"""Beaker utilities"""

try:
    import thread as _thread
    import threading as _threading
except ImportError:
    import dummy_thread as _thread
    import dummy_threading as _threading

from datetime import datetime, timedelta
import os
import re
import string
import types
import weakref
import warnings
import sys
import inspect

py3k = getattr(sys, 'py3kwarning', False) or sys.version_info >= (3, 0)
py24 = sys.version_info < (2,5)
jython = sys.platform.startswith('java')

if py3k or jython:
    import pickle
else:
    import cPickle as pickle

from beaker.converters import asbool
from beaker import exceptions
from threading import local as _tlocal


__all__  = ["ThreadLocal", "Registry", "WeakValuedRegistry", "SyncDict",
            "encoded_path", "verify_directory"]

def function_named(fn, name):
    """Return a function with a given __name__.

    Will assign to __name__ and return the original function if possible on
    the Python implementation, otherwise a new function will be constructed.

    """
    fn.__name__ = name
    return fn

def skip_if(predicate, reason=None):
    """Skip a test if predicate is true."""
    reason = reason or predicate.__name__

    from nose import SkipTest
    def decorate(fn):
        fn_name = fn.__name__
        def maybe(*args, **kw):
            if predicate():
                msg = "'%s' skipped: %s" % (
                    fn_name, reason)
                raise SkipTest(msg)
            else:
                return fn(*args, **kw)
        return function_named(maybe, fn_name)
    return decorate

def assert_raises(except_cls, callable_, *args, **kw):
    """Assert the given exception is raised by the given function + arguments."""

    try:
        callable_(*args, **kw)
        success = False
    except except_cls, e:
        success = True
 
    # assert outside the block so it works for AssertionError too !
    assert success, "Callable did not raise an exception"


def verify_directory(dir):
    """verifies and creates a directory.  tries to
    ignore collisions with other threads and processes."""

    tries = 0
    while not os.access(dir, os.F_OK):
        try:
            tries += 1
            os.makedirs(dir)
        except:
            if tries > 5:
                raise

def has_self_arg(func):
    """Return True if the given function has a 'self' argument."""
    args = inspect.getargspec(func)
    if args and args[0] and args[0][0] in ('self', 'cls'):
        return True
    else:
        return False


def warn(msg, stacklevel=3):
    """Issue a warning."""
    if isinstance(msg, basestring):
        warnings.warn(msg, exceptions.BeakerWarning, stacklevel=stacklevel)
    else:
        warnings.warn(msg, stacklevel=stacklevel)


def deprecated(message):
    def wrapper(fn):
        def deprecated_method(*args, **kargs):
            warnings.warn(message, DeprecationWarning, 2)
            return fn(*args, **kargs)
        # TODO: use decorator ?  functools.wrapper ?
        deprecated_method.__name__ = fn.__name__
        deprecated_method.__doc__ = "%s\n\n%s" % (message, fn.__doc__)
        return deprecated_method
    return wrapper


class ThreadLocal(object):
    """stores a value on a per-thread basis"""

    __slots__ = '_tlocal'

    def __init__(self):
        self._tlocal = _tlocal()

    def put(self, value):
        self._tlocal.value = value

    def has(self):
        return hasattr(self._tlocal, 'value')

    def get(self, default=None):
        return getattr(self._tlocal, 'value', default)

    def remove(self):
        del self._tlocal.value

class SyncDict(object):
    """
    An efficient/threadsafe singleton map algorithm, a.k.a.
    "get a value based on this key, and create if not found or not
    valid" paradigm:

        exists && isvalid ? get : create

    Designed to work with weakref dictionaries to expect items
    to asynchronously disappear from the dictionary.

    Use python 2.3.3 or greater !  a major bug was just fixed in Nov.
    2003 that was driving me nuts with garbage collection/weakrefs in
    this section.

    """
    def __init__(self):
        self.mutex = _thread.allocate_lock()
        self.dict = {}

    def get(self, key, createfunc, *args, **kwargs):
        try:
            if self.has_key(key):
                return self.dict[key]
            else:
                return self.sync_get(key, createfunc, *args, **kwargs)
        except KeyError:
            return self.sync_get(key, createfunc, *args, **kwargs)

    def sync_get(self, key, createfunc, *args, **kwargs):
        self.mutex.acquire()
        try:
            try:
                if self.has_key(key):
                    return self.dict[key]
                else:
                    return self._create(key, createfunc, *args, **kwargs)
            except KeyError:
                return self._create(key, createfunc, *args, **kwargs)
        finally:
            self.mutex.release()

    def _create(self, key, createfunc, *args, **kwargs):
        self[key] = obj = createfunc(*args, **kwargs)
        return obj

    def has_key(self, key):
        return self.dict.has_key(key)

    def __contains__(self, key):
        return self.dict.__contains__(key)
    def __getitem__(self, key):
        return self.dict.__getitem__(key)
    def __setitem__(self, key, value):
        self.dict.__setitem__(key, value)
    def __delitem__(self, key):
        return self.dict.__delitem__(key)
    def clear(self):
        self.dict.clear()


class WeakValuedRegistry(SyncDict):
    def __init__(self):
        self.mutex = _threading.RLock()
        self.dict = weakref.WeakValueDictionary()

sha1 = None
def encoded_path(root, identifiers, extension = ".enc", depth = 3,
                 digest_filenames=True):

