import types
import string
import re
import math
import operator
import inspect
import os
import sys
import random
if __debug__:
    import traceback

from direct.directutil import Verify


# NOTE: ifAbsentPut has been replaced with Python's dictionary's builtin setdefault
# before:
#     ifAbsentPut(dict, key, defaultValue)
# after:
#     dict.setdefault(key, defaultValue)
# Please use setdefault instead -- Joe


def unique(L1, L2):
    """Return a list containing all items in 'L1' that are not in 'L2'"""
    L2 = dict([(k,None) for k in L2])
    return [item for item in L1 if item not in L2]

def indent(stream, numIndents, str):
    """
    Write str to stream with numIndents in front of it
    """
    # To match emacs, instead of a tab character we will use 4 spaces
    stream.write('    ' * numIndents + str)



def writeFsmTree(instance, indent = 0):
    if hasattr(instance, 'parentFSM'):
        writeFsmTree(instance.parentFSM, indent-2)
    elif hasattr(instance, 'fsm'):
        name = ''
        if hasattr(instance.fsm, 'state'):
            name = instance.fsm.state.name
        print "%s: %s"%(instance.fsm.name, name)
        



if __debug__:
    class StackTrace:
        def __init__(self, label="", start=0, limit=None):
            """
            label is a string (or anything that be be a string)
                that is printed as part of the trace back.
                This is just to make it easier to tell what the
                stack trace is referring to.
            start is an integer number of stack frames back 
                from the most recent.  (This is automatically
                bumped up by one to skip the __init__ call
                to the StackTrace).
            limit is an integer number of stack frames
                to record (or None for unlimited).
            """
            self.label = label
            self.trace = traceback.extract_stack(sys._getframe(1+start), limit=10)

        def __str__(self):
            r = "Debug stack trace of %s (back %s frames):\n"%(
                self.label, len(self.trace),)
            for i in traceback.format_list(self.trace):
                r+=i
            return r



def traceFunctionCall(frame):
    """
    return a string that shows the call frame with calling arguments.
    e.g.
    foo(x=234, y=135)
    """
    f = frame
    co = f.f_code
    dict = f.f_locals
    n = co.co_argcount
    if co.co_flags & 4: n = n+1
    if co.co_flags & 8: n = n+1
    r=f.f_code.co_name+'('
    comma=0 # formatting, whether we should type a comma.
    for i in range(n):
        name = co.co_varnames[i]
        if name=='self':
            continue
        if comma:
            r+=', '
        else:
            # ok, we skipped the first one, the rest get commas:
            comma=1
        r+=name
        r+='='
        if dict.has_key(name):
            v=str(dict[name])
            if len(v)>200:
                r+="<too big for debug>"
            else:
                r+=str(dict[name])
        else: r+="*** undefined ***"
    return r+')'

def traceParentCall():
    return traceFunctionCall(sys._getframe(2))

def printThisCall():
    print traceFunctionCall(sys._getframe(1))
    return 1 # to allow "assert printThisCall()"


def tron():
    sys.settrace(trace)
def trace(frame, event, arg):
    if event == 'line':
        pass
    elif event == 'call':
        print traceFunctionCall(sys._getframe(1))
    elif event == 'return':
        print "returning"
    elif event == 'exception':
        print "exception"
    return trace
def troff():
    sys.settrace(None)




def apropos(obj, *args):
    """
    Obsolete, use pdir
    """
    print 'Use pdir instead'

def getClassLineage(obj):
    """
    print object inheritance list
    """
    if type(obj) == types.DictionaryType:
        # Just a dictionary, return dictionary
        return [obj]
    elif type(obj) == types.InstanceType:
        # Instance, make a list with the instance and its class interitance
        return [obj] + getClassLineage(obj.__class__)
    elif type(obj) == types.ClassType:
        # Class, see what it derives from
        lineage = [obj]
        for c in obj.__bases__:
            lineage = lineage + getClassLineage(c)
        return lineage
    else:
        # Not what I'm looking for
        return []

