package cn.com.ty.lift.common.sql;

import com.baomidou.mybatisplus.core.parser.SqlParserHelper;
import lombok.Data;
import lombok.extern.slf4j.Slf4j;
import net.sf.jsqlparser.expression.BinaryExpression;
import net.sf.jsqlparser.expression.Expression;
import net.sf.jsqlparser.expression.Function;
import net.sf.jsqlparser.expression.operators.conditional.OrExpression;
import net.sf.jsqlparser.expression.operators.relational.InExpression;
import net.sf.jsqlparser.expression.operators.relational.ItemsList;
import net.sf.jsqlparser.expression.operators.relational.NotEqualsTo;
import net.sf.jsqlparser.parser.CCJSqlParserUtil;
import net.sf.jsqlparser.schema.Column;
import net.sf.jsqlparser.schema.Table;
import net.sf.jsqlparser.statement.Statement;
import net.sf.jsqlparser.statement.delete.Delete;
import net.sf.jsqlparser.statement.select.Join;
import net.sf.jsqlparser.statement.select.PlainSelect;
import net.sf.jsqlparser.statement.select.Select;
import net.sf.jsqlparser.statement.select.SubSelect;
import net.sf.jsqlparser.statement.update.Update;
import org.apache.ibatis.executor.statement.StatementHandler;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.mapping.SqlCommandType;
import org.apache.ibatis.plugin.*;
import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.reflection.SystemMetaObject;

import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;

/**
 * 由于开发人员水平参差不齐，即使订了开发规范很多人也不遵守
 * <p>SQL是影响系统性能最重要的因素，所以拦截掉垃圾SQL语句</p>
 * <br>
 * <p>拦截SQL类型的场景</p>
 * <p>1.必须使用到索引，包含left join连接字段，符合索引最左原则</p>
 * <p>必须使用索引好处，</p>
 * <p>1.1 如果因为动态SQL，bug导致update的where条件没有带上，全表更新上万条数据</p>
 * <p>1.2 如果检查到使用了索引，SQL性能基本不会太差</p>
 * <br>
 * <p>2.SQL尽量单表执行，有查询left join的语句，必须在注释里面允许该SQL运行，否则会被拦截，有left join的语句，如果不能拆成单表执行的SQL，请leader商量在做</p>
 * <p>https://gaoxianglong.github.io/shark</p>
 * <p>SQL尽量单表执行的好处</p>
 * <p>2.1 查询条件简单、易于开理解和维护；</p>
 * <p>2.2 扩展性极强；（可为分库分表做准备）</p>
 * <p>2.3 缓存利用率高；</p>
 * <p>2.在字段上使用函数</p>
 * <br>
 * <p>3.where条件为空</p>
 * <p>4.where条件使用了 !=</p>
 * <p>5.where条件使用了 not 关键字</p>
 * <p>6.where条件使用了 or 关键字</p>
 * <p>7.where条件使用了 使用子查询</p>
 *
 * @author willenfoo
 * @since 2018-03-22
 */
@Slf4j
@Intercepts({@Signature(type = StatementHandler.class, method = "prepare", args = {Connection.class, Integer.class})})
public class IllegalSqlInterceptor implements Interceptor {

    /**
     * 缓存验证结果，提高性能
     */
    private final Set<String>                  cacheValidResult = new HashSet<>();
    /**
     * 缓存表的索引信息
     */
    private final Map<String, IndexInfo> indexInfoCacheMap     = new ConcurrentHashMap<>();

    private final int indexValidColumnIndex = 8;
    private final int indexDBNameColumnIndex = 1;
    private final int indexTableNameColumnIndex = 3;
    private final int indexColumnNameColumnIndex = 9;
    private boolean             failFast = false;
    private ThreadLocal<String> message  = new ThreadLocal<>();

    private void set(String message) {
        this.message.set(message);
    }
    /**
     * 验证expression对象是不是 or、not等等
     *
     * @param expression ignore
     */
    private boolean validExpression(Expression expression) {
        //where条件使用了 or 关键字
        if (expression instanceof OrExpression) {
            OrExpression or = (OrExpression) expression;
            set(String.format("Should not use [%s] in WHERE condition. illegal sql: %s", or.getStringExpression(), or.toString()));
            return true;
        } else if (expression instanceof NotEqualsTo) {
            NotEqualsTo notEqTo = (NotEqualsTo) expression;
            set(String.format("Should not use [%s] in WHERE condition. illegal sql: %s", notEqTo.getStringExpression(), notEqTo.toString()));
            return true;
        } else if (expression instanceof BinaryExpression) {
            BinaryExpression binary = (BinaryExpression) expression;
            if (binary.isNot()) {
                set(String.format("Should not use [%s] in WHERE condition. illegal sql: %s", binary.getStringExpression(), binary.toString()));
                return true;
            }
            Expression leftExpression = binary.getLeftExpression();
            if (leftExpression instanceof Function) {
                Function function = (Function) leftExpression;
                set(String.format("Should not use db function in WHERE condition. illegal sql: %s", function.toString()));
                return true;
            }
            Expression rightExpression = binary.getRightExpression();
            if (rightExpression instanceof SubSelect) {
                SubSelect subSelect = (SubSelect) rightExpression;
                set(String.format("Should not use subSelect in WHERE condition. illegal sql: %s", subSelect.toString()));
                return true;
            }
        } else if (expression instanceof InExpression) {
            InExpression in = (InExpression) expression;
            ItemsList rightItemsList = in.getRightItemsList();
            if (rightItemsList instanceof SubSelect) {
                SubSelect subSelect = (SubSelect) rightItemsList;
                set(String.format("Should not use subSelect in WHERE condition. illegal sql: %s", subSelect.toString()));
                return true;
            }
        }
        return false;
    }

