"""
Callable objects that generate numbers according to different distributions.
"""

import random
import operator
import hashlib
import struct
import fractions

from math import e,pi

import param


from param import __version__  # noqa: API import

class TimeAware(param.Parameterized):
    """
    Class of objects that have access to a global time function
    and have the option of using it to generate time-dependent values
    as necessary.

    In the simplest case, an object could act as a strict function of
    time, returning the current time transformed according to a fixed
    equation.  Other objects may support locking their results to a
    timebase, but also work without time.  For instance, objects with
    random state could return a new random value for every call, with
    no notion of time, or could always return the same value until the
    global time changes.  Subclasses should thus provide an ability to
    return a time-dependent value, but may not always do so.
    """

    time_dependent = param.Boolean(default=False,  doc="""
       Whether the given time_fn should be used to constrain the
       results generated.""")

    time_fn = param.Callable(default=param.Dynamic.time_fn, doc="""
        Callable used to specify the time that determines the state
        and return value of the object, if time_dependent=True.""")


    def __init__(self, **params):
        super(TimeAware, self).__init__(**params)
        self._check_time_fn()


    def _check_time_fn(self, time_instance=False):
        """
        If time_fn is the global time function supplied by
        param.Dynamic.time_fn, make sure Dynamic parameters are using
        this time function to control their behaviour.

        If time_instance is True, time_fn must be a param.Time instance.
        """
        if time_instance and not isinstance(self.time_fn, param.Time):
            raise AssertionError("%s requires a Time object"
                                 % self.__class__.__name__)

        if self.time_dependent:
            global_timefn = self.time_fn is param.Dynamic.time_fn
            if global_timefn and not param.Dynamic.time_dependent:
                raise AssertionError("Cannot use Dynamic.time_fn as"
                                     " parameters are ignoring time.")


class TimeDependent(TimeAware):
    """
    Objects that have access to a time function that determines the
    output value. As a function of time, this type of object should
    allow time values to be randomly jumped forwards or backwards,
    but for a given time point, the results should remain constant.

    The time_fn must be an instance of param.Time, to ensure all the
    facilities necessary for safely navigating the timeline are
    available.
    """

    time_dependent = param.Boolean(default=True, readonly=True, doc="""
       Read-only parameter that is always True.""")

    def _check_time_fn(self):
        super(TimeDependent,self)._check_time_fn(time_instance=True)



class NumberGenerator(param.Parameterized):
    """
    Abstract base class for any object that when called produces a number.

    Primarily provides support for using NumberGenerators in simple
    arithmetic expressions, such as abs((x+y)/z), where x,y,z are
    NumberGenerators or numbers.
    """

    def __call__(self):
        raise NotImplementedError

    # Could define any of Python's operators here, esp. if they have operator or ufunc equivalents
    def __add__      (self,operand): return BinaryOperator(self,operand,operator.add)
    def __sub__      (self,operand): return BinaryOperator(self,operand,operator.sub)
    def __mul__      (self,operand): return BinaryOperator(self,operand,operator.mul)
    def __mod__      (self,operand): return BinaryOperator(self,operand,operator.mod)
    def __pow__      (self,operand): return BinaryOperator(self,operand,operator.pow)
    def __div__      (self,operand): return BinaryOperator(self,operand,operator.div)
    def __truediv__  (self,operand): return BinaryOperator(self,operand,operator.truediv)
    def __floordiv__ (self,operand): return BinaryOperator(self,operand,operator.floordiv)

    def __radd__     (self,operand): return BinaryOperator(self,operand,operator.add,True)
    def __rsub__     (self,operand): return BinaryOperator(self,operand,operator.sub,True)
    def __rmul__     (self,operand): return BinaryOperator(self,operand,operator.mul,True)
    def __rmod__     (self,operand): return BinaryOperator(self,operand,operator.mod,True)
    def __rpow__     (self,operand): return BinaryOperator(self,operand,operator.pow,True)
    def __rdiv__     (self,operand): return BinaryOperator(self,operand,operator.div,True)
    def __rtruediv__ (self,operand): return BinaryOperator(self,operand,operator.truediv,True)
    def __rfloordiv__(self,operand): return BinaryOperator(self,operand,operator.floordiv,True)

    def __neg__ (self): return UnaryOperator(self,operator.neg)
    def __pos__ (self): return UnaryOperator(self,operator.pos)
    def __abs__ (self): return UnaryOperator(self,operator.abs)



class BinaryOperator(NumberGenerator):
    """Applies any binary operator to NumberGenerators or numbers to yield a NumberGenerator."""

