From 4789f36e0beb2aaa1649eb700d14a199259c9171 Mon Sep 17 00:00:00 2001
From: atymic <atymicq@gmail.com>
Date: Wed, 14 Jul 2021 12:50:41 +1000
Subject: [PATCH] feat: truncate to length + tests

---
 src/SmsLength.php       | 98 +++++++++++++++++++++++++++++++++++++++++
 tests/SmsLengthTest.php | 59 +++++++++++++++++++++++++
 2 files changed, 157 insertions(+)

diff --git a/src/SmsLength.php b/src/SmsLength.php
index 93da5a1..f15024d 100644
--- a/src/SmsLength.php
+++ b/src/SmsLength.php
@@ -82,11 +82,19 @@ class SmsLength
      */
     private $messageCount;
 
+    /**
+     * @var string
+     */
+    private $messageContent;
+
     /**
      * @param string $messageContent SMS message content (UTF-8)
+     *
+     * @throws InvalidArgumentException
      */
     public function __construct(string $messageContent)
     {
+        $this->messageContent = $messageContent;
         $this->inspect($messageContent);
     }
 
@@ -116,6 +124,16 @@ public function getMessageCount(): int
         return $this->messageCount;
     }
 
+    /**
+     * Get number of message content
+     *
+     * @return string
+     */
+    public function getMessageContent()
+    {
+        return $this->messageContent;
+    }
+
     /**
      * Get upper breakpoint for the current message count
      */
@@ -147,6 +165,86 @@ public function validate(): bool
         return true;
     }
 
+    /**
+     * Return a new instance with the message truncated to a set part count
+     *
+     * @param int $parts
+     *
+     * @return self
+     */
+    public function truncate($parts)
+    {
+        if ($this->messageCount <= $parts) {
+            return $this;
+        }
+
+        if ($this->encoding === '7-bit') {
+            return new self($this->truncate7Bit($this->messageContent, $parts));
+        }
+
+        return new self($this->truncateUcs2($this->messageContent, $parts));
+    }
+
+    private function truncate7Bit($message, $parts)
+    {
+        $size = 0;
+        $newMessage = '';
+
+        $mbLength = mb_strlen($message, 'UTF-8');
+
+        for ($i = 0; $i < $mbLength; $i++) {
+            $char = mb_substr($message, $i, 1, 'UTF-8');
+
+            if (in_array($char, self::GSM0338_BASIC)) {
+                $charSize = 1;
+            } elseif (in_array($char, self::GSM0338_EXTENDED)) {
+                $charSize = 2;
+            } else {
+                continue;
+            }
+
+            if ($parts === 1 && $size + $charSize > self::MAXIMUM_CHARACTERS_7BIT_SINGLE) {
+                return $newMessage;
+            }
+
+            if ($parts > 1 && $size + $charSize > $parts * self::MAXIMUM_CHARACTERS_7BIT_CONCATENATED) {
+                return $newMessage;
+            }
+
+            $size += $charSize;
+            $newMessage .= $char;
+        }
+
+        return $newMessage;
+    }
+
+    private function truncateUcs2($message, $parts)
+    {
+        $size = 0;
+        $newMessage = '';
+
+        $mbLength = mb_strlen($message, 'UTF-8');
+
+        for ($i = 0; $i < $mbLength; $i++) {
+            $char = mb_substr($message, $i, 1, 'UTF-8');
+            $utf16Hex = bin2hex(mb_convert_encoding($char, 'UTF-16', 'UTF-8'));
+            $charSize = strlen($utf16Hex) / 4;
+
+            if ($parts === 1 && $size + $charSize > self::MAXIMUM_CHARACTERS_UCS2_SINGLE) {
+                return $newMessage;
+            }
+
+            if ($parts > 1 && $size + $charSize >= $parts *  self::MAXIMUM_CHARACTERS_UCS2_CONCATENATED) {
+                return $newMessage;
+            }
+
+            $size += $charSize;
+            $newMessage .= $char;
+        }
+
+        return $newMessage;
+    }
+
     /**
      * Parse content to discover size characteristics
      */
diff --git a/tests/SmsLengthTest.php b/tests/SmsLengthTest.php
index 011bf83..1fc542a 100644
--- a/tests/SmsLengthTest.php
+++ b/tests/SmsLengthTest.php
@@ -133,4 +133,63 @@ public function providerTooLarge(): array
             'ucs-2' => [str_repeat("simple msg plus \xf0\x9f\x93\xb1", 950), 'ucs-2', 17100, 256, 17152],
         ];
     }
+
+    /**
+     * @dataProvider providerTruncate
+     */
+    public function testTruncate($content, $parts, $expected)
+    {
+        $original = new SmsLength($content);
+
+        $new = $original->truncate($parts);
+
+        $this->assertSame($parts, $new->getMessageCount());
+        $this->assertSame($expected, $new->getMessageContent());
+    }
+
+    public function providerTruncate()
+    {
+        return [
+            'message under one part' => [
+                'message' => 'La La La',
+                'parts' => 1,
+                'expected' => 'La La La',
+            ],
+            'message over one part, gsm7' => [
+                'message' => str_repeat('abcd', 45),
+                'parts' => 1,
+                'expected' => str_repeat('abcd', 40),
+            ],
+            'message over two part, gsm7' => [
+                'message' => str_repeat('abcd', 100),
+                'parts' => 2,
+                'expected' => str_repeat('abcd', 76) . 'ab',
+            ],
+            'message over one part, gsm7 + ext' => [
+                'message' => str_repeat('abcd[', 30),
+                'parts' => 1,
+                'expected' => str_repeat('abcd[', 26) . 'abcd', // each part is 6 chars, should be 26 reps + 4 chars leftover
+            ],
+            'message over one part, uc2 1 part char' => [
+                'message' => str_repeat('•', 100),
+                'parts' => 1,
+                'expected' => str_repeat('•', 70),
+            ],
+            'message over one part, uc2 3 byte' => [
+                'message' => str_repeat('⏩', 100),
+                'parts' => 1,
+                'expected' => str_repeat('⏩', 70),
+            ],
+            'message over one part, uc2 4 byte' => [
+                'message' => str_repeat('🌐', 100),
+                'parts' => 1,
+                'expected' => str_repeat('🌐', 35),
+            ],
+            'message over two parts, uc2 4 byte' => [
+                'message' => str_repeat('🌐', 200),
+                'parts' => 2,
+                'expected' => str_repeat('🌐', 66),
+            ]
+        ];
+    }
 }