3 files changed, 192 insertions, 0 deletions
diff --git a/library/cpp/yt/string/format-inl.h b/library/cpp/yt/string/format-inl.h
index d286f3afbb..83d6198674 100644
--- a/library/cpp/yt/string/format-inl.h
+++ b/library/cpp/yt/string/format-inl.h
@@ -232,6 +232,43 @@ void FormatKeyValueRange(TStringBuilderBase* builder, const TRange& range, const
 
 ////////////////////////////////////////////////////////////////////////////////
 
+template <class TRange, class TValueGetter, class TIntervalFormatter>
+void FormatCompactIntervalRange(
+    TStringBuilderBase* builder,
+    const TRange& range,
+    const TValueGetter& valueGetter,
+    const TIntervalFormatter& intervalFormatter)
+{
+    if (range.begin() == range.end()) {
+        builder->AppendString("[]");
+        return;
+    }
+
+    builder->AppendChar('[');
+
+    auto first = range.begin();
+    auto last = first;
+    auto current = first + 1;
+
+    while (current != range.end()) {
+        if (valueGetter(current) != valueGetter(last) + 1) {
+            bool firstInterval = first == range.begin();
+            intervalFormatter(builder, first, last, valueGetter, firstInterval);
+            first = current;
+        }
+
+        last = current;
+        ++current;
+    }
+
+    bool firstInterval = first == range.begin();
+    intervalFormatter(builder, first, last, valueGetter, firstInterval);
+
+    builder->AppendChar(']');
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
 template <class R>
 concept CFormattableRange =
     NDetail::CKnownRange<R> &&
@@ -303,6 +340,59 @@ TFormatterWrapper<TFormatter> MakeFormatterWrapper(
     };
 }
 
+template <class TRange, class TValueGetter, class TIntervalFormatter>
+auto TCompactIntervalView<TRange, TValueGetter, TIntervalFormatter>::begin() const
+    -> TBegin
+{
+    return RangeBegin;
+}
+
+template <class TRange, class TValueGetter, class TIntervalFormatter>
+auto TCompactIntervalView<TRange, TValueGetter, TIntervalFormatter>::end() const
+    -> TEnd
+{
+    return RangeEnd;
+}
+
+template <class TRange>
+auto TDefaultValueGetter<TRange>::operator()(const TIterator& iterator) const
+    -> typename std::iterator_traits<TIterator>::value_type
+{
+    return *iterator;
+}
+
+template <class TRange, class TValueGetter>
+void TDefaultIntervalFormatter<TRange, TValueGetter>::operator()(
+    TStringBuilderBase* builder,
+    const TIterator& first,
+    const TIterator& last,
+    const TValueGetter& valueGetter,
+    bool firstInterval) const
+{
+    if (!firstInterval) {
+        builder->AppendString(DefaultJoinToStringDelimiter);
+    }
+
+    if (first == last) {
+        builder->AppendFormat("%v", valueGetter(first));
+    } else {
+        builder->AppendFormat("%v-%v", valueGetter(first), valueGetter(last));
+    }
+}
+
+template <class TRange, class TValueGetter, class TIntervalFormatter>
+TCompactIntervalView<TRange, TValueGetter, TIntervalFormatter> MakeCompactIntervalView(
+    const TRange& range,
+    TValueGetter&& valueGetter,
+    TIntervalFormatter&& intervalFormatter)
+{
+    return TCompactIntervalView<TRange, TValueGetter, TIntervalFormatter>{
+        range.begin(),
+        range.end(),
+        std::forward<TValueGetter>(valueGetter),
+        std::forward<TIntervalFormatter>(intervalFormatter)};
+}
+
 template <class... TArgs>
 TLazyMultiValueFormatter<TArgs...>::TLazyMultiValueFormatter(
     TStringBuf format,
@@ -671,6 +761,27 @@ void FormatValue(
     const TFormatterWrapper<TFormatter>& wrapper,
     TStringBuf spec);
 
+// TCompactIntervalView
+
+template <class TRange, class TValueGetter, class TIntervalFormatter>
+concept CCompactIntervalView = requires (
+    TRange range,
+    TValueGetter valueGetter,
+    TIntervalFormatter intervalFormatter)
+{
+    { valueGetter(range.begin()) } -> std::integral;
+    {
+        intervalFormatter(nullptr, range.begin(), range.begin(), valueGetter, true)
+    } -> std::same_as<void>;
+};
+
+template <class TRange, class TValueGetter, class TIntervalFormatter>
+    requires CCompactIntervalView<TRange, TValueGetter, TIntervalFormatter>
+void FormatValue(
+    TStringBuilderBase* builder,
+    const TCompactIntervalView<TRange, TValueGetter, TIntervalFormatter>& compactIntervalView,
+    TStringBuf spec);
+
 // TLazyMultiValueFormatter
 template <class... TArgs>
 void FormatValue(
@@ -773,6 +884,21 @@ void FormatValue(
     NYT::FormatRange(builder, formattableView, formattableView.Formatter, formattableView.Limit);
 }
 