    def __init__(self,lhs,rhs,operator,reverse=False,**args):
        """
        Accepts two NumberGenerator operands, an operator, and
        optional arguments to be provided to the operator when calling
        it on the two operands.
        """
        # Note that it's currently not possible to set
        # parameters in the superclass when creating an instance,
        # because **args is used by this class itself.
        super(BinaryOperator,self).__init__()

        if reverse:
            self.lhs=rhs
            self.rhs=lhs
        else:
            self.lhs=lhs
            self.rhs=rhs
        self.operator=operator
        self.args=args

    def __call__(self):
        return self.operator(self.lhs() if callable(self.lhs) else self.lhs,
                             self.rhs() if callable(self.rhs) else self.rhs, **self.args)



class UnaryOperator(NumberGenerator):
    """Applies any unary operator to a NumberGenerator to yield another NumberGenerator."""

    def __init__(self,operand,operator,**args):
        """
        Accepts a NumberGenerator operand, an operator, and
        optional arguments to be provided to the operator when calling
        it on the operand.
        """
        # Note that it's currently not possible to set
        # parameters in the superclass when creating an instance,
        # because **args is used by this class itself.
        super(UnaryOperator,self).__init__()

        self.operand=operand
        self.operator=operator
        self.args=args

    def __call__(self):
        return self.operator(self.operand(),**self.args)



class Hash(object):
    """
    A platform- and architecture-independent hash function (unlike
    Python's inbuilt hash function) for use with an ordered collection
    of rationals or integers.

    The supplied name sets the initial hash state.  The output from
    each call is a 32-bit integer to ensure the value is a regular
    Python integer (and not a Python long) on both 32-bit and 64-bit
    platforms. This can be important to seed Numpy's random number
    generator safely (a bad Numpy bug!).

    The number of inputs (integer or rational numbers) to be supplied
    for __call__ must be specified in the constructor and must stay
    constant across calls.
    """
    def __init__(self, name, input_count):
        self.name = name
        self.input_count = input_count
        self._digest = hashlib.md5()
        self._digest.update(name.encode())
        self._hash_struct = struct.Struct( "!" +" ".join(["I"] * (input_count * 2)))


    def _rational(self, val):
        """Convert the given value to a rational, if necessary."""

        I32 = 4294967296 # Maximum 32 bit unsigned int (i.e. 'I') value
        if isinstance(val, int):
             numer, denom = val, 1
        elif isinstance(val, fractions.Fraction):
            numer, denom = val.numerator, val.denominator
        elif hasattr(val, 'numer'):
            (numer, denom) = (int(val.numer()), int(val.denom()))
        else:
            param.main.param.warning("Casting type '%s' to Fraction.fraction"
                               % type(val).__name__)
            frac = fractions.Fraction(str(val))
            numer, denom = frac.numerator, frac.denominator
        return numer % I32, denom % I32


    def __getstate__(self):
        """
        Avoid Hashlib.md5 TypeError in deepcopy (hashlib issue)
        """
        d = self.__dict__.copy()
        d.pop('_digest')
        d.pop('_hash_struct')
        return d


    def __setstate__(self, d):
        self._digest = hashlib.md5()
        name, input_count = d['name'], d['input_count']
        self._digest.update(name.encode())
        self._hash_struct = struct.Struct( "!" +" ".join(["I"] * (input_count * 2)))
        self.__dict__.update(d)


    def __call__(self, *vals):
        """
        Given integer or rational inputs, generate a cross-platform,
        architecture-independent 32-bit integer hash.
        """
        # Convert inputs to (numer, denom) pairs with integers
        # becoming (int, 1) pairs to match gmpy.mpqs for int values.
        pairs = [self._rational(val) for val in vals]
        # Unpack pairs and fill struct with ints to update md5 hash
        ints = [el for pair in pairs for el in pair]
        digest = self._digest.copy()
        digest.update(self._hash_struct.pack(*ints))
        # Convert from hex string to 32 bit int
        return int(digest.hexdigest()[:7], 16)



class TimeAwareRandomState(TimeAware):
    """
    Generic base class to enable time-dependent random
    streams. Although this class is the basis of all random numbergen
    classes, it is designed to be useful whenever time-dependent
    randomness is needed using param's notion of time. For instance,
    this class is used by the imagen package to define time-dependent,
    random distributions over 2D arrays.

    For generality, this class may use either the Random class from
    Python's random module or numpy.random.RandomState. Either of
    these random state objects may be used to generate numbers from
    any of several different random distributions (e.g. uniform,
    Gaussian). The latter offers the ability to generate
    multi-dimensional random arrays and more random distributions but
    requires numpy as a dependency.

