1 | package bargainingchips.protocol;
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2 |
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3 | import java.util.List;
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4 |
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5 | import java.util.ArrayList;
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6 | import java.util.concurrent.BlockingQueue;
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7 |
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8 | import bargainingchips.actions.Offer;
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9 | import bargainingchips.actions.OfferBy;
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10 |
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11 | /**
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12 | * A (possibly asynchronous) protocol between two agents A and B.
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13 | * The protocol acts as the postman of delivering messages between the agents and validates their messages.
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14 | * The protocol keeps the one official (synchronized) log of what has happened.
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15 | */
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16 | public abstract class BilateralProtocol implements Runnable
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17 | {
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18 | // Messaging to and from A and B
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19 | protected final BlockingQueue<OfferBy> from;
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20 |
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21 | // Should be considered final
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22 | protected String nameA;
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23 | protected BlockingQueue<Offer> toA;
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24 | protected String nameB;
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25 | protected BlockingQueue<Offer> toB;
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26 |
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27 | protected final List<OfferBy> log;
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28 |
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29 | public BilateralProtocol(BlockingQueue<OfferBy> from, String nameA,
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30 | BlockingQueue<Offer> toA, String nameB, BlockingQueue<Offer> toB) {
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31 | super();
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32 | this.from = from;
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33 | this.nameA = nameA;
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34 | this.toA = toA;
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35 | this.nameB = nameB;
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36 | this.toB = toB;
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37 | this.log = new ArrayList<OfferBy>();
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38 | }
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39 |
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40 | protected abstract ValidationResult validate(OfferBy o);
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41 |
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42 | @Override
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43 | public void run()
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44 | {
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45 | // Wait for a message from A or B
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46 | try {
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47 | while (true)
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48 | {
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49 | OfferBy ob = from.poll();
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50 |
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51 | if (ob != null)
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52 | {
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53 | String sender = ob.getSender();
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54 | Offer o = ob.getOffer();
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55 | ValidationResult validationResult = validate(ob);
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56 |
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57 | if (validationResult.isValid()) // if the offer was valid
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58 | {
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59 | log(ob); // make it official
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60 | BlockingQueue<Offer> to = addressee(sender); // put it in the right outbox by looking up sender among nameA and nameB
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61 | to.put(o);
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62 | }
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63 | else // drop!
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64 | System.err.println("Warning: " + ob + " was not a valid offer and was dropped. Log: " + log.toString());
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65 |
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66 | // The validation could result in a state where the negotiation ended.
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67 | // We have an outcome, we let both agents know and clean up
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68 | if (validationResult.hasEnded())
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69 | {
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70 | Offer finalOutcome = validationResult.getOutcome();
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71 | toA.put(finalOutcome);
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72 | toB.put(finalOutcome);
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73 | System.out.println("Protocol detected final outcome: " + finalOutcome +
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74 | ". Notified agents and quitting.");
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75 | return;
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76 | }
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77 | }
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78 | }
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79 | } catch (InterruptedException e) {
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80 | // TODO Auto-generated catch block
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81 | e.printStackTrace();
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82 | }
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83 | }
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84 |
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85 | /**
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86 | * Gives the correct outbox for the sender
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87 | */
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88 | private BlockingQueue<Offer> addressee(String sender)
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89 | {
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90 | if (nameA.equals(sender))
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91 | return toB;
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92 |
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93 | if (nameB.equals(sender))
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94 | return toA;
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95 |
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96 | throw new IllegalStateException("Sender " + sender + " unknown! Should be either " + nameA + " or " + nameB);
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97 | }
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98 |
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99 | private void log(OfferBy ob)
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100 | {
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101 | log.add(ob);
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102 | System.out.println("Logged: " + ob);
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103 | }
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104 |
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105 | protected OfferBy getLastOffer()
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106 | {
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107 | return log.get(log.size() - 1);
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108 | }
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109 |
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110 | }
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