lvim/lua/user/cmp.lua

local has_words_before = function()
  local line, col = unpack(vim.api.nvim_win_get_cursor(0))
  return col ~= 0 and vim.api.nvim_buf_get_lines(0, line - 1, line, true)[1]:sub(col, col):match "%s" == nil
end

local function jumpable(dir)
  local luasnip_ok, luasnip = pcall(require, "luasnip")
  if not luasnip_ok then
    return false
  end

  local win_get_cursor = vim.api.nvim_win_get_cursor
  local get_current_buf = vim.api.nvim_get_current_buf

  ---sets the current buffer's luasnip to the one nearest the cursor
  ---@return boolean true if a node is found, false otherwise
  local function seek_luasnip_cursor_node()
    -- TODO(kylo252): upstream this
    -- for outdated versions of luasnip
    if not luasnip.session.current_nodes then
      return false
    end

    local node = luasnip.session.current_nodes[get_current_buf()]
    if not node then
      return false
    end

    local snippet = node.parent.snippet
    local exit_node = snippet.insert_nodes[0]

    local pos = win_get_cursor(0)
    pos[1] = pos[1] - 1

    -- exit early if we're past the exit node
    if exit_node then
      local exit_pos_end = exit_node.mark:pos_end()
      if (pos[1] > exit_pos_end[1]) or (pos[1] == exit_pos_end[1] and pos[2] > exit_pos_end[2]) then
        snippet:remove_from_jumplist()
        luasnip.session.current_nodes[get_current_buf()] = nil

        return false
      end
    end

    node = snippet.inner_first:jump_into(1, true)
    while node ~= nil and node.next ~= nil and node ~= snippet do
      local n_next = node.next
      local next_pos = n_next and n_next.mark:pos_begin()
      local candidate = n_next ~= snippet and next_pos and (pos[1] < next_pos[1])
      or (pos[1] == next_pos[1] and pos[2] < next_pos[2])

      -- Past unmarked exit node, exit early
      if n_next == nil or n_next == snippet.next then
        snippet:remove_from_jumplist()
        luasnip.session.current_nodes[get_current_buf()] = nil

        return false
      end

      if candidate then
        luasnip.session.current_nodes[get_current_buf()] = node
        return true
      end

      local ok
      ok, node = pcall(node.jump_from, node, 1, true) -- no_move until last stop
      if not ok then
        snippet:remove_from_jumplist()
        luasnip.session.current_nodes[get_current_buf()] = nil

        return false
      end
    end

    -- No candidate, but have an exit node
    if exit_node then
      -- to jump to the exit node, seek to snippet
      luasnip.session.current_nodes[get_current_buf()] = snippet
      return true
    end

    -- No exit node, exit from snippet
    snippet:remove_from_jumplist()
    luasnip.session.current_nodes[get_current_buf()] = nil
    return false
  end

  if dir == -1 then
    return luasnip.in_snippet() and luasnip.jumpable(-1)
  else
    return luasnip.in_snippet() and seek_luasnip_cursor_node() and luasnip.jumpable(1)
  end
end

local t = function(str)
  return vim.api.nvim_replace_termcodes(str, true, true, true)
end


local status_cmp_ok, cmp = pcall(require, "cmp")
if not status_cmp_ok then
  return
end
local status_luasnip_ok, luasnip = pcall(require, "luasnip")
if not status_luasnip_ok then
  return
end

local setup = {
  confirm_opts = lvim.builtin.cmp.confirm_opts,
  completion = {
    keyword_length = 1,
  },
  experimental = {
    ghost_text = false,
    native_menu = false,
  },
  formatting = {
    fields = { "kind", "abbr", "menu" },
    max_width = 0,
    kind_icons = lvim.icons.kind,
    source_names = {
      nvim_lsp = "(LSP)",
      emoji = "(Emoji)",
      path = "(Path)",
      calc = "(Calc)",
      cmp_tabnine = "(Tabnine)",
      vsnip = "(Snippet)",
      luasnip = "(Snippet)",
      ultisnips = "(Snippet)",
      latex_symbols = "(LaTeX)",
      buffer = "(Buffer)",
      tmux = "(TMUX)",
    },
    duplicates = lvim.builtin.cmp.duplicates,
    duplicates_default = 0,
    format = lvim.builtin.cmp.format,
  },
  snippet = {
    expand = function(args)
      vim.fn["UltiSnips#Anon"](args.body)
    end,
  },
  window = lvim.builtin.cmp.window,
  sources = {
    { name = "nvim_lsp" },
    { name = "path" },
    { name = "luasnip" },
    { name = "cmp_tabnine" },
    { name = "nvim_lua" },
    { name = "buffer" },
    { name = "calc" },
    { name = "emoji" },
    { name = "treesitter" },
    { name = "ultisnips" },
    { name = "latex_symbols" },
    { name = "crates" },
    { name = "tmux" },
  },
  mapping = cmp.mapping.preset.insert {
    ["<C-k>"] = cmp.mapping.select_prev_item(),
    ["<C-j>"] = cmp.mapping.select_next_item(),
    ["<Down>"] = cmp.mapping(cmp.mapping.select_next_item { behavior = cmp.SelectBehavior.Select }, { "i" }),
    ["<Up>"] = cmp.mapping(cmp.mapping.select_prev_item { behavior = cmp.SelectBehavior.Select }, { "i" }),
    ["<C-d>"] = cmp.mapping.scroll_docs(-4),
    ["<C-f>"] = cmp.mapping.scroll_docs(4),
    ["<C-y>"] = cmp.mapping {
      i = cmp.mapping.confirm { behavior = cmp.ConfirmBehavior.Replace, select = false },
      c = function(fallback)
        if cmp.visible() then
          cmp.confirm { behavior = cmp.ConfirmBehavior.Replace, select = false }
        else
          fallback()
        end
      end,
    },
    ["<Tab>"] = cmp.mapping(function(fallback)
      if cmp.visible() then
        cmp.select_next_item()
      elseif vim.fn["UltiSnips#CanJumpForwards"]() == 1 then
        vim.api.nvim_feedkeys(t("<Plug>(ultisnips_jump_forward)"), "m", true)
      elseif has_words_before() then
        fallback()
      else
        fallback()
      end
    end, { "i", "s" }),
    ["<S-Tab>"] = cmp.mapping(function(fallback)
      if cmp.visible() then
        cmp.select_prev_item()
      elseif vim.fn["UltiSnips#CanJumpBackwards"]() == 1 then
        vim.api.nvim_feedkeys(t("<Plug>(ultisnips_jump_backward)"), "m", true)
      else
        fallback()
      end
    end, { "i", "s" }),
    ["<C-Space>"] = cmp.mapping.complete(),
    ["<C-e>"] = cmp.mapping.abort(),
    ["<CR>"] = cmp.mapping(function(fallback)
      if cmp.visible() then
        local confirm_opts = vim.deepcopy(lvim.builtin.cmp.confirm_opts) -- avoid mutating the original opts below
        local is_insert_mode = function()
          return vim.api.nvim_get_mode().mode:sub(1, 1) == "i"
        end
        if is_insert_mode() then -- prevent overwriting brackets
          confirm_opts.behavior = cmp.ConfirmBehavior.Insert
        end
        if cmp.confirm(confirm_opts) then
          return -- success, exit early
        end
      end

      if jumpable(1) and luasnip.jump(1) then
        return -- success, exit early
      end
      fallback() -- if not exited early, always fallback
    end),
  },
}

require("cmp").setup(setup)