    If declared time_dependent, the random state is fully determined
    by a hash value per call. The hash is initialized once with the
    object name and then per call using a tuple consisting of the time
    (via time_fn) and the global param.random_seed.  As a consequence,
    for a given name and fixed value of param.random_seed, the random
    values generated will be a fixed function of time.

    If the object name has not been set and time_dependent is True, a
    message is generated warning that the default object name is
    dependent on the order of instantiation.  To ensure that the
    random number stream will remain constant even if other objects
    are added or reordered in your file, supply a unique name
    explicitly when you construct the RandomDistribution object.
    """

    random_generator = param.Parameter(
        default=random.Random((500,500)), doc=
        """
        Random state used by the object. This may may be an instance
        of random.Random from the Python standard library or an
        instance of numpy.random.RandomState.

        This random state may be exclusively owned by the object or
        may be shared by all instance of the same class. It is always
        possible to give an object its own unique random state by
        setting this parameter with a new random state instance.
        """)

    __abstract = True

    def _initialize_random_state(self, seed=None, shared=True, name=None):
        """
        Initialization method to be called in the constructor of
        subclasses to initialize the random state correctly.

        If seed is None, there is no control over the random stream
        (no reproducibility of the stream).

        If shared is True (and not time-dependent), the random state
        is shared across all objects of the given class. This can be
        overridden per object by creating new random state to assign
        to the random_generator parameter.
        """
        if seed is None: # Equivalent to an uncontrolled seed.
            seed = random.Random().randint(0, 1000000)
            suffix = ''
        else:
            suffix = str(seed)

        # If time_dependent, independent state required: otherwise
        # time-dependent seeding (via hash) will affect shared
        # state. Note that if all objects have time_dependent=True
        # shared random state is safe and more memory efficient.
        if self.time_dependent or not shared:
            self.random_generator = type(self.random_generator)(seed)

        # Seed appropriately (if not shared)
        if not shared:
            self.random_generator.seed(seed)

        if name is None:
            self._verify_constrained_hash()

        hash_name = name if name else self.name
        if not shared:  hash_name += suffix
        self._hashfn = Hash(hash_name, input_count=2)

        if self.time_dependent:
            self._hash_and_seed()


    def _verify_constrained_hash(self):
        """
        Warn if the object name is not explicitly set.
        """
        changed_params = dict(self.param.get_param_values(onlychanged=True))
        if self.time_dependent and ('name' not in changed_params):
            self.param.warning("Default object name used to set the seed: "
                               "random values conditional on object instantiation order.")

    def _hash_and_seed(self):
        """
        To be called between blocks of random number generation. A
        'block' can be an unbounded sequence of random numbers so long
        as the time value (as returned by time_fn) is guaranteed not
        to change within the block. If this condition holds, each
        block of random numbers is time-dependent.

        Note: param.random_seed is assumed to be integer or rational.
        """
        hashval = self._hashfn(self.time_fn(), param.random_seed)
        self.random_generator.seed(hashval)



class RandomDistribution(NumberGenerator, TimeAwareRandomState):
    """
    The base class for all Numbergenerators using random state.

    Numbergen provides a hierarchy of classes to make it easier to use
    the random distributions made available in Python's random module,
    where each class is tied to a particular random distribution.

    RandomDistributions support setting parameters on creation rather
    than passing them each call, and allow pickling to work properly.
    Code that uses these classes will be independent of how many
    parameters are used by the underlying distribution, and can simply
    treat them as a generic source of random numbers.

    RandomDistributions are examples of TimeAwareRandomState, and thus
    can be locked to a global time if desired.  By default,
    time_dependent=False, and so a new random value will be generated
    each time these objects are called.  If you have a global time
    function, you can set time_dependent=True, so that the random
    values will instead be constant at any given time, changing only
    when the time changes.  Using time_dependent values can help you
    obtain fully reproducible streams of random numbers, even if you
    e.g. move time forwards and backwards for testing.

    Note: Each RandomDistribution object has independent random state.
    """

    seed = param.Integer(default=None, allow_None=True, doc="""
       Sets the seed of the random number generator and can be used to
       randomize time dependent streams.

       If seed is None, there is no control over the random stream
       (i.e. no reproducibility of the stream).""")

    __abstract = True

    def __init__(self,**params):
        """
        Initialize a new Random() instance and store the supplied
        positional and keyword arguments.

