Swap selected block of code upward/downward?

Question

I want to write a Vim Script which can achieve the following function, which is my favorite feature in some IDE. Say I have the following example code:

I'm a line and I just stay here.
I'm another line and I also stay here.

I'm the line to be selected and swapped upward 1.    (1)
I'm the line to be selected and swapped upward 2.    (2)

Then I can move the cursor to line (1) and Vj to select both (1), (2), then now I can hold some custom key combination, say ⌘ + option + k, and I hit these combination twice, then the expected result will be:

I'm the line to be selected and swapped upward 1.    (3)
I'm the line to be selected and swapped upward 2.    (4)
I'm a line and I just stay here.
I'm another line and I also stay here.
                                                     (1)
                                                     (2)

(The idea of swap selected lines downward is similar so I skip it.)

To avoid re-invent the wheel, is there any plugin already done this feature for us? If not, what are required for me to learn to write the above function?

Answer 1

There are too many plugins to move lines of text to mention them here.

An example to exchange (move) selected lines, more or less like in tpope/vim-unimpaired:

xnoremap <expr><silent>[e printf(":move '<--%d<CR>gv", v:count1)
xnoremap <expr><silent>]e printf(":move '>+%d<CR>gv", v:count1)

So [count][e moves selection by [count] lines up, and [count]]e moves down.

Of course, you can do the same simply by selecting block and then typing :m N, where N is the number of line to put the block after.

Also, to swap two adjacent :h paragraph(s) quickly: dap}p or dap2{p. Creating a mapping that also accepts count is left as an excercise.

Answer 2

My own mappings for this purpose:

" Bubble single lines up and down
nnoremap - :.move +1<CR>
nnoremap _ :.move -2<CR>
" Bubble lines up and down in visual mode
vnoremap - :'<,'>move '>+1 \| normal! gv<CR>
vnoremap _ :'<,'>move '<-2 \| normal! gv<CR>