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 feedkey = function(key, mode)
  vim.api.nvim_feedkeys(
    vim.api.nvim_replace_termcodes(key, true, true, true),
    mode,
    true
  )
end

return {
  "hrsh7th/nvim-cmp",
  config = function()
    local cmp = require("cmp")

    cmp.setup({
      snippet = {
        expand = function(args)
          vim.fn["vsnip#anonymous"](args.body)
        end,
      },
      window = {
        -- completion = cmp.config.window.bordered(),
        -- documentation = cmp.config.window.bordered(),
      },
      mapping = cmp.mapping.preset.insert({
        ["<C-b>"] = cmp.mapping.scroll_docs(-4),
        ["<C-f>"] = cmp.mapping.scroll_docs(4),
        ["<C-Space>"] = cmp.mapping.complete(),
        ["<C-e>"] = cmp.mapping.abort(),
        ["<Tab>"] = cmp.mapping(function(fallback)
          if cmp.visible() then
            cmp.select_next_item()
          elseif vim.fn["vsnip#available"](1) == 1 then
            feedkey("<Plug>(vsnip-expand-or-jump)", "")
          elseif has_words_before() then
            cmp.complete()
          else
            fallback()
          end
        end, { "i", "s" }),
        ["<S-Tab>"] = cmp.mapping(function()
          if cmp.visible() then
            cmp.select_prev_item()
          elseif vim.fn["vsnip#jumpable"](-1) == 1 then
            feedkey("<Plug>(vsnip-jump-prev)", "")
          end
        end, { "i", "s" }),
      }),
      sources = cmp.config.sources({
        { name = "nvim_lsp" },
        { name = "vsnip" },
      }, {
        { name = "buffer" },
      }),
    })
  end,
}