⚡ Performance Optimization: Eliminate Repeated Regex Compilation in TextUtils

app/src/main/java/io/aatricks/novelscraper/util/TextUtils.kt

@@ -23,6 +23,37 @@ object TextUtils {
     private val SINGLE_NEWLINE_REGEX = Regex("(?<!\\n)\\n(?!\\n)")
     private val TWO_PLUS_SPACES_REGEX = Regex("[ ]{2,}")
 
+    private val EXTRACT_CHAPTER_LABEL_REGEX_1 = Regex("(?i)(?:chapter|ch|ch\\.|c)\\s*(\\d+)")
+    private val EXTRACT_CHAPTER_LABEL_REGEX_2 = Regex("[\\s:\\-—–|](\\d+)\\s*$")
+    private val EXTRACT_CHAPTER_LABEL_REGEX_3 = Regex("\\b(\\d+)\\b")
+
+    private val EXTRACT_CHAPTER_LABEL_URL_PATTERNS = listOf(
+        Regex("chapter\\s*(\\d+)", RegexOption.IGNORE_CASE),
+        Regex("ch(?:apter)?\\D*(\\d+)", RegexOption.IGNORE_CASE),
+        Regex("/(\\d+)(?:/|$)"),
+        Regex("-" + "(\\d+)(?:\\D|$)")
+    )
+
+    private val JUNK_PATTERNS = listOf(
+        Regex("(?i)^read\\s+"),
+        Regex("(?i)\\s+free\\s+online.*\$"),
+        Regex("(?i)\\s+online\\s+free.*\$"),
+        Regex("(?i)\\s*\\|\\s*.*\$"),
+        Regex("(?i)\\s+at\\s+.*\$"),
+        Regex("(?i)[\\s–—\\-:]*(MangaBat|NovelFire|MangaPark|MangaKakalot).*\$"),
+        Regex("(?i)[\\s–—\\-:]*Scan.*\$")
+    )
+
+    private val CHAPTER_MARKER_PATTERNS = listOf(
+        Regex("[–—\\-:]?\\s*(?:chapter|ch|ch\\.)\\s*\\d+.*$", RegexOption.IGNORE_CASE),
+        Regex("\\s*[–—\\-]\\s*\\d+.*$"),
+        Regex("\\s*:\\s*\\d+.*$")
+    )
+
+    private val CLEAN_SEPARATORS_START_REGEX = Regex("^[\\s–—\\-:\\|]+")
+    private val CLEAN_SEPARATORS_END_REGEX = Regex("[\\s–—\\-:\\|]+$")
+    private val CLEAN_CHAPTER_TITLE_SUBTITLE_REGEX = Regex("(?i)(?:chapter|ch|ch\\.)\\s*\\d+[\\s:\\-—–|]+(.+)")
+
     private val SENTENCE_ENDERS = setOf('.', '!', '?', '…', '"', '\'', '‘', '’', '“', '”', '»', ':', ';')
     private val CONTINUATION_WORDS = setOf(
         "of",
@@ -133,30 +164,16 @@ object TextUtils {
     }
 
     private fun removeCommonJunk(text: String): String {
-        val patterns = listOf(
-            Regex("(?i)^read\\s+"),
-            Regex("(?i)\\s+free\\s+online.*\$"),
-            Regex("(?i)\\s+online\\s+free.*\$"),
-            Regex("(?i)\\s*\\|\\s*.*\$"),
-            Regex("(?i)\\s+at\\s+.*\$"),
-            Regex("(?i)[\\s–—\\-:]*(MangaBat|NovelFire|MangaPark|MangaKakalot).*\$"),
-            Regex("(?i)[\\s–—\\-:]*Scan.*\$")
-        )
-        return patterns.fold(text) { acc, pattern -> acc.replace(pattern, "") }
+        return JUNK_PATTERNS.fold(text) { acc, pattern -> acc.replace(pattern, "") }
     }
 
     private fun removeChapterMarkers(text: String): String {
-        val patterns = listOf(
-            Regex("[–—\\-:]?\\s*(?:chapter|ch|ch\\.)\\s*\\d+.*$", RegexOption.IGNORE_CASE),
-            Regex("\\s*[–—\\-]\\s*\\d+.*$"),
-            Regex("\\s*:\\s*\\d+.*$")
-        )
-        return patterns.fold(text) { acc, pattern -> acc.replace(pattern, "").trim() }
+        return CHAPTER_MARKER_PATTERNS.fold(text) { acc, pattern -> acc.replace(pattern, "").trim() }
     }
 
