Help with mappings

[SingularisArt]

I'm currently using UltiSnips and Neogen. Here's what I would like to have:

Ctrl+j will first check if there's a neogen placeholder in front, if so, jump to it, if not, go to the next UltiSnip placeholder.
Ctrl+k will first check if there's a neogen placeholder previously, if so, jump to it, if not, go to the previous UltiSnip placeholder.
Tab will expand UltiSnip snippets.
Ctrl+Space will all available cmp completions.

[smabbasht]

I also wanted mappings for Ctrl+j and Ctrl+k and the snippet below worked for me, found this from nvm-cmp language specific samples ironically. It should be in the main docs I think.

local ls = require("luasnip")
vim.keymap.set({ "i", "s" }, "<C-k>", function()
	if ls.expand_or_jumpable() then
		ls.expand_or_jump()
	end
end, { silent = true })

vim.keymap.set({ "i", "s" }, "<C-j>", function()
	if ls.jumpable(-1) then
		ls.jump(-1)
	end
end, { silent = true })