src/main/java/net/pterodactylus/sone/core/SoneModificationDetector.java

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