Blackboard Pattern

"""
  Blackboard system
  by Andy Bulka
  Prepared for the Melbourne Patterns group - August 2004
"""
import random
True = 1
False = 0

print "Welcome to my blackboard system"

class Blackboard:
    def __init__(self):
        self.experts = []
        self.commonState = {}

    def AddExpert(self, expert):
        self.experts.append(expert)

class Controller:
    def __init__(self, blackboard):
        self.blackboard = blackboard
        # init blackboard
        self.blackboard.commonState['answer'] = 0
        self.blackboard.commonState['answerCorrectness'] = 0

    def Loop(self):
        while self.blackboard.commonState['answerCorrectness'] < 90:
            candidates = []
            for expert in self.blackboard.experts:
                eagerness = expert.CanContribute()
                if eagerness:
                    candidates.append((eagerness,expert))  # append a tuple

            candidates.sort()    # move winning tuple to the end of the list
            winningExpert = candidates[-1][1]  # -1 means the last item in list.
            winningExpert.execAction()

        return self.blackboard.commonState['answer']

    def Loop_OLD(self):
        while self.blackboard.commonState['answerCorrectness'] < 90:
            for expert in self.blackboard.experts:
                if expert.CanContribute():
                    expert.execAction()
        return self.blackboard.commonState['answer']


class AbstractExpert:
    def __init__(self, blackboard, outtext):
        self.blackboard = blackboard
        self.outtext = outtext

    def CanContribute(self):
        raise 'not implemented'

    def execAction(self):
        raise 'not implemented'

class SmartAss(AbstractExpert):

    def CanContribute(self):
        return random.randint(1,20)

    def execAction(self):
        self.blackboard.commonState['answer'] += random.randint(1,20)
        print '.',
        self.outtext.text += '.'

class WiseMan(AbstractExpert):

    def CanContribute(self):
        if self.blackboard.commonState['answer'] > 200:
            return random.randint(1,20)
        else:
            return False

    def execAction(self):
        self.blackboard.commonState['answer'] += 1
        self.blackboard.commonState['answerCorrectness'] += 5
        print '*',
        self.outtext.text += '*'

WANT_JAVA_GUI = False

if WANT_JAVA_GUI:
    from javax.swing import JFrame, JLabel, JButton, JTextField

    class JHutton(JButton):
        pass

    class GUI:
        def __init__(self):
            f = JFrame()
            f.show()
            f.size = 200,200
            f.title = "Blackboard Jungle"

            f.contentPane.add(JLabel("Expert1"))

            self.txt1 = JTextField(30)
            f.contentPane.add(self.txt1)

            f.contentPane.add(JLabel("Expert2"))

            self.txt2 = JTextField(30)
            f.contentPane.add(self.txt2)

            button = JHutton("Think")
            f.contentPane.add(button)
            button.actionPerformed = self.onClick

            from java.awt import FlowLayout
            f.contentPane.layout = FlowLayout()

            f.pack()
            f.visible = 1
            self.f = f

            blackboard = Blackboard()
            blackboard.AddExpert( SmartAss(blackboard, self.txt1) )
            blackboard.AddExpert( WiseMan(blackboard, self.txt2) )
            self.c = Controller(blackboard)

        def onClick(self, event):
            result = self.c.Loop()
            print
            print result
            print 'done'

    gui = GUI()
else:
    # Pure text
    class DummyTextWidget:
        def __init__(self):
            self.text = ''

    import sys
    blackboard = Blackboard()
    blackboard.AddExpert( SmartAss(blackboard, DummyTextWidget()))
    blackboard.AddExpert( WiseMan(blackboard, DummyTextWidget()))
    c = Controller(blackboard)
    result = c.Loop()
    print
    print result
    print 'done'