/*
    * 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.shardingsphere.sharding.route.engine.condition;
  
  import lombok.Getter;
  import lombok.ToString;
  import org.apache.shardingsphere.infra.binder.context.statement.SQLStatementContext;
  import org.apache.shardingsphere.infra.binder.context.statement.dml.InsertStatementContext;
  import org.apache.shardingsphere.infra.binder.context.statement.dml.SelectStatementContext;
  import org.apache.shardingsphere.sharding.api.config.strategy.sharding.HintShardingStrategyConfiguration;
  import org.apache.shardingsphere.sharding.api.config.strategy.sharding.NoneShardingStrategyConfiguration;
  import org.apache.shardingsphere.sharding.api.config.strategy.sharding.ShardingStrategyConfiguration;
  import org.apache.shardingsphere.sharding.route.engine.condition.value.ListShardingConditionValue;
  import org.apache.shardingsphere.sharding.route.engine.condition.value.RangeShardingConditionValue;
  import org.apache.shardingsphere.sharding.route.engine.condition.value.ShardingConditionValue;
  import org.apache.shardingsphere.sharding.rule.BindingTableRule;
  import org.apache.shardingsphere.sharding.rule.ShardingRule;
  import org.apache.shardingsphere.sharding.rule.ShardingTable;
  import org.apache.shardingsphere.sql.parser.sql.common.segment.generic.table.SubqueryTableSegment;
  import org.apache.shardingsphere.sql.parser.sql.common.statement.dml.SelectStatement;
  import org.apache.shardingsphere.sql.parser.sql.common.util.SafeNumberOperationUtils;
  
  import java.util.Collection;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.Map;
  import java.util.Optional;
  
  /**
   * Sharding conditions.
   */
  @Getter
  @ToString
  public final class ShardingConditions {
      
      private final List<ShardingCondition> conditions;
      
      private final SQLStatementContext sqlStatementContext;
      
      private final ShardingRule rule;
      
      private final boolean subqueryContainsShardingCondition;
      
      public ShardingConditions(final List<ShardingCondition> conditions, final SQLStatementContext sqlStatementContext, final ShardingRule rule) {
          this.conditions = conditions;
          this.sqlStatementContext = sqlStatementContext;
          this.rule = rule;
          subqueryContainsShardingCondition = isSubqueryContainsShardingCondition(conditions, sqlStatementContext);
      }
      
      /**
       * Judge sharding conditions is always false or not.
       *
       * @return sharding conditions is always false or not
       */
      public boolean isAlwaysFalse() {
          if (conditions.isEmpty()) {
              return false;
          }
          for (ShardingCondition each : conditions) {
              if (!(each instanceof AlwaysFalseShardingCondition)) {
                  return false;
              }
          }
          return true;
      }
      
      /**
       * Merge sharding conditions.
       */
      public void merge() {
          if (conditions.size() > 1) {
              Collection<ShardingCondition> result = new LinkedList<>();
              result.add(conditions.remove(conditions.size() - 1));
              while (!conditions.isEmpty()) {
                  findUniqueShardingCondition(result, conditions.remove(conditions.size() - 1)).ifPresent(result::add);
              }
              conditions.addAll(result);
          }
      }
      
      private Optional<ShardingCondition> findUniqueShardingCondition(final Collection<ShardingCondition> conditions, final ShardingCondition condition) {
         for (ShardingCondition each : conditions) {
             if (isSameShardingCondition(rule, condition, each)) {
                 return Optional.empty();
             }
         }
         return Optional.of(condition);
     }
     
     /**
      * Judge whether sharding condition need merge or not.
      *
      * @return whether sharding condition need merge or not
      */
     public boolean isNeedMerge() {
         boolean selectContainsSubquery = sqlStatementContext instanceof SelectStatementContext && ((SelectStatementContext) sqlStatementContext).isContainsSubquery();
         boolean insertSelectContainsSubquery = sqlStatementContext instanceof InsertStatementContext && null != ((InsertStatementContext) sqlStatementContext).getInsertSelectContext()
                 && ((InsertStatementContext) sqlStatementContext).getInsertSelectContext().getSelectStatementContext().isContainsSubquery();
         return (selectContainsSubquery || insertSelectContainsSubquery) && !rule.getShardingLogicTableNames(sqlStatementContext.getTablesContext().getTableNames()).isEmpty();
     }
     
     private boolean isSubqueryContainsShardingCondition(final List<ShardingCondition> conditions, final SQLStatementContext sqlStatementContext) {
         Collection<SelectStatement> selectStatements = getSelectStatements(sqlStatementContext);
         if (selectStatements.size() > 1) {
             Map<Integer, List<ShardingCondition>> startIndexShardingConditions = new HashMap<>(conditions.size(), 1F);
             for (ShardingCondition each : conditions) {
                 startIndexShardingConditions.computeIfAbsent(each.getStartIndex(), unused -> new LinkedList<>()).add(each);
             }
             for (SelectStatement each : selectStatements) {
                 if (each.getFrom().isPresent() && each.getFrom().get() instanceof SubqueryTableSegment) {
                     continue;
                 }
                 if (!each.getWhere().isPresent() || !startIndexShardingConditions.containsKey(each.getWhere().get().getExpr().getStartIndex())) {
                     return false;
                 }
             }
         }
         return true;
     }
     