     private fun cleanSeparators(text: String): String {
-        return text.replace(Regex("^[\\s–—\\-:\\|]+"), "")
-            .replace(Regex("[\\s–—\\-:\\|]+$"), "")
+        return text.replace(CLEAN_SEPARATORS_START_REGEX, "")
+            .replace(CLEAN_SEPARATORS_END_REGEX, "")
             .trim()
     }
 
@@ -166,15 +183,15 @@ object TextUtils {
     fun extractChapterLabel(title: String?): String? {
         if (title.isNullOrBlank()) return null
 
-        Regex("(?i)(?:chapter|ch|ch\\.|c)\\s*(\\d+)").find(title)?.let {
+        EXTRACT_CHAPTER_LABEL_REGEX_1.find(title)?.let {
             return "Chapter " + it.groupValues[1]
         }
 
-        Regex("[\\s:\\-—–|](\\d+)\\s*$").find(title)?.let {
+        EXTRACT_CHAPTER_LABEL_REGEX_2.find(title)?.let {
             return "Chapter " + it.groupValues[1]
         }
 
-        return Regex("\\b(\\d+)\\b").findAll(title).lastOrNull()?.let {
+        return EXTRACT_CHAPTER_LABEL_REGEX_3.findAll(title).lastOrNull()?.let {
             "Chapter " + it.groupValues[1]
         }
     }
@@ -183,13 +200,7 @@ object TextUtils {
      * Extract chapter label from URL
      */
     fun extractChapterLabelFromUrl(url: String): String? {
-        val patterns = listOf(
-            Regex("chapter\\s*(\\d+)", RegexOption.IGNORE_CASE),
-            Regex("ch(?:apter)?\\D*(\\d+)", RegexOption.IGNORE_CASE),
-            Regex("/(\\d+)(?:/|$)"),
-            Regex("-" + "(\\d+)(?:\\D|$)")
-        )
-        return patterns.firstNotNullOfOrNull { r ->
+        return EXTRACT_CHAPTER_LABEL_URL_PATTERNS.firstNotNullOfOrNull { r ->
             r.find(url)?.groupValues?.get(1)?.let { "Chapter " + it }
         }
     }
@@ -439,8 +450,7 @@ object TextUtils {
         ) {
             val label = extractChapterLabel(cleaned)
             if (label != null) {
-                val subTitleRegex = Regex("(?i)(?:chapter|ch|ch\\.)\\s*\\d+[\\s:\\-—–|]+(.+)")
-                val subTitle = subTitleRegex.find(cleaned)?.groupValues?.get(1)?.trim()
+                val subTitle = CLEAN_CHAPTER_TITLE_SUBTITLE_REGEX.find(cleaned)?.groupValues?.get(1)?.trim()
                 return if (!subTitle.isNullOrBlank() && subTitle.length > 2) (label + ": " + subTitle) else label
             }
         }

app/src/test/java/io/aatricks/novelscraper/util/TextUtilsBenchmarkTest.kt

@@ -0,0 +1,34 @@
+package io.aatricks.novelscraper.util
+
+import org.junit.Test
+import kotlin.system.measureTimeMillis
+
+class TextUtilsBenchmarkTest {
+
+    @Test
+    fun benchmarkExtractChapterLabel() {
+        val iterations = 100_000
+        val inputs = listOf(
+            "Read Chapter 233 Free Online | MangaBat",
+            "Chapter 175 - The End",
+            "The Great Mage Returns After 4000 Years: 150",
+            "Ch. 10",
+            "Just some title",
+            null,
+            ""
+        )
+
+        // Warmup
+        for (i in 0 until 1000) {
+            inputs.forEach { TextUtils.extractChapterLabel(it) }
+        }
+
+        val timeTaken = measureTimeMillis {
+            for (i in 0 until iterations) {
+                inputs.forEach { TextUtils.extractChapterLabel(it) }
+            }
+        }
+
+        println("Baseline: extractChapterLabel took ${timeTaken}ms for ${iterations * inputs.size} invocations.")
+    }
+}