    """Generate a unique file-accessible path from the given list of
    identifiers starting at the given root directory."""
    ident = "_".join(identifiers)

    global sha1
    if sha1 is None:
        from beaker.crypto import sha1

    if digest_filenames:
        if py3k:
            ident = sha1(ident.encode('utf-8')).hexdigest()
        else:
            ident = sha1(ident).hexdigest()

    ident = os.path.basename(ident)

    tokens = []
    for d in range(1, depth):
        tokens.append(ident[0:d])

    dir = os.path.join(root, *tokens)
    verify_directory(dir)

    return os.path.join(dir, ident + extension)


def asint(obj):
    if isinstance(obj, int):
        return obj
    elif isinstance(obj, basestring) and re.match(r'^\d+$', obj):
        return int(obj)
    else:
        raise Exception("This is not a proper int")


def verify_options(opt, types, error):
    if not isinstance(opt, types):
        if not isinstance(types, tuple):
            types = (types,)
        coerced = False
        for typ in types:
            try:
                if typ in (list, tuple):
                    opt = [x.strip() for x in opt.split(',')]
                else:
                    if typ == bool:
                        typ = asbool
                    elif typ == int:
                        typ = asint
                    elif typ in (timedelta, datetime):
                        if not isinstance(opt, typ):
                            raise Exception("%s requires a timedelta type", typ)
                    opt = typ(opt)
                coerced = True
            except:
                pass
            if coerced:
                break
        if not coerced:
            raise Exception(error)
    elif isinstance(opt, str) and not opt.strip():
        raise Exception("Empty strings are invalid for: %s" % error)
    return opt


def verify_rules(params, ruleset):
    for key, types, message in ruleset:
        if key in params:
            params[key] = verify_options(params[key], types, message)
    return params


def coerce_session_params(params):
    rules = [
        ('data_dir', (str, types.NoneType), "data_dir must be a string "
         "referring to a directory."),
        ('lock_dir', (str, types.NoneType), "lock_dir must be a string referring to a "
         "directory."),
        ('type', (str, types.NoneType), "Session type must be a string."),
        ('cookie_expires', (bool, datetime, timedelta, int), "Cookie expires was "
         "not a boolean, datetime, int, or timedelta instance."),
        ('cookie_domain', (str, types.NoneType), "Cookie domain must be a "
         "string."),
        ('id', (str,), "Session id must be a string."),
        ('key', (str,), "Session key must be a string."),
        ('secret', (str, types.NoneType), "Session secret must be a string."),
        ('validate_key', (str, types.NoneType), "Session encrypt_key must be "
         "a string."),
        ('encrypt_key', (str, types.NoneType), "Session validate_key must be "
         "a string."),
        ('secure', (bool, types.NoneType), "Session secure must be a boolean."),
        ('httponly', (bool, types.NoneType), "Session httponly must be a boolean."),
        ('timeout', (int, types.NoneType), "Session timeout must be an "
         "integer."),
        ('auto', (bool, types.NoneType), "Session is created if accessed."),
        ('webtest_varname', (str, types.NoneType), "Session varname must be "
         "a string."),
    ]
    opts = verify_rules(params, rules)
    cookie_expires = opts.get('cookie_expires')
    if cookie_expires and isinstance(cookie_expires, int) and \
       not isinstance(cookie_expires, bool):
        opts['cookie_expires'] = timedelta(seconds=cookie_expires)
    return opts


def coerce_cache_params(params):
    rules = [
        ('data_dir', (str, types.NoneType), "data_dir must be a string "
         "referring to a directory."),
        ('lock_dir', (str, types.NoneType), "lock_dir must be a string referring to a "
         "directory."),
        ('type', (str,), "Cache type must be a string."),
        ('enabled', (bool, types.NoneType), "enabled must be true/false "
         "if present."),
        ('expire', (int, types.NoneType), "expire must be an integer representing "
         "how many seconds the cache is valid for"),
        ('regions', (list, tuple, types.NoneType), "Regions must be a "
         "comma seperated list of valid regions"),
        ('key_length', (int, types.NoneType), "key_length must be an integer "
         "which indicates the longest a key can be before hashing"),
    ]
    return verify_rules(params, rules)


def parse_cache_config_options(config, include_defaults=True):
    """Parse configuration options and validate for use with the
    CacheManager"""

    # Load default cache options
    if include_defaults:
        options= dict(type='memory', data_dir=None, expire=None, 
                           log_file=None)
    else:
        options = {}
    for key, val in config.iteritems():
        if key.startswith('beaker.cache.'):
            options[key[13:]] = val
        if key.startswith('cache.'):
            options[key[6:]] = val
    coerce_cache_params(options)

    # Set cache to enabled if not turned off
    if 'enabled' not in options and include_defaults:
        options['enabled'] = True

    # Configure region dict if regions are available
    regions = options.pop('regions', None)
    if regions:
        region_configs = {}
        for region in regions:
            if not region: # ensure region name is valid
                continue
            # Setup the default cache options
            region_options = dict(data_dir=options.get('data_dir'),
                                  lock_dir=options.get('lock_dir'),
                                  type=options.get('type'),
                                  enabled=options['enabled'],
                                  expire=options.get('expire'),
                                  key_length=options.get('key_length', 250))
            region_prefix = '%s.' % region
            region_len = len(region_prefix)
            for key in options.keys():
                if key.startswith(region_prefix):
                    region_options[key[region_len:]] = options.pop(key)
            coerce_cache_params(region_options)
            region_configs[region] = region_options
        options['cache_regions'] = region_configs
    return options

def func_namespace(func):
    """Generates a unique namespace for a function"""
    kls = None
    if hasattr(func, 'im_func'):
        kls = func.im_class
        func = func.im_func

    if kls:
        return '%s.%s' % (kls.__module__, kls.__name__)
    else:
        return '%s.%s' % (func.__module__, func.__name__)