    /**
     * 如果SQL用了 left Join，验证是否有or、not等等，并且验证是否使用了索引
     *
     * @param joins      ignore
     * @param table      ignore
     * @param connection ignore
     */
    private void validJoins(List<Join> joins, Table table, Connection connection) {
        //允许执行join，验证join是否使用索引等等
        if (SqlUtils.notEmpty(joins)) {
            for (Join join : joins) {
                Table rightTable = (Table) join.getRightItem();
                Expression expression = join.getOnExpression();
                validWhere(expression, table, rightTable, connection);
            }
        }
    }

    /**
     * 检查是否使用索引
     *
     * @param table      ignore
     * @param columnName ignore
     * @param connection ignore
     */
    private void validUseIndex(Table table, String columnName, Connection connection) {
        String tableInfo = table.getName();
        //表存在的索引
        String dbName = null;
        String tableName;
        String[] tableArray = tableInfo.split("\\.");
        if (tableArray.length == 1) {
            tableName = tableArray[0];
        } else {
            dbName = tableArray[0];
            tableName = tableArray[1];
        }
        String cacheKey = String.format("%s::%s::%s", dbName, tableName, columnName);
        boolean useIndexFlag = getIndexInfos(cacheKey, dbName,tableName, connection);

        if (!useIndexFlag) {
            throw new SqlAnalysisException("非法SQL，SQL未使用到索引, table:" + table + ", columnName:" + columnName);
        }
    }

    /**
     * 验证where条件的字段，是否有not、or等等，并且where的第一个字段，必须使用索引
     *
     * @param expression ignore
     * @param table      ignore
     * @param connection ignore
     */
    private void validWhere(Expression expression, Table table, Connection connection) {
        validWhere(expression, table, null, connection);
    }

    /**
     * 验证where条件的字段，是否有not、or等等，并且where的第一个字段，必须使用索引
     *
     * @param expression ignore
     * @param table      ignore
     * @param joinTable  ignore
     * @param connection ignore
     */
    private boolean validWhere(Expression expression, Table table, Table joinTable, Connection connection) {
        boolean valid = validExpression(expression);
        if(valid){
            return valid;
        }
        if (expression instanceof BinaryExpression) {
            //获得左边表达式
            Expression leftExpression = ((BinaryExpression) expression).getLeftExpression();
            boolean left = validExpression(leftExpression);
            if(left){
                return left;
            }
            //如果左边表达式为Column对象，则直接获得列名
            if (leftExpression instanceof Column) {
                Expression rightExpression = ((BinaryExpression) expression).getRightExpression();
                if (joinTable != null && rightExpression instanceof Column) {
                    if (Objects.equals(((Column) rightExpression).getTable().getName(), table.getAlias().getName())) {
                        validUseIndex(table, ((Column) rightExpression).getColumnName(), connection);
                        validUseIndex(joinTable, ((Column) leftExpression).getColumnName(), connection);
                    } else {
                        validUseIndex(joinTable, ((Column) rightExpression).getColumnName(), connection);
                        validUseIndex(table, ((Column) leftExpression).getColumnName(), connection);
                    }
                } else {
                    //获得列名
                    validUseIndex(table, ((Column) leftExpression).getColumnName(), connection);
                }
            }
            //如果BinaryExpression，进行迭代
            else if (leftExpression instanceof BinaryExpression) {
                validWhere(leftExpression, table, joinTable, connection);
            }

            //获得右边表达式，并分解
            Expression rightExpression = ((BinaryExpression) expression).getRightExpression();
            validExpression(rightExpression);
        }
        return true;
    }

    /**
     * 得到表的索引信息
     *
     * @param dbName    ignore
     * @param tableName ignore
     * @param conn      ignore
     * @return ignore
     */
    public boolean getIndexInfos(String dbName, String tableName, Connection conn) {
        return getIndexInfos(null, dbName, tableName, conn);
    }

