feat: Support custom punctuation marks in TokenTextSplitter

spring-ai-commons/src/main/java/org/springframework/ai/transformer/splitter/TokenTextSplitter.java

@@ -46,6 +46,8 @@ public class TokenTextSplitter extends TextSplitter {
 
 	private static final boolean KEEP_SEPARATOR = true;
 
+	private static final List<Character> DEFAULT_PUNCTUATION_MARKS = List.of('.', '?', '!', '\n');
+
 	private final EncodingRegistry registry = Encodings.newLazyEncodingRegistry();
 
 	private final Encoding encoding = this.registry.getEncoding(EncodingType.CL100K_BASE);
@@ -64,21 +66,27 @@ public class TokenTextSplitter extends TextSplitter {
 
 	private final boolean keepSeparator;
 
+	private final List<Character> punctuationMarks;
+
 	public TokenTextSplitter() {
-		this(DEFAULT_CHUNK_SIZE, MIN_CHUNK_SIZE_CHARS, MIN_CHUNK_LENGTH_TO_EMBED, MAX_NUM_CHUNKS, KEEP_SEPARATOR);
+		this(DEFAULT_CHUNK_SIZE, MIN_CHUNK_SIZE_CHARS, MIN_CHUNK_LENGTH_TO_EMBED, MAX_NUM_CHUNKS, KEEP_SEPARATOR,
+				DEFAULT_PUNCTUATION_MARKS);
 	}
 
 	public TokenTextSplitter(boolean keepSeparator) {
-		this(DEFAULT_CHUNK_SIZE, MIN_CHUNK_SIZE_CHARS, MIN_CHUNK_LENGTH_TO_EMBED, MAX_NUM_CHUNKS, keepSeparator);
+		this(DEFAULT_CHUNK_SIZE, MIN_CHUNK_SIZE_CHARS, MIN_CHUNK_LENGTH_TO_EMBED, MAX_NUM_CHUNKS, keepSeparator,
+				DEFAULT_PUNCTUATION_MARKS);
 	}
 
 	public TokenTextSplitter(int chunkSize, int minChunkSizeChars, int minChunkLengthToEmbed, int maxNumChunks,
-			boolean keepSeparator) {
+			boolean keepSeparator, List<Character> punctuationMarks) {
 		this.chunkSize = chunkSize;
 		this.minChunkSizeChars = minChunkSizeChars;
 		this.minChunkLengthToEmbed = minChunkLengthToEmbed;
 		this.maxNumChunks = maxNumChunks;
 		this.keepSeparator = keepSeparator;
+		Assert.notEmpty(punctuationMarks, "punctuationMarks must not be empty");
+		this.punctuationMarks = punctuationMarks;
 	}
 
 	public static Builder builder() {
@@ -109,8 +117,7 @@ protected List<String> doSplit(String text, int chunkSize) {
 			}
 
 			// Find the last period or punctuation mark in the chunk
-			int lastPunctuation = Math.max(chunkText.lastIndexOf('.'), Math.max(chunkText.lastIndexOf('?'),
-					Math.max(chunkText.lastIndexOf('!'), chunkText.lastIndexOf('\n'))));
+			int lastPunctuation = getLastPunctuationIndex(chunkText);
 
 			if (lastPunctuation != -1 && lastPunctuation > this.minChunkSizeChars) {
 				// Truncate the chunk text at the punctuation mark
@@ -140,6 +147,16 @@ protected List<String> doSplit(String text, int chunkSize) {
 		return chunks;
 	}
 
+	protected int getLastPunctuationIndex(String chunkText) {
+		// find the max index of any punctuation mark
+		int maxLastPunctuation = -1;
+		for (Character punctuationMark : this.punctuationMarks) {
+			int lastPunctuation = chunkText.lastIndexOf(punctuationMark);
+			maxLastPunctuation = Math.max(maxLastPunctuation, lastPunctuation);
+		}
+		return maxLastPunctuation;
+	}
+
 	private List<Integer> getEncodedTokens(String text) {
 		Assert.notNull(text, "Text must not be null");
 		return this.encoding.encode(text).boxed();
@@ -164,6 +181,8 @@ public static final class Builder {
 
 		private boolean keepSeparator = KEEP_SEPARATOR;
 
+		private List<Character> punctuationMarks = DEFAULT_PUNCTUATION_MARKS;
+
 		private Builder() {
 		}
 
@@ -192,9 +211,14 @@ public Builder withKeepSeparator(boolean keepSeparator) {
 			return this;
 		}
 
+		public Builder withPunctuationMarks(List<Character> punctuationMarks) {
+			this.punctuationMarks = punctuationMarks;
+			return this;
+		}
+
 		public TokenTextSplitter build() {
 			return new TokenTextSplitter(this.chunkSize, this.minChunkSizeChars, this.minChunkLengthToEmbed,
-					this.maxNumChunks, this.keepSeparator);
+					this.maxNumChunks, this.keepSeparator, this.punctuationMarks);
 		}
 
 	}

spring-ai-commons/src/test/java/org/springframework/ai/transformer/splitter/TokenTextSplitterTest.java

@@ -125,4 +125,44 @@ public void testTokenTextSplitterBuilderWithAllFields() {
 		assertThat(chunks.get(2).getMetadata()).containsKeys("key2", "key3").doesNotContainKeys("key1");
 	}
 
+	@Test
+	public void testTokenTextSplitterWithCustomPunctuationMarks() {
+		var contentFormatter1 = DefaultContentFormatter.defaultConfig();
+		var contentFormatter2 = DefaultContentFormatter.defaultConfig();
+
+		assertThat(contentFormatter1).isNotSameAs(contentFormatter2);
+
+		var doc1 = new Document("Here, we set custom punctuation marks。？！. We just want to test it works or not？");
+		doc1.setContentFormatter(contentFormatter1);
+
+		var doc2 = new Document("And more, we add protected method getLastPunctuationIndex in TokenTextSplitter class！"
+				+ "The subclasses can override this method to achieve their own business logic。We just want to test it works or not？");
+		doc2.setContentFormatter(contentFormatter2);
+
+		var tokenTextSplitter = TokenTextSplitter.builder()
+			.withChunkSize(10)
+			.withMinChunkSizeChars(5)
+			.withMinChunkLengthToEmbed(3)
+			.withMaxNumChunks(50)
+			.withKeepSeparator(true)
+			.withPunctuationMarks(List.of('。', '？', '！'))
+			.build();
+
+		var chunks = tokenTextSplitter.apply(List.of(doc1, doc2));
+
+		assertThat(chunks.size()).isEqualTo(7);
+
+		// Doc 1
+		assertThat(chunks.get(0).getText()).isEqualTo("Here, we set custom punctuation marks。？！");
+		assertThat(chunks.get(1).getText()).isEqualTo(". We just want to test it works or not");
+
+		// Doc 2
+		assertThat(chunks.get(2).getText()).isEqualTo("And more, we add protected method getLastPunctuation");
+		assertThat(chunks.get(3).getText()).isEqualTo("Index in TokenTextSplitter class！");
+		assertThat(chunks.get(4).getText()).isEqualTo("The subclasses can override this method to achieve their own");
+		assertThat(chunks.get(5).getText()).isEqualTo("business logic。");
+		assertThat(chunks.get(6).getText()).isEqualTo("We just want to test it works or not？");
+
+	}
+
 }