def pdir(obj, str = None, fOverloaded = 0, width = None,
            fTruncate = 1, lineWidth = 75, wantPrivate = 0):
    # Remove redundant class entries
    uniqueLineage = []
    for l in getClassLineage(obj):
        if type(l) == types.ClassType:
            if l in uniqueLineage:
                break
        uniqueLineage.append(l)
    # Pretty print out directory info
    uniqueLineage.reverse()
    for obj in uniqueLineage:
        _pdir(obj, str, fOverloaded, width, fTruncate, lineWidth, wantPrivate)
        print

def _pdir(obj, str = None, fOverloaded = 0, width = None,
            fTruncate = 1, lineWidth = 75, wantPrivate = 0):
    """
    Print out a formatted list of members and methods of an instance or class
    """
    def printHeader(name):
        name = ' ' + name + ' '
        length = len(name)
        if length < 70:
            padBefore = int((70 - length)/2.0)
            padAfter = max(0,70 - length - padBefore)
            header = '*' * padBefore + name + '*' * padAfter
        print header
        print
    def printInstanceHeader(i, printHeader = printHeader):
        printHeader(i.__class__.__name__ + ' INSTANCE INFO')
    def printClassHeader(c, printHeader = printHeader):
        printHeader(c.__name__ + ' CLASS INFO')
    def printDictionaryHeader(d, printHeader = printHeader):
        printHeader('DICTIONARY INFO')
    # Print Header
    if type(obj) == types.InstanceType:
        printInstanceHeader(obj)
    elif type(obj) == types.ClassType:
        printClassHeader(obj)
    elif type (obj) == types.DictionaryType:
        printDictionaryHeader(obj)
    # Get dict
    if type(obj) == types.DictionaryType:
        dict = obj
    else:
        dict = obj.__dict__
    # Adjust width
    if width:
        maxWidth = width
    else:
        maxWidth = 10
    keyWidth = 0
    aproposKeys = []
    privateKeys = []
    remainingKeys = []
    for key in dict.keys():
        if not width:
            keyWidth = len(key)
        if str:
            if re.search(str, key, re.I):
                aproposKeys.append(key)
                if (not width) and (keyWidth > maxWidth):
                    maxWidth = keyWidth
        else:
            if key[:1] == '_':
                if wantPrivate:
                    privateKeys.append(key)
                    if (not width) and (keyWidth > maxWidth):
                        maxWidth = keyWidth
            else:
                remainingKeys.append(key)
                if (not width) and (keyWidth > maxWidth):
                    maxWidth = keyWidth
    # Sort appropriate keys
    if str:
        aproposKeys.sort()
    else:
        privateKeys.sort()
        remainingKeys.sort()
    # Print out results
    if wantPrivate:
        keys = aproposKeys + privateKeys + remainingKeys
    else:
        keys = aproposKeys + remainingKeys
    format = '%-' + `maxWidth` + 's'
    for key in keys:
        value = dict[key]
        if callable(value):
            strvalue = `Signature(value)`
        else:
            strvalue = `value`
        if fTruncate:
            # Cut off line (keeping at least 1 char)
            strvalue = strvalue[:max(1,lineWidth - maxWidth)]
        print (format % key)[:maxWidth] + '\t' + strvalue

# Magic numbers: These are the bit masks in func_code.co_flags that
# reveal whether or not the function has a *arg or **kw argument.
_POS_LIST = 4
_KEY_DICT = 8

def _is_variadic(function):
    return function.func_code.co_flags & _POS_LIST

def _has_keywordargs(function):
    return function.func_code.co_flags & _KEY_DICT

