refactor: extract _get_split_pattern into domain/split_pattern.py

- Extract unified split pattern logic to domain/split_pattern.py
- Add get_split_pattern() function with language and subtitle_mode support
- Remove duplicated logic from pyqt/conversion.py
- Update pyqt/conversion.py to use domain.split_pattern.get_split_pattern
- Add tests/test_split_pattern.py with 20 tests covering English, CJK, Spanish, French, and pattern structure

abogen/domain/split_pattern.py

@@ -0,0 +1,40 @@
+from __future__ import annotations
+
+"""Unified split pattern logic extracted from 3 copies."""
+import re
+
+
+PUNCTUATION_SENTENCE = r".!?。！？"
+PUNCTUATION_SENTENCE_COMMA = r".!?,。！？、，"
+
+
+def get_split_pattern(language: str, subtitle_mode: str) -> str:
+    """Get the appropriate split pattern based on language and subtitle mode.
+
+    Args:
+        language: Language code (a, b, e, f, etc.)
+        subtitle_mode: Subtitle mode ("Sentence", "Sentence + Comma", "Line", etc.)
+
+    Returns:
+        Split pattern string
+    """
+    # For English, always use newline splitting only
+    if language in ("a", "b"):
+        return "\n"
+
+    # Determine spacing pattern based on language
+    spacing = r"\s*" if language in ("z", "j") else r"\s+"
+
+    # For CJK languages, when subtitle mode is Disabled or Line, prefer
+    # punctuation-based splitting instead of plain newline splitting.
+    if subtitle_mode in ("Disabled", "Line") and language in ("z", "j"):
+        return rf"(?<=[{PUNCTUATION_SENTENCE}]){spacing}|\n+"
+
+    if subtitle_mode == "Line":
+        return "\n"
+    elif subtitle_mode == "Sentence":
+        return rf"(?<=[{PUNCTUATION_SENTENCE}]){spacing}|\n+"
+    elif subtitle_mode == "Sentence + Comma":
+        return rf"(?<=[{PUNCTUATION_SENTENCE_COMMA}]){spacing}|\n+"
+    else:
+        return r"\n+"

abogen/pyqt/conversion.py

@@ -14,7 +14,6 @@ from abogen.utils import (
 )
 from abogen.constants import (
     LANGUAGE_DESCRIPTIONS,
-    SAMPLE_VOICE_TEXTS,
     COLORS,
     CHAPTER_OPTIONS_COUNTDOWN,
     SUBTITLE_FORMATS,
@@ -22,11 +21,11 @@ from abogen.constants import (
     SUPPORTED_SUBTITLE_FORMATS,
 )
 from abogen.voice_formulas import get_new_voice
+from abogen.domain.split_pattern import get_split_pattern
 import abogen.hf_tracker as hf_tracker
 import static_ffmpeg
 import threading  # for efficient waiting
 import subprocess
-import platform
 
 # Configuration constants
 _USER_RESPONSE_TIMEOUT = (
@@ -43,10 +42,7 @@ from abogen.subtitle_utils import (
     get_sample_voice_text,
     sanitize_name_for_os,
     _CHAPTER_MARKER_SEARCH_PATTERN,
-    _VOICE_MARKER_PATTERN,
-    _VOICE_MARKER_SEARCH_PATTERN,
-    split_text_by_voice_markers,
-    validate_voice_name,
+    split_text_by_voice_markers
 )
 
 class CountdownDialog(QDialog):
@@ -216,40 +212,6 @@ class ConversionThread(QThread):
     PUNCTUATION_SENTENCE_COMMA = ".!?,।。！？、，"
     PUNCTUATION_COMMAS = ",，、"
 
