Commonize Char.titlecaseChar() and Char.titlecase() #KT-44369

libraries/tools/kotlin-stdlib-gen/src/generators/unicode/GenerateUnicodeData.kt

@@ -92,10 +92,8 @@ fun main(args: Array<String>) {
     fun addOneToManyMappingsGenerators(generatedDir: File, target: KotlinTarget) {
         val uppercase = OneToManyMappingsGenerator.forUppercase(generatedDir.resolve("_OneToManyUppercaseMappings.kt"), target, bmpUnicodeDataLines)
         val lowercase = OneToManyMappingsGenerator.forLowercase(generatedDir.resolve("_OneToManyLowercaseMappings.kt"), target, bmpUnicodeDataLines)
-        val titlecase = OneToManyMappingsGenerator.forTitlecase(generatedDir.resolve("_OneToManyTitlecaseMappings.kt"), target, bmpUnicodeDataLines)
         oneToManyMappingsGenerators.add(uppercase)
         oneToManyMappingsGenerators.add(lowercase)
-        oneToManyMappingsGenerators.add(titlecase)
     }
 
     var categoryTestGenerator: CharCategoryTestGenerator? = null
@@ -112,11 +110,16 @@ fun main(args: Array<String>) {
             val categoryTestFile = baseDir.resolve("libraries/stdlib/js/test/text/unicodeData/_CharCategoryTest.kt")
             categoryTestGenerator = CharCategoryTestGenerator(categoryTestFile)
 
+            val commonGeneratedDir = baseDir.resolve("libraries/stdlib/common/src/generated")
+            oneToManyMappingsGenerators.add(OneToManyMappingsGenerator.forTitlecase(commonGeneratedDir.resolve("_OneToManyTitlecaseMappings.kt"), bmpUnicodeDataLines))
+
             val jsGeneratedDir = baseDir.resolve("libraries/stdlib/js/src/generated/")
             addRangesGenerators(jsGeneratedDir, KotlinTarget.JS)
+            oneToOneMappingsGenerators.add(MappingsGenerator.forTitlecase(jsGeneratedDir.resolve("_TitlecaseMappings.kt")))
 
             val jsIrGeneratedDir = baseDir.resolve("libraries/stdlib/js-ir/src/generated/")
             addRangesGenerators(jsIrGeneratedDir, KotlinTarget.JS_IR)
+            oneToOneMappingsGenerators.add(MappingsGenerator.forTitlecase(jsIrGeneratedDir.resolve("_TitlecaseMappings.kt")))
 
             // For debugging. To see the file content
             fun downloadFile(fromUrl: String) {

libraries/tools/kotlin-stdlib-gen/src/generators/unicode/mappings/oneToMany/builders/OneToManyMappingsBuilder.kt

@@ -11,7 +11,7 @@ import generators.unicode.hexToInt
 import java.util.TreeMap
 
 internal abstract class OneToManyMappingsBuilder(bmpUnicodeDataLines: List<UnicodeDataLine>) {
-    private val bmpUnicodeDataLines = bmpUnicodeDataLines.associateBy { it.char.hexToInt() }
+    protected val bmpUnicodeDataLines = bmpUnicodeDataLines.associateBy { it.char.hexToInt() }
     private val mappings = TreeMap<Int, List<String>>()
 
     fun append(line: SpecialCasingLine) {
@@ -33,7 +33,7 @@ internal abstract class OneToManyMappingsBuilder(bmpUnicodeDataLines: List<Unico
     }
 
     private fun mapping(charCode: Int, line: SpecialCasingLine): List<String>? {
-        val mapping = line.mapping()
+        val mapping = line.mapping() ?: return null
 
         check(mapping.isNotEmpty() && mapping.all { it.isNotEmpty() })
 
@@ -53,6 +53,6 @@ internal abstract class OneToManyMappingsBuilder(bmpUnicodeDataLines: List<Unico
         return mapping
     }
 
-    abstract fun SpecialCasingLine.mapping(): List<String>
+    abstract fun SpecialCasingLine.mapping(): List<String>?
     abstract fun UnicodeDataLine.mapping(): String
 }

libraries/tools/kotlin-stdlib-gen/src/generators/unicode/mappings/oneToMany/builders/OneToManyTitlecaseMappingsBuilder.kt