        If seed=X is specified, sets the Random() instance's seed.
        Otherwise, calls creates an unseeded Random instance which is
        likely to result in a state very different from any just used.
        """
        super(RandomDistribution,self).__init__(**params)
        self._initialize_random_state(seed=self.seed, shared=False)

    def __call__(self):
        if self.time_dependent:
            self._hash_and_seed()



class UniformRandom(RandomDistribution):
    """
    Specified with lbound and ubound; when called, return a random
    number in the range [lbound, ubound).

    See the random module for further details.
    """

    lbound = param.Number(default=0.0,doc="inclusive lower bound")

    ubound = param.Number(default=1.0,doc="exclusive upper bound")


    def __call__(self):
        super(UniformRandom, self).__call__()
        return self.random_generator.uniform(self.lbound,self.ubound)



class UniformRandomOffset(RandomDistribution):
    """
    Identical to UniformRandom, but specified by mean and range.
    When called, return a random number in the range
    [mean - range/2, mean + range/2).

    See the random module for further details.
    """

    mean = param.Number(default=0.0, doc="""Mean value""")

    range = param.Number(default=1.0, bounds=(0.0,None), doc="""
        Difference of maximum and minimum value""")


    def __call__(self):
        super(UniformRandomOffset, self).__call__()
        return self.random_generator.uniform(
                self.mean - self.range / 2.0,
                self.mean + self.range / 2.0)



class UniformRandomInt(RandomDistribution):
    """
    Specified with lbound and ubound; when called, return a random
    number in the inclusive range [lbound, ubound].

    See the randint function in the random module for further details.
    """

    lbound = param.Number(default=0,doc="inclusive lower bound")
    ubound = param.Number(default=1000,doc="inclusive upper bound")


    def __call__(self):
        super(UniformRandomInt, self).__call__()
        x = self.random_generator.randint(self.lbound,self.ubound)
        return x



class Choice(RandomDistribution):
    """
    Return a random element from the specified list of choices.

    Accepts items of any type, though they are typically numbers.
    See the choice() function in the random module for further details.
    """

    choices = param.List(default=[0,1],
        doc="List of items from which to select.")


    def __call__(self):
        super(Choice, self).__call__()
        return self.random_generator.choice(self.choices)



class NormalRandom(RandomDistribution):
    """
    Normally distributed (Gaussian) random number.

    Specified with mean mu and standard deviation sigma.
    See the random module for further details.
    """

    mu = param.Number(default=0.0,doc="Mean value.")

    sigma = param.Number(default=1.0,bounds=(0.0,None),doc="Standard deviation.")


    def __call__(self):
        super(NormalRandom, self).__call__()
        return self.random_generator.normalvariate(self.mu,self.sigma)



class VonMisesRandom(RandomDistribution):
    """
    Circularly normal distributed random number.

    If kappa is zero, this distribution reduces to a uniform random
    angle over the range 0 to 2*pi.  Otherwise, it is concentrated to
    a greater or lesser degree (determined by kappa) around the mean
    mu.  For large kappa (narrow peaks), this distribution approaches
    the Gaussian (normal) distribution with variance 1/kappa.  See the
    random module for further details.
    """

    mu = param.Number(default=0.0,softbounds=(0.0,2*pi),doc="""
        Mean value, typically in the range 0 to 2*pi.""")

    kappa = param.Number(default=1.0,bounds=(0.0,None),softbounds=(0.0,50.0),doc="""
        Concentration (inverse variance).""")


    def __call__(self):
        super(VonMisesRandom, self).__call__()
        return self.random_generator.vonmisesvariate(self.mu,self.kappa)




class ScaledTime(NumberGenerator, TimeDependent):
    """
    The current time multiplied by some conversion factor.
    """

    factor = param.Number(default=1.0, doc="""
       The factor to be multiplied by the current time value.""")


    def __call__(self):
        return float(self.time_fn() * self.factor)



class BoxCar(NumberGenerator, TimeDependent):
    """
    The boxcar function over the specified time interval. The bounds
    are exclusive: zero is returned at the onset time and at the
    offset (onset+duration).

    If duration is None, then this reduces to a step function around the
    onset value with no offset.

    See http://en.wikipedia.org/wiki/Boxcar_function
    """

    onset = param.Number(0.0, doc="Time of onset.")

    duration = param.Number(None, allow_None=True, bounds=(0.0,None), doc="""
        Duration of step value.""")


    def __call__(self):
        if self.time_fn() <= self.onset:
            return 0.0
        elif (self.duration is not None) and (self.time_fn() > self.onset + self.duration):
            return 0.0
        else:
            return 1.0



class SquareWave(NumberGenerator, TimeDependent):
    """
    Generate a square wave with 'on' periods returning 1.0 and
    'off'periods returning 0.0 of specified duration(s). By default
    the portion of time spent in the high state matches the time spent
    in the low state (a duty cycle of 50%), but the duty cycle can be
    controlled if desired.