-    def _get_split_pattern(self, lang_code, subtitle_mode):
-        """
-        Get the appropriate split pattern based on language and subtitle mode.
-
-        Args:
-            lang_code: Language code (a, b, e, f, etc.)
-            subtitle_mode: Subtitle mode ("Sentence", "Sentence + Comma", "Line", etc.)
-
-        Returns:
-            Split pattern string
-        """
-        # For English, always use newline splitting only
-        if lang_code in ["a", "b"]:
-            return "\n"
-
-        # Determine spacing pattern based on language
-        spacing_pattern = r"\s*" if lang_code in ["z", "j"] else r"\s+"
-
-        # For Chinese/Japanese, when subtitle mode is Disabled or Line, prefer
-        # punctuation-based splitting instead of plain newline splitting.
-        if subtitle_mode in ("Disabled", "Line") and lang_code in ["z", "j"]:
-            return r"(?<=[{}]){}|\n+".format(self.PUNCTUATION_SENTENCE, spacing_pattern)
-
-        if subtitle_mode == "Line":
-            return "\n"
-        elif subtitle_mode == "Sentence":
-            return r"(?<=[{}]){}|\n+".format(self.PUNCTUATION_SENTENCE, spacing_pattern)
-        elif subtitle_mode == "Sentence + Comma":
-            return r"(?<=[{}]){}|\n+".format(
-                self.PUNCTUATION_SENTENCE_COMMA, spacing_pattern
-            )
-        else:
-            return r"\n+"  # Default to line breaks
-
     def __init__(
         self,
         file_name,
@@ -298,7 +260,7 @@ class ConversionThread(QThread):
         self.silence_duration = 2.0  # Default value, will be overridden from GUI
         self.use_spacy_segmentation = True  # Default, will be overridden from GUI
         # Set split pattern based on language and subtitle mode
-        self.split_pattern = self._get_split_pattern(lang_code, subtitle_mode)
+        self.split_pattern = get_split_pattern(lang_code, subtitle_mode)
         self.voice_cache = {}  # Cache for loaded voices
 
     def load_voice_cached(self, voice_name, tts):

tests/test_split_pattern.py

@@ -0,0 +1,101 @@
+"""Tests for split pattern logic (3 identical copies in codebase)."""
+import os
+import sys
+sys.path.insert(0, os.path.abspath(os.path.join(os.path.dirname(__file__), "..")))
+
+import pytest
+
+from abogen.domain.split_pattern import get_split_pattern
+
+
+# --- English always returns \n ---
+
+class TestEnglish:
+    def test_english_sentence(self):
+        assert get_split_pattern("a", "Sentence") == "\n"
+
+    def test_english_sentence_comma(self):
+        assert get_split_pattern("a", "Sentence + Comma") == "\n"
+
+    def test_english_line(self):
+        assert get_split_pattern("a", "Line") == "\n"
+
+    def test_english_disabled(self):
+        assert get_split_pattern("a", "Disabled") == "\n"
+
+    def test_english_b(self):
+        assert get_split_pattern("b", "Sentence") == "\n"
+
+
+# --- CJK languages ---
+
+class TestCJK:
+    def test_chinese_disabled(self):
+        pattern = get_split_pattern("z", "Disabled")
+        assert pattern != "\n"
+        assert r"\n+" in pattern
+
+    def test_chinese_line(self):
+        pattern = get_split_pattern("z", "Line")
+        assert pattern != "\n"
+        assert r"\n+" in pattern
+
+    def test_chinese_sentence(self):
+        pattern = get_split_pattern("z", "Sentence")
+        assert r"\n+" in pattern
+
+    def test_chinese_sentence_comma(self):
+        pattern = get_split_pattern("z", "Sentence + Comma")
+        assert r"\n+" in pattern
+
+    def test_japanese_disabled(self):
+        pattern = get_split_pattern("j", "Disabled")
+        assert pattern != "\n"
+        assert r"\n+" in pattern
+
+    def test_japanese_sentence(self):
+        pattern = get_split_pattern("j", "Sentence")
+        assert r"\n+" in pattern
+
+
+# --- Other languages ---
+
+class TestOtherLanguages:
+    def test_spanish_sentence(self):
+        pattern = get_split_pattern("e", "Sentence")
+        assert r"\n+" in pattern
+
+    def test_spanish_line(self):
+        assert get_split_pattern("e", "Line") == "\n"
+
+    def test_spanish_disabled(self):
+        # canonical: \n+ for non-CJK Disabled
+        assert get_split_pattern("e", "Disabled") == r"\n+"
+
+    def test_french_sentence_comma(self):
+        pattern = get_split_pattern("f", "Sentence + Comma")
+        assert r"\n+" in pattern
+
+    def test_unknown_lang(self):
+        pattern = get_split_pattern("x", "Sentence")
+        assert r"\n+" in pattern
+
+
+# --- Pattern structure ---
+
+class TestPatternStructure:
+    def test_sentence_has_lookbehind(self):
+        pattern = get_split_pattern("e", "Sentence")
+        assert r"(?<=" in pattern
+
+    def test_sentence_comma_has_comma_chars(self):
+        pattern = get_split_pattern("e", "Sentence + Comma")
+        assert "," in pattern
+
+    def test_cjk_spacing_uses_star(self):
+        pattern = get_split_pattern("z", "Sentence")
+        assert r"\s*" in pattern
+
+    def test_non_cjk_spacing_uses_plus(self):
+        pattern = get_split_pattern("e", "Sentence")
+        assert r"\s+" in pattern