#  ___________________________________________________________________________
#
#  Pyomo: Python Optimization Modeling Objects
#  Copyright 2017 National Technology and Engineering Solutions of Sandia, LLC
#  Under the terms of Contract DE-NA0003525 with National Technology and 
#  Engineering Solutions of Sandia, LLC, the U.S. Government retains certain 
#  rights in this software.
#  This software is distributed under the 3-clause BSD License.
#  ___________________________________________________________________________

from pyomo.core.base import Var, Param, Expression, Objective, Block, \
    Constraint, Suffix
from pyomo.core.expr.numvalue import native_numeric_types, is_fixed, value
import logging

logger = logging.getLogger('pyomo.core')

valid_expr_ctypes_minlp = {Var, Param, Expression, Objective}
valid_active_ctypes_minlp = {Block, Constraint, Objective, Suffix}

# Copied from cpxlp.py:
# Keven Hunter made a nice point about using %.16g in his attachment
# to ticket #4319. I am adjusting this to %.17g as this mocks the
# behavior of using %r (i.e., float('%r'%<number>) == <number>) with
# the added benefit of outputting (+/-). The only case where this
# fails to mock the behavior of %r is for large (long) integers (L),
# which is a rare case to run into and is probably indicative of
# other issues with the model.
# *** NOTE ***: If you use 'r' or 's' here, it will break code that
#               relies on using '%+' before the formatting character
#               and you will need to go add extra logic to output
#               the number's sign.
_ftoa_precision_str = '%.17g'


def ftoa(val):
    if val is None:
        return val
    #
    # Basic checking, including conversion of *fixed* Pyomo types to floats
    if type(val) in native_numeric_types:
        _val = val
    else:
        if is_fixed(val):
            _val = value(val)
        else:
            raise ValueError(
                "Converting non-fixed bound or value to string: %s" % (val,))
    #
    # Convert to string
    a = _ftoa_precision_str % _val
    #
    # Remove unnecessary least significant digits.  While not strictly
    # necessary, this helps keep the emitted string consistent between
    # python versions by simplifying things like "1.0000000000001" to
    # "1".
    i = len(a)
    try:
        while i > 1:
            if float(a[:i-1]) == _val:
                i -= 1
            else:
                break
    except:
        pass
    #
    # It is important to issue a warning if the conversion loses
    # precision (as the emitted model is not exactly what the user
    # specified)
    if i == len(a) and float(a) != _val:
        logger.warning(
            "Converting %s to string resulted in loss of precision" % val)
    #
    return a[:i]