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<?php

/**
 * SQL 简单查询工具类
 * <code>
 * 		$tools = new SQLTools("表名", "数据库操作对象实例");
 *		$tools->query("字段默认为*") 							//（如无后续操作此处返回查询结果集）
 * 			  ->where( '条件', PDO参数化查询参数 ) 				//（如无后续操作此处返回查询结果集）
 * 			  ->group( 'id' ) 									//（如无后续操作此处返回查询结果集）
 * 			  ->order( 'id', 'desc' ) 							//（如无后续操作此处返回查询结果集）
 * 			  ->limit( 0, 100 ) 								//（如无后续操作此处返回查询结果集）
 * 			  ->toSQL(); 										// 返回拼接出来的SQL
 *
 * </code>
 */

defined( 'SQL_TAG_QUERY' ) OR define( 'SQL_TAG_QUERY', 'query' );
defined( 'SQL_TAG_LIMIG' ) OR define( 'SQL_TAG_LIMIT', 'limit' );
defined( 'SQL_TAG_WHERE' ) OR define( 'SQL_TAG_WHERE', 'where' );
defined( 'SQL_TAG_ORDER' ) OR define( 'SQL_TAG_ORDER', 'order' );
defined( 'SQL_TAG_GROUP' ) OR define( 'SQL_TAG_GROUP', 'group' );

// to xx 自己加吧
defined( 'TO_SQL' ) OR define( 'TO_SQL', 'toSQL' );

class SQLTools{

	public $id 			= null;
	public $db 			= null;
	public $tableName 	= null;

	private $__code  	= null;
	private $__query 	= null;
	private $__where 	= null;
	private $__param 	= null;
	private $__limit 	= null;
	private $__order 	= null;
	private $__group 	= null;
	
	/**
	 * 实例化
	 * @param $tableName stirng 表名
	 * @param $db 一个数据库操作对象，且必须有个叫query的方法，接受两个参数  sql 及 params
	 * @param $id 主键字段名
	 */
	public function __construct( $tableName, $db, $id=null ){
		$this->db = $db;
		$this->id = $id;
		$this->tableName = $tableName;
	}
	
	public function query( $fields='*', $tableName=null ){
		$tableName === null && ( $tableName = $this->tableName );
		$this->__query = "SELECT $fields FROM $tableName ";
		return $this->__setResultByCallCode( SQL_TAG_QUERY );
	}

	public function where( $where, $params ){
		$this->__where = "WHERE $where ";
		$this->__param = $params;
		return $this->__setResultByCallCode( SQL_TAG_WHERE );
	}

	public function order( $fields, $sort ){
		$this->__order = "ORDER BY $fields $sort ";
		return $this->__setResultByCallCode( SQL_TAG_ORDER );
	}

	public function group( $fields ){
		$this->__group = "GROUP BY $fields";
		return $this->__setResultByCallCode( SQL_TAG_GROUP );
	}

	public function limit( $m, $n ){
		$this->__limit = sprintf( 'LIMIT %d,%s ', $m, $n );
		return $this->__setResultByCallCode( SQL_TAG_LIMIT );
	}

	public function toSQL(){ return $this->__setResultByCallCode( TO_SQL ); }

	public function clear(){
		$this->__code  	= null;
		$this->__query 	= null;
		$this->__where 	= null;
		$this->__param 	= null;
		$this->__limit 	= null;
		$this->__order 	= null;
		$this->__group 	= null;
	}

	// 真正查询的地方
	private function __query( $tag ){
		$__sql = $this->__query;

		$this->__where !== null && ( $__sql .= $this->__where );
		$this->__group !== null && ( $__sql .= $this->__group );
		$this->__order !== null && ( $__sql .= $this->__order );
		$this->__limit !== null && ( $__sql .= $this->__limit );
		
		$result = $tag === TO_SQL ? $__sql : $this->db->query( $__sql, $this->__param );
		$this->clear();

		return $result;
	}

	/**
	 * 通过堆栈信息获取调用脚本后面调用方法，
	 * 根据方法生成相关返回对象
	 * @param $tag sql标签
	 * @return object
	 **/
	private function __setResultByCallCode( $tag ){
		if( $this->__code !== null ){
			return $this->__createResult( $this->__code, $tag );
		}

		$info = debug_backtrace();
		if( !is_array($info) ){
			return null;
		}
		
		// 找到调用文件索引 ( 这里是通过文件名匹配的，如果改了文件名请自行修改这段代码 )
		$index = -1;
		foreach( $info as $counter => $item ){
			if( isset($item['file']) ){
				if( stripos($item['file'], 'SQLTools.class.php') > 0 ){
					$index = $counter + 1;  // 下一个item即调用文件
					break;
				}
			}
		}

		// 没有找到调用信息
		if( $index === -1 ){
			return null;
		}

		// 堆栈中没有找到相关信息
		$caller = $info[$index];
		if( !isset($caller['file']) || !file_exists($caller['file']) || !isset($caller['line']) ){
			return null;
		}

		$line = $caller['line'];
		$file = @fopen( $caller['file'], "r" );
		$counter = 1;

		$code = '';
		while( ($buffer = fgets($file)) !== false ){
			if( $counter >= $line ){
				$code .= $buffer;
				if( substr( $buffer, -2, 1 ) == ';' ){
					goto end;
				}
			}
			$counter++;
		}

		end: isset( $file ) && @fclose( $file );

		$code = str_replace( ' ',  '', $code );
		$code = str_replace( "\t", '', $code );
		$code = str_replace( "\n", '', $code );
		$code = explode( '->', $code );
		
		return $this->__createResult( $code, $tag );
	}

	// 返回$this起到链接作用，又判断当前调用tag是否已经结束
	private function __createResult( $code, $tag ){
		$this->__code = $code;

		foreach( $this->__code as $code){
			if( stripos($code, $tag) === 0 && substr( $code, -1 ) === ';' ){  // 判断查询结束
				return $this->__query( $tag );
			}
		}

		return $this;
	}
}