From 255654b2845044bf537bee042913e4d7db9f1408 Mon Sep 17 00:00:00 2001
From: Pagwin <pgp2024@pagwin.xyz>
Date: Wed, 11 Dec 2024 16:25:58 -0500
Subject: [PATCH] negatives in addition are handled just need to do abs_sub and
 I'm done with draft

---
 integer.cpp | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/integer.cpp b/integer.cpp
index 4448de8..3b26cc6 100644
--- a/integer.cpp
+++ b/integer.cpp
@@ -95,8 +95,8 @@ public:
     }
     return false;
   }
-  friend Integer &operator+=(Integer &lhs, Integer const &rhs) {
-    // TODO: negative numbers
+
+  friend Integer &abs_add(Integer &lhs, Integer const &rhs) {
     bool overflow = false;
     for (std::size_t i = 0; i < std::min(lhs.size, rhs.size); i++) {
       if (std::numeric_limits<byte>::max() - lhs.bytes[i] <= rhs.bytes[i]) {
@@ -124,9 +124,26 @@ public:
     }
     return lhs;
   }
+  friend Integer &abs_sub(Integer &lhs, Integer const &rhs) { return lhs; }
+  friend Integer &operator+=(Integer &lhs, Integer const &rhs) {
+    // TODO: negative numbers
+    if (lhs.isNegative == rhs.isNegative) {
+      return abs_add(lhs, rhs);
+    } else {
+      if (abs_lt(rhs, lhs)) {
+        return abs_sub(lhs, rhs);
+      } else if (abs_lt(lhs, rhs)) {
+        Integer tmp = std::move(lhs);
+        lhs = rhs;
+        return abs_sub(lhs, tmp);
+      } else {
+        lhs = 0;
+        return lhs;
+      }
+    }
+  }
   friend Integer &operator-=(Integer &lhs, Integer const &rhs) {
-    todo("-=");
-    return lhs;
+    return lhs += -rhs;
   }
   friend Integer &operator*=(Integer &lhs, Integer const &rhs) {
     Integer tmp = std::move(lhs);