restriction_predicate.hxx

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 *
 * The MIT License
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#include <graphene/protocol/restriction_predicate.hpp>

#include <fc/exception/exception.hpp>

#include "safe_compare.hpp"

namespace graphene { namespace protocol {
namespace typelist = fc::typelist;
using std::declval;
using std::size_t;
using restriction_function = restriction::function_type;
using restriction_argument = restriction::argument_type;

// Make our own std::void_t since the real one isn't available in C++14
template<typename...> using make_void = void;

// Metafunction to check if type is some instantiation of fc::safe
template<typename> constexpr static bool is_safe = false;
template<typename I> constexpr static bool is_safe<fc::safe<I>> = true;

// Metafunction to check if type is a flat_set of any element type
template<typename> struct is_flat_set_impl : std::false_type {};
template<typename T> struct is_flat_set_impl<flat_set<T>> : std::true_type {};
template<typename T> constexpr static bool is_flat_set = is_flat_set_impl<T>::value;

// We use our own is_integral which does not consider bools integral (to disallow comparison between bool and ints)
template<typename T> constexpr static bool is_integral = !std::is_same<T, bool>::value &&
                                                         !std::is_same<T, safe<bool>>::value &&
                                                         (is_safe<T> || std::is_integral<T>::value);

// Metafunction to check if two types are comparable, which means not void_t, and either the same or both integral
template<typename T, typename U>
constexpr static bool comparable_types = !std::is_same<T, void_t>::value &&
                                         (std::is_same<T, U>::value || (is_integral<T> && is_integral<U>));

// Metafunction to check if type is a container
template<typename, typename = void>
struct is_container_impl : std::false_type {};
template<typename T>
struct is_container_impl<T, make_void<typename T::value_type, decltype(declval<T>().size())>> : std::true_type {};
template<typename T> constexpr static bool is_container = is_container_impl<T>::value;

// Type alias for a predicate on a particular field type
template<typename Field>
using object_restriction_predicate = std::function<predicate_result(const Field&)>;

// Get the actual number when type might be a safe<I>
template<typename I, typename=std::enable_if_t<std::is_integral<I>::value>>
const auto& to_num(const I& i) { return i; }
template<typename I>
const auto& to_num(const fc::safe<I>& i) { return i.value; }
inline auto to_num(const fc::time_point_sec& t) { return t.sec_since_epoch(); }

namespace safenum = boost::safe_numerics::safe_compare;

// *** Restriction Predicate Logic ***
//
// This file implements the core logic of Custom Active Authorities. A CAA is an authority which is permitted by an
// account to execute a particular authority on that account's behalf, with some restrictions on the content of that
// operation. This file implements the logic to validate those restrictions, and create a predicate function which
// takes a particular operation and determines whether it complies with the restrictions or not.
//
// The restrictions are a recursive structure, which applies to a particular operation struct, but may recurse to
// specify restrictions on fields or subfields of that struct. This file explores the restriction structure in tandem
// with the operation struct to verify that all of the restrictions are valid and to produce a predicate function.
// Note that this file operates primarily on restriction data, but only operation *types*, meaning the actual
// operation value does not appear until the predicate returned by this file is run.
//
// As a result, this file is very template heavy, and does a good deal of type manipulation. Its contents are
// organized as a series of layers, which recursively examine the restrictions and types they apply to, and finally,
// once all the types have been resolved, a predicate function is created which evaluates the restrictions on an
// operation.
//
// To give an overview of the logic, the layers stack up like so, from beginning (bottom of file) to end:
//  - restrictions_to_predicate<Object>() -- takes a vector<restriction> and creates a predicate for each of them,
//    but returns a single predicate that returns true only if all sub-predicates return true
//    - create_field_predicate<Object>() -- Resolves which field of Object the restriction is referencing by indexing
//      into the object's reflected fields with the predicate's member_index
//    - create_logical_or_predicate<Object>() -- If the predicate is a logical OR function, the predicate does not
//      specify a field to examine; rather, the predicates in its branches do. Thus this function recurses into
//      restrictions_to_predicate for each branch of the OR, and combines the resulting predicates in a predicate
//      which returns true if any branch of the OR passes
//  - create_predicate_function<Field>() -- switches on restriction type to determine which predicate template to use
//    going forward
//    - make_predicate<Predicate, Field, ArgVariant> -- Determines what type the restriction argument is and creates
//      a predicate functor for that type
//    - attribute_assertion<Field> -- If the restriction is an attribute assertion, instead of using make_predicate
//      to create a predicate function, we first recurse into restrictions_to_predicate with Field as the Object
//    - variant_assertion<Field> -- If the restriction is a variant assertion, instead of using make_predicate, we
//      recurse into restrictions_to_predicate with the variant value as the Object
//  - embed_argument<Field, Predicate, Argument>() -- Embeds the argument into the predicate if it is a valid type
//    for the predicate, and throws otherwise.
//  - predicate_xyz<Argument> -- These are functors implementing the various predicate function types

