From 53091a30cd6ad8b22ac31b4a571594ecf6d16f76 Mon Sep 17 00:00:00 2001
From: Andreas Tsouchlos <an.tsouchlos@gmail.com>
Date: Sun, 21 Nov 2021 18:52:07 +0100
Subject: [PATCH] Added format_arg() for integral and floating point types and
 char arrays

---
 inc/format.h | 71 ++++++++++++++++++++++++++++++++++++++--------------
 src/main.cpp |  4 +--
 2 files changed, 53 insertions(+), 22 deletions(-)

diff --git a/inc/format.h b/inc/format.h
index d65ad46..0446e90 100644
--- a/inc/format.h
+++ b/inc/format.h
@@ -11,7 +11,7 @@ namespace detail {
 template <ConstString s>
 constexpr int get_output_len() {
     constexpr auto parse_result = parse_string<s>();
-    static_assert(parse_result.is_valid, "Syntax error in log string");
+    static_assert(parse_result.is_valid, "Syntax error in format string");
 
     unsigned result = 0;
 
@@ -25,42 +25,75 @@ constexpr int get_output_len() {
     return result;
 }
 
-template <typename T, fmt_node_t fmt_node>
-constexpr bool is_valid_type() {
-    // TODO
-    return true;
-}
-
-template <fmt_node_t fmt_node, typename T>
-constexpr std::array<char, fmt_node.length> format_arg(T arg) {
-    static_assert(is_valid_type<T, fmt_node>(), "Invalid argument type");
 
+template <fmt_node_t fmt_node, std::integral arg_t>
+constexpr std::array<char, fmt_node.length> format_arg(arg_t arg) {
     std::array<char, fmt_node.length> result;
 
+    // TODO: See if this is possible with charconv
+    for (unsigned i = 1; i <= result.size(); ++i) {
+        result[result.size() - i] = arg % 10 + 48;
+        arg = arg / 10;
+    }
+
+    return result;
+}
+
+template <fmt_node_t fmt_node, std::floating_point arg_t>
+constexpr std::array<char, fmt_node.length> format_arg(arg_t) {
+    std::array<char, fmt_node.length> result;
+
+    // TODO: See if this is possible with charconv
     for (auto& c : result)
         c = 'f';
 
     return result;
 }
 
+template <fmt_node_t fmt_node>
+constexpr std::array<char, fmt_node.length> format_arg(const char* arg) {
+    std::array<char, fmt_node.length> result;
 
-template<auto t_ast, unsigned t_ast_i=0, unsigned t_result_i=0, typename char_array_t, typename first_arg_t, typename... other_args_t>
-constexpr char_array_t format_args(char_array_t result, first_arg_t first_arg, other_args_t... other_args) {
-    if constexpr(t_ast_i >= t_ast.size()) {
+    for (auto& c : result) {
+        if (*arg != '\0')
+            c = *(arg++);
+        else
+            c = '-';
+    }
+
+    return result;
+}
+
+template <auto t_ast, unsigned t_ast_i = 0, unsigned t_result_i = 0,
+        typename char_array_t>
+constexpr char_array_t format_args(char_array_t result) {
+    return result;
+}
+
+
+
+template <auto t_ast, unsigned t_ast_i = 0, unsigned t_result_i = 0,
+          typename char_array_t, typename first_arg_t, typename... other_args_t>
+constexpr char_array_t format_args(char_array_t result, first_arg_t first_arg,
+                                   other_args_t... other_args) {
+    if constexpr (t_ast_i >= t_ast.size()) {
         return result;
     } else {
         constexpr auto ast_node = t_ast[t_ast_i];
 
         if (ast_node.is_char()) {
             result[t_result_i] = ast_node.get_char();
-            return format_args<t_ast, t_ast_i+1, t_result_i+1>(result, first_arg, other_args...);
+            return format_args<t_ast, t_ast_i + 1, t_result_i + 1>(
+                result, first_arg, other_args...);
         } else {
-            constexpr auto fmt_node = ast_node.get_node();
-            const auto formatted_arg = format_arg<fmt_node>(first_arg);
+            constexpr auto fmt_node      = ast_node.get_node();
+            const auto     formatted_arg = format_arg<fmt_node>(first_arg);
 
-            std::copy(formatted_arg.begin(), formatted_arg.end(), result.begin()+t_result_i);
+            std::copy(formatted_arg.begin(), formatted_arg.end(),
+                      result.begin() + t_result_i);
 
-            return format_args<t_ast, t_ast_i+1, t_result_i+fmt_node.length>(result, first_arg, other_args...);
+            return format_args<t_ast, t_ast_i + 1,
+                               t_result_i + fmt_node.length>(result, other_args...);
         }
     }
 }
@@ -72,7 +105,7 @@ constexpr char_array_t format_args(char_array_t result, first_arg_t first_arg, o
 template <detail::ConstString s, typename... args_t>
 std::array<char, detail::get_output_len<s>()> format(args_t... args) {
     constexpr auto parse_result = detail::parse_string<s>();
-    static_assert(parse_result.is_valid);
+    static_assert(parse_result.is_valid, "Syntax error in format string");
 
     std::array<char, detail::get_output_len<s>()> result;
 
diff --git a/src/main.cpp b/src/main.cpp
index 7c4986b..5fb0e56 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -12,9 +12,7 @@ public:
 
 
 int main() {
-    constexpr detail::ConstString s{"Test: {:3.8f} {:02.5} {:05.2}"};
-
-    const auto formatted = format<s>(3.4, "abc", 8.98754);
+    const auto formatted = format<"Test: {:3.8f} {:5.5} {:05.2}">(3.4, "abc", 1234);
 
     for (const auto& c : formatted)
         std::cout << c;