     private Collection<SelectStatement> getSelectStatements(final SQLStatementContext sqlStatementContext) {
         Collection<SelectStatement> result = new LinkedList<>();
         if (sqlStatementContext instanceof SelectStatementContext) {
             result.add(((SelectStatementContext) sqlStatementContext).getSqlStatement());
             for (SelectStatementContext each : ((SelectStatementContext) sqlStatementContext).getSubqueryContexts().values()) {
                 result.add(each.getSqlStatement());
             }
         }
         if (sqlStatementContext instanceof InsertStatementContext && null != ((InsertStatementContext) sqlStatementContext).getInsertSelectContext()) {
             SelectStatementContext selectStatementContext = ((InsertStatementContext) sqlStatementContext).getInsertSelectContext().getSelectStatementContext();
             result.add(selectStatementContext.getSqlStatement());
             for (SelectStatementContext each : selectStatementContext.getSubqueryContexts().values()) {
                 result.add(each.getSqlStatement());
             }
         }
         return result;
     }
     
     /**
      * Judge whether all sharding conditions are same or not.
      *
      * @return whether all sharding conditions are same or not
      */
     public boolean isSameShardingCondition() {
         Collection<String> hintStrategyTables = findHintStrategyTables(sqlStatementContext);
         return 1 == hintStrategyTables.size() || subqueryContainsShardingCondition && 1 == conditions.size();
     }
     
     private boolean isSameShardingCondition(final ShardingRule shardingRule, final ShardingCondition shardingCondition1, final ShardingCondition shardingCondition2) {
         if (shardingCondition1.getValues().size() != shardingCondition2.getValues().size()) {
             return false;
         }
         for (int i = 0; i < shardingCondition1.getValues().size(); i++) {
             ShardingConditionValue shardingValue1 = shardingCondition1.getValues().get(i);
             ShardingConditionValue shardingValue2 = shardingCondition2.getValues().get(i);
             if (!isSameShardingConditionValue(shardingRule, shardingValue1, shardingValue2)) {
                 return false;
             }
         }
         return true;
     }
     
     private boolean isSameShardingCondition(final ShardingConditionValue shardingValue1, final ShardingConditionValue shardingValue2) {
         return shardingValue1.getTableName().equals(shardingValue2.getTableName()) && shardingValue1.getColumnName().equals(shardingValue2.getColumnName());
     }
     
     private Collection<String> findHintStrategyTables(final SQLStatementContext sqlStatementContext) {
         Collection<String> result = new HashSet<>(sqlStatementContext.getTablesContext().getTableNames().size(), 1F);
         for (String each : sqlStatementContext.getTablesContext().getTableNames()) {
             Optional<ShardingTable> shardingTable = rule.findShardingTable(each);
             if (!shardingTable.isPresent()) {
                 continue;
             }
             ShardingStrategyConfiguration databaseHintStrategy = rule.getDatabaseShardingStrategyConfiguration(shardingTable.get());
             ShardingStrategyConfiguration tableHintStrategy = rule.getTableShardingStrategyConfiguration(shardingTable.get());
             boolean isDatabaseTableHintStrategy = databaseHintStrategy instanceof HintShardingStrategyConfiguration && tableHintStrategy instanceof HintShardingStrategyConfiguration;
             boolean isDatabaseHintStrategy = databaseHintStrategy instanceof HintShardingStrategyConfiguration && tableHintStrategy instanceof NoneShardingStrategyConfiguration;
             boolean isTableHintStrategy = databaseHintStrategy instanceof NoneShardingStrategyConfiguration && tableHintStrategy instanceof HintShardingStrategyConfiguration;
             if (isDatabaseTableHintStrategy || isDatabaseHintStrategy || isTableHintStrategy) {
                 result.add(each);
             }
         }
         return result;
     }
     
     private boolean isBindingTable(final ShardingRule shardingRule, final ShardingConditionValue shardingValue1, final ShardingConditionValue shardingValue2) {
         Optional<BindingTableRule> bindingRule = shardingRule.findBindingTableRule(shardingValue1.getTableName());
         return bindingRule.isPresent() && bindingRule.get().hasLogicTable(shardingValue2.getTableName());
     }
     
     private boolean isSameShardingConditionValue(final ShardingRule shardingRule, final ShardingConditionValue shardingValue1, final ShardingConditionValue shardingValue2) {
         if (isBindingTable(shardingRule, shardingValue1, shardingValue2)) {
             return true;
         }
         return isSameShardingCondition(shardingValue1, shardingValue2) && isSameShardingValue(shardingValue1, shardingValue2);
     }
     
     @SuppressWarnings({"rawtypes", "unchecked"})
     private boolean isSameShardingValue(final ShardingConditionValue shardingConditionValue1, final ShardingConditionValue shardingConditionValue2) {
         if (shardingConditionValue1 instanceof ListShardingConditionValue && shardingConditionValue2 instanceof ListShardingConditionValue) {
             return SafeNumberOperationUtils.safeCollectionEquals(
                     ((ListShardingConditionValue) shardingConditionValue1).getValues(), ((ListShardingConditionValue) shardingConditionValue2).getValues());
         }
         if (shardingConditionValue1 instanceof RangeShardingConditionValue && shardingConditionValue2 instanceof RangeShardingConditionValue) {
             return SafeNumberOperationUtils.safeRangeEquals(
                     ((RangeShardingConditionValue) shardingConditionValue1).getValueRange(), ((RangeShardingConditionValue) shardingConditionValue2).getValueRange());
         }
         return false;
     }
 }