intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 46 insertions, 0 deletions

diff --git a/library/cpp/json/easy_parse/json_easy_parser.h b/library/cpp/json/easy_parse/json_easy_parser.h
new file mode 100644
index 0000000000..59d7791ab1
--- /dev/null
+++ b/library/cpp/json/easy_parse/json_easy_parser.h
@@ -0,0 +1,46 @@
+#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;
+    };
+}