/*
    * 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.shadow.route.engine.dml;
  
  import lombok.AccessLevel;
  import lombok.Getter;
  import lombok.RequiredArgsConstructor;
  import org.apache.shardingsphere.infra.binder.context.statement.SQLStatementContext;
  import org.apache.shardingsphere.infra.binder.context.type.TableAvailable;
  import org.apache.shardingsphere.infra.route.context.RouteContext;
  import org.apache.shardingsphere.shadow.api.shadow.ShadowOperationType;
  import org.apache.shardingsphere.shadow.api.shadow.column.ColumnShadowAlgorithm;
  import org.apache.shardingsphere.shadow.api.shadow.hint.HintShadowAlgorithm;
  import org.apache.shardingsphere.shadow.condition.ShadowColumnCondition;
  import org.apache.shardingsphere.shadow.condition.ShadowDetermineCondition;
  import org.apache.shardingsphere.shadow.route.engine.ShadowRouteEngine;
  import org.apache.shardingsphere.shadow.route.engine.determiner.ColumnShadowAlgorithmDeterminer;
  import org.apache.shardingsphere.shadow.route.engine.determiner.HintShadowAlgorithmDeterminer;
  import org.apache.shardingsphere.shadow.rule.ShadowRule;
  import org.apache.shardingsphere.shadow.spi.ShadowAlgorithm;
  import org.apache.shardingsphere.sql.parser.sql.common.segment.generic.CommentSegment;
  import org.apache.shardingsphere.sql.parser.sql.common.segment.generic.table.SimpleTableSegment;
  import org.apache.shardingsphere.sql.parser.sql.common.statement.AbstractSQLStatement;
  import org.apache.shardingsphere.sql.parser.sql.common.statement.SQLStatement;
  
  import java.util.Collection;
  import java.util.Collections;
  import java.util.LinkedHashMap;
  import java.util.Map;
  import java.util.Optional;
  import java.util.stream.Collectors;
  
  /**
   * Abstract shadow DML statement route engine.
   */
  @RequiredArgsConstructor(access = AccessLevel.PROTECTED)
  @Getter
  public abstract class AbstractShadowDMLStatementRouteEngine implements ShadowRouteEngine {
      
      private final SQLStatementContext sqlStatementContext;
      
      private final ShadowOperationType operationType;
      
      private final Map<String, String> tableAliasNameMappings = new LinkedHashMap<>();
      
      @Override
      public final void route(final RouteContext routeContext, final ShadowRule rule) {
          tableAliasNameMappings.putAll(getTableAliasNameMappings(((TableAvailable) sqlStatementContext).getAllTables()));
          decorateRouteContext(routeContext, rule, findShadowDataSourceMappings(rule));
      }
      
      private Map<String, String> getTableAliasNameMappings(final Collection<SimpleTableSegment> tableSegments) {
          Map<String, String> result = new LinkedHashMap<>(tableSegments.size(), 1F);
          for (SimpleTableSegment each : tableSegments) {
              String tableName = each.getTableName().getIdentifier().getValue();
              String alias = each.getAliasName().isPresent() ? each.getAliasName().get() : tableName;
              result.put(alias, tableName);
          }
          return result;
      }
      
      private Map<String, String> findShadowDataSourceMappings(final ShadowRule rule) {
          Collection<String> relatedShadowTables = rule.getRelatedShadowTables(tableAliasNameMappings.values());
          Collection<String> sqlComments = getSQLComments();
          if (relatedShadowTables.isEmpty() && isMatchDefaultAlgorithm(rule, sqlComments)) {
              return rule.getAllShadowDataSourceMappings();
          }
          Map<String, String> result = findBySQLComments(rule, sqlComments, relatedShadowTables);
          return result.isEmpty() ? findByShadowColumn(rule, relatedShadowTables) : result;
      }
      
      private Collection<String> getSQLComments() {
          SQLStatement sqlStatement = sqlStatementContext.getSqlStatement();
          return ((AbstractSQLStatement) sqlStatement).getCommentSegments().stream().map(CommentSegment::getText).collect(Collectors.toList());
      }
      
