/*-
 * ============LICENSE_START=======================================================
 * openECOMP : SDN-C
 * ================================================================================
 * Copyright (C) 2017 AT&T Intellectual Property. All rights
 * 							reserved.
 * ================================================================================
 * Licensed 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.
 * ============LICENSE_END=========================================================
 */

package org.openecomp.sdnc.rm.util;

import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.openecomp.sdnc.rm.data.AllocationItem;
import org.openecomp.sdnc.rm.data.LimitAllocationItem;
import org.openecomp.sdnc.rm.data.LimitAllocationRequest;
import org.openecomp.sdnc.rm.data.LimitResource;
import org.openecomp.sdnc.rm.data.ResourceKey;
import org.openecomp.sdnc.rm.data.ResourceType;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class LimitUtil {

	private static final Logger log = LoggerFactory.getLogger(LimitUtil.class);

	public static boolean checkLimit(LimitResource l, LimitAllocationRequest req) {
		if (req.checkCount <= 0)
			return true;

		long checkCount = req.checkCount;
		long currentUsage = 0;
		if (req.resourceSetId != null) {
			LimitAllocationItem lai = (LimitAllocationItem) ResourceUtil.getAllocationItem(l, req.resourceSetId);
			if (lai != null)
				currentUsage = lai.used;
		}
		if (!req.replace)
			checkCount += currentUsage;

		long used = calculateLimitUsage(l, 0, null, null);
		long wouldUse = calculateLimitUsage(l, checkCount, req.resourceUnionId, req.resourceShareGroupList);

		// If usage is not increasing by this request, only check the limit if
		// strictCheck is true.
		if (wouldUse <= used && !req.strict)
			return true;

		return wouldUse <= req.checkLimit;
	}

	private static long calculateLimitUsage(
	        LimitResource l,
	        long checkCount,
	        String resourceUnionId,
	        Set<String> resourceShareGroupList) {
		if ((l.allocationItems == null || l.allocationItems.isEmpty()) &&
		        (resourceUnionId == null || resourceUnionId.length() == 0))
			return 0;

		long t1 = System.currentTimeMillis();
		boolean logit = false;
		String rn = "Resource: " + l.resourceKey.resourceName + " - " + l.resourceKey.assetId;

		// In order to best utilize the resource, we need to take not the sum of all allocation items, but
		// instead the maximum usage that could happen at any moment of time (given not all allocation items are active
		// at the same time), also taking into account possible resource sharing.
		// Thus we need to find all combinations of allocation items that can be active at the same time (allocation
		// items with the same first union cannot be active at the same time), compute the usage for each (again,
		// taking into account resource sharing), and take the maximum.
		//
		// Example:
		// Let's have the following allocation items:
		// ai1: sdid1, vrf1 - usage 5
		// ai2: sdid2, vrf1 - usage 10
		// ai3: sdid3, vrf2 - usage 15
		// ai4: sdid1, vrf3 - usage 20
		// ai5: sdid3, vrf1 - usage 25
		// The following combinations of active allocation items are possible:
		// 1) ai1, ai2, ai3
		// 2) ai1, ai2, ai5
		// 3) ai2, ai3, ai4
		// 4) ai2, ai3, ai5
		// Here is how we calculate the usage for combination 1:
		// ai1 and ai2 contain the same resource union vrf1, so they share the resource - we take the max of usage,
		// so we have:
		// max(5, 10) + 15 = 25
		// Similarly, we calculate the usage of the other combinations:
		// 2) max(5, 10, 25) = 25
		// 3) 10 + 15 + 20 = 45
		// 4) max(10, 25) + 15 = 40
		// So, the result in this case is:
		// max(25, 25, 45, 40) = 45
		//
		// We might have a problem with this approach, if we have a lot of combinations. Assuming we have at most 2
		// allocation items with the same resource union (sdid), the number of combinations would be
		// 2 ^ n
		// where n is the number of allocation items that have the same resource union (sdid). That would be
		// the number of change orders currently in progress.
		//
		// Here is one optimization that we can do:
		// If we have allocation items that have all resource unions the same, we don't need to generate combinations
		// with each of them, we can just take the one of them with the maximum usage, as it is clear that the others
		// will not lead to a bigger usage.
		// For example, if we had the following allocation items:
		// ai1: sdid1, vrf1 - usage 10
		// ai2: sdid1, vrf1 - usage 20
		// We only need to take the combinations with ai2, as they will always lead to bigger usage than the remaining
		// combinations with ai1.

