \
     } while (0)
 
-#define JS_O(k, t)                            \
-    do {                                      \
-        if (j.contains(k)) j.at(k).get_to(t); \
+#define JS_O(k, t)                      \
+    do {                                \
+        detail::json_optional(j, k, t); \
     } while (0)
 
-#define JS_N(k, t)                                 \
-    do {                                           \
-        if (!j.at(k).is_null()) j.at(k).get_to(t); \
+#define JS_N(k, t)                      \
+    do {                                \
+        detail::json_nullable(j, k, t); \
     } while (0)
 
 #define JS_ON(k, t)                              \
     do {                                         \
-        if (j.contains(k) && !j.at(k).is_null()) \
-            j.at(k).get_to(t);                   \
+        detail::json_optional_nullable(j, k, t); \
     } while (0)
 
-#define JS_RD(k, t)                  \
-    do {                             \
-        if (j.contains(k)) {         \
-            if (j.at(k).is_null()) { \
-                t = decltype(t)();   \
-            } else {                 \
-                j.at(k).get_to(t);   \
-            }                        \
-        }                            \
+#define JS_RD(k, t)                                     \
+    do {                                                \
+        detail::json_update_optional_nullable(j, k, t); \
     } while (0)
 
-#define JS_RV(k, t, d)               \
-    do {                             \
-        if (j.contains(k)) {         \
-            if (j.at(k).is_null()) { \
-                t = d;               \
-            } else {                 \
-                j.at(k).get_to(t);   \
-            }                        \
-        }                            \
+#define JS_RV(k, t, d)                                             \
+    do {                                                           \
+        detail::json_update_optional_nullable_default(j, k, t, d); \
     } while (0)