# -*- coding: utf-8 -*-

"""
Code from http://code.activestate.com/recipes/277940-decorator-for-bindingconstants-at-compile-time/

Decorator for automatic code optimization.
If a global is known at compile time, replace it with a constant.
Fold tuples of constants into a single constant.
Fold constant attribute lookups into a single constant.

Modifications:
Add constants values from opmap constants (STORE_GLOBAL, etc.) in order to
    avoid to update globals.
Modify verbose argument which is None or use a function with one argument which
    can be bound to a print function or a logging function.
"""

from opcode import opmap, HAVE_ARGUMENT, EXTENDED_ARG

from types import FunctionType, ModuleType
try:
    from types import ClassType
except ImportError:
    ClassType = type

from b3j0f.utils.version import PY3

try:
    import __builtin__
except ImportError:
    import builtins as __builtin__

STORE_GLOBAL = opmap['STORE_GLOBAL']
LOAD_GLOBAL = opmap['LOAD_GLOBAL']
LOAD_CONST = opmap['LOAD_CONST']
LOAD_ATTR = opmap['LOAD_ATTR']
BUILD_TUPLE = opmap['BUILD_TUPLE']
JUMP_FORWARD = opmap['JUMP_FORWARD']


def _make_constants(f, builtin_only=False, stoplist=[], verbose=None):

    result = f

    try:
        co = f.__code__
    except AttributeError:
        return f        # Jython doesn't have a __code__ attribute.
    newcode = list(co.co_code) if PY3 else map(ord, co.co_code)
    newconsts = list(co.co_consts)
    names = co.co_names
    codelen = len(newcode)

    env = vars(__builtin__).copy()
    if builtin_only:
        stoplist = dict.fromkeys(stoplist)
        stoplist.update(f.__globals__)
    else:
        env.update(f.__globals__)

    # First pass converts global lookups into constants
    changed = False
    i = 0
    while i < codelen:
        opcode = newcode[i]
        if opcode in (EXTENDED_ARG, STORE_GLOBAL):
            return f    # for simplicity, only optimize common cases
        if opcode == LOAD_GLOBAL:
            oparg = newcode[i + 1] + (newcode[i + 2] << 8)
            name = co.co_names[oparg]
            if name in env and name not in stoplist:
                value = env[name]
                for pos, v in enumerate(newconsts):
                    if v is value:
                        break
                else:
                    pos = len(newconsts)
                    newconsts.append(value)
                newcode[i] = LOAD_CONST
                newcode[i + 1] = pos & 0xFF
                newcode[i + 2] = pos >> 8
                changed = True
                if verbose is not None:
                    verbose("{0} --> {1}".format(name, value))
        i += 1
        if opcode >= HAVE_ARGUMENT:
            i += 2

    # Second pass folds tuples of constants and constant attribute lookups
    i = 0
    while i < codelen:

        newtuple = []
        while newcode[i] == LOAD_CONST:
            oparg = newcode[i + 1] + (newcode[i + 2] << 8)
            newtuple.append(newconsts[oparg])
            i += 3

        opcode = newcode[i]
        if not newtuple:
            i += 1
            if opcode >= HAVE_ARGUMENT:
                i += 2
            continue

        if opcode == LOAD_ATTR:
            obj = newtuple[-1]
            oparg = newcode[i + 1] + (newcode[i + 2] << 8)
            name = names[oparg]
            try:
                value = getattr(obj, name)
            except AttributeError:
                continue
            deletions = 1

        elif opcode == BUILD_TUPLE:
            oparg = newcode[i + 1] + (newcode[i + 2] << 8)
            if oparg != len(newtuple):
                continue
            deletions = len(newtuple)
            value = tuple(newtuple)

        else:
            continue

        reljump = deletions * 3
        newcode[i - reljump] = JUMP_FORWARD
        newcode[i - reljump + 1] = (reljump - 3) & 0xFF
        newcode[i - reljump + 2] = (reljump - 3) >> 8

        n = len(newconsts)
        newconsts.append(value)
        newcode[i] = LOAD_CONST
        newcode[i + 1] = n & 0xFF
        newcode[i + 2] = n >> 8
        i += 3
        changed = True
        if verbose is not None:
            verbose("new folded constant:{0}".format(value))

    if changed:

        codestr = bytes(newcode) if PY3 else ''.join(map(chr, newcode))
        vargs = [
            co.co_argcount, co.co_nlocals, co.co_stacksize,
            co.co_flags, codestr, tuple(newconsts), co.co_names,
            co.co_varnames, co.co_filename, co.co_name,
            co.co_firstlineno, co.co_lnotab, co.co_freevars,
            co.co_cellvars
        ]
        if PY3:
            vargs.insert(1, co.co_kwonlyargcount)

        codeobj = type(co)(*vargs)
        result = type(f)(codeobj, f.__globals__, f.__name__, f.__defaults__,
                    f.__closure__)

    return result

_make_constants = _make_constants(_make_constants)  # optimize thyself!


def bind_all(mc, builtin_only=False, stoplist=[], verbose=None):
    """Recursively apply constant binding to functions in a module or class.

    Use as the last line of the module (after everything is defined, but
    before test code). In modules that need modifiable globals, set
    builtin_only to True.

    """

    def _bind_all(mc, builtin_only=False, stoplist=[], verbose=False):

        if isinstance(mc, (ModuleType, type)):
            for k, v in list(vars(mc).items()):
                if type(v) is FunctionType:
                    newv = _make_constants(v, builtin_only, stoplist, verbose)
                    setattr(mc, k, newv)
                elif isinstance(v, type):
                    _bind_all(v, builtin_only, stoplist, verbose)

    if isinstance(mc, dict):  # allow: bind_all(globals())
        for k, v in list(mc.items()):
            if type(v) is FunctionType:
                newv = _make_constants(v, builtin_only, stoplist, verbose)
                mc[k] = newv
            elif isinstance(v, type):
                _bind_all(v, builtin_only, stoplist, verbose)
    else:
        _bind_all(mc, builtin_only, stoplist, verbose)

    """
    try:
        d = vars(mc)
    except TypeError:
        return
    for k, v in d.items():
        if type(v) is FunctionType:
            newv = _make_constants(v, builtin_only, stoplist, verbose)
            setattr(mc, k, newv)
        elif type(v) in (type, ClassType):
            bind_all(v, builtin_only, stoplist, verbose)
    """


@_make_constants
def make_constants(builtin_only=False, stoplist=[], verbose=None):
    """ Return a decorator for optimizing global references.

    Replaces global references with their currently defined values.
    If not defined, the dynamic (runtime) global lookup is left undisturbed.
    If builtin_only is True, then only builtins are optimized.
    Variable names in the stoplist are also left undisturbed.
    Also, folds constant attr lookups and tuples of constants.
    If verbose is True, prints each substitution as is occurs

    """
    if type(builtin_only) == type(make_constants):
        raise ValueError("The bind_constants decorator must have arguments.")
    return lambda f: _make_constants(f, builtin_only, stoplist, verbose)
