core/SoneModificationDetector.java

   1 package net.pterodactylus.sone.core;
   2
   3 import static com.google.common.base.Optional.absent;
   4 import static com.google.common.base.Optional.of;
   5 import static com.google.common.base.Ticker.systemTicker;
   6 import static java.util.concurrent.TimeUnit.NANOSECONDS;
   7
   8 import java.util.concurrent.atomic.AtomicInteger;
   9
  10 import net.pterodactylus.sone.data.Sone;
  11
  12 import com.google.common.annotations.VisibleForTesting;
  13 import com.google.common.base.Optional;
  14 import com.google.common.base.Ticker;
  15
  16 /**
  17  * Class that detects {@link Sone} modifications (as per their {@link
  18  * Sone#getFingerprint() fingerprints} and determines when a modified Sone may
  19  * be inserted.
  20  *
  21  * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
  22  */
  23 class SoneModificationDetector {
  24
  25         private final Ticker ticker;
  26         private final LockableFingerprintProvider lockableFingerprintProvider;
  27         private final AtomicInteger insertionDelay;
  28         private Optional<Long> lastModificationTime;
  29         private String originalFingerprint;
  30         private String lastFingerprint;
  31
  32         SoneModificationDetector(LockableFingerprintProvider lockableFingerprintProvider, AtomicInteger insertionDelay) {
  33                 this(systemTicker(), lockableFingerprintProvider, insertionDelay);
  34         }
  35
  36         @VisibleForTesting
  37         SoneModificationDetector(Ticker ticker, LockableFingerprintProvider lockableFingerprintProvider, AtomicInteger insertionDelay) {
  38                 this.ticker = ticker;
  39                 this.lockableFingerprintProvider = lockableFingerprintProvider;
  40                 this.insertionDelay = insertionDelay;
  41                 lastFingerprint = originalFingerprint;
  42         }
  43
  44         public boolean isEligibleForInsert() {
  45                 if (lockableFingerprintProvider.isLocked()) {
  46                         lastModificationTime = absent();
  47                         lastFingerprint = "";
  48                         return false;
  49                 }
  50                 String fingerprint = lockableFingerprintProvider.getFingerprint();
  51                 if (originalFingerprint.equals(fingerprint)) {
  52                         lastModificationTime = absent();
  53                         lastFingerprint = fingerprint;
  54                         return false;
  55                 }
  56                 if (!lastFingerprint.equals(fingerprint)) {
  57                         lastModificationTime = of(ticker.read());
  58                         lastFingerprint = fingerprint;
  59                         return false;
  60                 }
  61                 return insertionDelayHasPassed();
  62         }
  63
  64         public String getOriginalFingerprint() {
  65                 return originalFingerprint;
  66         }
  67
  68         public void setFingerprint(String fingerprint) {
  69                 originalFingerprint = fingerprint;
  70                 lastFingerprint = originalFingerprint;
  71                 lastModificationTime = absent();
  72         }
  73
  74         private boolean insertionDelayHasPassed() {
  75                 return NANOSECONDS.toSeconds(ticker.read() - lastModificationTime.get()) >= insertionDelay.get();
  76         }
  77
  78         public boolean isModified() {
  79                 return !lockableFingerprintProvider.getFingerprint().equals(originalFingerprint);
  80         }
  81
  82         /**
  83          * Provider for a fingerprint and the information if a {@link Sone} is locked. This
  84          * prevents us from having to lug a Sone object around.
  85          *
  86          * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
  87          */
  88         static interface LockableFingerprintProvider {
  89
  90                 boolean isLocked();
  91                 String getFingerprint();
  92
  93         }
  94
  95 }