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/*
 *    Copyright 2021 wwy
 *
 *    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.
 */
package com.gitee.cn9750wang.webtools.query;

import com.gitee.cn9750wang.webtools.error.P21Exception;

import java.io.Serializable;

/**
 * 分页查询对象
 *
 * @author wwy
 */
public class LimitPage implements Serializable {

    private static final long serialVersionUID = 1L;

    /** 默认 每页大小 */
    public static final int DEFAULT_SIZE = 10;
    /** 默认 每页最大200页 */
    public static final int DEFAULT_MAX_SIZE = 200;

    /** 当前所要查询的页码 */
    private long page = 1;
    /** 每页的大小 */
    private long size = DEFAULT_SIZE;

    /**
     * 构造函数
     * 通过一定格式的字符串方式查询
     * @param queryStr 按格式排布的字符串
     */
    public LimitPage(String queryStr){
        // 缺少必要参数
        if(queryStr == null || queryStr.isEmpty()){
            return;
        }
        // 按逗号分割字符串
        var split = queryStr.split(",");
        switch (split.length){
            case 1:page = Long.parseLong(split[0]);break;
            case 2:
                page = Long.parseLong(split[0]);
                size = Long.parseLong(split[1]);
                break;
            default:throw new P21Exception("分页查询参数格式不正确");
        }
        // 合理化参数
        this.rationalization();
    }

    /**
     * 构造函数
     * @param page 第几页
     */
    public LimitPage(long page){
        this(page,DEFAULT_SIZE);
    }

    /**
     * 构造函数
     * @param page 第几页
     * @param size 每页大小
     */
    public LimitPage(long page,long size){
        this.page = page;
        this.size = size;
    }

    public long getPage() {
        return page;
    }

    public long getSize() {
        return size;
    }

    /**
     * 数据库查询语句中 limit [limit] offset [offset] 的limit
     * @return 每页大小
     */
    public long getLimit() {
        return size;
    }

    /**
     * 数据库查询语句中 limit [index] offset [offset] 的offset
     * @return 分页偏移量
     */
    public long getOffset() {
        return (page - 1) * size;
    }

    /**
     * 合理化分页参数,默认每页不超过200条数据
     * @return LimitPage分页对象
     */
    public LimitPage rationalization(){
        return this.rationalization(DEFAULT_MAX_SIZE);
    }

    /**
     * 合理化分页参数
     * @param maxSize 自定义每页最大分页参数
     * @return LimitPage分页对象
     */
    public LimitPage rationalization(final long maxSize){
        // 页码应为正整数,否则默认从第一页开始
        page = page >= 1 ? page : 1;
        // 每页大小是否合理,否则默认每页10条数据
        size = size >= 1 && size <= maxSize ? size : DEFAULT_SIZE;
        return this;
    }

    /**
     * 限制每页大小为excel2007(xls格式)最大行数
     * @return LimitPage分页对象
     */
    public LimitPage xlsMaxRow(){
        return this.rationalization(256*256);
    }

    /**
     * 限制每页大小为excel2010(xlsx格式)最大行数
     * @return LimitPage分页对象
     */
    public LimitPage xlsxMaxRow(){
        return this.rationalization(1024*1024);
    }

    /**
     * 生成mysql limit查询语句
     * @return mysql limit查询语句
     */
    public String mysql(){
        return "limit " + getLimit() + " offset "+ getOffset();
    }

}