nvim/lua/init-cmp.lua

local cmp = require 'cmp'

cmp.setup({
    window = {documentation = cmp.config.window.bordered({border = "single"})},
    formatting = {
        format = function(entry, vim_item)
            -- set a name for each source
            vim_item.menu = ({
                nvim_lsp = "[LSP]",
                path = "[Path]",
                buffer = "[Buffer]",
                ultisnips = "[UltiSnips]"
            })[entry.source.name]
            return vim_item
        end
    },
    completion = {
        keyword_length = 1,
        max_item_count = 20
        -- autocomplete = false
    },
    snippet = {expand = function(args) vim.fn["UltiSnips#Anon"](args.body) end},
    mapping = {
        ['<C-u>'] = cmp.mapping.scroll_docs(-4),
        ['<C-d>'] = cmp.mapping.scroll_docs(4),
        ["<C-n>"] = cmp.mapping({
            i = function()
                if cmp.visible() then
                    cmp.select_next_item({behavior = cmp.SelectBehavior.Insert})
                else
                    cmp.complete()
                end
            end
        })
    },
    sources = {
        {name = 'nvim_lsp', max_item_count = 8, keyword_length = 3},
        {name = 'path'},
        {name = 'buffer', keyword_length = 4, max_item_count = 20},
        {name = 'ultisnips', priority_weight = 10, keyword_length = 1}
    }
})