def _varnames(function):
    return function.func_code.co_varnames

def _getcode(f):
    """
    _getcode(f)
    This function returns the name and function object of a callable
    object.
    """
    def method_get(f):
        return f.__name__, f.im_func
    def function_get(f):
        return f.__name__, f
    def instance_get(f):
        if hasattr(f, '__call__'):
            method = f.__call__
            if (type(method) == types.MethodType):
                func = method.im_func
            else:
                func = method
            return ("%s%s" % (f.__class__.__name__, '__call__'), func)
        else:
            s = ("Instance %s of class %s does not have a __call__ method" %
                 (f, f.__class__.__name__))
            raise TypeError, s
    def class_get(f):
        if hasattr(f, '__init__'):
            return f.__name__, f.__init__.im_func
        else:
            return f.__name__, lambda: None
    codedict = { types.UnboundMethodType: method_get,
                 types.MethodType       : method_get,
                 types.FunctionType     : function_get,
                 types.InstanceType     : instance_get,
                 types.ClassType        : class_get,
                 }
    try:
        return codedict[type(f)](f)
    except KeyError:
        if callable(f): # eg, built-in functions and methods
            # raise ValueError, "type %s not supported yet." % type(f)
            return f.__name__, None
        else:
            raise TypeError, ("object %s of type %s is not callable." %
                                     (f, type(f)))

class Signature:
    def __init__(self, func):
        self.type = type(func)
        self.name, self.func = _getcode(func)
    def ordinary_args(self):
        n = self.func.func_code.co_argcount
        return _varnames(self.func)[0:n]
    def special_args(self):
        n = self.func.func_code.co_argcount
        x = {}
        #
        if _is_variadic(self.func):
            x['positional'] = _varnames(self.func)[n]
            if _has_keywordargs(self.func):
                x['keyword'] = _varnames(self.func)[n+1]
        elif _has_keywordargs(self.func):
            x['keyword'] = _varnames(self.func)[n]
        else:
            pass
        return x
    def full_arglist(self):
        base = list(self.ordinary_args())
        x = self.special_args()
        if x.has_key('positional'):
            base.append(x['positional'])
        if x.has_key('keyword'):
            base.append(x['keyword'])
        return base
    def defaults(self):
        defargs = self.func.func_defaults
        args = self.ordinary_args()
        mapping = {}
        if defargs is not None:
            for i in range(-1, -(len(defargs)+1), -1):
                mapping[args[i]] = defargs[i]
        else:
            pass
        return mapping
    def __repr__(self):
        if self.func:
            defaults = self.defaults()
            specials = self.special_args()
            l = []
            for arg in self.ordinary_args():
                if defaults.has_key(arg):
                    l.append( arg + '=' + str(defaults[arg]) )
                else:
                    l.append( arg )
            if specials.has_key('positional'):
                l.append( '*' + specials['positional'] )
            if specials.has_key('keyword'):
                l.append( '**' + specials['keyword'] )
            return "%s(%s)" % (self.name, string.join(l, ', '))
        else:
            return "%s(?)" % self.name


def aproposAll(obj):
    """
    Print out a list of all members and methods (including overloaded methods)
    of an instance or class  
    """
    apropos(obj, fOverloaded = 1, fTruncate = 0)

def doc(obj):
    if (isinstance(obj, types.MethodType)) or \
       (isinstance(obj, types.FunctionType)):
        print obj.__doc__

def adjust(command = None, dim = 1, parent = None, **kw):
    """
    adjust(command = None, parent = None, **kw)
    Popup and entry scale to adjust a parameter
    
    Accepts any Slider keyword argument.  Typical arguments include:
    command: The one argument command to execute
    min: The min value of the slider
    max: The max value of the slider
    resolution: The resolution of the slider
    text: The label on the slider
    
    These values can be accessed and/or changed after the fact
    >>> vg = adjust()
    >>> vg['min']
    0.0
    >>> vg['min'] = 10.0
    >>> vg['min']
    10.0
    """
    # Make sure we enable Tk
    from direct.tkwidgets import Valuator
    # Set command if specified
    if command:
        kw['command'] = lambda x: apply(command, x)
        if parent is None:
            kw['title'] = command.__name__
    kw['dim'] = dim
    # Create toplevel if needed
    if not parent:
        vg = apply(Valuator.ValuatorGroupPanel, (parent,), kw)
    else:
        vg = apply(Valuator.ValuatorGroup,(parent,), kw)
        vg.pack(expand = 1, fill = 'x')
    return vg

