src/main/java/net/pterodactylus/sone/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.Objects;
  14 import com.google.common.base.Optional;
  15 import com.google.common.base.Ticker;
  16
  17 /**
  18  * Class that detects {@link Sone} modifications (as per their {@link
  19  * Sone#getFingerprint() fingerprints} and determines when a modified Sone may
  20  * be inserted.
  21  *
  22  * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
  23  */
  24 class SoneModificationDetector {
  25
  26         private final Ticker ticker;
  27         private final LockableFingerprintProvider lockableFingerprintProvider;
  28         private final AtomicInteger insertionDelay;
  29         private Optional<Long> lastModificationTime;
  30         private String lastInsertFingerprint;
  31         private String lastCheckFingerprint;
  32
  33         SoneModificationDetector(LockableFingerprintProvider lockableFingerprintProvider, AtomicInteger insertionDelay) {
  34                 this(systemTicker(), lockableFingerprintProvider, insertionDelay);
  35         }
  36
  37         @VisibleForTesting
  38         SoneModificationDetector(Ticker ticker, LockableFingerprintProvider lockableFingerprintProvider, AtomicInteger insertionDelay) {
  39                 this.ticker = ticker;
  40                 this.lockableFingerprintProvider = lockableFingerprintProvider;
  41                 this.insertionDelay = insertionDelay;
  42                 lastCheckFingerprint = lastInsertFingerprint;
  43         }
  44
  45         public boolean isEligibleForInsert() {
  46                 if (lockableFingerprintProvider.isLocked()) {
  47                         lastModificationTime = absent();
  48                         lastCheckFingerprint = "";
  49                         return false;
  50                 }
  51                 String fingerprint = lockableFingerprintProvider.getFingerprint();
  52                 if (fingerprint.equals(lastInsertFingerprint)) {
  53                         lastModificationTime = absent();
  54                         lastCheckFingerprint = fingerprint;
  55                         return false;
  56                 }
  57                 if (!Objects.equal(lastCheckFingerprint, fingerprint)) {
  58                         lastModificationTime = of(ticker.read());
  59                         lastCheckFingerprint = fingerprint;
  60                         return false;
  61                 }
  62                 return insertionDelayHasPassed();
  63         }
  64
  65         public String getLastInsertFingerprint() {
  66                 return lastInsertFingerprint;
  67         }
  68
  69         public void setFingerprint(String fingerprint) {
  70                 lastInsertFingerprint = fingerprint;
  71                 lastCheckFingerprint = lastInsertFingerprint;
  72                 lastModificationTime = absent();
  73         }
  74
  75         private boolean insertionDelayHasPassed() {
  76                 return NANOSECONDS.toSeconds(ticker.read() - lastModificationTime.get()) >= insertionDelay.get();
  77         }
  78
  79         public boolean isModified() {
  80                 return !Objects.equal(lockableFingerprintProvider.getFingerprint(), lastInsertFingerprint);
  81         }
  82
  83         /**
  84          * Provider for a fingerprint and the information if a {@link Sone} is locked. This
  85          * prevents us from having to lug a Sone object around.
  86          *
  87          * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
  88          */
  89         static interface LockableFingerprintProvider {
  90
  91                 boolean isLocked();
  92                 String getFingerprint();
  93
  94         }
  95
  96 }