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 Core core;
  27         private final Sone sone;
  28         private final AtomicInteger insertionDelay;
  29         private Optional<Long> lastModificationTime;
  30         private String originalFingerprint;
  31         private String lastFingerprint;
  32
  33         SoneModificationDetector(Core core, Sone sone, AtomicInteger insertionDelay) {
  34                 this(systemTicker(), core, sone, insertionDelay);
  35         }
  36
  37         @VisibleForTesting
  38         SoneModificationDetector(Ticker ticker, Core core, Sone sone, AtomicInteger insertionDelay) {
  39                 this.ticker = ticker;
  40                 this.core = core;
  41                 this.sone = sone;
  42                 this.insertionDelay = insertionDelay;
  43                 originalFingerprint = sone.getFingerprint();
  44                 lastFingerprint = originalFingerprint;
  45         }
  46
  47         public boolean isEligibleForInsert() {
  48                 if (core.isLocked(sone)) {
  49                         lastModificationTime = absent();
  50                         lastFingerprint = "";
  51                         return false;
  52                 }
  53                 String fingerprint = sone.getFingerprint();
  54                 if (originalFingerprint.equals(fingerprint)) {
  55                         lastModificationTime = absent();
  56                         lastFingerprint = fingerprint;
  57                         return false;
  58                 }
  59                 if (!lastFingerprint.equals(fingerprint)) {
  60                         lastModificationTime = of(ticker.read());
  61                         lastFingerprint = fingerprint;
  62                         return false;
  63                 }
  64                 return insertionDelayHasPassed();
  65         }
  66
  67         public String getOriginalFingerprint() {
  68                 return originalFingerprint;
  69         }
  70
  71         public void setFingerprint(String fingerprint) {
  72                 originalFingerprint = fingerprint;
  73                 lastFingerprint = originalFingerprint;
  74                 lastModificationTime = absent();
  75         }
  76
  77         private boolean insertionDelayHasPassed() {
  78                 return lastModificationTime.isPresent() && (NANOSECONDS.toSeconds(ticker.read() - lastModificationTime.get()) >= insertionDelay.get());
  79         }
  80
  81         public boolean isModified() {
  82                 return !sone.getFingerprint().equals(originalFingerprint);
  83         }
  84
  85 }