nix/nvim/config/lua/cmp-config.lua

local cmp = require('cmp')
require("luasnip.loaders.from_vscode").lazy_load()


-- Check Tab Completion
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

cmp.setup({
  snippet = {
    expand = function(args)
      require'luasnip'.lsp_expand(args.body)
    end
  },

  mapping = cmp.mapping.preset.insert({

    -- Tab Completion
    ["<Tab>"] = cmp.mapping(function(fallback)
      if cmp.visible() then
        cmp.select_next_item()
      elseif has_words_before() then
        cmp.complete()
      else
        fallback()
      end
    end, { "i", "s" }),

    -- Reverse Tab Completion
    ["<S-Tab>"] = cmp.mapping(function(fallback)
      if cmp.visible() then
        cmp.select_prev_item()
      else
        fallback()
      end
    end, { "i", "s" }),

    -- Misc Mappings
    ['<C-b>'] = cmp.mapping.scroll_docs(-4),
    ['<C-f>'] = cmp.mapping.scroll_docs(4),
    ['<C-Space>'] = cmp.mapping.complete(),
    ['<C-e>'] = cmp.mapping.abort(),
    ['<CR>'] = cmp.mapping.confirm({ select = true }),

  }),

  -- Default Sources
  sources = cmp.config.sources({
    { name = 'nvim_lsp' },
    { name = 'luasnip' },
    { name = 'path' },
    { name = 'buffer' },
  })

})

-- Completion - `/` and `?`
cmp.setup.cmdline({ '/', '?' }, {
  mapping = cmp.mapping.preset.cmdline(),
  sources = {
    { name = 'buffer' },
  }
})

-- Completion = `:`
cmp.setup.cmdline(':', {
  mapping = cmp.mapping.preset.cmdline(),
  sources = cmp.config.sources({
    { name = 'path' },
    { name = 'cmdline' },
  })
})

-- Autopairs
local cmp_autopairs = require('nvim-autopairs.completion.cmp')
cmp.event:on(
  'confirm_done',
  cmp_autopairs.on_confirm_done()
)