"""A few useful function/method decorators.

:copyright: 2006-2008 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
:contact: http://www.logilab.fr/ -- mailto:contact@logilab.fr
:license: General Public License version 2 - http://www.gnu.org/licenses
"""
__docformat__ = "restructuredtext en"

from types import MethodType
from time import clock
import sys, re

# XXX rewrite so we can use the decorator syntax when keyarg has to be specified

def cached(callableobj, keyarg=None):
    """Simple decorator to cache result of method call."""
    #print callableobj, keyarg, callableobj.func_code.co_argcount
    if callableobj.func_code.co_argcount == 1 or keyarg == 0:
        
        def cache_wrapper1(self, *args):
            cache = '_%s_cache_' % callableobj.__name__
            #print 'cache1?', cache
            try:
                return self.__dict__[cache]
            except KeyError:
                #print 'miss'
                value = callableobj(self, *args)
                setattr(self, cache, value)
                return value
        return cache_wrapper1
    
    elif keyarg:
        
        def cache_wrapper2(self, *args, **kwargs):
            cache = '_%s_cache_' % callableobj.__name__
            key = args[keyarg-1]
            #print 'cache2?', cache, self, key
            try:
                _cache = self.__dict__[cache]
            except KeyError:
                #print 'init'
                _cache = {}
                setattr(self, cache, _cache)
            try:
                return _cache[key]
            except KeyError:
                #print 'miss', self, cache, key
                _cache[key] = callableobj(self, *args, **kwargs)
            return _cache[key]
        return cache_wrapper2

    def cache_wrapper3(self, *args):
        cache = '_%s_cache_' % callableobj.__name__
        #print 'cache3?', cache, self, args
        try:
            _cache = self.__dict__[cache]
        except KeyError:
            #print 'init'
            _cache = {}
            setattr(self, cache, _cache)
        try:
            return _cache[args]
        except KeyError:
            #print 'miss'
            _cache[args] = callableobj(self, *args)
        return _cache[args]
    return cache_wrapper3

def clear_cache(obj, funcname):
    """Function to clear a cache handled by the cached decorator."""
    try:
        del obj.__dict__['_%s_cache_' % funcname]
    except KeyError:
        pass

def copy_cache(obj, funcname, cacheobj):
    """Copy cache for <funcname> from cacheobj to obj."""
    cache = '_%s_cache_' % funcname
    try:
        setattr(obj, cache, cacheobj.__dict__[cache])
    except KeyError:
        pass


class wproperty(object):
    """Simple descriptor expecting to take a modifier function as first argument
    and looking for a _<function name> to retrieve the attribute.
    """
    def __init__(self, setfunc):
        self.setfunc = setfunc
        self.attrname = '_%s' % setfunc.__name__
        
    def __set__(self, obj, value):
        self.setfunc(obj, value)
        
    def __get__(self, obj, cls):
        assert obj is not None
        return getattr(obj, self.attrname)


class classproperty(object):
    def __init__(self, get):
        self.get = get
    def __get__(self, inst, cls):
        return self.get(cls)


class iclassmethod(object):
    '''Descriptor for method which should be available as class method if called
    on the class or instance method if called on an instance.
    '''
    def __init__(self, func):
        self.func = func
    def __get__(self, instance, objtype):
        if instance is None:
            return MethodType(self.func, objtype, objtype.__class__)
        return MethodType(self.func, instance, objtype)
    def __set__(self, instance, value):
        raise AttributeError("can't set attribute")


def timed(f):
    def wrap(*args, **kwargs):
        t = clock()
        #for i in range(100):
        res = f(*args, **kwargs)
        print '%s time: %.9f' % (f.__name__, clock() - t)
        return res
    return wrap


def locked(acquire, release):
    """Decorator taking two methods to acquire/release a lock as argument,
    returning a decorator function which will call the inner method after
    having called acquire(self) et will call release(self) afterwards.
    """
    def decorator(f):
        def wrapper(self, *args, **kwargs):
            acquire(self)
            try:
                return f(self, *args, **kwargs)
            finally:
                release(self)
        return wrapper
    return decorator


def monkeypatch(klass, methodname=None):
    """Decorator extending class with the decorated function
    >>> class A:
    ...     pass
    >>> @monkeypatch(A)
    ... def meth(self):
    ...     return 12
    ...
    >>> a = A()
    >>> a.meth()
    12
    >>> @monkeypatch(A, 'foo')
    ... def meth(self):
    ...     return 12
    ...
    >>> a.foo()
    12
    """
    def decorator(func):
        setattr(klass, methodname or func.__name__, func)
        return func
    return decorator