// These typelists contain the argument types legal for various function types:

// Valid for magnitude comparisons and equality comparisons
using comparable_types_list = typelist::list<int64_t, string, time_point_sec, account_id_type, asset_id_type,
                                             force_settlement_id_type, committee_member_id_type, witness_id_type,
                                             limit_order_id_type, call_order_id_type, custom_id_type,
                                             proposal_id_type, withdraw_permission_id_type,
                                             vesting_balance_id_type, worker_id_type, balance_id_type>;
// Valid for list functions (in, not_in, has_all, has_none)
struct make_flat_set { template<typename T> struct transform { using type = flat_set<T>; }; };
using list_types_list = typelist::transform<typelist::concat<typelist::list<bool, public_key_type, fc::sha256>,
                                                             comparable_types_list>,
                                            make_flat_set>;
// Valid for equality comparisons but not necessarily magnitude comparisons
using equality_types_list = typename typelist::concat<typelist::list<void_t, bool, public_key_type, fc::sha256>,
                                                      comparable_types_list, list_types_list>;
// Valid for attritube assertions
using attr_types_list = typelist::list<vector<restriction>>;
// Valid for logical or assertions
using or_types_list = typelist::list<vector<vector<restriction>>>;

// An invalid predicate which throws upon construction. Inherited by other predicates when arg types are incompatible
template<typename A, typename B>
struct predicate_invalid {
   constexpr static bool valid = false;
   predicate_invalid() { FC_THROW_EXCEPTION(fc::assert_exception, "Invalid types for predicate"); }
   bool operator()(const A&, const B&) const { return false; }
};
// Equality comparison
template<typename A, typename B, typename = void> struct predicate_eq : predicate_invalid<A, B> {};
template<typename Field, typename Argument>
struct predicate_eq<Field, Argument, std::enable_if_t<std::is_same<Field, Argument>::value>> {
   // Simple comparison, same type
   constexpr static bool valid = true;
   constexpr bool operator()(const Field& f, const Argument& a) const { return f == a; }
};
template<typename Field, typename Argument>
struct predicate_eq<Field, Argument, std::enable_if_t<is_integral<Field> && is_integral<Argument> &&
                                                      !std::is_same<Field, Argument>::value>> {
   // Simple comparison, integral types
   constexpr static bool valid = true;
   constexpr bool operator()(const Field& f, const Argument& a) const { return safenum::equal(to_num(f), to_num(a)); }
};
template<typename Field, typename Argument>
struct predicate_eq<Field, Argument, std::enable_if_t<is_container<Field> && is_integral<Argument>>> {
   // Compare container size against int
   constexpr static bool valid = true;
   bool operator()(const Field& f, const Argument& a) const { return safenum::equal(f.size(), to_num(a)); }
};
template<typename Field, typename Argument>
struct predicate_eq<fc::optional<Field>, Argument, std::enable_if_t<comparable_types<Field, Argument>>>
   : predicate_eq<Field, Argument> {
   // Compare optional value against comparable type
   using base = predicate_eq<Field, Argument>;
   bool operator()(const fc::optional<Field>& f, const Argument& a) const {
      if (!f.valid()) return predicate_result::Rejection(predicate_result::null_optional);
      return (*this)(*f, a);
   }
};
template<typename Field>
struct predicate_eq<fc::optional<Field>, void_t, void> {
   // Compare optional value against void_t (checks that optional is null)
   constexpr static bool valid = true;
   bool operator()(const fc::optional<Field>& f, const void_t&) const { return !f.valid(); }
};
// Not-equal is just an equality comparison wrapped in a negator
template<typename Field, typename Argument> struct predicate_ne : predicate_eq<Field, Argument> {
   using equal = predicate_eq<Field, Argument>;
   bool operator()(const Field& f, const Argument& a) const { return !equal::operator()(f, a); }
};

