yacreader/YACReaderLibrary/db/query_parser.h
2021-01-14 12:25:24 +01:00

101 lines
3.0 KiB
C++

#ifndef QUERY_PARSER_H
#define QUERY_PARSER_H
#include "query_lexer.h"
#include <map>
#include <QSqlQuery>
#include <string>
#include <vector>
#include <list>
/**
* This class is used to generate an SQL query string from a search expression,
* with a syntax very similar to that used by the Google search engine.
*
* The code herein is based upon the SearchQueryParser python class written by
* Kovid Goyal as part of the Calibre eBook manager (https://calibre-ebook.com)
*
* Grammar:
* prog ::= or_expression
* or_expression ::= and_expression [ 'or' or_expression ]
* and_expression ::= not_expression [ [ 'and' ] and_expression ]
* not_expression ::= [ 'not' ] location_expression
* location_expression ::= base_token | ( '(' or_expression ')' )
* base_token ::= a sequence of letters and colons, perhaps quoted
*
* Usage Example:
* QSqlQuery selectQuery(db);
* std::string queryString("SELECT ... FROM ... WHERE ");
*
* QueryParser parser; // Create the parser object
* TreeNode result = parser.parse(expr); // Parse the query expression
*
* result.buildSqlString(queryString); // Append the SQL query to a string
*
* selectQuery.prepare(queryString.c_str()); // Convert the string to a query
* result.bindValues(selectQuery); // Populate the SQL query variables
*
* selectQuery.exec();
*/
class QueryParser
{
public:
struct TreeNode {
std::string t;
std::vector<TreeNode> children;
explicit TreeNode(std::string t, std::vector<TreeNode> children)
: t(t), children(children)
{
}
int buildSqlString(std::string &sqlString, int bindPosition = 0) const;
int bindValues(QSqlQuery &selectQuery, int bindPosition = 0) const;
};
explicit QueryParser();
TreeNode parse(const std::string &expr);
private:
static std::string toLower(const std::string &string);
std::string token(bool advance = false);
std::string lcaseToken(bool advance = false);
Token::Type tokenType();
bool isEof() const;
void advance();
QueryLexer lexer = QueryLexer("");
Token currentToken = Token(Token::Type::undefined);
template<typename T>
static bool isIn(const T &e, const std::list<T> &v)
{
return std::find(v.begin(), v.end(), e) != v.end();
}
enum class FieldType { unknown,
numeric,
text,
boolean,
date,
folder,
booleanFolder,
filename };
static FieldType fieldType(const std::string &str);
static std::string join(const QStringList &strings, const std::string &delim);
static QStringList split(const std::string &string, char delim);
TreeNode orExpression();
TreeNode andExpression();
TreeNode notExpression();
TreeNode locationExpression();
TreeNode baseToken();
static const std::map<FieldType, std::vector<std::string>> fieldNames;
};
#endif // QUERY_PARSER_H