@@ -7,8 +7,28 @@ package generators.unicode.mappings.oneToMany.builders
 
 import generators.unicode.SpecialCasingLine
 import generators.unicode.UnicodeDataLine
+import generators.unicode.hexToInt
 
 internal class OneToManyTitlecaseMappingsBuilder(bmpUnicodeDataLines: List<UnicodeDataLine>) : OneToManyMappingsBuilder(bmpUnicodeDataLines) {
-    override fun SpecialCasingLine.mapping(): List<String> = titlecaseMapping
+    private fun lower(char: Int): Int {
+        return bmpUnicodeDataLines[char]?.lowercaseMapping?.takeIf { it.isNotEmpty() }?.hexToInt() ?: char
+    }
+
+    override fun SpecialCasingLine.mapping(): List<String>? {
+        val title = titlecaseMapping.map { it.hexToInt().toChar() }.joinToString(separator = "")
+        val upperFirst = uppercaseMapping[0].hexToInt().toChar()
+
+        // The version of Unicode in JVM executing this code is likely different than the version of the Unicode being parsed.
+        // Thus use the Unicode data being parsed to convert chars to lowercase.
+        val lowercasedTail = uppercaseMapping.drop(1).map { lower(it.hexToInt()).toChar() }.joinToString(separator = "")
+
+        // Skip titlecase mappings that can be derived by lowercasing tail characters
+        if (title == upperFirst + lowercasedTail) {
+            return null
+        }
+
+        return titlecaseMapping
+    }
+
     override fun UnicodeDataLine.mapping(): String = titlecaseMapping
 }

libraries/tools/kotlin-stdlib-gen/src/generators/unicode/mappings/oneToMany/writers/OneToManyTitlecaseMappingsWriter.kt

@@ -5,27 +5,31 @@
 
 package generators.unicode.mappings.oneToMany.writers
 
-import generators.unicode.ranges.RangesWritingStrategy
-import generators.unicode.writeMappings
+import generators.unicode.toHexCharLiteral
 import java.io.FileWriter
 
-internal class OneToManyTitlecaseMappingsWriter(private val strategy: RangesWritingStrategy) : OneToManyMappingsWriter {
+internal class OneToManyTitlecaseMappingsWriter : OneToManyMappingsWriter {
     override fun write(mappings: Map<Int, List<String>>, writer: FileWriter) {
-        strategy.beforeWritingRanges(writer)
-        writer.writeMappings(mappings, strategy)
-        strategy.afterWritingRanges(writer)
-        writer.appendLine()
-        writer.appendLine(titlecaseImpl())
+        // We have decided to ignore GREEK EXTENDED block due to their rare usage.
+        // It also leads to decreased js code size and simplified implementation.
+        val nonGreekExtended = mappings.filterNot { it.key in 0x1f00..0x1fff }
+
+        check(nonGreekExtended.size == 1)
+        val n = nonGreekExtended.keys.single()
+        check(n == 0x0149) // LATIN SMALL LETTER N PRECEDED BY APOSTROPHE
+
+        // one-to-many titlecase equivalent of the char is "\u02BC\u004E", the same as the uppercase equivalent
+        writer.appendLine(titlecaseImpl(n.toHexCharLiteral()))
     }
 
-    private fun titlecaseImpl(): String = """
+    private fun titlecaseImpl(apostropheN: String): String = """
+        @OptIn(ExperimentalStdlibApi::class)
         internal fun Char.titlecaseImpl(): String {
-            val code = this.toInt()
-            val index = binarySearchRange(keys, code)
-            if (index >= 0 && keys[index] == code) {
-                return values[index]
+            val uppercase = uppercase()
+            if (uppercase.length > 1) {
+                return if (this == $apostropheN) uppercase else uppercase[0] + uppercase.substring(1).lowercase()
             }
-            return titlecaseCharImpl().toString()
+            return titlecaseChar().toString()
         }
     """.trimIndent()
 }

libraries/tools/kotlin-stdlib-gen/src/generators/unicode/mappings/oneToOne/writers/TitlecaseMappingsWriter.kt

@@ -22,15 +22,18 @@ internal class TitlecaseMappingsWriter : MappingsWriter {
 
         writer.append(
             """
+            @OptIn(ExperimentalStdlibApi::class)
             internal fun Char.titlecaseCharImpl(): Char {
                 val code = this.toInt()
+                // Letters repeating <Lu, Lt, Ll> sequence and code of the Lt is a multiple of 3, e.g. <DŽ, Dž, dž>
                 if (${rangeChecks(LuLtLlMappings, "code")}) {
                     return (3 * ((code + 1) / 3)).toChar()
                 }
+                // Lower case letters whose title case mapping equivalent is equal to the original letter
                 if (${rangeChecks(zeroMappings, "code")}) {
                     return this
                 }
-                return uppercaseCharImpl()
+                return uppercaseChar()
             }
             """.trimIndent()
         )