/**
 * 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.lens.cube.parse;

import static org.apache.lens.cube.parse.CandidateTablePruneCause.incompletePartitions;
import static org.apache.lens.cube.parse.CandidateTablePruneCause.partitionColumnsMissing;

import java.util.*;

import org.apache.lens.cube.metadata.*;
import org.apache.lens.cube.parse.CandidateTablePruneCause.CandidateTablePruneCode;
import org.apache.lens.cube.parse.CandidateTablePruneCause.SkipUpdatePeriodCode;
import org.apache.lens.server.api.error.LensException;

import org.apache.commons.lang.StringUtils;
import org.apache.hadoop.conf.Configuration;

import com.google.common.collect.Lists;
import lombok.extern.slf4j.Slf4j;
/**
 * Resolve storages and partitions of all candidate tables and prunes candidate tables with missing storages or
 * partitions.
 */
@Slf4j
class StorageTableResolver implements ContextRewriter {

  private final Configuration conf;
  private final List<String> supportedStorages;
  private final boolean allStoragesSupported;
  private final boolean failOnPartialData;
  private final List<String> validDimTables;
  private final UpdatePeriod maxInterval;
  // TODO union : Remove this. All partitions are stored in the StorageCandidate.
  private final Map<String, Set<String>> nonExistingPartitions = new HashMap<>();
  private CubeMetastoreClient client;
  private PHASE phase;

  StorageTableResolver(Configuration conf) {
    this.conf = conf;
    this.supportedStorages = getSupportedStorages(conf);
    this.allStoragesSupported = (supportedStorages == null);
    this.failOnPartialData = conf.getBoolean(CubeQueryConfUtil.FAIL_QUERY_ON_PARTIAL_DATA, false);
    String str = conf.get(CubeQueryConfUtil.VALID_STORAGE_DIM_TABLES);
    validDimTables = StringUtils.isBlank(str) ? null : Arrays.asList(StringUtils.split(str.toLowerCase(), ","));
    String maxIntervalStr = conf.get(CubeQueryConfUtil.QUERY_MAX_INTERVAL);
    if (maxIntervalStr != null) {
      this.maxInterval = UpdatePeriod.valueOf(maxIntervalStr.toUpperCase());
    } else {
      this.maxInterval = null;
    }
    this.phase = PHASE.first();
  }

  private List<String> getSupportedStorages(Configuration conf) {
    String[] storages = conf.getStrings(CubeQueryConfUtil.DRIVER_SUPPORTED_STORAGES);
    if (storages != null) {
      return Arrays.asList(storages);
    }
    return null;
  }

  private boolean isStorageSupportedOnDriver(String storage) {
    return allStoragesSupported || supportedStorages.contains(storage);
  }

  @Override
  public void rewriteContext(CubeQueryContext cubeql) throws LensException {
    client = cubeql.getMetastoreClient();

    switch (phase) {
    case STORAGE_TABLES:
      if (!cubeql.getCandidates().isEmpty()) {
        resolveStorageTable(cubeql);
      }
      break;
    case STORAGE_PARTITIONS:
      if (!cubeql.getCandidates().isEmpty()) {
        resolveStoragePartitions(cubeql);
      }
      break;
    case DIM_TABLE_AND_PARTITIONS:
      resolveDimStorageTablesAndPartitions(cubeql);
      if (cubeql.getAutoJoinCtx() != null) {
        // After all candidates are pruned after storage resolver, prune join paths.
        cubeql.getAutoJoinCtx()
          .pruneAllPaths(cubeql.getCube(), CandidateUtil.getStorageCandidates(cubeql.getCandidates()), null);
        cubeql.getAutoJoinCtx().pruneAllPathsForCandidateDims(cubeql.getCandidateDimTables());
        cubeql.getAutoJoinCtx().refreshJoinPathColumns();
      }
      // TODO union : What is this? We may not need this as it non existing partitions are stored in StorageCandidate
      cubeql.setNonexistingParts(nonExistingPartitions);
      break;
    }
    phase = phase.next();
  }