    /**
     * 得到表的索引信息
     *
     * @param key       ignore
     * @param dbName    ignore
     * @param tableName ignore
     * @param conn      ignore
     * @return ignore
     */
    public boolean getIndexInfos(String key, String dbName, String tableName, Connection conn) {
        //if the indexInfoCacheMap is empty, must get index info from the connection.
        if(indexInfoCacheMap.isEmpty()){
            try {
                DatabaseMetaData metadata = conn.getMetaData();
                ResultSet resultSet = metadata.getIndexInfo(dbName, dbName, tableName, false, true);
                while (resultSet.next()) {
                    //索引中的列序列号等于1，才有效
                    log.info("resultSet: {}", resultSet);
                    if ("1".equals(resultSet.getString(indexValidColumnIndex))) {
                        IndexInfo indexInfo = new IndexInfo();
                        indexInfo.setDbName(resultSet.getString(indexDBNameColumnIndex));
                        indexInfo.setTableName(resultSet.getString(indexTableNameColumnIndex));
                        indexInfo.setColumnName(resultSet.getString(indexColumnNameColumnIndex));
                        //index
                        indexInfoCacheMap.put(indexInfo.cacheKey(), indexInfo);
                    }
                }
            } catch (SQLException e) {
                log.error("get index info from connection fail.");
            }
        }
        try {
            DatabaseMetaData metadata = conn.getMetaData();
            ResultSet resultSet = metadata.getIndexInfo(dbName, dbName, tableName, false, true);
            while (resultSet.next()) {
                //索引中的列序列号等于1，才有效
                if (Objects.equals(resultSet.getString(8), "1")) {
                    IndexInfo indexInfo = new IndexInfo();
                    indexInfo.setDbName(resultSet.getString(1));
                    indexInfo.setTableName(resultSet.getString(3));
                    indexInfo.setColumnName(resultSet.getString(9));
                    //index
                    indexInfoCacheMap.put(indexInfo.cacheKey(), indexInfo);
                }
            }
        } catch (SQLException e) {
            log.error("get index info from connection fail.");
        }
        return true;
    }

    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        StatementHandler statementHandler = SqlUtils.realTarget(invocation.getTarget());
        MetaObject metaObject = SystemMetaObject.forObject(statementHandler);
        // 如果是insert操作， 或者 @SqlParser(filter = true) 跳过该方法解析 ， 不进行验证
        MappedStatement mappedStatement = SqlUtils.getMappedStatement(metaObject);
        if (SqlCommandType.INSERT.equals(mappedStatement.getSqlCommandType()) || SqlParserHelper.getSqlParserInfo(metaObject)) {
            return invocation.proceed();
        }
        BoundSql boundSql = SqlUtils.getBoundSql(metaObject);
        String originalSql = boundSql.getSql();
        log.info("检查SQL ID: {}", mappedStatement.getId());
        log.info("检查SQL是否合规，SQL: \n{}", originalSql);
        String md5Base64 = SqlUtils.md5Base64(originalSql);
        log.info("md5Base64: {}", md5Base64);
        if (cacheValidResult.contains(md5Base64)) {
            return invocation.proceed();
        }
        Statement statement = CCJSqlParserUtil.parse(originalSql);
        Expression where = null;
        Table table = null;
        List<Join> joins = null;
        if (statement instanceof Select) {
            PlainSelect plainSelect = (PlainSelect) ((Select) statement).getSelectBody();
            where = plainSelect.getWhere();
            //table = (Table) plainSelect.getFromItem();
            table = plainSelect.getForUpdateTable();
            joins = plainSelect.getJoins();
        } else if (statement instanceof Update) {
            Update update = (Update) statement;
            where = update.getWhere();
            table = update.getTables().get(0);
            joins = update.getJoins();
        } else if (statement instanceof Delete) {
            Delete delete = (Delete) statement;
            where = delete.getWhere();
            table = delete.getTable();
            joins = delete.getJoins();
        }
        //where条件不能为空
        if (SqlUtils.isNull(where)) {
            throw new SqlAnalysisException("非法SQL，必须要有where条件");
        }
        if(SqlUtils.isNull(table)){
            return invocation.proceed();
        }
        Connection connection = (Connection) invocation.getArgs()[0];
        validWhere(where, table, connection);
        validJoins(joins, table, connection);
        //缓存验证结果
        cacheValidResult.add(md5Base64);
        return invocation.proceed();
    }

    @Override
    public Object plugin(Object target) {
        if (target instanceof StatementHandler) {
            return Plugin.wrap(target, this);
        }
        return target;
    }

    @Override
    public void setProperties(Properties prop) {
        String failFast = prop.getProperty("failFast");
        if (SqlUtils.isBoolean(failFast)) {
            this.failFast = Boolean.valueOf(failFast);
        }
    }

    /**
     * the information of the index.
     */
    @Data
    private class IndexInfo {
        //the name of the db.
        private String dbName;
        //the name of the table.
        private String tableName;
        //the name of the column.
        private String columnName;

        public String cacheKey(){
            return String.format("%s::%s::%s",getDbName(), getTableName(), getColumnName());
        }
    }
}