"""
This file defines restricted arithmetic:

classes and operations to express integer arithmetic,
such that before and after translation semantics are
consistent

r_uint   an unsigned integer which has no overflow
         checking. It is always positive and always
         truncated to the internal machine word size.
intmask  mask a possibly long value when running on CPython
         back to a signed int value
ovfcheck check on CPython whether the result of a signed
         integer operation did overflow
ovfcheck_lshift
         << with oveflow checking
         catering to 2.3/2.4 differences about <<
ovfcheck_float_to_int
         convert to an integer or raise OverflowError
r_longlong
         like r_int but double word size
r_ulonglong
         like r_uint but double word size
widen(x)
         if x is of a type smaller than lltype.Signed or
         lltype.Unsigned, widen it to lltype.Signed.
         Useful because the translator doesn't support
         arithmetic on the smaller types.

These are meant to be erased by translation, r_uint
in the process should mark unsigned values, ovfcheck should
mark where overflow checking is required.


"""
import math
from pypy.rpython import extregistry

from pypy.rlib import objectmodel
# set up of machine internals
_bits = 0
_itest = 1
_Ltest = 1L
while _itest == _Ltest and type(_itest) is int:
    _itest *= 2
    _Ltest *= 2
    _bits += 1

LONG_BIT = _bits+1
LONG_MASK = _Ltest*2-1
LONG_TEST = _Ltest

INFINITY = 1e200 * 1e200
NAN = INFINITY / INFINITY

def isinf(x):
    return x != 0.0 and x / 2 == x

# To get isnan, working x-platform and both on 2.3 and 2.4, is a
# horror.  I think this works (for reasons I don't really want to talk
# about), and probably when implemented on top of pypy, too.
def isnan(v):
    return v != v*1.0 or (v == 1.0 and v == 2.0)

def intmask(n):
    if isinstance(n, int):
        return int(n)   # possibly bool->int
    if isinstance(n, objectmodel.Symbolic):
        return n        # assume Symbolics don't overflow
    assert not isinstance(n, float)
    n = long(n)
    n &= LONG_MASK
    if n >= LONG_TEST:
        n -= 2*LONG_TEST
    return int(n)

def widen(n):
    from pypy.rpython.lltypesystem import lltype
    if _should_widen_type(lltype.typeOf(n)):
        return int(n)
    else:
        return n
widen._annspecialcase_ = 'specialize:argtype(0)'

def _should_widen_type(tp):
    from pypy.rpython.lltypesystem import lltype, rffi
    if tp is lltype.Bool:
        return True
    if tp is lltype.Signed:
        return False
    r_class = rffi.platform.numbertype_to_rclass[tp]
    assert issubclass(r_class, base_int)
    return r_class.BITS < LONG_BIT
_should_widen_type._annspecialcase_ = 'specialize:memo'

del _bits, _itest, _Ltest

def ovfcheck(r):
    "NOT_RPYTHON"
    # to be used as ovfcheck(x <op> y)
    # raise OverflowError if the operation did overflow
    assert not isinstance(r, r_uint), "unexpected ovf check on unsigned"
    if type(r) is long:
        raise OverflowError, "signed integer expression did overflow"
    return r

def _local_ovfcheck(r):
    # a copy of the above, because we cannot call ovfcheck
    # in a context where no primitiveoperator is involved.
    assert not isinstance(r, r_uint), "unexpected ovf check on unsigned"
    if isinstance(r, long):
        raise OverflowError, "signed integer expression did overflow"
    return r

def ovfcheck_lshift(a, b):
    "NOT_RPYTHON"
    return _local_ovfcheck(int(long(a) << b))

FL_MAXINT = float(LONG_TEST-1)
FL_MININT = float(-LONG_TEST)

def ovfcheck_float_to_int(x):
    _, intp = math.modf(x)
    if FL_MININT < intp < FL_MAXINT:
        return int(intp)
    raise OverflowError

def compute_restype(self_type, other_type):
    if other_type in (bool, int, long):
        if self_type is bool:
            return int
        return self_type
    if self_type in (bool, int, long):
        return other_type
    return build_int(None, self_type.SIGNED and other_type.SIGNED, max(self_type.BITS, other_type.BITS))

def signedtype(t):
    if t in (bool, int, long):
        return True
    else:
        return t.SIGNED

def normalizedinttype(t):
    if t is int:
        return int
    if t.BITS <= r_int.BITS:
        return build_int(None, t.SIGNED, r_int.BITS)
    else:
        assert t.BITS <= r_longlong.BITS
        return build_int(None, t.SIGNED, r_longlong.BITS)

class base_int(long):
    """ fake unsigned integer implementation """