def intersection(a, b):
    """
    intersection(list, list):
    """
    if not a: return []
    if not b: return []
    d = []
    for i in a:
        if (i in b) and (i not in d):
            d.append(i)
    for i in b:
        if (i in a) and (i not in d):
            d.append(i)
    return d

def union(a, b):
    """
    union(list, list):
    """
    # Copy a
    c = a[:]
    for i in b:
        if (i not in c):
            c.append(i)
    return c

def sameElements(a, b):
    if len(a) != len(b):
        return 0
    for elem in a:
        if elem not in b:
            return 0
    for elem in b:
        if elem not in a:
            return 0
    return 1

def list2dict(L, value=None):
    """creates dict using elements of list, all assigned to same value"""
    return dict([(k,value) for k in L])

def invertDict(D):
    """creates a dictionary by 'inverting' D; keys are placed in the new
    dictionary under their corresponding value in the old dictionary.
    Data will be lost if D contains any duplicate values.

    >>> old = {'key1':1, 'key2':2}
    >>> invertDict(old)
    {1: 'key1', 2: 'key2'}
    """
    n = {}
    for key, value in D.items():
        n[value] = key
    return n

def invertDictLossless(D):
    """similar to invertDict, but values of new dict are lists of keys from
    old dict. No information is lost.

    >>> old = {'key1':1, 'key2':2, 'keyA':2}
    >>> invertDictLossless(old)
    {1: ['key1'], 2: ['key2', 'keyA']}
    """
    n = {}
    for key, value in D.items():
        n.setdefault(value, [])
        n[value].append(key)
    return n

def uniqueElements(L):
    """are all elements of list unique?"""
    return len(L) == len(list2dict(L))

def disjoint(L1, L2):
    """returns non-zero if L1 and L2 have no common elements"""
    used = dict([(k,None) for k in L1])
    for k in L2:
        if k in used:
            return 0
    return 1

def contains(whole, sub):
    """
    Return 1 if whole contains sub, 0 otherwise
    """
    if (whole == sub):
        return 1
    for elem in sub:
        # The first item you find not in whole, return 0
        if elem not in whole:
            return 0
    # If you got here, whole must contain sub
    return 1

def replace(list, old, new, all=0):
    """
    replace 'old' with 'new' in 'list'
    if all == 0, replace first occurrence
    otherwise replace all occurrences
    returns the number of items replaced
    """
    if old not in list:
        return 0

    if not all:
        i = list.index(old)
        list[i] = new
        return 1
    else:
        numReplaced = 0
        for i in xrange(len(list)):
            if list[i] == old:
                numReplaced += 1
                list[i] = new
        return numReplaced

def reduceAngle(deg):
    """
    Reduces an angle (in degrees) to a value in [-180..180)
    """
    return (((deg + 180.) % 360.) - 180.)
    
def fitSrcAngle2Dest(src, dest):
    """
    given a src and destination angle, returns an equivalent src angle
    that is within [-180..180) of dest
    examples:
    fitSrcAngle2Dest(30,60) == 30
    fitSrcAngle2Dest(60,30) == 60
    fitSrcAngle2Dest(0,180) == 0
    fitSrcAngle2Dest(-1,180) == 359
    fitSrcAngle2Dest(-180,180) == 180
    """
    return dest + reduceAngle(src - dest)

def fitDestAngle2Src(src, dest):
    """
    given a src and destination angle, returns an equivalent dest angle
    that is within [-180..180) of src
    examples:
    fitDestAngle2Src(30,60) == 60
    fitDestAngle2Src(60,30) == 30
    fitDestAngle2Src(0,180) == -180
    fitDestAngle2Src(1,180) == 180
    """
    return src + (reduceAngle(dest - src))

def closestDestAngle2(src, dest):
    # The function above didn't seem to do what I wanted. So I hacked
    # this one together. I can't really say I understand it. It's more
    # from impirical observation... GRW
    diff = src - dest
    if diff > 180:
        # if the difference is greater that 180 it's shorter to go the other way
        return dest - 360
    elif diff < -180:
        # or perhaps the OTHER other way...
        return dest + 360
    else:
        # otherwise just go to the original destination
        return dest

