Command to duplicate a filename and rename its class name

example.vim

" Duplicate class
command! -nargs=1 DuplicateClass :call DuplicateClass(<f-args>)
function! DuplicateClass(new_class)
    let l:original_class = expand('%:t:r')
    let l:original_extension = expand('%:e')
    let l:new_full_path = expand('%:h').'/'. a:new_class.'.'.l:original_extension

    " Copy contents of original file to new file
    execute 'silent execute "write ' .l:new_full_path.'"'
    execute 'silent execute "edit ' .l:new_full_path.'"'

    " Replace class name in new file
    let l:new_class_escaped = escape(a:new_class, '\/.*$^~[]')
    execute 'silent! %s/\vclass '.l:original_class.'/class ' . l:new_class_escaped . '/g'
endfunction