    def _widen(self, other, value):
        """
        if one argument is int or long, the other type wins.
        otherwise, produce the largest class to hold the result.
        """
        self_type = type(self)
        other_type = type(other)
        try:
            return self.typemap[self_type, other_type](value)
        except KeyError:
            pass
        restype = compute_restype(self_type, other_type)
        self.typemap[self_type, other_type] = restype
        return restype(value)

    def __new__(klass, val):
        if klass is base_int:
            raise TypeError("abstract base!")
        else:
            return super(base_int, klass).__new__(klass, val)

    def __int__(self):
        if self < LONG_TEST:
            return long.__int__(self)
        else:
            return intmask(self)

    def __add__(self, other):
        x = long(self)
        y = long(other)
        return self._widen(other, x + y)
    __radd__ = __add__
    
    def __sub__(self, other):
        x = long(self)
        y = long(other)
        return self._widen(other, x - y)

    def __rsub__(self, other):
        y = long(self)
        x = long(other)
        return self._widen(other, x - y)
    
    def __mul__(self, other):
        x = long(self)
        if not isinstance(other, (int, long)):
            return x * other
        y = long(other)
        return self._widen(other, x * y)
    __rmul__ = __mul__

    def __div__(self, other):
        x = long(self)
        y = long(other)
        return self._widen(other, x // y)

    __floordiv__ = __div__

    def __rdiv__(self, other):
        y = long(self)
        x = long(other)
        return self._widen(other, x // y)

    __rfloordiv__ = __rdiv__

    def __mod__(self, other):
        x = long(self)
        y = long(other)
        return self._widen(other, x % y)

    def __rmod__(self, other):
        y = long(self)
        x = long(other)
        return self._widen(other, x % y)

    def __divmod__(self, other):
        x = long(self)
        y = long(other)
        res = divmod(x, y)
        return (self.__class__(res[0]), self.__class__(res[1]))

    def __lshift__(self, n):
        x = long(self)
        y = long(n)
        return self.__class__(x << y)

    def __rlshift__(self, n):
        y = long(self)
        x = long(n)
        return self._widen(n, x << y)

    def __rshift__(self, n):
        x = long(self)
        y = long(n)
        return self._widen(n, x >> y)

    def __rrshift__(self, n):
        y = long(self)
        x = long(n)
        return self._widen(n, x >> y)

    def __or__(self, other):
        x = long(self)
        y = long(other)
        return self._widen(other, x | y)
    __ror__ = __or__

    def __and__(self, other):
        x = long(self)
        y = long(other)
        return self._widen(other, x & y)
    __rand__ = __and__

    def __xor__(self, other):
        x = long(self)
        y = long(other)
        return self._widen(other, x ^ y)
    __rxor__ = __xor__

    def __neg__(self):
        x = long(self)
        return self.__class__(-x)

    def __abs__(self):
        x = long(self)
        return self.__class__(abs(x))

    def __pos__(self):
        return self.__class__(self)

    def __invert__(self):
        x = long(self)
        return self.__class__(~x)

    def __pow__(self, other, m=None):
        x = long(self)
        y = long(other)
        res = pow(x, y, m)
        return self._widen(other, res)

    def __rpow__(self, other, m=None):
        y = long(self)
        x = long(other)
        res = pow(x, y, m)
        return self._widen(other, res)

class signed_int(base_int):
    SIGNED = True
    def __new__(klass, val=0):
        if type(val) is float:
            val = long(val)
        if val > klass.MASK>>1 or val < -(klass.MASK>>1)-1:
            raise OverflowError("%s does not fit in signed %d-bit integer"%(val, klass.BITS))
        if val < 0:
            val = - ((-val) & klass.MASK)
        return super(signed_int, klass).__new__(klass, val)
    typemap = {}

class unsigned_int(base_int):
    SIGNED = False
    def __new__(klass, val=0):
        if type(val) is float:
            val = long(val)
        return super(unsigned_int, klass).__new__(klass, val & klass.MASK)
    typemap = {}