def closestDestAngle(src, dest):
    # The function above didn't seem to do what I wanted. So I hacked
    # this one together. I can't really say I understand it. It's more
    # from impirical observation... GRW
    diff = src - dest
    if diff > 180:
        # if the difference is greater that 180 it's shorter to go the other way
        return src - (diff - 360)
    elif diff < -180:
        # or perhaps the OTHER other way...
        return src - (360 + diff)
    else:
        # otherwise just go to the original destination
        return dest


def binaryRepr(number, max_length = 32):
    # This will only work reliably for relatively small numbers.
    # Increase the value of max_length if you think you're going
    # to use long integers
    assert number < 2L << max_length
    shifts = map (operator.rshift, max_length * [number], \
                  range (max_length - 1, -1, -1))
    digits = map (operator.mod, shifts, max_length * [2])
    if not digits.count (1): return 0
    digits = digits [digits.index (1):]
    return string.join (map (repr, digits), '')

# constant profile defaults
PyUtilProfileDefaultFilename = 'profiledata'
PyUtilProfileDefaultLines = 80
PyUtilProfileDefaultSorts = ['cumulative', 'time', 'calls']

# call this from the prompt, and break back out to the prompt
# to stop profiling
#
# OR to do inline profiling, you must make a globally-visible
# function to be profiled, i.e. to profile 'self.load()', do
# something like this:
#
#        def func(self=self):
#            self.load()
#        import __builtin__
#        __builtin__.func = func
#        PythonUtil.startProfile(cmd='func()', filename='profileData')
#        del __builtin__.func
#
def startProfile(filename=PyUtilProfileDefaultFilename,
                 lines=PyUtilProfileDefaultLines,
                 sorts=PyUtilProfileDefaultSorts,
                 silent=0,
                 callInfo=1,
                 cmd='run()'):
    import profile
    profile.run(cmd, filename)
    if not silent:
        printProfile(filename, lines, sorts, callInfo)

# call this to see the results again
def printProfile(filename=PyUtilProfileDefaultFilename,
                 lines=PyUtilProfileDefaultLines,
                 sorts=PyUtilProfileDefaultSorts,
                 callInfo=1):
    import pstats
    s = pstats.Stats(filename)
    s.strip_dirs()
    for sort in sorts:
        s.sort_stats(sort)
        s.print_stats(lines)
        if callInfo:
            s.print_callees(lines)
            s.print_callers(lines)

class Functor:
    def __init__(self, function, *args, **kargs):
        assert callable(function), "function should be a callable obj"
        self._function = function
        self._args = args
        self._kargs = kargs
        self.__name__ = 'Functor: %s' % self._function.__name__
        self.__doc__ = self._function.__doc__
        
    def __call__(self, *args, **kargs):
        """call function"""
        _args = list(self._args)
        _args.extend(args)
        _kargs = self._kargs.copy()
        _kargs.update(kargs)
        return apply(self._function,_args,_kargs)

def bound(value, bound1, bound2):
    """
    returns value if value is between bound1 and bound2
    otherwise returns bound that is closer to value
    """
    if bound1 > bound2:
        return min(max(value, bound2), bound1)
    else:
        return min(max(value, bound1), bound2)

def lerp(v0, v1, t):
    """
    returns a value lerped between v0 and v1, according to t
    t == 0 maps to v0, t == 1 maps to v1
    """
    return v0 + (t * (v1 - v0))

def boolEqual(a, b):
    """
    returns true if a and b are both true or both false.
    returns false otherwise
    (a.k.a. xnor -- eXclusive Not OR).
    """
    return (a and b) or not (a or b)

def lineupPos(i, num, spacing):
    """
    use to line up a series of 'num' objects, in one dimension,
    centered around zero
    'i' is the index of the object in the lineup
    'spacing' is the amount of space between objects in the lineup
    """
    assert num >= 1
    assert i >= 0 and i < num
    pos = float(i) * spacing
    return pos - ((float(spacing) * (num-1))/2.)