		// First, group the allocation items by the first resource union, using the LimitUsage structure
		int regularChangeCount = 0;
		Map<String/* resourceUnionId */, List<LimitUsage>> limitUsageMap = new HashMap<String, List<LimitUsage>>();
		if (l.allocationItems != null)
			for (AllocationItem ai : l.allocationItems) {
				LimitAllocationItem lai = (LimitAllocationItem) ai;
				boolean regularChange =
				        addLimitUsage(limitUsageMap, lai.resourceUnionId, lai.resourceShareGroupList, lai.used);
				if (regularChange)
					regularChangeCount++;
			}
		if (checkCount > 0 && resourceUnionId != null) {
			boolean regularChange = addLimitUsage(limitUsageMap, resourceUnionId, resourceShareGroupList, checkCount);
			if (regularChange)
				regularChangeCount++;
		}

		// Generate all the combinations, containing one LimitUsage object for each firstResourceUnion
		int significantChangeCount = 0;
		List<List<LimitUsage>> allCombinations = new ArrayList<List<LimitUsage>>();
		for (String firstResourceUnion : limitUsageMap.keySet()) {
			List<LimitUsage> limitUsageList = limitUsageMap.get(firstResourceUnion);
			if (limitUsageList.size() > 1)
				significantChangeCount++;
			if (allCombinations.isEmpty()) {
				for (LimitUsage limitUsage : limitUsageList) {
					List<LimitUsage> newCombination = new ArrayList<LimitUsage>();
					newCombination.add(limitUsage);
					allCombinations.add(newCombination);
				}
			} else {
				if (limitUsageList.size() == 1) {
					// No new combinations are generated - just add this one to all combinations we have until now
					for (List<LimitUsage> combination : allCombinations)
						combination.add(limitUsageList.get(0));
				} else {
					// We have to duplicate each of the current combinations for each element of limitUsageList
					List<List<LimitUsage>> newAllCombinations = new ArrayList<List<LimitUsage>>();
					for (List<LimitUsage> combination : allCombinations)
						for (LimitUsage limitUsage : limitUsageList) {
							List<LimitUsage> newCombination = new ArrayList<LimitUsage>(combination);
							newCombination.add(limitUsage);
							newAllCombinations.add(newCombination);
						}
					allCombinations = newAllCombinations;
				}
			}
		}

		// Now, go through all combinations and calculate its usage, get the maximum
		long maxUsage = 0;
		for (List<LimitUsage> combination : allCombinations) {
			long usage = calculateUsage(combination);
			if (usage > maxUsage)
				maxUsage = usage;
		}

		long t2 = System.currentTimeMillis();
		if (logit) {
			log.debug(rn + ": Calculating usage completed:");
			log.debug(rn + ":     Regular changes: " + regularChangeCount);
			log.debug(rn + ":     Significant changes: " + significantChangeCount);
			log.debug(rn + ":     Combinations: " + allCombinations.size());
			log.debug(rn + ":     Usage: " + maxUsage);
			log.debug(rn + ":     Time: " + (t2 - t1));
		}

		return maxUsage;
	}

	private static boolean addLimitUsage(
	        Map<String/* resourceUnionId */, List<LimitUsage>> limitUsageMap,
	        String resourceUnionId,
	        Set<String> resourceShareGroupList,
	        long used) {
		List<LimitUsage> limitUsageList = limitUsageMap.get(resourceUnionId);
		if (limitUsageList == null) {
			limitUsageList = new ArrayList<LimitUsage>();
			limitUsageMap.put(resourceUnionId, limitUsageList);
		}
		// See if we already have the same shareResourceUnionSet in the list. In such case just update the usage
		// to the bigger value.
		LimitUsage limitUsage = null;
		for (LimitUsage limitUsage1 : limitUsageList) {
			if ((limitUsage1.resourceShareGroupList == null || limitUsage1.resourceShareGroupList.isEmpty()) &&
			        (resourceShareGroupList == null || resourceShareGroupList.isEmpty())) {
				limitUsage = limitUsage1;
				break;
			}
			if (limitUsage1.resourceShareGroupList != null &&
			        limitUsage1.resourceShareGroupList.equals(resourceShareGroupList)) {
				limitUsage = limitUsage1;
				break;
			}
		}
		if (limitUsage != null) {
			if (limitUsage.usage < used)
				limitUsage.usage = used;
			return true;
		}

