"""
Errors that can occur when solving a linear game.
"""

from cvxopt import matrix

class GameException(Exception):
    """
    The base class for all exceptions that can occur during the solution
    of a linear game.
    """
    def pretty_print_dict(self, solution_dict):
        """
        Return a pretty-printed string representation of a CVXOPT
        solution dictionary.
        """
        result = ''
        for (k,v) in solution_dict.items():
            if isinstance(v, matrix):
                # Try to display vectors as rows on one line.
                result += '  {:s}: {!s}'.format(k,v.trans())
            else:
                result += '  {:s}: {!s}\n'.format(k,v)

        return result


class GameUnsolvableException(GameException):
    """
    Every linear game has a solution (this follows from a general
    min-max theorem). If we can't solve the conic program associated
    with a linear game, then something is wrong with either the model of
    the input.
    """
    def __init__(self, status, solution, solution_dict):
        """
        Create a new GameUnsolvableException object.

        INPUT:

        - ``status`` -- the failure status code returned by CVXOPT.

        - ``solution`` -- a Solution object.

        - ``solution_dict`` -- the solution dictionary returned from the
          cone program.

        """
        tpl = 'Solution failed with error "{:s}".\n' \
              '{!s}\n' \
              'CVXOPT returned:\n{!s}'
              # TODO: dont convert the solution to a string, we need
              # to output the two values as well.
        self.message = tpl.format(status,
                                  solution,
                                  self.pretty_print_dict(solution_dict))