def formatElapsedSeconds(seconds):
    """
    Returns a string of the form "mm:ss" or "hh:mm:ss" or "n days",
    representing the indicated elapsed time in seconds.
    """
    sign = ''
    if seconds < 0:
        seconds = -seconds
        sign = '-'

    # We use math.floor() instead of casting to an int, so we avoid
    # problems with numbers that are too large to represent as
    # type int.
    seconds = math.floor(seconds)
    hours = math.floor(seconds / (60 * 60))
    if hours > 36:
        days = math.floor((hours + 12) / 24)
        return "%s%d days" % (sign, days)
    
    seconds -= hours * (60 * 60)
    minutes = (int)(seconds / 60)
    seconds -= minutes * 60
    if hours != 0:
        return "%s%d:%02d:%02d" % (sign, hours, minutes, seconds)
    else:
        return "%s%d:%02d" % (sign, minutes, seconds)

def solveQuadratic(a, b, c):
    # quadratic equation: ax^2 + bx + c = 0
    # quadratic formula:  x = [-b +/- sqrt(b^2 - 4ac)] / 2a
    # returns None, root, or [root1, root2]

    # a cannot be zero.
    if a == 0.:
        return None

    # calculate the determinant (b^2 - 4ac)
    D = (b * b) - (4. * a * c)

    if D < 0:
        # there are no solutions (sqrt(negative number) is undefined)
        return None
    elif D == 0:
        # only one root
        return (-b) / (2. * a)
    else:
        # OK, there are two roots
        sqrtD = math.sqrt(D)
        twoA = 2. * a
        root1 = ((-b) - sqrtD) / twoA
        root2 = ((-b) + sqrtD) / twoA
        return [root1, root2]

def stackEntryInfo(depth=0, baseFileName=1):
    """
    returns the sourcefilename, line number, and function name of
    an entry in the stack.
    'depth' is how far back to go in the stack; 0 is the caller of this
    function, 1 is the function that called the caller of this function, etc.
    by default, strips off the path of the filename; override with baseFileName
    returns (fileName, lineNum, funcName) --> (string, int, string)
    returns (None, None, None) on error
    """
    try:
        stack = None
        frame = None
        try:
            stack = inspect.stack()
            # add one to skip the frame associated with this function
            frame = stack[depth+1]
            filename = frame[1]
            if baseFileName:
                filename = os.path.basename(filename)
            lineNum = frame[2]
            funcName = frame[3]
            result = (filename, lineNum, funcName)
        finally:
            del stack
            del frame
    except:
        result = (None, None, None)

    return result

def lineInfo(baseFileName=1):
    """
    returns the sourcefilename, line number, and function name of the
    code that called this function
    (answers the question: 'hey lineInfo, where am I in the codebase?')
    see stackEntryInfo, above, for info on 'baseFileName' and return types
    """
    return stackEntryInfo(1)

def callerInfo(baseFileName=1):
    """
    returns the sourcefilename, line number, and function name of the
    caller of the function that called this function
    (answers the question: 'hey callerInfo, who called me?')
    see stackEntryInfo, above, for info on 'baseFileName' and return types
    """
    return stackEntryInfo(2)

def lineTag(baseFileName=1, verbose=0, separator=':'):
    """
    returns a string containing the sourcefilename and line number
    of the code that called this function
    (equivalent to lineInfo, above, with different return type)
    see stackEntryInfo, above, for info on 'baseFileName'

    if 'verbose' is false, returns a compact string of the form
    'fileName:lineNum:funcName'
    if 'verbose' is true, returns a longer string that matches the
    format of Python stack trace dumps

    returns empty string on error
    """
    fileName, lineNum, funcName = callerInfo()
    if fileName is None:
        return ''
    if verbose:
        return 'File "%s", line %s, in %s' % (fileName, lineNum, funcName)
    else:
        return '%s%s%s%s%s' % (fileName, separator, lineNum, separator,
                               funcName)

def findPythonModule(module):
    # Look along the python load path for the indicated filename.
    # Returns the located pathname, or None if the filename is not
    # found.
    filename = module + '.py'
    for dir in sys.path:
        pathname = os.path.join(dir, filename)
        if os.path.exists(pathname):
            return pathname
        
    return None

def describeException(backTrace = 4):
    # When called in an exception handler, returns a string describing
    # the current exception.