		limitUsage = new LimitUsage();
		limitUsage.resourceUnion = resourceUnionId;
		limitUsage.resourceShareGroupList = resourceShareGroupList;
		limitUsage.usage = used;
		limitUsageList.add(limitUsage);
		return false;
	}

	private static class LimitUsage {

		@SuppressWarnings("unused")
		public String resourceUnion;
		public Set<String> resourceShareGroupList;
		public long usage;
	}

	private static boolean hasCommonSharedResource(LimitUsage limitUsage1, LimitUsage limitUsage2) {
		if (limitUsage1.resourceShareGroupList == null || limitUsage1.resourceShareGroupList.isEmpty())
			return false;
		if (limitUsage2.resourceShareGroupList == null || limitUsage2.resourceShareGroupList.isEmpty())
			return false;

		for (String resourceUnion : limitUsage1.resourceShareGroupList)
			if (limitUsage2.resourceShareGroupList.contains(resourceUnion))
				return true;

		return false;
	}

	private static long calculateUsage(List<LimitUsage> combination) {
		// All LimitUsage objects that have a common value in their sharedResourceUnionSet reuse the resource, so
		// split the combination in sets that have common value. Then the usage of each set will be the maximum of
		// the usages of the LimitUsage objects in the set. The usage of the combination will be the sum of the usages
		// of all sets.
		List<List<LimitUsage>> sharedSets = new ArrayList<List<LimitUsage>>();
		for (LimitUsage limitUsage : combination) {
			// See if we can put limitUsage in any of the existing sets - is it has a common resource union with
			// any of the LimitUsage objects in a set.
			boolean found = false;
			for (List<LimitUsage> sharedSet : sharedSets) {
				for (LimitUsage limitUsage1 : sharedSet) {
					if (hasCommonSharedResource(limitUsage, limitUsage1)) {
						found = true;
						break;
					}
				}
				if (found) {
					sharedSet.add(limitUsage);
					break;
				}
			}
			if (!found) {
				// Start a new set
				List<LimitUsage> newSharedSet = new ArrayList<LimitUsage>();
				newSharedSet.add(limitUsage);
				sharedSets.add(newSharedSet);
			}
		}

		long sum = 0;
		for (List<LimitUsage> sharedSet : sharedSets) {
			float max = 0;
			for (LimitUsage limitUsage : sharedSet)
				if (max < limitUsage.usage)
					max = limitUsage.usage;
			sum += max;
		}

		return sum;
	}

	public static long allocateLimit(LimitResource l, LimitAllocationRequest req, String applicationId) {
		if (req.allocateCount <= 0)
			return 0;
		long uu = l.used;

		LimitAllocationItem lai = (LimitAllocationItem) ResourceUtil.getAllocationItem(l, req.resourceSetId);
		if (lai == null) {
			lai = new LimitAllocationItem();
			lai.resourceType = ResourceType.Limit;
			lai.resourceKey = new ResourceKey();
			lai.resourceKey.assetId = req.assetId;
			lai.resourceKey.resourceName = req.resourceName;
			lai.applicationId = applicationId;
			lai.resourceSetId = req.resourceSetId;
			lai.resourceUnionId = req.resourceUnionId;
			lai.resourceShareGroupList = req.resourceShareGroupList;
			lai.used = req.allocateCount;

			if (l.allocationItems == null)
				l.allocationItems = new ArrayList<AllocationItem>();
			l.allocationItems.add(lai);
		} else
			lai.used = req.replace ? req.allocateCount : lai.used + req.allocateCount;

		lai.allocationTime = new Date();

		recalculate(l);

		return l.used - uu;
	}

	public static void recalculate(LimitResource l) {
		l.used = calculateLimitUsage(l, 0, null, null);
	}
}