/**
 * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.  The ASF licenses this file to you under the Apache License, Version
 * 2.0 (the "License"); you may not use this file except in compliance with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions
 * and limitations under the License.
 */

package org.apache.storm.scheduler.multitenant;

import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.Set;
import org.apache.storm.scheduler.SchedulerAssignment;
import org.apache.storm.scheduler.TopologyDetails;
import org.apache.storm.scheduler.WorkerSlot;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * A pool of machines that anyone can use, but topologies are not isolated
 */
public class DefaultPool extends NodePool {
    private static final Logger LOG = LoggerFactory.getLogger(DefaultPool.class);
    private Set<Node> _nodes = new HashSet<>();
    private HashMap<String, TopologyDetails> _tds = new HashMap<>();

    @Override
    public void addTopology(TopologyDetails td) {
        String topId = td.getId();
        LOG.debug("Adding in Topology {}", topId);
        _tds.put(topId, td);
        SchedulerAssignment assignment = _cluster.getAssignmentById(topId);
        if (assignment != null) {
            for (WorkerSlot ws : assignment.getSlots()) {
                Node n = _nodeIdToNode.get(ws.getNodeId());
                _nodes.add(n);
            }
        }
    }

    @Override
    public boolean canAdd(TopologyDetails td) {
        return true;
    }

    @Override
    public Collection<Node> takeNodes(int nodesNeeded) {
        HashSet<Node> ret = new HashSet<>();
        LinkedList<Node> sortedNodes = new LinkedList<>(_nodes);
        Collections.sort(sortedNodes, Node.FREE_NODE_COMPARATOR_DEC);
        for (Node n : sortedNodes) {
            if (nodesNeeded <= ret.size()) {
                break;
            }
            if (n.isAlive()) {
                n.freeAllSlots(_cluster);
                _nodes.remove(n);
                ret.add(n);
            }
        }
        return ret;
    }

    @Override
    public int nodesAvailable() {
        int total = 0;
        for (Node n : _nodes) {
            if (n.isAlive()) total++;
        }
        return total;
    }

    @Override
    public int slotsAvailable() {
        return Node.countTotalSlotsAlive(_nodes);
    }

    @Override
    public NodeAndSlotCounts getNodeAndSlotCountIfSlotsWereTaken(int slotsNeeded) {
        int nodesFound = 0;
        int slotsFound = 0;
        LinkedList<Node> sortedNodes = new LinkedList<>(_nodes);
        Collections.sort(sortedNodes, Node.FREE_NODE_COMPARATOR_DEC);
        for (Node n : sortedNodes) {
            if (slotsNeeded <= 0) {
                break;
            }
            if (n.isAlive()) {
                nodesFound++;
                int totalSlotsFree = n.totalSlots();
                slotsFound += totalSlotsFree;
                slotsNeeded -= totalSlotsFree;
            }
        }
        return new NodeAndSlotCounts(nodesFound, slotsFound);
    }

    @Override
    public Collection<Node> takeNodesBySlots(int slotsNeeded) {
        HashSet<Node> ret = new HashSet<>();
        LinkedList<Node> sortedNodes = new LinkedList<>(_nodes);
        Collections.sort(sortedNodes, Node.FREE_NODE_COMPARATOR_DEC);
        for (Node n : sortedNodes) {
            if (slotsNeeded <= 0) {
                break;
            }
            if (n.isAlive()) {
                n.freeAllSlots(_cluster);
                _nodes.remove(n);
                ret.add(n);
                slotsNeeded -= n.totalSlotsFree();
            }
        }
        return ret;
    }

    @Override
    public void scheduleAsNeeded(NodePool... lesserPools) {
        for (TopologyDetails td : _tds.values()) {
            String topId = td.getId();
            if (_cluster.needsScheduling(td)) {
                LOG.debug("Scheduling topology {}", topId);
                int totalTasks = td.getExecutors().size();
                int origRequest = td.getNumWorkers();
                int slotsRequested = Math.min(totalTasks, origRequest);
                int slotsUsed = Node.countSlotsUsed(topId, _nodes);
                int slotsFree = Node.countFreeSlotsAlive(_nodes);
                //Check to see if we have enough slots before trying to get them
                int slotsAvailable = 0;
                if (slotsRequested > slotsFree) {
                    slotsAvailable = NodePool.slotsAvailable(lesserPools);
                }
                int slotsToUse = Math.min(slotsRequested - slotsUsed, slotsFree + slotsAvailable);
                int executorsNotRunning = _cluster.getUnassignedExecutors(td).size();
                LOG.debug("Slots... requested {} used {} free {} available {} to be used {}, executors not running {}",
                          slotsRequested, slotsUsed, slotsFree, slotsAvailable, slotsToUse, executorsNotRunning);
                if (slotsToUse <= 0) {
                    if (executorsNotRunning > 0) {
                        _cluster.setStatus(topId, "Not fully scheduled (No free slots in default pool) " + executorsNotRunning +
                                                  " executors not scheduled");
                    } else {
                        if (slotsUsed < slotsRequested) {
                            _cluster.setStatus(topId, "Running with fewer slots than requested (" + slotsUsed + "/" + origRequest + ")");
                        } else { //slotsUsed < origRequest
                            _cluster.setStatus(topId,
                                               "Fully Scheduled (requested " + origRequest + " slots, but could only use " + slotsUsed +
                                               ")");
                        }
                    }
                    continue;
                }

                int slotsNeeded = slotsToUse - slotsFree;
                if (slotsNeeded > 0) {
                    _nodes.addAll(NodePool.takeNodesBySlot(slotsNeeded, lesserPools));
                }

                if (executorsNotRunning <= 0) {
                    //There are free slots that we can take advantage of now.
                    for (Node n : _nodes) {
                        n.freeTopology(topId, _cluster);
                    }
                    slotsFree = Node.countFreeSlotsAlive(_nodes);
                    slotsToUse = Math.min(slotsRequested, slotsFree);
                }

                RoundRobinSlotScheduler slotSched =
                    new RoundRobinSlotScheduler(td, slotsToUse, _cluster);

                LinkedList<Node> nodes = new LinkedList<>(_nodes);
                while (true) {
                    Node n;
                    do {
                        if (nodes.isEmpty()) {
                            throw new IllegalStateException("This should not happen, we" +
                                                            " messed up and did not get enough slots");
                        }
                        n = nodes.peekFirst();
                        if (n.totalSlotsFree() == 0) {
                            nodes.remove();
                            n = null;
                        }
                    } while (n == null);
                    if (!slotSched.assignSlotTo(n)) {
                        break;
                    }
                }
                int afterSchedSlotsUsed = Node.countSlotsUsed(topId, _nodes);
                if (afterSchedSlotsUsed < slotsRequested) {
                    _cluster.setStatus(topId, "Running with fewer slots than requested (" + afterSchedSlotsUsed + "/" + origRequest + ")");
                } else if (afterSchedSlotsUsed < origRequest) {
                    _cluster.setStatus(topId,
                                       "Fully Scheduled (requested " + origRequest + " slots, but could only use " + afterSchedSlotsUsed +
                                       ")");
                } else {
                    _cluster.setStatus(topId, "Fully Scheduled");
                }
            } else {
                _cluster.setStatus(topId, "Fully Scheduled");
            }
        }
    }

    @Override
    public String toString() {
        return "DefaultPool  " + _nodes.size() + " nodes " + _tds.size() + " topologies";
    }
}