    def byteOffsetToLineno(code, byte):
        # Returns the source line number corresponding to the given byte
        # offset into the indicated Python code module.

        import array
        lnotab = array.array('B', code.co_lnotab)

        line   = code.co_firstlineno
        for i in range(0, len(lnotab),2):
            byte -= lnotab[i]
            if byte <= 0:
                return line
            line += lnotab[i+1]

        return line
    
    infoArr = sys.exc_info()
    exception = infoArr[0]
    exceptionName = getattr(exception, '__name__', None)
    extraInfo = infoArr[1]
    trace = infoArr[2]

    stack = []
    while trace.tb_next:
        # We need to call byteOffsetToLineno to determine the true
        # line number at which the exception occurred, even though we
        # have both trace.tb_lineno and frame.f_lineno, which return
        # the correct line number only in non-optimized mode.
        frame = trace.tb_frame
        module = frame.f_globals.get('__name__', None)
        lineno = byteOffsetToLineno(frame.f_code, frame.f_lasti)
        stack.append("%s:%s, " % (module, lineno))
        trace = trace.tb_next

    frame = trace.tb_frame
    module = frame.f_globals.get('__name__', None)
    lineno = byteOffsetToLineno(frame.f_code, frame.f_lasti)
    stack.append("%s:%s, " % (module, lineno))

    description = ""
    for i in range(len(stack) - 1, max(len(stack) - backTrace, 0) - 1, -1):
        description += stack[i]
        
    description += "%s: %s" % (exceptionName, extraInfo)
    return description

def mostDerivedLast(classList):
    """pass in list of classes. sorts list in-place, with derived classes
    appearing after their bases"""
    def compare(a,b):
        if issubclass(a,b):
            result=1
        elif issubclass(b,a):
            result=-1
        else:
            result=0
        #print a,b,result
        return result
    classList.sort(compare)

def weightedChoice(choiceList, rng=random.random, sum=None):
    """given a list of (weight,item) pairs, chooses an item based on the
    weights. rng must return 0..1. if you happen to have the sum of the
    weights, pass it in 'sum'."""
    # TODO: add support for dicts
    if sum is None:
        sum = 0.
        for weight, item in choiceList:
            sum += weight

    rand = rng()
    accum = rand * sum
    for weight, item in choiceList:
        accum -= weight
        if accum <= 0.:
            return item
    # rand is ~1., and floating-point error prevented accum from hitting 0.
    # Or you passed in a 'sum' that was was too large.
    # Return the last item.
    return item

def randFloat(a, b=0., rng=random.random):
    """returns a random float in [a,b]
    call with single argument to generate random float between arg and zero
    """
    return lerp(a,b,rng())

def normalDistrib(a, b, gauss=random.gauss):
    """
    NOTE: assumes a < b

    Returns random number between a and b, using gaussian distribution, with
    mean=avg(a,b), and a standard deviation that fits ~99.7% of the curve
    between a and b. Outlying results are clipped to a and b.

    ------------------------------------------------------------------------
    http://www-stat.stanford.edu/~naras/jsm/NormalDensity/NormalDensity.html

    The 68-95-99.7% Rule
    ====================
    All normal density curves satisfy the following property which is often
      referred to as the Empirical Rule:
    68% of the observations fall within 1 standard deviation of the mean. 
    95% of the observations fall within 2 standard deviations of the mean.
    99.7% of the observations fall within 3 standard deviations of the mean.
    