  /**
   * Each candidate in the set is a complex candidate. We will evaluate each one to get
   * all the partitions needed to answer the query.
   *
   * @param cubeql cube query context
   */
  private void resolveStoragePartitions(CubeQueryContext cubeql) throws LensException {
    Iterator<Candidate> candidateIterator = cubeql.getCandidates().iterator();
    while (candidateIterator.hasNext()) {
      Candidate candidate = candidateIterator.next();
      boolean isComplete = true;
      boolean isTimeRangeAnswerableByThisCandidate = true;
      for (TimeRange range : cubeql.getTimeRanges()) {
        if (!candidate.isTimeRangeCoverable(range)) {
          isTimeRangeAnswerableByThisCandidate = false;
          log.info("Not considering candidate:{} as it can not cover time range {}", candidate, range);
          cubeql.addCandidatePruningMsg(candidate,
            CandidateTablePruneCause.storageNotAvailableInRange(Lists.newArrayList(range)));
          break;
        }
        isComplete &= candidate.evaluateCompleteness(range, range, failOnPartialData);
      }
      if (!isTimeRangeAnswerableByThisCandidate) {
        candidateIterator.remove();
      } else if (failOnPartialData && !isComplete) {
        candidateIterator.remove();
        log.info("Not considering candidate:{} as its data is not is not complete", candidate);
        Set<StorageCandidate> scSet = CandidateUtil.getStorageCandidates(candidate);
        for (StorageCandidate sc : scSet) {
          if (!sc.getNonExistingPartitions().isEmpty()) {
            cubeql.addStoragePruningMsg(sc, CandidateTablePruneCause.missingPartitions(sc.getNonExistingPartitions()));
          } else if (!sc.getDataCompletenessMap().isEmpty()) {
            cubeql.addStoragePruningMsg(sc, incompletePartitions(sc.getDataCompletenessMap()));
          }
        }
      } else if (candidate.getParticipatingPartitions().isEmpty()
        && candidate instanceof StorageCandidate
        && ((StorageCandidate) candidate).getNonExistingPartitions().isEmpty()) {
        candidateIterator.remove();
        cubeql.addCandidatePruningMsg(candidate,
          new CandidateTablePruneCause(CandidateTablePruneCode.NO_FACT_UPDATE_PERIODS_FOR_GIVEN_RANGE));
      }
    }
  }

  private void resolveDimStorageTablesAndPartitions(CubeQueryContext cubeql) throws LensException {
    Set<Dimension> allDims = new HashSet<>(cubeql.getDimensions());
    for (Aliased<Dimension> dim : cubeql.getOptionalDimensions()) {
      allDims.add(dim.getObject());
    }
    for (Dimension dim : allDims) {
      Set<CandidateDim> dimTables = cubeql.getCandidateDimTables().get(dim);
      if (dimTables == null || dimTables.isEmpty()) {
        continue;
      }
      Iterator<CandidateDim> i = dimTables.iterator();
      while (i.hasNext()) {
        CandidateDim candidate = i.next();
        CubeDimensionTable dimtable = candidate.dimtable;
        if (dimtable.getStorages().isEmpty()) {
          cubeql
            .addDimPruningMsgs(dim, dimtable, new CandidateTablePruneCause(CandidateTablePruneCode.MISSING_STORAGES));
          i.remove();
          continue;
        }
        Set<String> storageTables = new HashSet<>();
        Map<String, String> whereClauses = new HashMap<String, String>();
        boolean foundPart = false;
        // TODO union : We have to remove all usages of a deprecated class.
        Map<String, CandidateTablePruneCode> skipStorageCauses = new HashMap<>();
        for (String storage : dimtable.getStorages()) {
          if (isStorageSupportedOnDriver(storage)) {
            String tableName = MetastoreUtil.getFactOrDimtableStorageTableName(dimtable.getName(),
                storage).toLowerCase();
            if (validDimTables != null && !validDimTables.contains(tableName)) {
              log.info("Not considering dim storage table:{} as it is not a valid dim storage", tableName);
              skipStorageCauses.put(tableName, CandidateTablePruneCode.INVALID);
              continue;
            }

