import inspect
from opcode import opname
from collections import defaultdict

def get_var_name(frame):
	code = frame.f_code
	call_index = frame.f_lasti
	if opname[code.co_code[call_index]] != "CALL_FUNCTION":
		return None
	index = call_index+3
	while True:
		opc = opname[code.co_code[index]]
		if opc == "STORE_NAME" or opc == "STORE_ATTR":
			name_index = int(code.co_code[index+1])
			return code.co_names[name_index]
		elif opc == "STORE_FAST":
			name_index = int(code.co_code[index+1])
			return code.co_varnames[name_index]
		elif opc == "STORE_DEREF":
			name_index = int(code.co_code[index+1])
			return code.co_cellvars[name_index]
		elif opc == "LOAD_GLOBAL" or opc == "LOAD_ATTR" or opc == "LOAD_FAST":
			index += 3
		elif opc == "DUP_TOP":
			index += 1
		elif opc == "BUILD_LIST":
			index += 3
		else:
			return None

name_to_idx = defaultdict(int)
classname_to_objs = dict()

def index_id(l, obj):
	for n, e in enumerate(l):
		if id(e) == id(obj):
			return n
	raise ValueError

def trace_back(varname=None):
	l = []
	frame = inspect.currentframe().f_back.f_back
	while frame is not None:
		if varname is None:
			varname = get_var_name(frame)
		if varname is not None:
			l.insert(0, (varname, name_to_idx[varname]))
			name_to_idx[varname] += 1
		
		try:
			obj = frame.f_locals["self"]
		except KeyError:
			obj = None
		if hasattr(obj, "__del__"):
			obj = None
		
		if obj is None:
			if varname is not None:
				coname = frame.f_code.co_name
				if coname == "<module>":
					modules = frame.f_globals["__name__"]
					modules = modules.split(".")
					coname = modules[len(modules)-1]
				l.insert(0, (coname, -1))
		else:
			classname = obj.__class__.__name__.lower()
			try:
				objs = classname_to_objs[classname]
			except KeyError:
				classname_to_objs[classname] = [obj]
				idx = 0
			else:
				try:
					idx = index_id(objs, obj)
				except ValueError:
					idx = len(objs)
					objs.append(obj)
			l.insert(0, (classname, idx))
		
		varname = None
		frame = frame.f_back
	return l