    Thus, for a normal distribution, almost all values lie within 3 standard
      deviations of the mean.
    ------------------------------------------------------------------------

    In calculating our standard deviation, we divide (b-a) by 6, since the
    99.7% figure includes 3 standard deviations _on_either_side_ of the mean.
    """
    return max(a, min(b, gauss((a+b)*.5, (b-a)/6.)))

def randUint31(rng=random.random):
    """returns a random integer in [0..2^31).
    rng must return float in [0..1]"""
    return int(rng() * 0x7FFFFFFF)

def randInt32(rng=random.random):
    """returns a random integer in [-2147483648..2147483647].
    rng must return float in [0..1]
    """
    i = int(rng() * 0x7FFFFFFF)
    if rng() < .5:
        i += 0x80000000
    return i

class Enum:
    """Pass in list of strings or string of comma-separated strings.
    Items are accessible as instance.item, and are assigned unique,
    increasing integer values. Pass in integer for 'start' to override
    starting value.

    Example:
    
    >>> colors = Enum('red, green, blue')
    >>> colors.red
    0
    >>> colors.green
    1
    >>> colors.blue
    2
    >>> colors.getString(colors.red)
    'red'
    """

    if __debug__:
        # chars that cannot appear within an item string.
        InvalidChars = string.whitespace
        def _checkValidIdentifier(item):
            invalidChars = string.whitespace+string.punctuation
            invalidChars = invalidChars.replace('_','')
            invalidFirstChars = invalidChars+string.digits
            if item[0] in invalidFirstChars:
                raise SyntaxError, ("Enum '%s' contains invalid first char" %
                                    item)
            if not disjoint(item, invalidChars):
                for char in item:
                    if char in invalidChars:
                        raise SyntaxError, (
                            "Enum\n'%s'\ncontains illegal char '%s'" %
                            (item, char))
            return 1
        _checkValidIdentifier = staticmethod(_checkValidIdentifier)

    def __init__(self, items, start=0):
        if type(items) == types.StringType:
            items = items.split(',')

        self._stringTable = {}

        # make sure we don't overwrite an existing element of the class
        assert(self._checkExistingMembers(items))
        assert(uniqueElements(items))

        i = start
        for item in items:
            # remove leading/trailing whitespace
            item = string.strip(item)
            # is there anything left?
            if len(item) == 0:
                continue
            # make sure there are no invalid characters
            assert(Enum._checkValidIdentifier(item))
            self.__dict__[item] = i
            self._stringTable[i] = item
            i += 1

    def getString(self, value):
        return self._stringTable[value]

    def __contains__(self, value):
        return value in self._stringTable

    def __len__(self):
        return len(self._stringTable)

    if __debug__:
        def _checkExistingMembers(self, items):
            for item in items:
                if hasattr(self, item):
                    return 0
            return 1

############################################################
# class: Singleton  
# Purpose: This provides a base metaclass for all classes
#          that require one and only one instance.
#
# Example: class mySingleton:
#              __metaclass__ = PythonUtil.Singleton
#              def __init__(self,...):
#                  ...
#
# Note: This class is based on Python's New-Style Class
#       design. An error will occur if a defined class
#       attemps to inherit from a Classic-Style Class only,
#       ie: class myClassX:
#               def __init__(self, ...):
#                   ...
#
#           class myNewClassX(myClassX):
#               __metaclass__ = PythonUtil.Singleton
#               def __init__(self, ...):
#                   myClassX.__init__(self, ...)
#                   ...
#
#           This causes problems because myNewClassX is a
#           New-Style class that inherits from only a
#           Classic-Style base class. There are two ways 
#           simple ways to resolve this issue.
#
#           First, if possible, make myClassX a
#           New-Style class by inheriting from object
#           object. IE:  class myClassX(object):
#
#           If for some reason that is not an option, make
#           myNewClassX inherit from object and myClassX.
#           IE: class myNewClassX(object, myClassX):
############################################################
class Singleton(type):
    def __init__(cls,name,bases,dic):
        super(Singleton,cls).__init__(name,bases,dic)
        cls.instance=None
    def __call__(cls,*args,**kw):
        if cls.instance is None:
            cls.instance=super(Singleton,cls).__call__(*args,**kw)
        return cls.instance

class SingletonError(ValueError):
    """ Used to indicate an inappropriate value for a Singleton."""