From 04683077fbd54d72e5d96658e04a26300323c714 Mon Sep 17 00:00:00 2001
From: Peter Palfrader <peter@palfrader.org>
Date: Tue, 11 Nov 2003 20:16:39 +0000
Subject: Rework PathSpec based on the now specified algorith.  Some questions
 are still open

---
 src/org/noreply/fancydress/type3/PathSpec.java | 106 +++++++++++--------------
 1 file changed, 47 insertions(+), 59 deletions(-)

diff --git a/src/org/noreply/fancydress/type3/PathSpec.java b/src/org/noreply/fancydress/type3/PathSpec.java
index bf5f1b5..a0e5d47 100644
--- a/src/org/noreply/fancydress/type3/PathSpec.java
+++ b/src/org/noreply/fancydress/type3/PathSpec.java
@@ -97,6 +97,15 @@ public class PathSpec {
 			return (type == TYPE_CROSSOVER);
 		}
 
+		/**
+		 * If this path component is a ByNickname component.
+		 *
+		 * @return true if this path component is a ByNickname component.
+		 */
+		public boolean isByNickname() {
+			return (type == TYPE_NICKNAME);
+		}
+
 		/**
 		 * Get a number of hops statisfyi8ng this path component.
 		 *
@@ -202,20 +211,13 @@ public class PathSpec {
 	/**
 	 * A class holding a list of Servers and a Crossover point location.
 	 */
-	private class ServerWithCrossover {
+	private class ServerlistWithCrossover {
 		public Server[] servers;
 		public int crossoverPoint;
 
-		public Server getLastServer() {
-			return (servers[servers.length - 1]);
-		}
-
-		public void setLastServer(Server s) {
-			servers[servers.length - 1] = s;
-		}
-
-		public Server getSecondToLastServer() {
-			return (servers[servers.length - 2]);
+		public ServerlistWithCrossover(Server[] servers, int crossoverPoint) {
+			this.servers = servers;
+			this.crossoverPoint = crossoverPoint;
 		}
 
 		private void fillInRandoms() throws Mix3PathProblemException {
@@ -267,9 +269,11 @@ public class PathSpec {
 	/**
 	 * Concat path components, getting random amount of hops where requested.
 	 *
-	 * @return a list of servers and a crossover point as an ServerWithCrossover object.
+	 * @param chopOffRandomLast remove the last component if it is a RandomHop Component.  // FIXME: understand what the spec says
+	 * @param exitHop the exit hop to use.
+	 * @return a list of servers and a crossover point as an ServerlistWithCrossover object.
 	 */
-	private ServerWithCrossover concatComponents() throws Mix3PathProblemException {
+	private ServerlistWithCrossover concatComponents(boolean chopOffRandomLast, Server exitHop) throws Mix3PathProblemException {
 		Server[][] components = new Server[pathComponents.length][];
 		int length = 0;
 		int crossoverBefore = -1;
@@ -292,9 +296,13 @@ public class PathSpec {
 		if (c != length)
 			throw new Error ("Did not fill in length hops ("+c+" vs "+length+")");
 
-		ServerWithCrossover result = new ServerWithCrossover();
-		result.servers = servers;
-		result.crossoverPoint = crossoverBefore;
+		if (chopOffRandomLast && servers[servers.length-1] == null) {
+			Server[] newServers = new Server[servers.length-1];
+			System.arraycopy(servers, 0, newServers, 0, servers.length-1);
+			servers = newServers;
+		}
+
+		ServerlistWithCrossover result = new ServerlistWithCrossover(servers, crossoverBefore);
 		return result;
 	}
 
@@ -311,63 +319,43 @@ public class PathSpec {
 	 *
 	 * @param payload the payload
 	 * @return paths constructed from the PathSpec
+	 * @throws IllegalArgumentException if this is a single leg path spec.
 	 */
 	public Path[] getPath(Payload payload) throws Mix3PathProblemException {
 		if (singleLeg)
 			throw new IllegalArgumentException("getPath() may not be called for single leg path specs.");
 
 
-		ServerWithCrossover[] paths = new ServerWithCrossover[payload.numPackets()];
-		for (int i=0; i<paths.length; i++) {
-			paths[i] = concatComponents();
-			if (paths[i].servers.length < 2)
-				throw new Mix3PathProblemException("Path too short.");
-		}
-
-		Server lastHop = paths[0].getLastServer();
-		for (int i=1; i<paths.length; i++)
-			if (lastHop != paths[i].getLastServer())
-				throw new Mix3PathProblemException("Exit hop must be the same in all paths (random or fixed)");
-
-		Server[] possibleExitHops = payload.filterExithops( dir.getRecommendedServers() );
-		if (lastHop == null) {
-			boolean[] unuseable = new boolean[possibleExitHops.length];
-			for (int i=0; i<paths.length; i++) {
-				Server stls = paths[i].getSecondToLastServer();
-				if (stls == null)
-					continue;
-				for (int j=0; j<unuseable.length; j++)
-					if (unuseable[j])
-						continue;
-					else
-						if (! dir.areFriends(stls, possibleExitHops[j] ))
-							unuseable[j] = true;
-			}
-			ArrayList list = new ArrayList();
-			for (int j=0; j<unuseable.length; j++)
-				if (! unuseable[j])
-					list.add(possibleExitHops[j]);
+		Server[] validExitHops = payload.filterExithops( dir.getRecommendedServers() );
+		Server[] recommendedExitHops = payload.filterExithops( dir.getRecommendedServers() );
+		Server exitHop;
+		boolean randomExitHop = ! pathComponents[pathComponents.length-1].isByNickname();
+		if (! randomExitHop) {
+			exitHop = pathComponents[ pathComponents.length-1 ].getHops()[0];
 
-			if (list.size() == 0)
-				throw new Mix3PathProblemException("No useable exit hops found");
-
-			lastHop = (Server) list.get( CryptoPrimitives.randInt(list.size()) );
-			for (int i=0; i<paths.length; i++)
-				paths[i].setLastServer(lastHop);
-		} else {
+			/* Check whether exitHop is valid. */
 			boolean exitHopOK = false;
-			for (int j=0; j<possibleExitHops.length; j++)
-				if (possibleExitHops[j] == lastHop) {
+			for (int j=0; j<validExitHops.length; j++)
+				if (exitHop == validExitHops[j]) {
 					exitHopOK = true;
 					break;
 				}
 			if (! exitHopOK)
-				throw new Mix3PathProblemException("Exit hop "+lastHop.getNickname()+" does not meet constraints.");
+				throw new Mix3PathProblemException("Exit hop "+exitHop.getNickname()+" does not meet constraints.");
+		} else
+			exitHop = recommendedExitHops[ CryptoPrimitives.randInt(recommendedExitHops.length) ];
+
+
+		ServerlistWithCrossover[] serverlists = new ServerlistWithCrossover[payload.numPackets()];
+		for (int i=0; i<serverlists.length; i++) {
+			serverlists[i] = concatComponents( randomExitHop, exitHop );
+			if (serverlists[i].servers.length < 2)
+				throw new Mix3PathProblemException("Path too short.");
 		}
 
-		Path[] result = new Path[paths.length];
-		for (int i=0; i<paths.length; i++)
-			result[i] = paths[i].getPath();
+		Path[] result = new Path[serverlists.length];
+		for (int i=0; i<serverlists.length; i++)
+			result[i] = serverlists[i].getPath();
 
 		return result;
 	}
-- 
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