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+/**
+ *    Copyright (C) 2022-present MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the Server Side Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#pragma once
+
+#include <stack>
+
+#include "mongo/db/matcher/expression.h"
+#include "mongo/db/matcher/expression_leaf.h"
+#include "mongo/db/query/index_bounds.h"
+#include "mongo/db/query/index_entry.h"
+#include "mongo/db/query/optimizer/algebra/operator.h"
+#include "mongo/db/query/optimizer/algebra/polyvalue.h"
+
+namespace mongo {
+
+class ConstInterval;
+class EvalInterval;
+class IntersectInterval;
+class UnionInterval;
+class ComplementInterval;
+
+/**
+ *  A polyvalue which represents a node of Interval Evalution Tree.
+ */
+using IET = optimizer::algebra::
+    PolyValue<ConstInterval, EvalInterval, IntersectInterval, UnionInterval, ComplementInterval>;
+
+/**
+ *  Represents an interval with the constant bounds, such as (MinKey, MaxKey)
+ */
+class ConstInterval : public optimizer::algebra::OpSpecificArity<IET, ConstInterval, 0> {
+public:
+    explicit ConstInterval(const std::vector<Interval>& intervals) : intervals{intervals} {}
+
+    std::vector<Interval> intervals;
+};
+
+/**
+ * Evaluates an interval from a simple predicate such as {$gt: p1} where p1 is a parameter value
+ * known at runtime.
+ */
+class EvalInterval : public optimizer::algebra::OpSpecificArity<IET, EvalInterval, 0> {
+public:
+    using InputParamId = MatchExpression::InputParamId;
+
+    EvalInterval(InputParamId inputParamId, MatchExpression::MatchType matchType)
+        : _inputParamId{inputParamId}, _matchType{matchType} {}
+
+    InputParamId inputParamId() const {
+        return _inputParamId;
+    }
+
+    MatchExpression::MatchType matchType() const {
+        return _matchType;
+    }
+
+private:
+    const InputParamId _inputParamId;
+    const MatchExpression::MatchType _matchType;
+};
+
+/**
+ * Intersects two intervals.
+ */
+class IntersectInterval : public optimizer::algebra::OpSpecificArity<IET, IntersectInterval, 2> {
+public:
+    using Base = optimizer::algebra::OpSpecificArity<IET, IntersectInterval, 2>;
+
+    IntersectInterval(IET lhs, IET rhs) : Base(std::move(lhs), std::move(rhs)) {}
+};
+
+/**
+ * Unions two intervals.
+ */
+class UnionInterval : public optimizer::algebra::OpSpecificArity<IET, UnionInterval, 2> {
+public:
+    using Base = optimizer::algebra::OpSpecificArity<IET, UnionInterval, 2>;
+
+    UnionInterval(IET lhs, IET rhs) : Base(std::move(lhs), std::move(rhs)) {}
+};
+
+/**
+ * ComplementInterval represent operand $not on the child.
+ */
+class ComplementInterval : public optimizer::algebra::OpSpecificArity<IET, ComplementInterval, 1> {
+public:
+    using Base = optimizer::algebra::OpSpecificArity<IET, ComplementInterval, 1>;
+
+    ComplementInterval(IET child) : Base(std::move(child)) {}
+};
+
+std::string ietToString(const IET& iet);
+std::string ietsToString(const IndexEntry& index, const std::vector<IET>& iets);
+
+class IETBuilder {
+public:
+    void intersectIntervals();
+    void unionIntervals();
+    void complementInterval();
+    void translate(const MatchExpression& expr, const OrderedIntervalList& oil);
+    void appendIntervalList(const OrderedIntervalList& oil);
+
+    boost::optional<IET> done() const;
+
+private:
+    std::stack<IET> _intervals;
+};
+}  // namespace mongo