toggle.vim

" usage: \b toggles the file browser, open to the directory containing the current file

nnoremap <leader>b :call ToggleNERDTree()<Cr>

function! ToggleNERDTree()
    if !g:NERDTree.ExistsForTab() || !g:NERDTree.IsOpen()
        if <SID>WindowFileExists()
            :NERDTreeFind
        else
            let cwd = getcwd()
            execute 'NERDTree ' . cwd
        endif
    else
        :NERDTreeClose | :cclose
    endif
endfunction

function! <SID>WindowFileExists()
    let bn = getwininfo(win_getid())[0]['bufnr']
    let b = filter(getbufinfo(), 'v:val["bufnr"] == ' . bn)[0]
    return filereadable(b['name'])
endfunction