            if (dimtable.hasStorageSnapshots(storage)) {
              // check if partition exists
              foundPart = client.dimTableLatestPartitionExists(tableName);
              if (foundPart) {
                log.debug("Adding existing partition {}", StorageConstants.LATEST_PARTITION_VALUE);
              } else {
                log.info("Partition {} does not exist on {}", StorageConstants.LATEST_PARTITION_VALUE, tableName);
              }
              if (!failOnPartialData || foundPart) {
                storageTables.add(tableName);
                String whereClause = StorageUtil
                  .getWherePartClause(dim.getTimedDimension(), null, StorageConstants.getPartitionsForLatest());
                whereClauses.put(tableName, whereClause);
              } else {
                log.info("Not considering dim storage table:{} as no dim partitions exist", tableName);
                skipStorageCauses.put(tableName, CandidateTablePruneCode.NO_PARTITIONS);
              }
            } else {
              storageTables.add(tableName);
              foundPart = true;
            }
          } else {
            log.info("Storage:{} is not supported", storage);
            skipStorageCauses.put(storage, CandidateTablePruneCode.UNSUPPORTED_STORAGE);
          }
        }
        if (!foundPart) {
          addNonExistingParts(dim.getName(), StorageConstants.getPartitionsForLatest());
        }
        if (storageTables.isEmpty()) {
          log.info("Not considering dim table:{} as no candidate storage tables eixst", dimtable);
          cubeql.addDimPruningMsgs(dim, dimtable,
              CandidateTablePruneCause.noCandidateStoragesForDimtable(skipStorageCauses));
          i.remove();
          continue;
        }
        // pick the first storage table
        candidate.setStorageTable(storageTables.iterator().next());
        candidate.setWhereClause(whereClauses.get(candidate.getStorageTable()));
      }
    }
  }

  /**
   * Following storages are removed:
   * 1. The storage is not supported by driver.
   * 2. The storage is not in the valid storage list.
   * 3. The storage is not in any time range in the query.
   * 4. The storage having no valid update period.
   *
   * This method also creates a list of valid update periods and stores them into {@link StorageCandidate}.
   *
   * TODO union : Do fourth point before 3.
   */
  private void resolveStorageTable(CubeQueryContext cubeql) throws LensException {
    Iterator<Candidate> it = cubeql.getCandidates().iterator();
    while (it.hasNext()) {
      Candidate c = it.next();
      assert (c instanceof StorageCandidate);
      StorageCandidate sc = (StorageCandidate) c;
      String storageTable = sc.getStorageName();
      // first check: if the storage is supported on driver
      if (!isStorageSupportedOnDriver(storageTable)) {
        log.info("Skipping storage: {} as it is not supported", storageTable);
        cubeql.addStoragePruningMsg(sc, new CandidateTablePruneCause(CandidateTablePruneCode.UNSUPPORTED_STORAGE));
        it.remove();
        continue;
      }
      String str = conf.get(CubeQueryConfUtil.getValidStorageTablesKey(sc.getFact().getName()));
      List<String> validFactStorageTables =
        StringUtils.isBlank(str) ? null : Arrays.asList(StringUtils.split(str.toLowerCase(), ","));
      storageTable = sc.getStorageTable();
      // Check if storagetable is in the list of valid storages.
      if (validFactStorageTables != null && !validFactStorageTables.contains(storageTable)) {
        log.info("Skipping storage table {} as it is not valid", storageTable);
        cubeql.addStoragePruningMsg(sc, new CandidateTablePruneCause(CandidateTablePruneCode.INVALID_STORAGE));
        it.remove();
        continue;
      }
      List<String> validUpdatePeriods = CubeQueryConfUtil
        .getStringList(conf, CubeQueryConfUtil.getValidUpdatePeriodsKey(sc.getFact().getName(), sc.getStorageName()));
      boolean isUpdatePeriodForStorageAdded = false;
      Map<String, SkipUpdatePeriodCode> skipUpdatePeriodCauses = new HashMap<>();

      if (cubeql.getTimeRanges().stream().noneMatch(range -> CandidateUtil.isPartiallyValidForTimeRange(sc, range))) {
        cubeql.addStoragePruningMsg(sc,
          new CandidateTablePruneCause(CandidateTablePruneCode.TIME_RANGE_NOT_ANSWERABLE));
        it.remove();
        continue;
      }

