Skip TA1 segment when checking interchange version

src/main/java/com/imsweb/x12/reader/X12Reader.java

@@ -398,20 +398,32 @@ private boolean checkVersionsAreConsistent(Separators separators, Reader reader)
         char segmentSeparator = separators.getSegment();
         char elementSeparator = separators.getElement();
         int c;
-        StringBuilder line = new StringBuilder();
-
-        while ((c = reader.read()) != -1 && c != segmentSeparator)
-            line.append((char)c);
 
-        // The version is the last element
-        // If we got to the end of the file before the end of the line, don't get the version
+        // The version is held in the last element of the GS segment. The GS segment normally
+        // immediately follows the ISA segment, but interchange-level segments such as TA1 may
+        // appear between them (a TA1 acknowledgement is sometimes included even when accepted).
+        // Skip any such segments and read up to the GS segment to find the version.
         String version = null;
-        if (c == segmentSeparator) {
-            String lineString = line.toString();
-            int versionStartPos = lineString.lastIndexOf(elementSeparator);
-            if (versionStartPos != -1)
-                version = lineString.substring(versionStartPos + 1);
+        StringBuilder line = new StringBuilder();
+        boolean foundSegment = false;
+        while ((c = reader.read()) != -1) {
+            if (c == segmentSeparator) {
+                String lineString = line.toString().trim();
+                if (lineString.startsWith("GS" + elementSeparator) || lineString.equals("GS")) {
+                    foundSegment = true;
+                    int versionStartPos = lineString.lastIndexOf(elementSeparator);
+                    if (versionStartPos != -1)
+                        version = lineString.substring(versionStartPos + 1);
+                    break;
+                }
+                line.setLength(0);
+            }
+            else
+                line.append((char)c);
         }
+        // If we never reached a GS segment (e.g. end of file), the file is not valid for a version check
+        if (!foundSegment)
+            version = null;
         reader.reset();
 
         boolean result = _TYPES.get(_type).equals(version);

src/test/java/com/imsweb/x12/reader/X12ReaderTest.java

@@ -1492,6 +1492,21 @@ void test999Accepted() throws Exception {
 
     }
 
+    @Test
+    void test999AcceptedWithTA1() throws Exception {
+        URL url = this.getClass().getResource("/837_5010/x12_999_accepted_ta1.txt");
+        assertNotNull(url);
+        X12Reader reader = new X12Reader(FileType.ANSI837_5010_X231, new File(url.getFile()));
+
+        // A TA1 segment between ISA and GS must not break the version check or parsing
+        assertTrue(reader.getFatalErrors().isEmpty());
+        List<Loop> loops = reader.getLoops();
+        assertEquals(1, loops.size());
+        Loop loop = reader.getLoops().get(0);
+        assertEquals(1, loop.getLoops().size());
+        assertEquals("R", loop.getLoop("GS_LOOP").getLoop("ST_LOOP").getLoop("HEADER").getLoop("2000").getSegment("IK5").getElement("IK501").getValue());
+    }
+
     @Test
     void test999Rejected() throws Exception {
         URL url = this.getClass().getResource("/837_5010/x12_999_rejected.txt");

src/test/resources/837_5010/x12_999_accepted_ta1.txt

@@ -0,0 +1,13 @@
+ISA*00*          *00*          *ZZ*330897513      *ZZ*YAXBCX         *241018*0307*^*00501*000000101*0*P*:~
+TA1*101*241018*0307*A*000~
+GS*FA*330897513*ABCDEF*20241018*0307*294082671*X*005010X231A1~
+ST*999*0001*005010X231A1~
+AK1*HC*101*005010X222A1~
+AK2*837*101*005010X222A1~
+IK3*CLM*289*2010*6~
+IK3*CLM*381*2010*6~
+IK5*R*5~
+AK9*R*1*1*0~
+SE*8*0001~
+GE*1*294082671~
+IEA*1*000000101~