// Shared implementation for all inequality comparisons
template<typename A, typename B, typename = void> struct predicate_compare : predicate_invalid<A, B> {};
template<typename Field, typename Argument>
struct predicate_compare<Field, Argument, std::enable_if_t<std::is_same<Field, Argument>::value>> {
   // Simple comparison, same types
   constexpr static bool valid = true;
   constexpr int8_t operator()(const Field& f, const Argument& a) const {
      return f<a? -1 : (f>a? 1 : 0);
   }
};
template<typename Field, typename Argument>
struct predicate_compare<Field, Argument, std::enable_if_t<is_integral<Field> && is_integral<Argument> &&
                                                           !std::is_same<Field, Argument>::value>> {
   // Simple comparison, integral types
   constexpr static bool valid = true;
   constexpr int8_t operator()(const Field& f, const Argument& a) const {
      auto nf = to_num(f);
      auto na = to_num(a);
      return safenum::less_than(nf, na)? -1 : (safenum::greater_than(nf, na)? 1 : 0);
   }
};
template<typename Field, typename Argument>
struct predicate_compare<fc::optional<Field>, Argument, void> : predicate_compare<Field, Argument> {
   // Compare optional value against comparable type
   constexpr static bool valid = true;
   constexpr int8_t operator()(const fc::optional<Field>& f, const Argument& a) const {
      if (!f.valid()) return predicate_result::Rejection(predicate_result::null_optional);
       return (*this)(*f, a);
   }
};
// The actual inequality predicates
template<typename Field, typename Argument> struct predicate_lt : predicate_compare<Field, Argument> {
   using base = predicate_compare<Field, Argument>;
   constexpr bool operator()(const Field& f, const Argument& a) const { return base::operator()(f, a) < 0; }
};
template<typename Field, typename Argument> struct predicate_le : predicate_compare<Field, Argument> {
   using base = predicate_compare<Field, Argument>;
   constexpr bool operator()(const Field& f, const Argument& a) const { return base::operator()(f, a) <= 0; }
};
template<typename Field, typename Argument> struct predicate_gt : predicate_compare<Field, Argument> {
   using base = predicate_compare<Field, Argument>;
   constexpr bool operator()(const Field& f, const Argument& a) const { return base::operator()(f, a) > 0; }
};
template<typename Field, typename Argument> struct predicate_ge : predicate_compare<Field, Argument> {
   using base = predicate_compare<Field, Argument>;
   constexpr bool operator()(const Field& f, const Argument& a) const { return base::operator()(f, a) >= 0; }
};

