From ecdf6944a7939569faf161c704574158a94022b2 Mon Sep 17 00:00:00 2001
From: CHatingPython <chatingpython@kpgpmc.org>
Date: Fri, 7 Aug 2026 11:59:45 +0200
Subject: [PATCH] feat(furc/lexer): add integers

---
 furc/include/furc/front/token.hpp |  2 ++
 furc/src/front/lexer.cpp          | 24 +++++++++++++++++++++++-
 furc/src/main.cpp                 |  2 +-
 3 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/furc/include/furc/front/token.hpp b/furc/include/furc/front/token.hpp
index 79350e0..39382db 100644
--- a/furc/include/furc/front/token.hpp
+++ b/furc/include/furc/front/token.hpp
@@ -93,6 +93,7 @@ struct token {
         // Errors:
         UnexpectedCharacter,
         UnexpectedEOF,
+        InvalidInteger,
         EndOfFile,
     } type;
     union value {
@@ -198,6 +199,7 @@ struct token {
         case token::U64: return os << "u64";
         case token::UnexpectedCharacter: return os << "Unexpected character `" << token.value.character << "`";
         case token::UnexpectedEOF: return os << "Unexpected End Of File";
+        case token::InvalidInteger: return os << "Invalid Integer";
         case token::EndOfFile: return os << "End Of File";
         }
 
diff --git a/furc/src/front/lexer.cpp b/furc/src/front/lexer.cpp
index 6e9756c..0b11fbb 100644
--- a/furc/src/front/lexer.cpp
+++ b/furc/src/front/lexer.cpp
@@ -1,6 +1,7 @@
 #include "furc/front/lexer.hpp"
 
 #include <cctype>
+#include <limits>
 #include <string_view>
 #include <unordered_map>
 
@@ -19,7 +20,28 @@ token lexer::next_token() {
 
     auto loc = location();
 
-    if (std::isdigit(get()) != 0) {}
+    if (std::isdigit(get()) != 0) {
+        std::uint64_t value = get() - '0';
+        next();
+        while (m_cursor < m_content.size() && std::isdigit(get()) != 0) {
+            static constexpr std::uint64_t MAX        = std::numeric_limits<std::uint64_t>::max();
+            static constexpr std::uint64_t MAX_MULTS  = MAX / 10;
+            static constexpr std::uint64_t LAST_DIGIT = MAX % 10;
+
+            if (value > MAX_MULTS) {
+                return { location(), token::InvalidInteger };
+            }
+            std::uint64_t digit = get() - '0';
+            if (value == MAX_MULTS && digit > LAST_DIGIT) {
+                return { location(), token::InvalidInteger };
+            }
+
+            value *= 10;
+            value += digit;
+            next();
+        }
+        return { loc, value };
+    }
 
     if (std::isalnum(get()) != 0 || get() == '_') {
         static std::unordered_map<std::string_view, token_t> s_keywords = {
diff --git a/furc/src/main.cpp b/furc/src/main.cpp
index c2c4bd8..cb0cf8f 100644
--- a/furc/src/main.cpp
+++ b/furc/src/main.cpp
@@ -5,7 +5,7 @@
 int main(void) {
     furlang::arena arena;
 
-    furc::lexer  lexer  = { "<AK>", "func main(argc: u64) -> s32 { x: s32 = '\\\\' + 'u' - 'c' * 'd'; }" };
+    furc::lexer  lexer  = { "<AK>", "func main(argc: u64) -> s32 { x: s32 = 10 + 67 - 6 * 7; }" };
     furc::parser parser = { std::move(lexer), arena };
 
     auto program = parser.parse();