import py

import sys, os.path

builtin_repr = repr

reprlib = py.builtin._tryimport('repr', 'reprlib')

class SafeRepr(reprlib.Repr):

    """ subclass of repr.Repr that limits the resulting size of repr()

        and includes information on exceptions raised during the call.

    """

    def repr(self, x):

        return self._callhelper(reprlib.Repr.repr, self, x)

    def repr_instance(self, x, level):

        return self._callhelper(builtin_repr, x)

    def _callhelper(self, call, x, *args):

        try:

            # Try the vanilla repr and make sure that the result is a string

            s = call(x, *args)

        except py.builtin._sysex:

            raise

        except:

            cls, e, tb = sys.exc_info()

            exc_name = getattr(cls, '__name__', 'unknown')

            try:

                exc_info = str(e)

            except sysex:

                raise

            except:

                exc_info = 'unknown'

            return '<[%s("%s") raised in repr()] %s object at 0x%x>' % (

                exc_name, exc_info, x.__class__.__name__, id(x))

        else:

            if len(s) > self.maxsize:

                i = max(0, (self.maxsize-3)//2)

                j = max(0, self.maxsize-3-i)

                s = s[:i] + '...' + s[len(s)-j:]

            return s

def saferepr(obj, maxsize=240):

    """ return a size-limited safe repr-string for the given object.

    Failing __repr__ functions of user instances will be represented

    with a short exception info and 'saferepr' generally takes

    care to never raise exceptions itself.  This function is a wrapper

    around the Repr/reprlib functionality of the standard 2.6 lib.

    """

    # review exception handling

    srepr = SafeRepr()

    srepr.maxstring = maxsize

    srepr.maxsize = maxsize

    srepr.maxother = 160

    return srepr.repr(obj)