Cyrilic transliterator

-- Cyrilic <-> Latin transliterator for CC:T
-- Made by timuzkas, donated thru CC0

local Transliteration = {}
Transliteration.__index = Transliteration

local cyrillicAlphabet = {
  {"А", "а", "A", "a"}, {"Б", "б", "B", "b"}, {"В", "в", "V", "v"}, {"Г", "г", "G", "g"}, {"Д", "д", "D", "d"},
  {"Е", "е", "E", "e"}, {"Ё", "ё", "YO", "yo"}, {"Ж", "ж", "ZH", "zh"}, {"З", "з", "Z", "z"}, {"И", "и", "I", "i"},
  {"Й", "й", "Y", "y"}, {"К", "к", "K", "k"}, {"Л", "л", "L", "l"}, {"М", "м", "M", "m"}, {"Н", "н", "N", "n"},
  {"О", "о", "O", "o"}, {"П", "п", "P", "p"}, {"Р", "р", "R", "r"}, {"С", "с", "S", "s"}, {"Т", "т", "T", "t"},
  {"У", "у", "U", "u"}, {"Ф", "ф", "F", "f"}, {"Х", "х", "KH", "kh"}, {"Ц", "ц", "TS", "ts"}, {"Ч", "ч", "CH", "ch"},
  {"Ш", "ш", "SH", "sh"}, {"Щ", "щ", "SHCH", "shch"}, {"Ъ", "ъ", "", ""}, {"Ы", "ы", "Y", "y"}, {"Ь", "ь", "", ""},
  {"Э", "э", "E", "e"}, {"Ю", "ю", "YU", "yu"}, {"Я", "я", "YA", "ya"}
}

function Transliteration.new()
  local self = setmetatable({}, Transliteration)
  self.cyrillicToLatin = {}
  self.latinToCyrillic = {}
  self.isSetup = false
  return self
end

function Transliteration:setup()
  if self.isSetup then return end
  for _, pair in ipairs(cyrillicAlphabet) do
    self.cyrillicToLatin[utf8.codepoint(pair[1])] = pair[3]
    self.cyrillicToLatin[utf8.codepoint(pair[2])] = pair[4]
    if pair[3] ~= "" then
      if not self.latinToCyrillic[pair[3]] then
        self.latinToCyrillic[pair[3]] = {}
      end
      table.insert(self.latinToCyrillic[pair[3]], pair[1])
      table.insert(self.latinToCyrillic[pair[3]], pair[2])
    end
    if pair[4] ~= "" then
      if not self.latinToCyrillic[pair[4]] then
        self.latinToCyrillic[pair[4]] = {}
      end
      table.insert(self.latinToCyrillic[pair[4]], pair[1])
      table.insert(self.latinToCyrillic[pair[4]], pair[2])
    end
  end
  self.isSetup = true
end

function Transliteration:translate(str)
  if not self.isSetup then self:setup() end
  local result = ""

  local chars = {}
  for char in str:gmatch(utf8.charpattern) do
    table.insert(chars, char)
  end

  for _, char in ipairs(chars) do
    local codepoint = utf8.codepoint(char)
    local latin = self.cyrillicToLatin[codepoint]
    if latin then
      result = result .. latin
    else
      result = result .. char
    end
  end

  return result
end

function Transliteration:print(str)
  if not self.isSetup then self:setup() end
  print(self:translate(str))
end

function Transliteration:write(str, source)
  if not self.isSetup then self:setup() end
  if source and source.write then
    source:write(self:translate(str))
  else
    io.write(self:translate(str))
  end
end

function Transliteration:to_cyrilic(str)
  if not self.isSetup then self:setup() end
  local result = ""
  local i = 1
  while i <= #str do
    local found = false
    for latin, cyrillicChars in pairs(self.latinToCyrillic) do
      if str:sub(i, i + #latin - 1) == latin then
        result = result .. cyrillicChars[1]
        i = i + #latin
        found = true
        break
      end
    end
    if not found then
      result = result .. str:sub(i, i)
      i = i + 1
    end
  end
  return result
end

function Transliteration:overrideGlobal()
  if not self.isSetup then self:setup() end

  local originalPrint = _G.print
  _G.print = function(...)
    local args = {...}
    for i, arg in ipairs(args) do
      if type(arg) == "string" then
        args[i] = self:translate(arg)
      end
    end
    originalPrint(unpack(args))
  end

  if _G.term and _G.term.write then
    local originalTermWrite = _G.term.write
    _G.term.write = function(...)
      local args = {...}
      for i, arg in ipairs(args) do
        if type(arg) == "string" then
          args[i] = self:translate(arg)
        end
      end
      originalTermWrite(unpack(args))
    end
  end
end

return Transliteration