import sys
from ast_token import tokenmap
from ast_grammar import symbolmap

debug = 0

def st2ast(st):
    """Transform a concrete syntax tree into an abstract one."""
    if not isinstance(st, tuple):
        st = st.totuple()
    return sttuple2ast(st)


stmap = {}
stmap.update(tokenmap)
stmap.update(symbolmap)


##def sttuple2ast(sttuple):
##    if isinstance(sttuple, tuple):
##        fn = stmap[sttuple[0]]
##        nodes = [sttuple2ast(t) for t in sttuple[1:]]
##        if debug:
##            print >> sys.stderr, '%s(%s)' % (
##                fn.func_name, ', '.join([repr(n) for n in nodes])),
##        result = fn(*nodes)
##        if debug:
##            print >> sys.stderr, '->', repr(result)
##        return result
##    else:
##        return sttuple

def sttuple2ast(sttuple):
    # non-recursive version
    stack = [0, sttuple]
    stackpos = 1
    while stackpos:
        sttuple = stack[stackpos]
        n = len(stack) - stackpos
        if n < len(sttuple):
            result = sttuple[n]
            if isinstance(result, tuple):
                stack.append(stackpos)
                stackpos = len(stack)
        else:
            fn = stmap[sttuple[0]]
            nodes = stack[stackpos+1:]
            del stack[stackpos:]
            if debug:
                print >> sys.stderr, '%s(%s)' % (
                    fn.func_name, ', '.join([repr(n) for n in nodes])),
            result = fn(*nodes)
            if debug:
                print >> sys.stderr, '->', repr(result)
            stackpos = stack.pop()
        stack.append(result)
    assert len(stack) == 1
    return stack.pop()

def DISABLED_sttuple2ast(sttuple):
    # another non-recursive version
    previous = None
    it       = iter(sttuple)
    nodes    = [stmap[it.next()]]
    while True:
        for arg in it:
            if isinstance(arg, tuple):
                previous = previous, it, nodes
                it       = iter(arg)
                nodes    = [stmap[it.next()]]
                break
            nodes.append(arg)
        else:
            fn = nodes[0]
            if debug:
                print >> sys.stderr, '%s(%s)' % (
                    fn.func_name, ', '.join([repr(n) for n in nodes[1:]])),
            result = fn(*nodes[1:])
            if debug:
                print >> sys.stderr, '->', repr(result)
            if previous is None:
                return result
            previous, it, nodes = previous
            nodes.append(result)