+// TCompactIntervalView
+template <class TRange, class TValueGetter, class TIntervalFormatter>
+    requires CCompactIntervalView<TRange, TValueGetter, TIntervalFormatter>
+void FormatValue(
+    TStringBuilderBase* builder,
+    const TCompactIntervalView<TRange, TValueGetter, TIntervalFormatter>& compactIntervalView,
+    TStringBuf /*spec*/)
+{
+    NYT::FormatCompactIntervalRange(
+        builder,
+        compactIntervalView,
+        compactIntervalView.ValueGetter,
+        compactIntervalView.IntervalFormatter);
+}
+
 // TFormatterWrapper
 template <class TFormatter>
 void FormatValue(
diff --git a/library/cpp/yt/string/format.h b/library/cpp/yt/string/format.h
index 5e5a76db9d..d15127fae0 100644
--- a/library/cpp/yt/string/format.h
+++ b/library/cpp/yt/string/format.h
@@ -5,6 +5,8 @@
 
 #include <util/generic/string.h>
 
+#include <iterator>
+
 namespace NYT {
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -101,6 +103,63 @@ TFormattableView<TRange, TFormatter> MakeShrunkFormattableView(
 
 ////////////////////////////////////////////////////////////////////////////////
 
+template <class TRange, class TValueGetter, class TIntervalFormatter>
+struct TCompactIntervalView
+{
+    using TBegin = std::decay_t<decltype(std::declval<const TRange>().begin())>;
+    using TEnd = std::decay_t<decltype(std::declval<const TRange>().end())>;
+
+    TBegin RangeBegin;
+    TEnd RangeEnd;
+
+    TValueGetter ValueGetter;
+    TIntervalFormatter IntervalFormatter;
+
+    TBegin begin() const;
+    TEnd end() const;
+};
+
+template <class TRange>
+struct TDefaultValueGetter
+{
+    using TIterator = std::decay_t<decltype(std::declval<const TRange>().begin())>;
+
+    auto operator()(const TIterator& iterator) const
+        -> typename std::iterator_traits<TIterator>::value_type;
+};
+
+template <class TRange, class TValueGetter>
+struct TDefaultIntervalFormatter
+{
+    using TIterator = std::decay_t<decltype(std::declval<const TRange>().begin())>;
+
+    void operator()(
+        TStringBuilderBase* builder,
+        const TIterator& first,
+        const TIterator& last,
+        const TValueGetter& valueGetter,
+        bool firstInterval) const;
+};
+
+////////////////////////////////////////////////////////////////////////////////
+
+//! Writes a given integral #range as a sequence of intervals.
+//! Example:
+// MakeCompactIntervalView(std::vector {1, 2, 3, 5, 7, 8})
+// => [1-3,5,7-8]
+
+template <
+    class TRange,
+    class TValueGetter = TDefaultValueGetter<TRange>,
+    class TIntervalFormatter = TDefaultIntervalFormatter<TRange, TValueGetter>
+>
+TCompactIntervalView<TRange, TValueGetter, TIntervalFormatter> MakeCompactIntervalView(
+    const TRange& range,
+    TValueGetter&& valueGetter = {},
+    TIntervalFormatter&& intervalFormatter = {});
+
+////////////////////////////////////////////////////////////////////////////////
+
 template <class TFormatter>
 struct TFormatterWrapper
 {
diff --git a/library/cpp/yt/string/unittests/format_ut.cpp b/library/cpp/yt/string/unittests/format_ut.cpp
index 5ec4a1ffa8..f783efcf11 100644
--- a/library/cpp/yt/string/unittests/format_ut.cpp
+++ b/library/cpp/yt/string/unittests/format_ut.cpp
@@ -246,6 +246,13 @@ TEST(TFormatTest, Tuples)
     EXPECT_EQ("{1, 2}", Format("%v", std::pair(1, 2)));
 }
 
+TEST(TFormatTest, CompactIntervalView)
+{
+    EXPECT_EQ("[]", Format("%v", MakeCompactIntervalView(std::vector<int>{})));
+    EXPECT_EQ("[1]", Format("%v", MakeCompactIntervalView(std::vector<int>{1})));
+    EXPECT_EQ("[0, 2-4, 7]", Format("%v", MakeCompactIntervalView(std::vector<int>{0, 2, 3, 4, 7})));
+}
+
 TEST(TFormatTest, LazyMultiValueFormatter)
 {
     int i = 1;