package net.onrc.onos.core.intent;

import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedList;

import net.onrc.onos.core.topology.Link;
import net.onrc.onos.core.topology.LinkEvent;
import net.onrc.onos.core.topology.Path;
import net.onrc.onos.core.topology.Switch;

/**
 * This class creates bandwidth constrained breadth first tree
 * and returns paths from root switch to leaf switches
 * which satisfies the bandwidth condition.
 * If bandwidth parameter is not specified, the normal breadth first tree will be calculated.
 * The paths are snapshot paths at the point of the class instantiation.
 * @author Toshio Koide (t-koide@onlab.us)
 */
public class ConstrainedBFSTree {
	LinkedList<Switch> switchQueue = new LinkedList<>();
	HashSet<Switch> switchSearched = new HashSet<>();
	HashMap<Long, LinkEvent> upstreamLinks = new HashMap<>();
	HashMap<Switch, Path> paths = new HashMap<>();
	Switch rootSwitch;
	PathIntentMap intents = null;
	double bandwidth = 0.0; // 0.0 means no limit for bandwidth (normal BFS tree)

	public ConstrainedBFSTree(Switch rootSwitch) {
		this.rootSwitch = rootSwitch;
		calcTree();
	}

	public ConstrainedBFSTree(Switch rootSwitch, PathIntentMap intents, double bandwidth) {
		this.rootSwitch = rootSwitch;
		this.intents = intents;
		this.bandwidth = bandwidth;
		calcTree();
	}

	protected void calcTree() {
		switchQueue.add(rootSwitch);
		switchSearched.add(rootSwitch);
		while (!switchQueue.isEmpty()) {
			Switch sw = switchQueue.poll();
			for (Link link: sw.getOutgoingLinks()) {
				Switch reachedSwitch = link.getDstPort().getSwitch();
				if (switchSearched.contains(reachedSwitch)) continue;
				if (intents != null && intents.getAvailableBandwidth(link) < bandwidth) continue;
				switchQueue.add(reachedSwitch);
				switchSearched.add(reachedSwitch);
				upstreamLinks.put(reachedSwitch.getDpid(), new LinkEvent(link));
			}
		}
	}

	public Path getPath(Switch leafSwitch) {
		Path path = paths.get(leafSwitch);
		Long rootSwitchDpid = rootSwitch.getDpid();
		if (path == null && switchSearched.contains(leafSwitch)) {
			path = new Path();
			Long sw = leafSwitch.getDpid();
			while (!sw.equals(rootSwitchDpid)) {
				LinkEvent upstreamLink = upstreamLinks.get(sw);
				path.add(0, upstreamLink);
				sw = upstreamLink.getSrc().getDpid();
			}
			paths.put(leafSwitch, path);
		}
		return path;
	}
}