using System;

namespace func.brainfuck
{
    public class BrainfuckBasicCommands
    {
        public static int BitShift(IVirtualMachine vm, char symbol)
        {
            switch(symbol)
            {
                case '+':
                    return (vm.Memory[vm.MemoryPointer] + 1) % 256;
                case '-':
                    return (vm.Memory[vm.MemoryPointer] + 255) % 256;
                case '>':
                    return (vm.MemoryPointer + 1) % vm.Memory.Length;
                default:
                    return (vm.MemoryPointer + vm.Memory.Length - 1) % vm.Memory.Length;
            }
        }

        public static void RegisterTo(IVirtualMachine vm, Func<int> read, Action<char> write)
        {
            var characters = "QWERTYUIOPASDFGHJKLZXCVBNMqwertyuiopasdfghjklzxcvbnm1234567890";
            vm.RegisterCommand('.', b => { write((char)b.Memory[b.MemoryPointer]); });
            vm.RegisterCommand('+', b => {b.Memory[b.MemoryPointer] = (byte)BitShift(vm, '+');});
            vm.RegisterCommand('-', b => {b.Memory[b.MemoryPointer] = (byte)BitShift(vm, '-');});
            vm.RegisterCommand(',', b => { b.Memory[b.MemoryPointer] = (byte)read(); });
            vm.RegisterCommand('>', b => { b.MemoryPointer = BitShift(vm, '>'); });
            vm.RegisterCommand('<', b => { b.MemoryPointer = BitShift(vm, '<'); });
            foreach (var item in characters)
            {
                vm.RegisterCommand(item, b => { b.Memory[b.MemoryPointer] = (byte)item; });
            }
        }
    }
}