From b2ce89eccea76255a44152c9841ac88857404525 Mon Sep 17 00:00:00 2001
From: Aranya Sen <sen.aranya@gmail.com>
Date: Mon, 28 Oct 2019 16:54:08 +0530
Subject: [PATCH] Add helper to check if message is empty

---
 README.md                       |  4 ++++
 src/HL7/Message.php             |  9 ++++++---
 src/HL7/MessageHelpersTrait.php |  9 +++++++++
 tests/MessageTest.php           | 16 ++++++++++++++++
 4 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/README.md b/README.md
index b580c9b..3311d1a 100644
--- a/README.md
+++ b/README.md
@@ -32,6 +32,10 @@ $msg->getFirstSegmentInstance('PID'); // Returns the first PID segment. Same as
 
 // Check if a segment is present in the message object
 $msg->hasSegment('PID'); // return true or false based on whether PID is present in the $msg object
+
+// Check if a message is empty
+$msg = new Message();
+$msg->isempty(); // Returns true
 ```
 
 ### Creating new messages
diff --git a/src/HL7/Message.php b/src/HL7/Message.php
index ee3418a..f1f9451 100644
--- a/src/HL7/Message.php
+++ b/src/HL7/Message.php
@@ -363,15 +363,18 @@ public function getSegments(): array
      * @param boolean $pretty Whether to use \n as separator or default (\r).
      * @return mixed String representation of HL7 message
      * @access public
+     * @throws HL7Exception
      */
     public function toString(bool $pretty = false)
     {
-        $message = '';
+        if (empty($this->segments)) {
+            throw new HL7Exception('Message contains no data. Can not convert to string');
+        }
 
         // Make sure MSH(1) and MSH(2) are ok, even if someone has changed these values
-        $msh = $this->segments[0];
-        $this->resetCtrl($msh);
+        $this->resetCtrl($this->segments[0]);
 
+        $message = '';
         foreach ($this->segments as $segment) {
             $segmentString = $this->segmentToString($segment);
             if (!$this->segmentEndingBar) {
diff --git a/src/HL7/MessageHelpersTrait.php b/src/HL7/MessageHelpersTrait.php
index 25ad354..989fd15 100644
--- a/src/HL7/MessageHelpersTrait.php
+++ b/src/HL7/MessageHelpersTrait.php
@@ -167,4 +167,13 @@ public function removeSegment(Segment $segment, bool $reIndex = false): void
         }
     }
 
+    /**
+     * Check if the message has any data
+     *
+     * @return bool
+     */
+    public function isEmpty(): bool
+    {
+        return empty($this->getSegments());
+    }
 }
diff --git a/tests/MessageTest.php b/tests/MessageTest.php
index 78d3397..8ca3d02 100644
--- a/tests/MessageTest.php
+++ b/tests/MessageTest.php
@@ -3,6 +3,7 @@
 
 namespace Aranyasen\HL7\Tests;
 
+use Aranyasen\Exceptions\HL7Exception;
 use Aranyasen\HL7\Message;
 use Aranyasen\HL7\Segment;
 use Aranyasen\HL7\Segments\MSH;
@@ -77,6 +78,14 @@ public function message_can_be_converted_to_string(): void
             'Pretty print representation of message');
     }
 
+    /** @test */
+    public function toString_method_throws_exception_when_message_empty(): void
+    {
+        $msg = new Message();
+        $this->expectException(HL7Exception::class);
+        $msg->toString();
+    }
+
     /** @test */
     public function fields_and_subfields_can_be_set_properly(): void
     {
@@ -374,4 +383,11 @@ public function first_of_the_given_segment_name_can_be_easily_obtained_using_a_h
 
         $this->assertNull($message->getFirstSegmentInstance('XXX'), 'Non existing segment should return null');
     }
+
+    /** @test */
+    public function message_can_be_verified_as_empty(): void
+    {
+        $this->assertTrue((new Message())->isEmpty());
+        $this->assertFalse((new Message("MSH|^~\&|||||||ORM^O01||P|2.3.1|"))->isEmpty());
+    }
 }