Add Russian language support

Author: kdarkhan

shared/src/main/scala/translit/Russian.scala

@@ -0,0 +1,115 @@
+package translit
+
+import translit.Helpers._
+
+object Russian extends Language {
+  val uniGrams = Map(
+    'a' -> 'а',
+    'b' -> 'б',
+    'v' -> 'в',
+    'g' -> 'г',
+    'd' -> 'д',
+    'e' -> 'е',
+    'z' -> 'з',
+    'i' -> 'и',
+    'j' -> 'й',
+    'k' -> 'к',
+    'l' -> 'л',
+    'm' -> 'м',
+    'n' -> 'н',
+    'o' -> 'о',
+    'p' -> 'п',
+    'r' -> 'р',
+    's' -> 'с',
+    't' -> 'т',
+    'u' -> 'у',
+    'f' -> 'ф',
+    'x' -> 'х',
+    'h' -> 'х',
+    'c' -> 'ц',
+    'w' -> 'щ',
+    '#' -> 'ъ',
+    'y' -> 'ы'
+  )
+
+  val biGrams = Map(
+    "jo" -> 'ё',
+    "yo" -> 'ё',
+    "zh" -> 'ж',
+    "ch" -> 'ч',
+    "sh" -> 'ш',
+    "ye" -> 'э',
+    "yu" -> 'ю',
+    "ju" -> 'ю',
+    "ya" -> 'я',
+    "ja" -> 'я'
+  )
+
+  val triGrams = Map(
+    "shh" -> 'щ'
+  )
+
+  // tried to use prefix rules but there are many exceptions in Russian language
+  // Ex.: фольклор, пальцем
+  val apostropheSuffix = Set(
+    "ya",
+    "ja",
+    "yo",
+    "jo",
+    "i",
+    "e",
+    "yu",
+    "yu",
+    "",
+  )
+
+  val apostrophePrefix = Set(
+    "b",
+    "v",
+    "d",
+    "z",
+    "k",
+    "l",
+    "m",
+    "n",
+    "p",
+    "r",
+    "c",
+    "t",
+    "sh"
+  )
+
+  /**
+    * Converts one character starting from `offset`
+    *
+    * @return (-2, c)  Replace last two characters by `c`
+    *         (-1, c)  Replace last character by `c`
+    *         ( 0, c)  Append character `c`
+    */
+  def latinToCyrillicOfs(text: String,
+                         offset: Int,
+                         apostrophes: Boolean = true): (Int, Char) = {
+    val ofs = offset + 1
+    if (ofs >= 3 &&
+        triGrams.contains(text.substring(ofs - 3, ofs).toLowerCase)) {
+      val chars = text.substring(ofs - 3, ofs)
+      val cyrillic = triGrams(chars.toLowerCase)
+      (-1, restoreCaseAll(chars, cyrillic))
+    } else if (ofs >= 2 &&
+               biGrams.contains(text.substring(ofs - 2, ofs).toLowerCase)) {
+      val chars = text.substring(ofs - 2, ofs)
+      val cyrillic = biGrams(chars.toLowerCase)
+      (-1, restoreCaseFirst(chars, cyrillic))
+    } else if (uniGrams.contains(text(ofs - 1).toLower)) {
+      val cyrillic = uniGrams(text(ofs - 1).toLower)
+      (0, if (text(ofs - 1).isUpper) cyrillic.toUpper else cyrillic)
+    } else if (text(ofs - 1) == '\'' && apostrophes && (
+                 apostrophePrefix.contains(text.slice(ofs - 3, ofs - 1)) ||
+                 apostrophePrefix.contains(text.slice(ofs - 2, ofs - 1))
+               )) {
+      if (text(ofs - 2).isUpper) (0, 'Ь') else (0, 'ь')
+    } else {
+      (0, text(ofs - 1))
+    }
+  }
+}

shared/src/test/scala/translit/RussianSpec.scala

@@ -0,0 +1,54 @@
+package translit
+
+import org.scalatest.FunSuite
+
+class RussianSpec extends FunSuite {
+  val correctMapping = List(
+    "Андрей" -> "Andrej",
+    "Борис" -> "Boris",
+    "Валера" -> "Valera",
+    "гвоздь" -> "gvozd'",
+    "днище" -> "dnishhe",
+    "Емеля" -> "Emelya",
+    "ёлка" -> "yolka",
+    "ёлка" -> "jolka",
+    "железо" -> "zhelezo",
+    "зыбь" -> "zyb'",
+    "Ильин" -> "Il'in",
+    "Йемен" -> "Jemen",
+    "киянка" -> "kiyanka",
+    "лещ" -> "leshh",
+    "мышьяк" -> "mysh'yak",
+    "Новгород" -> "Novgorod",
+    "овраг" -> "ovrag",
+    "пьянство" -> "p'yanstvo",
+    "роща" -> "roshha",
+    "съел" -> "s#el",
+    "тележка" -> "telezhka",
+    "ухват" -> "uxvat",
+    "ухват" -> "uhvat",
+    "фольклор" -> "fol'klor",
+    "халтура" -> "haltura",
+    "цвет" -> "cvet",
+    "червь" -> "cherv'",
+    "швея" -> "shveya",
+    "щавель" -> "shhavel'",
+    "электровоз" -> "yelektrovoz",
+    "юла" -> "yula",
+    "ягненок" -> "yagnenok",
+  )
+
+  def removeApostropheAndSoftSign(str: String): String =
+    str
+      .replaceAll("ь", "")
+      .replaceAll("'", "")
+
+  correctMapping.foreach {
+    case (cyrillic, latin) =>
+      test(s"$latin -> $cyrillic") {
+        assert(
+          Russian.latinToCyrillic(latin) ==
+            cyrillic)
+      }
+  }
+}