#format python

"""TemplateMethodPattern in DesignPatterns Example
"""

import unittest, sys
from cStringIO import StringIO

class Singer:
    """children should implement..."""
    def __init__(self,aStream):
        self.stream=aStream
    def sing(self):
        self.beforeSing()
        self.singTheSong()
        self.endingWords()
    def beforeSing(self):
        raise NotImplementedError    
        
class PoPSinger(Singer):
    def beforeSing(self):
        self.askAudience()
    def singTheSong(self):
        raise NotImplementedError
    
class FolkSongSinger(Singer):
    def beforeSing(self):
        self.gatherMoney()
    def singTheSong(self):
        raise NotImplementedError
        
class HeavyMetalSinger(PoPSinger):
    def askAudience(self):
        print >>self.stream,"Are you ready?"
    def singTheSong(self):
        print >>self.stream,"blah blah blah metal and blah..."
        print >>self.stream,"(He's jumping into the audience)"
        print >>self.stream,"(comes back to the stage crawling)"
    def endingWords(self):
        print >>self.stream,"Thank you, guys!"        

class OperaSinger(PoPSinger):
    def askAudience(self):
        print >>self.stream,"Ladies, and gentlemen..."
    def singTheSong(self):
        print >>self.stream,"blah blah very romantic blah blah..."
        print >>self.stream,"(He's waving his hands very gracefully)"
    def endingWords(self):
        print >>self.stream,"Thank you very much."
        
class TestAll(unittest.TestCase):
    def testAll(self):
        testStream=StringIO()
        heavyMetalSinger=HeavyMetalSinger(testStream)
        heavyMetalSinger.sing()
        expected="""Are you ready?
blah blah blah metal and blah...
(He's jumping into the audience)
(comes back to the stage crawling)
Thank you, guys!
"""
        self.assertEquals(expected,testStream.getvalue())
        testStream=StringIO()
        operaSinger=OperaSinger(testStream)
        operaSinger.sing()
        expected="""Ladies, and gentlemen...
blah blah very romantic blah blah...
(He's waving his hands very gracefully)
Thank you very much.
"""
        self.assertEquals(expected,testStream.getvalue())

if __name__=='__main__':
    unittest.main()