HostCache functionality

core/src/main/groovy/com/muwire/core/hostcache/HostCache.groovy

@@ -1,12 +1,89 @@
 package com.muwire.core.hostcache
 
+import java.util.concurrent.ConcurrentHashMap
+
+import com.muwire.core.MuWireSettings
+import com.muwire.core.trust.TrustLevel
 import com.muwire.core.trust.TrustService
 
+import groovy.json.JsonOutput
+import groovy.json.JsonSlurper
+import net.i2p.data.Destination
+
 class HostCache {
 
 	final TrustService trustService
-	public HostCache(TrustService trustService) {
+	final File storage
+	final int interval
+	final Timer timer
+	final MuWireSettings settings
+	final Map<Destination, Host> hosts = new ConcurrentHashMap<>()
+	
+	public HostCache(TrustService trustService, File storage, int interval, MuWireSettings settings) {
 		this.trustService = trustService
+		this.storage = storage
+		this.interval = interval
+		this.settings = settings
+		this.timer = new Timer("host-persister",true)
 	}
 
+	void start() {
+		timer.schedule({load()} as TimerTask, 1)
+	}
+	
+	void stop() {
+		timer.cancel()
+	}
+	
+	List<Destination> getHosts(int n) {
+		List<Destination> rv = new ArrayList<>(hosts.keySet())
+		rv.retainAll {allowHost(it)}
+		if (rv.size() <= n)
+			return rv
+		Collections.shuffle(rv)
+		rv[0..n-1]
+	}
+	
+	private void load() {
+		if (storage.exists()) {
+			JsonSlurper slurper = new JsonSlurper()
+			storage.eachLine {
+				def entry = slurper.parseText(it)
+				Destination dest = new Destination(entry.destination)
+				Host host = new Host(dest)
+				host.failures = Integer.valueOf(String.valueOf(entry.failures))
+				if (allowHost(host))
+					hosts.put(dest, host)
+			}
+		}
+		timer.schedule({save()} as TimerTask, interval, interval)
+	}
+	
+	private boolean allowHost(Host host) {
+		if (host.isFailed())
+			return false
+		TrustLevel trust = trustService.getLevel(host.destination)
+		switch(trust) {
+			case TrustLevel.DISTRUSTED :
+				return false
+			case TrustLevel.TRUSTED :
+				return true
+			case TrustLevel.NEUTRAL :
+				return settings.allowUntrusted()
+		}
+		false
+	}
+	
+	private void save() {
+		storage.delete()
+		hosts.each { dest, host ->
+			if (allowHost(host)) {
+				def map = [:]
+				map.destination = dest.toBase64()
+				map.failures = host.failures
+				def json = JsonOutput.toJson(map)
+				storage.append("${json}\n")
+			}
+		}
+	}
 }