add daitomath

@@ -50,3 +50,43 @@ composer require daito/lib:^1.0
 # or
 composer update daito/lib
 ```
+
+## Performance note (DaitoMath)
+
+`DaitoMath` uses `brick/math` for precise decimal calculations (financial-safe).
+
+- It can run without extra PHP extensions.
+- For better performance on production, enable one of:
+  - `ext-gmp` (recommended)
+  - `ext-bcmath`
+- `brick/math` will automatically use the fastest available calculator at runtime.
+
+Quick check:
+
+```bash
+php -m | grep -Ei "gmp|bcmath"
+```
+
+Install extensions if missing:
+
+```bash
+# Ubuntu / Debian
+sudo apt-get update
+sudo apt-get install -y php-gmp php-bcmath
+sudo systemctl restart php8.2-fpm || sudo systemctl restart apache2
+```
+
+```bash
+# CentOS / RHEL / Rocky / AlmaLinux
+sudo yum install -y php-gmp php-bcmath
+sudo systemctl restart php-fpm || sudo systemctl restart httpd
+```
+
+```powershell
+# Windows (php.ini)
+# 1) Open php.ini
+# 2) Enable these lines:
+extension=gmp
+extension=bcmath
+# 3) Restart web server / PHP-FPM service
+```
\ No newline at end of file

@@ -8,7 +8,12 @@
     }
   },
   "require": {
+    "brick/math": "^0.9 || ^0.10 || ^0.11 || ^0.13",
     "php": "^7.3 || ^8.0",
     "laravel/framework": "^8.0 || ^9.0 || ^10.0 || ^11.0 || ^12.0"
+  },
+  "suggest": {
+    "ext-gmp": "Faster big-number calculations",
+    "ext-bcmath": "Faster decimal calculations when GMP is unavailable"
   }
 }

@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "f0e944fbfbea5c3b7cd02a9cd33e3cea",
+    "content-hash": "0c23b9705a5fe293b678d1bbc5020207",
     "packages": [
         {
             "name": "brick/math",

+<?php
+
+namespace Daito\Lib;
+
+use Brick\Math\BigDecimal;
+use Brick\Math\Exception\DivisionByZeroException;
+use Brick\Math\RoundingMode;
+use RuntimeException;
+
+class DaitoMath
+{
+    const DEFAULT_SCALE = 12;
+
+    public static function add($left, $right, $scale = self::DEFAULT_SCALE)
+    {
+        $bigDecimal = self::toBigDecimal($left)->plus(self::toBigDecimal($right));
+
+        return self::normalize((string) $bigDecimal->toScale((int) $scale));
+    }
+
+    public static function sub($left, $right, $scale = self::DEFAULT_SCALE)
+    {
+        $bigDecimal = self::toBigDecimal($left)->minus(self::toBigDecimal($right));
+
+        return self::normalize((string) $bigDecimal->toScale((int) $scale));
+    }
+
+    public static function mul($left, $right, $scale = self::DEFAULT_SCALE)
+    {
+        $bigDecimal = self::toBigDecimal($left)->multipliedBy(self::toBigDecimal($right));
+
+        return self::normalize((string) $bigDecimal->toScale((int) $scale));
+    }
+
+    public static function div($left, $right, $scale = self::DEFAULT_SCALE)
+    {
+        $leftValue = self::toBigDecimal($left);
+        $rightValue = self::toBigDecimal($right);
+
+        if ($rightValue->isZero()) {
+            throw new RuntimeException('Can not divide by zero.');
+        }
+
+        try {
+            $bigDecimal = $leftValue->dividedBy($rightValue, (int) $scale, RoundingMode::HALF_UP);
+        } catch (DivisionByZeroException $exception) {
+            throw new RuntimeException('Can not divide by zero.');
+        }
+
+        return self::normalize((string) $bigDecimal);
+    }
+
+    public static function floor($value)
+    {
+        return (string) self::toBigDecimal($value)->toScale(0, RoundingMode::FLOOR);
+    }
+
+    public static function ceil($value)
+    {
+        return (string) self::toBigDecimal($value)->toScale(0, RoundingMode::CEILING);
+    }
+
+    public static function round($value, $scale = 0)
+    {
+        return self::normalize((string) self::toBigDecimal($value)->toScale((int) $scale, RoundingMode::HALF_UP));
+    }
+
+    public static function mulFloor($left, $right, $scale = self::DEFAULT_SCALE)
+    {
+        return self::floor(self::mul($left, $right, $scale));
+    }
+
+    private static function toBigDecimal($value)
+    {
+        if (is_int($value) || is_string($value)) {
+            return BigDecimal::of((string) $value);
+        }
+
+        if (is_float($value)) {
+            return BigDecimal::of(self::normalize(sprintf('%.14F', $value)));
+        }
+
+        throw new RuntimeException('DaitoMath only supports int, float, or numeric string.');
+    }
+
+    private static function normalize($number)
+    {
+        $number = (string) $number;
+        if (strpos($number, '.') === false) {
+            return $number;
+        }
+
+        $number = rtrim($number, '0');
+        $number = rtrim($number, '.');
+
+        if ($number === '-0') {
+            return '0';
+        }
+
+        return $number === '' ? '0' : $number;
+    }
+}