-- remove trailing whitespace
function my_remove_trailing_whitespace()
    local curpos = vim.api.nvim_win_get_cursor(0)
    vim.cmd([[keeppatterns %s/\s\+$//e]])
    vim.api.nvim_win_set_cursor(0, curpos)
end

vim.api.nvim_create_autocmd(
    { 'BufWritePre' },
    {
        pattern = {
            '*.lua', '*.cpp', '*.hpp'
        },
        callback = my_remove_trailing_whitespace
    }
)

function my_insert_modeline()
    local comment_string = vim.o.commentstring
    local space_maybe = ''
    if (string.match(comment_string, '%%s(.*)') ~= '') then
        space_maybe = ' '
    end

    local fenc = vim.o.fileencoding
    if (fenc == '') then
        fenc = 'utf-8'
    end

    local modeline_elements = {
        ' vim: set',
        ' fenc=' .. fenc,
        ' ts=' .. vim.o.tabstop,
        ' sw=' .. vim.o.shiftwidth,
        (vim.o.expandtab and ' et' or ' noet'),
        ' tw=' .. vim.o.textwidth,
        ':',
        space_maybe
    }
    local modeline = comment_string:gsub('%%s', table.concat(modeline_elements))
    modeline = modeline:gsub('  ', ' ')

    local buffer = vim.api.nvim_win_get_buf(0)
    local current = vim.api.nvim_buf_get_lines(buffer, -2, -1, true)[1]
    if (current == modeline) then
        print('modeline already exists')
    elseif (string.match(current, 'vim:')) then
        vim.api.nvim_buf_set_lines(buffer, -2, -1, true, { modeline })
        print('modeline updated')
    else
        vim.api.nvim_buf_set_lines(buffer, -1, -1, true, { '', modeline })
        print('modeline inserted')
    end
end
vim.cmd([[command! ModelineInsert lua my_insert_modeline()]])