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mcc_error.h

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+#pragma once
+
+/****************************************************************************************
+ *                                                                                      *
+ *                          MOUNT CONTROL COMPONENTS LIBRARY                            *
+ *                                                                                      *
+ *                                                                                      *
+ *                        IMPLEMENTATION OF OPERATIONAL ERROR                           *
+ *                                                                                      *
+ ****************************************************************************************/
+
+
+
+#include <format>
+#include <sstream>
+#include <system_error>
+
+#include "mcc_concepts.h"
+
+namespace mcc::impl
+{
+
+typedef std::error_code MccError;  // library-wide definition of operational error
+
+}  // namespace mcc::impl
+
+template <>
+struct std::formatter<mcc::impl::MccError, char> {
+    template <class ParseContext>
+    constexpr ParseContext::iterator parse(ParseContext& ctx)
+    {
+        auto it = ctx.begin();
+        if (it == ctx.end()) {
+            return it;
+        }
+
+        _currFmt.clear();
+        _delim = " ";
+
+        for (; it != ctx.end(); ++it) {
+            switch (*it) {
+                case '#':  // numerical error value
+                    _currFmt.push_back(*it);
+                    break;
+                case '@':  // error category name
+                    _currFmt.push_back(*it);
+                    break;
+                case '^':  // error message
+                    _currFmt.push_back(*it);
+                    break;
+                case '_':
+                    // while (it++ != ctx.end() || it++ != '}' || it++ != '_') {
+                    //     _currFmt.push_back(*(++it));
+                    // }
+
+                    if (it++ != ctx.end() || it++ != '}') {
+                        _delim = *(++it);
+                    }
+                case '}':
+                    if (_currFmt.empty()) {
+                        _currFmt = "#@^";
+                    }
+                    return it;
+                default:
+                    break;
+            }
+        }
+
+        return it;
+    }
+
+    template <class FmtContext>
+    FmtContext::iterator format(mcc::impl::MccError const& err, FmtContext& ctx) const
+    {
+        std::ostringstream out;
+
+        size_t idx = 0;
+        for (auto const& fmt_sym : _currFmt) {
+            switch (fmt_sym) {
+                case '#':
+                    out << err.value();
+                    ++idx;
+                    break;
+                case '@':
+                    out << err.category().name();
+                    ++idx;
+                    break;
+                case '^':
+                    out << err.message();
+                    ++idx;
+                    break;
+                default:
+                    break;
+            }
+            if (idx < _currFmt.size()) {
+                out << _delim;
+            }
+        }
+
+        return std::ranges::copy(std::move(out).str(), ctx.out()).out;
+    }
+
+private:
+    std::string _currFmt{}, _delim{" "};
+};
+
+
+static_assert(mcc::mcc_error_c<mcc::impl::MccError>, "");
+
+
+// a helper formatter impelementation
+
+template <typename T>
+    requires std::is_enum_v<T>
+struct std::formatter<T, char> : std::formatter<std::underlying_type_t<T>, char> {
+    auto format(T e, auto& ctx) const
+    {
+        return formatter<std::underlying_type_t<T>>::format(std::underlying_type_t<T>(e), ctx);
+    }
+};
+
+enum class EE : int { A, B, C };
+
+static_assert(mcc::mcc_error_c<EE>, "");