# CSE 143, Winter 2009, Marty Stepp
# Homework 3: Stable Marriage, in Python

# A Person object represents one person in the simulation along with an
# ordered list of the person's preferred choices of people to marry.
class Person:
    # Constructs a new person with the given name.
    # Precondition: name is not None
    def __init__(self, name):
        self.name = name
        self.fiancee = None                 # None if single
        self.preferences = []               # queue from most to least liked
        self.rankings = {}                  # name -> preference (1=best)
    
    # Sets this person to be engaged to the given other person.  Subsequent 
    # calls to getFiancee on this person will return other, and subsequent 
    # calls to getFiancee on other will return this person.  If either this
    # person or other were previously engaged, their previous engagement is
    # called off and the previous partner is set to be single.
    # 
    # Precondition: other is not None
    def engage(self, other):
        if not self.single():  # break up
            self.fiancee.fiancee = None
        self.fiancee = other

        if not other.single():  # break up
            other.fiancee.fiancee = None
        other.fiancee = self
    
    # Returns True if this person has no current engagement partner
    # (if this person's fiancee is None) otherwise returns False.
    def single(self):
        return self.fiancee is None
    
    # Comparison function between Person objects, comparing by name.
    # Returns < 0 if self comes before other, > 0 if self comes after other,
    # or 0 if these two people have the same name.
    def __cmp__(self, other):
        return -1 if self.name < other.name else 1 if self.name > other.name else 0
    
    # Returns a string representation of this Person that includes the
    # person's name and fiancee status if any, such as "Newman: single"
    # or "George: engaged to Charlotte (rank 1)".
    def __str__(self):
        result = self.name
        if self.single():
            result += ": single"
        else:
            result += ": engaged to " + self.fiancee.name + \
                    " (rank " + str(self.rankings[self.fiancee.name]) + ")"
        return result