feat: add functions to retrieve character on position and byte count

lua/data/func.lua

@@ -1777,5 +1777,57 @@ function M.convert_path(path)
   end
 end
 
+function M.char_on_pos(pos)
+  pos = pos or vim.fn.getpos(".")
+  return tostring(vim.fn.getline(pos[1])):sub(pos[2], pos[2])
+end
+
+-- From: https://neovim.discourse.group/t/how-do-you-work-with-strings-with-multibyte-characters-in-lua/2437/4
+function M.char_byte_count(s, i)
+  if not s or s == "" then
+    return 1
+  end
+
+  local char = string.byte(s, i or 1)
+
+  -- Get byte count of unicode character (RFC 3629)
+  if char > 0 and char <= 127 then
+    return 1
+  elseif char >= 194 and char <= 223 then
+    return 2
+  elseif char >= 224 and char <= 239 then
+    return 3
+  elseif char >= 240 and char <= 244 then
+    return 4
+  end
+end
+
+function M.get_visual_range()
+  local sr, sc = unpack(vim.fn.getpos("v"), 2, 3)
+  local er, ec = unpack(vim.fn.getpos("."), 2, 3)
+
+  -- To correct work with non-single byte chars
+  local byte_c = M.char_byte_count(M.char_on_pos({ er, ec }))
+  ec = ec + (byte_c - 1)
+
+  local range = {}
+
+  if sr == er then
+    local cols = sc >= ec and { ec, sc } or { sc, ec }
+    range = { sr, cols[1] - 1, er, cols[2] }
+  elseif sr > er then
+    range = { er, ec - 1, sr, sc }
+  else
+    range = { sr, sc - 1, er, ec }
+  end
+
+  return range
+end
+
+function M.to_api_range(range)
+  local sr, sc, er, ec = unpack(range)
+  return sr - 1, sc, er - 1, ec
+end
+
 -- Export the module
 return M