Make cpp for snippet dynamic

snippets/cpp.lua

@@ -1,5 +1,48 @@
-# C++ LuaSnip Snippets
+-- C++ LuaSnip Snippets
 
 local luasnip = require('luasnip')
-
 luasnip.filetype_extend('cpp', { 'c' })
+local snip = luasnip.snippet
+local text = luasnip.text_node
+local ins = luasnip.insert_node
+local dyn = luasnip.dynamic_node
+local node = luasnip.snippet_node
+local key = require("luasnip.nodes.key_indexer").new_key
+
+local snippets = {
+
+  snip('for', {
+    text('for ('),
+    ins(1, 'auto'),
+    text(' '),
+    ins(2, 'index'),
+    text(' '),
+    ins(3, '='),
+    dyn(4, function(args)
+      local choice = args[2][1]
+      if choice == '=' then -- index based for loop
+        local var = args[1][1]
+        return node(nil, {
+          text(' '),
+          ins(1, '0'),
+          text('; ' .. var .. ' < '),
+          ins(2, 'count'),
+          text('; '),
+          ins(3, var .. '++'),
+        })
+      elseif choice == ':' then -- range based for loop
+        return node(nil, {
+          text(' '),
+          ins(1, 'container')
+        })
+      end
+      return node(nil, {})
+    end, { 2, 3 }, key('var')),
+    text({ ') {', '\t' }),
+    ins(0, ''),
+    text({ '', '}' })
+  }),
+
+}
+
+return snippets