      @SuppressWarnings("unchecked")
      private boolean isMatchDefaultAlgorithm(final ShadowRule rule, final Collection<String> sqlComments) {
          Optional<ShadowAlgorithm> defaultAlgorithm = rule.getDefaultShadowAlgorithm();
          if (defaultAlgorithm.isPresent() && defaultAlgorithm.get() instanceof HintShadowAlgorithm<?>) {
              ShadowDetermineCondition determineCondition = new ShadowDetermineCondition("", ShadowOperationType.HINT_MATCH);
              return HintShadowAlgorithmDeterminer.isShadow((HintShadowAlgorithm<Comparable<?>>) defaultAlgorithm.get(), determineCondition.initSQLComments(sqlComments), rule);
          }
          return false;
     }
     
     private Map<String, String> findBySQLComments(final ShadowRule rule, final Collection<String> sqlComments, final Collection<String> relatedShadowTables) {
         Map<String, String> result = new LinkedHashMap<>();
         for (String each : relatedShadowTables) {
             if (isContainsShadowInSQLComments(rule, each, sqlComments, new ShadowDetermineCondition(each, operationType))) {
                 result.putAll(rule.getRelatedShadowDataSourceMappings(each));
                 return result;
             }
         }
         return result;
     }
     
     private boolean isContainsShadowInSQLComments(final ShadowRule rule, final String tableName, final Collection<String> sqlComments, final ShadowDetermineCondition shadowCondition) {
         ShadowDetermineCondition shadowConditionWithComments = shadowCondition.initSQLComments(sqlComments);
         for (HintShadowAlgorithm<Comparable<?>> each : rule.getRelatedHintShadowAlgorithms(tableName)) {
             if (HintShadowAlgorithmDeterminer.isShadow(each, shadowConditionWithComments, rule)) {
                 return true;
             }
         }
         return false;
     }
     
     private Map<String, String> findByShadowColumn(final ShadowRule rule, final Collection<String> relatedShadowTables) {
         for (String each : relatedShadowTables) {
             Collection<String> relatedShadowColumnNames = rule.getRelatedShadowColumnNames(operationType, each);
             if (!relatedShadowColumnNames.isEmpty() && isMatchAnyColumnShadowAlgorithms(rule, each, relatedShadowColumnNames)) {
                 return rule.getRelatedShadowDataSourceMappings(each);
             }
         }
         return Collections.emptyMap();
     }
     
     private boolean isMatchAnyColumnShadowAlgorithms(final ShadowRule rule, final String shadowTable, final Collection<String> shadowColumnNames) {
         for (String each : shadowColumnNames) {
             if (isMatchAnyColumnShadowAlgorithms(rule, shadowTable, each)) {
                 return true;
             }
         }
         return false;
     }
     
     private boolean isMatchAnyColumnShadowAlgorithms(final ShadowRule rule, final String shadowTable, final String shadowColumn) {
         Collection<ColumnShadowAlgorithm<Comparable<?>>> columnShadowAlgorithms = rule.getRelatedColumnShadowAlgorithms(operationType, shadowTable, shadowColumn);
         if (columnShadowAlgorithms.isEmpty()) {
             return false;
         }
         for (ShadowColumnCondition each : getShadowColumnConditions(shadowColumn)) {
             if (isMatchColumnShadowAlgorithm(shadowTable, columnShadowAlgorithms, each)) {
                 return true;
             }
         }
         return false;
     }
     
     private boolean isMatchColumnShadowAlgorithm(final String shadowTable, final Collection<ColumnShadowAlgorithm<Comparable<?>>> algorithms, final ShadowColumnCondition condition) {
         for (ColumnShadowAlgorithm<Comparable<?>> each : algorithms) {
             if (ColumnShadowAlgorithmDeterminer.isShadow(each, new ShadowDetermineCondition(shadowTable, operationType).initShadowColumnCondition(condition))) {
                 return true;
             }
         }
         return false;
     }
     
     protected abstract Collection<ShadowColumnCondition> getShadowColumnConditions(String shadowColumnName);
     
     protected final String getSingleTableName() {
         return tableAliasNameMappings.entrySet().iterator().next().getValue();
     }
 }