Titlecasing english texts because Polyglot ain't doing it

src/net/torvald/terrarum/langpack/TitlecaseConverter.kt

@@ -0,0 +1,65 @@
+package net.torvald.terrarum.langpack
+
+import java.util.*
+
+/**
+ * Created by minjaesong on 2024-02-17.
+ */
+object TitlecaseConverter {
+
+    /**
+     * @param localecode int the form of "en", "de" or "daDK" or something
+     */
+    private fun getJavaLocaleFromTerrarumLocaleCode(localecode: String): Locale {
+        val localecode = localecode.substring(0 until minOf(4, localecode.length))
+        val lang = localecode.substring(0..1)
+        val country = if (localecode.length == 4) localecode.substring(2..3) else null
+        return if (country == null) Locale(lang) else Locale(lang, country)
+    }
+
+    private val locEN = getJavaLocaleFromTerrarumLocaleCode("en")
+
+    operator fun invoke(s: String, localeCode: String): String {
+        return if (localeCode.startsWith("en")) titlecaseEn(s)
+        else if (
+            localeCode.startsWith("ja") ||
+            localeCode.startsWith("ko") ||
+            localeCode.startsWith("th") ||
+            localeCode.startsWith("zh")
+            ) passThru(s)
+        else titlecaseGeneric(s, getJavaLocaleFromTerrarumLocaleCode(localeCode))
+    }
+
+    private fun passThru(s: String) = s
+
+    private fun titlecaseGeneric(s: String, loc: Locale) = s.replaceFirstChar {
+        if (it.isLowerCase()) it.titlecase(loc)
+        else it.toString()
+    }
+
+    private val englishWordsNoCapital = hashSetOf(
+        "a", "an",
+        "the", "to", "but", "for", "or", "and", "nor", "as",
+        "amid", "mid", "anti", "at", "atop", "by", "but", "come", "in", "including", "into", "less", "like", "near",
+        "next", "of", "off", "on", "onto", "out", "over", "past", "per", "plus", "post", "pre", "pro",
+        "re", "sans", "sub", "than", "till", "until", "under", "up", "upon", "via", "with", "within", "without",
+        "except"
+    )
+
+    private fun titlecaseEn(s: String): String {
+        val ssplit = s.split(' ')
+        return ssplit.mapIndexed { index, it ->
+            if (index == 0 || index == ssplit.lastIndex) it.capitalise(locEN)
+            else if (it[0].isUpperCase()) it
+            else {
+                if (englishWordsNoCapital.contains(it)) it else it.capitalise(locEN)
+            }
+        }.joinToString(" ")
+    }
+
+    private fun String.capitalise(loc: Locale) = this.replaceFirstChar {
+        if (it.isLowerCase()) it.titlecase(loc)
+        else it.toString()
+    }
+
+}