Setup cmp somewhat

.config/nvim/lua/plugins/lsp.lua

@@ -10,6 +10,48 @@ return {
     local nvim_lsp = require("lspconfig")
     local capabilities = require('cmp_nvim_lsp').default_capabilities()
 
+    local cmp = require("cmp")
+    cmp.setup({
+      expand = function ()
+        require("cmp.config").set_onetime({ sources = {} })
+      end,
+      window = {
+        completion = cmp.config.window.bordered(),
+        documentation = cmp.config.window.bordered()
+      },
+      sources = {
+        { name = "path" },
+        { name = "nvim_lsp" },
+        { name = "buffer" }
+      },
+      formatting = {
+        fields = {"menu", "abbr", "kind"},
+        format = function(entry, item)
+          local menu_icon = {
+            nvim_lsp = 'λ',
+            buffer = 'Ω',
+            path = '⊏',
+          }
+
+          item.menu = menu_icon[entry.source.name]
+          return item
+        end
+      },
+      mapping = cmp.mapping.preset.insert({
+        ["<Tab>"] = cmp.mapping(function(fallback)
+          if cmp.visible() then
+            local entry = cmp.get_selected_entry()
+            if not entry then
+              cmp.select_next_item({ behavior = cmp.SelectBehavior.Select })
+            end
+            cmp.confirm()
+          else
+            fallback()
+          end
+        end, {"i","s","c",}),
+      })
+    })
+
     nvim_lsp.lua_ls.setup({
       capabilities = capabilities,
       settings = {