      // Populate valid update periods abd check validity at update period level
      for (UpdatePeriod updatePeriod : sc.getFact().getUpdatePeriods().get(sc.getStorageName())) {
        if (maxInterval != null && updatePeriod.compareTo(maxInterval) > 0) {
          // if user supplied max interval, all intervals larger than that are useless.
          log.info("Skipping update period {} for candidate {} since it's more than max interval supplied({})",
            updatePeriod, sc.getStorageTable(), maxInterval);
          skipUpdatePeriodCauses.put(updatePeriod.toString(), SkipUpdatePeriodCode.UPDATE_PERIOD_BIGGER_THAN_MAX);
        } else if (validUpdatePeriods != null && !validUpdatePeriods.contains(updatePeriod.name().toLowerCase())) {
          // if user supplied valid update periods, other update periods are useless
          log.info("Skipping update period {} for candidate {} for storage {} since it's invalid",
            updatePeriod, sc.getStorageTable(), storageTable);
          skipUpdatePeriodCauses.put(updatePeriod.toString(), SkipUpdatePeriodCode.INVALID);
        } else if (!sc.isUpdatePeriodUseful(updatePeriod)) {
          // if the storage candidate finds this update useful to keep looking at the time ranges queried
          skipUpdatePeriodCauses.put(updatePeriod.toString(),
            SkipUpdatePeriodCode.TIME_RANGE_NOT_ANSWERABLE_BY_UPDATE_PERIOD);
        } else {
          isUpdatePeriodForStorageAdded = true;
          sc.addValidUpdatePeriod(updatePeriod);
        }
      }
      // For DEBUG purpose only to see why some update periods are skipped.
      if (!skipUpdatePeriodCauses.isEmpty()) {
        sc.setUpdatePeriodRejectionCause(skipUpdatePeriodCauses);
      }
      // if no update periods were added in previous section, we skip this storage candidate
      if (!isUpdatePeriodForStorageAdded) {
        if (skipUpdatePeriodCauses.values().stream().allMatch(
          SkipUpdatePeriodCode.TIME_RANGE_NOT_ANSWERABLE_BY_UPDATE_PERIOD::equals)) {
          // all update periods bigger than query range, it means time range not answerable.
          cubeql.addStoragePruningMsg(sc,
            new CandidateTablePruneCause(CandidateTablePruneCode.TIME_RANGE_NOT_ANSWERABLE));
        } else { // Update periods are rejected for multiple reasons.
          cubeql.addStoragePruningMsg(sc, CandidateTablePruneCause.updatePeriodsRejected(skipUpdatePeriodCauses));
        }
        it.remove();
      } else {
        //set the dates again as they can change based on ValidUpdatePeriod
        sc.setStorageStartAndEndDate();
        Set<CandidateTablePruneCause> allPruningCauses = new HashSet<>(cubeql.getTimeRanges().size());
        for (TimeRange range : cubeql.getTimeRanges()) {
          CandidateTablePruneCause pruningCauseForThisTimeRange = null;
          if (!CandidateUtil.isPartiallyValidForTimeRange(sc, range)) {
            //This is the prune cause
            pruningCauseForThisTimeRange =
              new CandidateTablePruneCause(CandidateTablePruneCode.TIME_RANGE_NOT_ANSWERABLE);
          } else if (cubeql.shouldReplaceTimeDimWithPart()) {
            if (!client.partColExists(sc.getFact().getName(), sc.getStorageName(), range.getPartitionColumn())) {
              pruningCauseForThisTimeRange = partitionColumnsMissing(range.getPartitionColumn());
              TimeRange fallBackRange = StorageUtil.getFallbackRange(range, sc.getFact().getName(), cubeql);
              while (fallBackRange != null) {
                pruningCauseForThisTimeRange = null;
                if (!client.partColExists(sc.getFact().getName(), sc.getStorageName(),
                  fallBackRange.getPartitionColumn())) {
                  pruningCauseForThisTimeRange = partitionColumnsMissing(fallBackRange.getPartitionColumn());
                  fallBackRange = StorageUtil.getFallbackRange(fallBackRange, sc.getFact().getName(), cubeql);
                } else {
                  if (!CandidateUtil.isPartiallyValidForTimeRange(sc, fallBackRange)) {
                    pruningCauseForThisTimeRange =
                      new CandidateTablePruneCause(CandidateTablePruneCode.TIME_RANGE_NOT_ANSWERABLE);
                  }
                  break;
                }
              }
            }
          }

          if (pruningCauseForThisTimeRange != null) {
            allPruningCauses.add(pruningCauseForThisTimeRange);
          }
        }
        if (!allPruningCauses.isEmpty()) {
          // TODO if this storage can answer atleast one time range , why prune it ?
          it.remove();
          cubeql.addStoragePruningMsg(sc, allPruningCauses.toArray(new CandidateTablePruneCause[0]));
        }
      }
    }
  }

  private void addNonExistingParts(String name, Set<String> nonExistingParts) {
    nonExistingPartitions.put(name, nonExistingParts);
  }

  enum PHASE {
    STORAGE_TABLES, STORAGE_PARTITIONS, DIM_TABLE_AND_PARTITIONS;

    static PHASE first() {
      return values()[0];
    }

    static PHASE last() {
      return values()[values().length - 1];
    }

    PHASE next() {
      return values()[(this.ordinal() + 1) % values().length];
    }
  }
}