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 class SoneModificationDetector {
  23
  24         private final Ticker ticker;
  25         private final LockableFingerprintProvider lockableFingerprintProvider;
  26         private final AtomicInteger insertionDelay;
  27         private Optional<Long> lastModificationTime;
  28         private String lastInsertFingerprint;
  29         private String lastCheckFingerprint;
  30
  31         SoneModificationDetector(LockableFingerprintProvider lockableFingerprintProvider, AtomicInteger insertionDelay) {
  32                 this(systemTicker(), lockableFingerprintProvider, insertionDelay);
  33         }
  34
  35         @VisibleForTesting
  36         SoneModificationDetector(Ticker ticker, LockableFingerprintProvider lockableFingerprintProvider, AtomicInteger insertionDelay) {
  37                 this.ticker = ticker;
  38                 this.lockableFingerprintProvider = lockableFingerprintProvider;
  39                 this.insertionDelay = insertionDelay;
  40                 lastCheckFingerprint = lastInsertFingerprint;
  41         }
  42
  43         public boolean isEligibleForInsert() {
  44                 if (lockableFingerprintProvider.isLocked()) {
  45                         lastModificationTime = absent();
  46                         lastCheckFingerprint = "";
  47                         return false;
  48                 }
  49                 String fingerprint = lockableFingerprintProvider.getFingerprint();
  50                 if (fingerprint.equals(lastInsertFingerprint)) {
  51                         lastModificationTime = absent();
  52                         lastCheckFingerprint = fingerprint;
  53                         return false;
  54                 }
  55                 if (!Objects.equal(lastCheckFingerprint, fingerprint)) {
  56                         lastModificationTime = of(ticker.read());
  57                         lastCheckFingerprint = fingerprint;
  58                         return false;
  59                 }
  60                 return insertionDelayHasPassed();
  61         }
  62
  63         public String getLastInsertFingerprint() {
  64                 return lastInsertFingerprint;
  65         }
  66
  67         public void setFingerprint(String fingerprint) {
  68                 lastInsertFingerprint = fingerprint;
  69                 lastCheckFingerprint = lastInsertFingerprint;
  70                 lastModificationTime = absent();
  71         }
  72
  73         private boolean insertionDelayHasPassed() {
  74                 return NANOSECONDS.toSeconds(ticker.read() - lastModificationTime.get()) >= insertionDelay.get();
  75         }
  76
  77         public boolean isModified() {
  78                 return !Objects.equal(lockableFingerprintProvider.getFingerprint(), lastInsertFingerprint);
  79         }
  80
  81         /**
  82          * Provider for a fingerprint and the information if a {@link Sone} is locked. This
  83          * prevents us from having to lug a Sone object around.
  84          */
  85         static interface LockableFingerprintProvider {
  86
  87                 boolean isLocked();
  88                 String getFingerprint();
  89
  90         }
  91
  92 }