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#pragma once
#include <util/generic/string.h>
#include <util/generic/vector.h>
#include <util/stream/input.h>
#include <util/stream/output.h>
#include "json_easy_parser_impl.h"
namespace NJson {
/* This class filters out nodes from a source JSON by a xpath-style description. It represent these nodes as a tab-delimited string (or a vector).
* It is useful if you need to parse a data which comes into JSON in a known and fixed format.
* Fields are set as a list of keys separated by slash, for example:
* Field x/y/z in JSON { "x" : { "y" : { "w" : 1, "z" : 2 } } contains number 2.
* In a path to a field you can also provide a special array identifier "[]", identifier of a particular field in an array (for example "[4]") or wildcard "*".
*
* The parser of the class supports parsing of several fields. Each of them could be marked as mandatory or as optional.
* If a mandatory field is not found in JSON, then Parse() returns false and ConvertToTabDelimited() returns an empty string.
* If an optional field is not found in JSON, then it's value in Parse()/ConvertToTabDelimited() is an empty string.
* In particular ConvertToTabDelimited() always returns either an empty string, or a string of the same number of tab-delimited fields starting from the same Prefix.
*
* NB! Library can not extract values of not a simple type (namely it doesn't support the case when a result is a vocabulary or an array) from JSON.
* If you expect such a case, please check json_value.h.
*/
class TJsonParser {
TString Prefix;
struct TField {
TVector<TPathElem> Path;
bool NonEmpty;
};
TVector<TField> Fields;
friend class TRewriteJsonImpl;
void ConvertToTabDelimited(IInputStream& in, IOutputStream& out) const;
public:
void SetPrefix(const TString& prefix) {
Prefix = prefix;
}
void AddField(const TString& path, bool mustExist);
TString ConvertToTabDelimited(const TString& json) const;
bool Parse(const TString& json, TVector<TString>* res) const;
};
}
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