feat: simplify BlingFireSentenceDetector by removing external model dependency

Author: lfoppiano

grobid-core/localLibs/blingfire-java-0.2.1.jar

@@ -5,34 +5,21 @@
 import org.grobid.core.lang.SentenceDetector;
 import org.grobid.core.lang.Language;
 import org.grobid.core.utilities.OffsetPosition;
-import org.grobid.core.utilities.GrobidProperties;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.io.File;
 import java.util.ArrayList;
 import java.util.List;
 
 /**
  * Implementation of sentence segmentation via Microsoft BlingFire.
- * BlingFire's sbd.bin model is language-agnostic.
+ * Uses the built-in default model (no external sbd.bin file required).
+ * BlingFire's sentence segmentation is language-agnostic.
  */
 public class BlingFireSentenceDetector implements SentenceDetector {
     private static final Logger LOGGER = LoggerFactory.getLogger(BlingFireSentenceDetector.class);
 
-    private final BlingFire.Model model;
-
-    public BlingFireSentenceDetector() {
-        this(GrobidProperties.getGrobidHomePath() + File.separator
-            + "sentence-segmentation" + File.separator + "blingfire" + File.separator + "sbd.bin");
-    }
-
-    BlingFireSentenceDetector(String modelPath) {
-        LOGGER.info("Loading BlingFire sentence segmentation model from: " + modelPath);
-        model = new BlingFire.Model(modelPath);
-    }
-
     @Override
     public List<OffsetPosition> detect(String text) {
         return detect(text, new Language(Language.EN));
@@ -44,13 +31,30 @@ public List<OffsetPosition> detect(String text, Language lang) {
             return new ArrayList<>();
         }
 
-        List<BlingFire.TokenWithOffset> sentencesWithOffsets = model.textToSentencesWithOffsets(text);
+        String[] sentences = BlingFire.textToSentences(text);
         List<OffsetPosition> result = new ArrayList<>();
-
-        for (BlingFire.TokenWithOffset token : sentencesWithOffsets) {
-            // BlingFire returns inclusive end offset, convert to exclusive to match OffsetPosition convention
-            int end = Math.min(token.getEndOffset() + 1, text.length());
-            result.add(new OffsetPosition(token.getStartOffset(), end));
+        int pos = 0;
+
+        for (String sentence : sentences) {
+            // BlingFire's native TextToSentences includes a trailing null byte in output;
+            // the last sentence may contain a \0 character that prevents matching
+            if (!sentence.isEmpty() && sentence.charAt(sentence.length() - 1) == '\0') {
+                sentence = sentence.substring(0, sentence.length() - 1);
+            }
+            if (sentence.isEmpty()) {
+                continue;
+            }
+            int start = text.indexOf(sentence, pos);
+            if (start == -1) {
+                LOGGER.warn("Extracted sentence does not match original text - " + sentence);
+                start = pos;
+            }
+            int end = start + sentence.length();
+            if (end > text.length()) {
+                end = text.length();
+            }
+            result.add(new OffsetPosition(start, end));
+            pos = end;
         }
 
         return result;

grobid-core/src/main/java/org/grobid/core/lang/impl/BlingFireSentenceDetector.java

@@ -1,27 +1,16 @@
 package org.grobid.core.lang.impl;
 
 import org.grobid.core.utilities.OffsetPosition;
-import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
 
-import java.io.File;
 import java.util.List;
 
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.*;
 
 public class BlingFireSentenceDetectorTest {
 
-    private static BlingFireSentenceDetector detector;
-
-    @BeforeAll
-    static void setUp() {
-        // Resolve from project root (parent of grobid-core module directory)
-        File moduleDir = new File(System.getProperty("user.dir"));
-        File projectRoot = moduleDir.getName().equals("grobid-core") ? moduleDir.getParentFile() : moduleDir;
-        String modelPath = new File(projectRoot, "grobid-home/sentence-segmentation/blingfire/sbd.bin").getAbsolutePath();
-        detector = new BlingFireSentenceDetector(modelPath);
-    }
+    private final BlingFireSentenceDetector detector = new BlingFireSentenceDetector();
 
     @Test
     public void testDetect_singleSentence() {