    The 'on' state begins after a time specified by the 'onset'
    parameter.  The onset duration supplied must be less than the off
    duration.
    """

    onset = param.Number(0.0, doc="""Time of onset of the first 'on'
        state relative to time 0. Must be set to a value less than the
        'off_duration' parameter.""")

    duration = param.Number(1.0, allow_None=False, bounds=(0.0,None), doc="""
         Duration of the 'on' state during which a value of 1.0 is
         returned.""")

    off_duration = param.Number(default=None, allow_None=True,
                                bounds=(0.0,None), doc="""
        Duration of the 'off' value state during which a value of 0.0
        is returned. By default, this duration matches the value of
        the 'duration' parameter.""")


    def __init__(self, **params):
        super(SquareWave,self).__init__(**params)

        if self.off_duration is None:
            self.off_duration = self.duration

        if self.onset > self.off_duration:
            raise AssertionError("Onset value needs to be less than %s" % self.onset)


    def __call__(self):
        phase_offset = (self.time_fn() - self.onset) % (self.duration + self.off_duration)
        if phase_offset < self.duration:
            return 1.0
        else:
            return 0.0



class ExponentialDecay(NumberGenerator, TimeDependent):
    """
    Function object that provides a value that decays according to an
    exponential function, based on a given time function.

    Returns starting_value*base^(-time/time_constant).

    See http://en.wikipedia.org/wiki/Exponential_decay.
    """

    starting_value = param.Number(1.0, doc="Value used for time zero.")

    ending_value = param.Number(0.0, doc="Value used for time infinity.")

    time_constant = param.Number(10000,doc="""
        Time scale for the exponential; large values give slow decay.""")

    base = param.Number(e, doc="""
        Base of the exponent; the default yields starting_value*exp(-t/time_constant).
        Another popular choice of base is 2, which allows the
        time_constant to be interpreted as a half-life.""")


    def __call__(self):
        Vi = self.starting_value
        Vm = self.ending_value
        exp = -1.0*float(self.time_fn())/float(self.time_constant)
        return Vm + (Vi - Vm) * self.base**exp



class TimeSampledFn(NumberGenerator, TimeDependent):
    """
    Samples the values supplied by a time_dependent callable at
    regular intervals of duration 'period', with the sampled value
    held constant within each interval.
    """

    period = param.Number(default=1.0, bounds=(0.0,None),
        inclusive_bounds=(False,True), softbounds=(0.0,5.0), doc="""
        The periodicity with which the values of fn are sampled.""")

    offset = param.Number(default=0.0, bounds=(0.0,None),
                          softbounds=(0.0,5.0), doc="""
        The offset from time 0.0 at which the first sample will be drawn.
        Must be less than the value of period.""")

    fn = param.Callable(doc="""
        The time-dependent function used to generate the sampled values.""")


    def __init__(self, **params):
        super(TimeSampledFn, self).__init__(**params)

        if not getattr(self.fn,'time_dependent', False):
            raise Exception("The function 'fn' needs to be time dependent.")

        if self.time_fn != self.fn.time_fn:
            raise Exception("Objects do not share the same time_fn")

        if self.offset >= self.period:
            raise Exception("The onset value must be less than the period.")


    def __call__(self):
        current_time = self.time_fn()
        current_time += self.offset
        difference = current_time % self.period
        with self.time_fn as t:
            t(current_time - difference - self.offset)
            value = self.fn()
        return value



class BoundedNumber(NumberGenerator):
    """
    Function object that silently enforces numeric bounds on values
    returned by a callable object.
    """

    generator = param.Callable(None, doc="Object to call to generate values.")

    bounds = param.Parameter((None,None), doc="""
        Legal range for the value returned, as a pair.

        The default bounds are (None,None), meaning there are actually
        no bounds.  One or both bounds can be set by specifying a
        value.  For instance, bounds=(None,10) means there is no lower
        bound, and an upper bound of 10.""")


    def __call__(self):
        val = self.generator()
        min_, max_ = self.bounds
        if   min_ is not None and val < min_: return min_
        elif max_ is not None and val > max_: return max_
        else: return val


_public = list(set([_k for _k,_v in locals().items() if isinstance(_v,type) and issubclass(_v,NumberGenerator)]))
__all__ = _public
