From c84bf48a1caebf4aadc1f6bac81abc4f32d0deac Mon Sep 17 00:00:00 2001
From: atymic <atymicq@gmail.com>
Date: Wed, 14 Jul 2021 13:21:33 +1000
Subject: [PATCH] fix: straddle message bug

---
 src/SmsLength.php       | 35 +++++++++++++++++++++++++++++++++--
 tests/SmsLengthTest.php | 17 ++++++++++++++++-
 2 files changed, 49 insertions(+), 3 deletions(-)

diff --git a/src/SmsLength.php b/src/SmsLength.php
index b767887..04f71e0 100644
--- a/src/SmsLength.php
+++ b/src/SmsLength.php
@@ -75,6 +75,11 @@ class SmsLength
      */
     private $size;
 
+    /**
+     * @var int
+     */
+    private $padding;
+
     /**
      * @var int
      */
@@ -111,6 +116,16 @@ public function getSize()
         return $this->size;
     }
 
+    /**
+     * Get size of message padding used in the determined encoding
+     *
+     * @return int
+     */
+    public function getPadding()
+    {
+        return $this->padding;
+    }
+
     /**
      * Get number of messages that would be used to send the given content size
      *
@@ -175,12 +190,19 @@ private function inspect($messageContent)
         // Any character outside the 7-bit alphabet switches the entire encoding to UCS-2
         $this->encoding = '7-bit';
         $this->size = 0;
+        $this->padding = 0;
+
         $mbLength = mb_strlen($messageContent, 'UTF-8');
         for ($i = 0; $i < $mbLength; $i++) {
             $char = mb_substr($messageContent, $i, 1, 'UTF-8');
             if (in_array($char, self::GSM0338_BASIC)) {
                 $this->size++;
             } elseif (in_array($char, self::GSM0338_EXTENDED)) {
+                // In cases where a double counted char straddles two messages, add padding to push it to the next part
+                if (($this->size + 2) % self::MAXIMUM_CHARACTERS_7BIT_CONCATENATED === 1) {
+                    $this->padding++;
+                }
+
                 $this->size += 2;
             } else {
                 $this->encoding = 'ucs-2';
@@ -195,7 +217,14 @@ private function inspect($messageContent)
             for ($i = 0; $i < $mbLength; $i++) {
                 $char = mb_substr($messageContent, $i, 1, 'UTF-8');
                 $utf16Hex = bin2hex(mb_convert_encoding($char, 'UTF-16', 'UTF-8'));
-                $this->size += strlen($utf16Hex) / 4;
+                $charSize = strlen($utf16Hex) / 4;
+
+                // In cases where a double counted char straddles two messages, add padding to push it to the next part
+                if ($charSize > 1 && ($this->size + $charSize) % self::MAXIMUM_CHARACTERS_UCS2_CONCATENATED === 1) {
+                    $this->padding++;
+                }
+
+                $this->size += $charSize;
             }
         }
 
@@ -207,9 +236,11 @@ private function inspect($messageContent)
             $concatSize = self::MAXIMUM_CHARACTERS_UCS2_CONCATENATED;
         }
 
+        $sizeIncludingPadding = $this->size + $this->padding;
+
         $this->messageCount = 1;
         if ($this->size > $singleSize) {
-            $this->messageCount = (int)ceil($this->size / $concatSize);
+            $this->messageCount = (int)ceil($sizeIncludingPadding / $concatSize);
         }
     }
 }
diff --git a/tests/SmsLengthTest.php b/tests/SmsLengthTest.php
index c03ebd6..94794da 100644
--- a/tests/SmsLengthTest.php
+++ b/tests/SmsLengthTest.php
@@ -84,7 +84,22 @@ public function providerSize()
             [str_repeat("exact•max", 67), 'ucs-2', 603, 9, 603],
 
             // empty
-            ['', '7-bit', 0, 1, 160]
+            ['', '7-bit', 0, 1, 160],
+
+            [
+                'The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown f[x jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the lazy dog. The quick brown fox jumps over the.',
+                '7-bit',
+                306,
+                3,
+                459,
+            ],
+            [
+                str_repeat('🌐', 67),
+                'ucs-2',
+                134,
+                3,
+                201
+            ],
         ];
     }