Cut the pork into bite-sized cubes. Mix the rice wine and soy sauce in a large bowl, add the pork and toss well.
Mix the egg with the flour in a bowl.
Slice the peppers and spring onion into thin strips.
Drain the pineapple and cut, if necessary, into small pieces. Keep the juice.
Drain bamboo shoots, add to the pineapple.
Put the sauce ingredients in a pan, the cook for about 3 minutes until you get a thick, silky sauce. Put the lid on and set aside.
Take the pork out of the marinade, place on a plate. Dust with a little cornflour.
Heat a wok with plenty of oil over medium heat. When it begins to smoke, dip the pork cubes into the batter, then put them carefully in the hot oil. Fry them in bathes for 2-3 minutes until golden, then place them onto a plate lined with kitchen paper towels.
Heat 2 Tbsp oil in another wok. When it begins to smoke, throw in the sliced onions and peppers and stir-fry to 2 minutes. Add the bamboo shoots and pineapple then pour in the sauce. Taste, if necessary, add salt, pepper or sugar - if it is too thick, add more pineapple juice or some water.
Meanwhile put the pork cubes back into the hot oil for a couple of minutes, then transfer the sizzling pork with a slotted spoon to the the bubbling sweet-and sour sauce. Coat the pork in the sauce well then serve immediately.