_inttypes = {}

def build_int(name, sign, bits):
    sign = bool(sign)
    try:
        return _inttypes[sign, bits]
    except KeyError:
        pass
    if sign:
        base_int_type = signed_int
    else:
        base_int_type = unsigned_int
    mask = (2 ** bits) - 1
    if name is None:
        raise TypeError('No predefined %sint%d'%(['u', ''][sign], bits))
    int_type = _inttypes[sign, bits] = type(name, (base_int_type,), {'MASK': mask,
                                                           'BITS': bits})
    class ForValuesEntry(extregistry.ExtRegistryEntry):
        _type_ = int_type

        def compute_annotation(self):
            from pypy.annotation import model as annmodel
            return annmodel.SomeInteger(knowntype=int_type)
            
    class ForTypeEntry(extregistry.ExtRegistryEntry):
        _about_ = int_type

        def compute_result_annotation(self, *args_s, **kwds_s):
            from pypy.annotation import model as annmodel
            return annmodel.SomeInteger(knowntype=int_type)

        def specialize_call(self, hop):
            v_result, = hop.inputargs(hop.r_result.lowleveltype)
            hop.exception_cannot_occur()
            return v_result
            
    return int_type

class BaseIntValueEntry(extregistry.ExtRegistryEntry):
    _type_ = base_int

    def compute_annotation(self):
        from pypy.annotation import model as annmodel
        return annmodel.SomeInteger(knowntype=r_ulonglong)
        
class BaseIntTypeEntry(extregistry.ExtRegistryEntry):
    _about_ = base_int

    def compute_result_annotation(self, *args_s, **kwds_s):
        raise TypeError("abstract base!")

r_int = build_int('r_int', True, LONG_BIT)
r_uint = build_int('r_uint', False, LONG_BIT)

r_longlong = build_int('r_longlong', True, 64)
r_ulonglong = build_int('r_ulonglong', False, 64)


# float as string  -> sign, beforept, afterpt, exponent

def break_up_float(s):
    i = 0

    sign = ''
    before_point = ''
    after_point = ''
    exponent = ''

    if s[i] in '+-':
        sign = s[i]
        i += 1

    while i < len(s) and s[i] in '0123456789':
        before_point += s[i]
        i += 1

    if i == len(s):
        return sign, before_point, after_point, exponent

    if s[i] == '.':
        i += 1
        while i < len(s) and s[i] in '0123456789':
            after_point += s[i]
            i += 1
            
        if i == len(s):
            return sign, before_point, after_point, exponent

    if s[i] not in  'eE':
        raise ValueError

    i += 1
    if i == len(s):
        raise ValueError

    if s[i] in '-+':
        exponent += s[i]
        i += 1

    if i == len(s):
        raise ValueError
    
    while i < len(s) and s[i] in '0123456789':
        exponent += s[i]
        i += 1

    if i != len(s):
        raise ValueError

    return sign, before_point, after_point, exponent

# string -> float helper

def parts_to_float(sign, beforept, afterpt, exponent):
    if not exponent:
        exponent = '0'
    return float("%s%s.%se%s" % (sign, beforept, afterpt, exponent))

# float -> string

formatd_max_length = 120

def formatd(fmt, x):
    return fmt % (x,)

def formatd_overflow(alt, prec, kind, x):
    # msvcrt does not support the %F format.
    # OTOH %F and %f only differ for 'inf' or 'nan' numbers
    # which are already handled elsewhere
    if kind == 'F':
        kind = 'f'

    if ((kind in 'gG' and formatd_max_length <= 10+prec) or
        (kind in 'fF' and formatd_max_length <= 53+prec)):
        raise OverflowError("formatted float is too long (precision too large?)")
    if alt:
        alt = '#'
    else:
        alt = ''

    fmt = "%%%s.%d%s" % (alt, prec, kind)

    return formatd(fmt, x)

# the 'float' C type

class r_singlefloat(object):
    """A value of the C type 'float'.

    This is a single-precision floating-point number.
    Regular 'float' values in Python and RPython are double-precision.
    Note that we consider this as a black box for now - the only thing
    you can do with it is cast it back to a regular float."""

    def __init__(self, floatval):
        import struct
        # simulates the loss of precision
        self._bytes = struct.pack("f", floatval)

    def __float__(self):
        import struct
        return struct.unpack("f", self._bytes)[0]

    def __nonzero__(self):
        raise TypeError("not supported on r_singlefloat instances")

    def __cmp__(self, other):
        raise TypeError("not supported on r_singlefloat instances")


class For_r_singlefloat_values_Entry(extregistry.ExtRegistryEntry):
    _type_ = r_singlefloat

    def compute_annotation(self):
        from pypy.annotation import model as annmodel
        return annmodel.SomeSingleFloat()

class For_r_singlefloat_type_Entry(extregistry.ExtRegistryEntry):
    _about_ = r_singlefloat

    def compute_result_annotation(self, *args_s, **kwds_s):
        from pypy.annotation import model as annmodel
        return annmodel.SomeSingleFloat()

    def specialize_call(self, hop):
        from pypy.rpython.lltypesystem import lltype
        v, = hop.inputargs(lltype.Float)
        hop.exception_cannot_occur()
        # we use cast_primitive to go between Float and SingleFloat.
        return hop.genop('cast_primitive', [v],
                         resulttype = lltype.SingleFloat)