refactor: reorganize post-configuration functions into utils module

lua/plugins/cmp.lua

@@ -57,6 +57,17 @@ return { -- cmp
     }
     luasnip.config.setup({})
 
+    local has_words_before = function()
+      unpack = unpack or table.unpack
+      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)
@@ -78,14 +89,33 @@ return { -- cmp
         ["<C-f>"] = cmp.mapping.scroll_docs(4),
         ["<C-y>"] = cmp.mapping.confirm({ select = true }),
         ["<C-Space>"] = cmp.mapping.complete({}),
-        ["<Tab>"] = cmp.mapping(function()
-          if luasnip.expand_or_locally_jumpable() then
+        ["<Tab>"] = cmp.mapping(function(fallback)
+          if cmp.visible() then
+            cmp.select_next_item()
+            -- cmp.confirm({ select = true })
+          elseif luasnip.expand_or_locally_jumpable() then
             luasnip.expand_or_jump()
+          elseif vim.snippet.active({ direction = 1 }) then
+            vim.schedule(function()
+              vim.snippet.jump(1)
+            end)
+          elseif has_words_before() then
+            cmp.complete()
+          else
+            fallback()
           end
         end, { "i", "s" }),
-        ["<S-Tab>"] = cmp.mapping(function()
-          if luasnip.locally_jumpable(-1) then
+        ["<S-Tab>"] = cmp.mapping(function(fallback)
+          if cmp.visible() then
+            cmp.select_prev_item()
+          elseif luasnip.locally_jumpable(-1) then
             luasnip.jump(-1)
+          elseif vim.snippet.active({ direction = -1 }) then
+            vim.schedule(function()
+              vim.snippet.jump(-1)
+            end)
+          else
+            fallback()
           end
         end, { "i", "s" }),
       }),
@@ -98,8 +128,10 @@ return { -- cmp
         { name = "dotenv" },
         { name = "calc" },
         { name = "conventionalcommits" },
+        { name = "nerd", priority = 9997 },
         { name = "gitmoji", priority = 9998 },
         { name = "emoji", priority = 9999 },
+        { name = "math", priority = 9999 },
       },
       formatting = {
         fields = { "abbr", "kind", "menu" },