// Field-in-list predicate
template<typename F, typename C, typename = void> struct predicate_in : predicate_invalid<F, C> {};
template<typename Field, typename Element>
struct predicate_in<Field, flat_set<Element>, std::enable_if_t<comparable_types<Field, Element> && !is_safe<Field>>> {
   // Simple inclusion check
   constexpr static bool valid = true;
   bool operator()(const Field& f, const flat_set<Element>& c) const { return c.count(f) != 0; }
};
template<typename Field, typename Element>
struct predicate_in<fc::safe<Field>, flat_set<Element>, std::enable_if_t<comparable_types<Field, Element>>> {
   // Check for safe value
   constexpr static bool valid = true;
   bool operator()(const fc::safe<Field>& f, const flat_set<Element>& c) const { return c.count(f.value) != 0; }
};
template<typename Field, typename Element>
struct predicate_in<fc::optional<Field>, flat_set<Element>, std::enable_if_t<comparable_types<Field, Element>>> {
   // Check for optional value
   constexpr static bool valid = true;
   bool operator()(const fc::optional<Field>& f, const flat_set<Element>& c) const {
      if (!f.valid()) return predicate_result::Rejection(predicate_result::null_optional);
       return c.count(*f) != 0;
   }
};
template<typename Container, typename Element>
struct predicate_in<Container, flat_set<Element>,
                    std::enable_if_t<is_container<Container> &&
                                     comparable_types<typename Container::value_type, Element>>> {
   // Check all values in container are in argument
   constexpr static bool valid = true;
   // Unsorted container
   template<typename C = Container, std::enable_if_t<!is_flat_set<C>, bool> = true>
   bool operator()(const Container& c, const flat_set<Element>& a) const {
      return std::all_of(c.begin(), c.end(), [&a](const auto& ce) { return a.count(ce) > 0; });
   }
   // Sorted container
   template<typename C = Container, std::enable_if_t<is_flat_set<C>, bool> = true>
   bool operator()(const Container& c, const flat_set<Element>& a) const {
      return std::includes(a.begin(), a.end(), c.begin(), c.end());
   }
};
// Field-not-in-list is just field-in-list wrapped in a negator
template<typename Field, typename Container, typename=void> struct predicate_not_in : predicate_in<Field, Container> {
   using base = predicate_in<Field, Container>;
   bool operator()(const Field& f, const Container& c) const { return !base::operator()(f, c); }
};
// Container-field-not-in-list is not a simple negation of predicate_in, specialize here
template<typename Container, typename Element>
struct predicate_not_in<Container, flat_set<Element>,
                        std::enable_if_t<is_container<Container> &&
                                         comparable_types<typename Container::value_type, Element>>> {
   constexpr static bool valid = true;
   // Unsorted container
   template<typename C = Container, std::enable_if_t<!is_flat_set<C>, bool> = true>
   bool operator()(const Container& c, const flat_set<Element>& a) const {
      return std::none_of(c.begin(), c.end(), [&a](const auto& ce) { return a.count(ce) > 0; });
   }
   // Sorted container
   template<typename C = Container, std::enable_if_t<is_flat_set<C>, bool> = true>
   bool operator()(const Container& c, const flat_set<Element>& a) const {
      flat_set<typename Container::value_type> intersection;
      std::set_intersection(c.begin(), c.end(), a.begin(), a.end(),
                            std::inserter(intersection, intersection.begin()));
      return intersection.empty();
   }
};

// List-contains-list predicate
template<typename C1, typename C2, typename = void> struct predicate_has_all : predicate_invalid<C1, C2> {};
template<typename FieldElement, typename ArgumentElement>
struct predicate_has_all<flat_set<FieldElement>, flat_set<ArgumentElement>,
                         std::enable_if_t<comparable_types<FieldElement, ArgumentElement>>> {
   // Field is already flat_set
   constexpr static bool valid = true;
   bool operator()(const flat_set<FieldElement>& f, const flat_set<ArgumentElement>& a) const {
      if (f.size() < a.size()) return false;
      return std::includes(f.begin(), f.end(), a.begin(), a.end());
   }
};
template<typename FieldContainer, typename ArgumentElement>
struct predicate_has_all<FieldContainer, flat_set<ArgumentElement>,
                         std::enable_if_t<is_container<FieldContainer> && !is_flat_set<FieldContainer> &&
                                          comparable_types<typename FieldContainer::value_type, ArgumentElement>>> {
   // Field is other container; convert to flat_set
   constexpr static bool valid = true;
   bool operator()(const FieldContainer& f, const flat_set<ArgumentElement>& a) const {
      if (f.size() < a.size()) return false;
      std::set<typename FieldContainer::value_type> fs(f.begin(), f.end());
      return std::includes(fs.begin(), fs.end(), a.begin(), a.end());
   }
};
template<typename OptionalType, typename Argument>
struct predicate_has_all<fc::optional<OptionalType>, Argument, void> : predicate_has_all<OptionalType, Argument> {
   // Field is optional container
   bool operator()(const fc::optional<OptionalType>& f, const Argument& a) const {
      if (!f.valid()) return predicate_result::Rejection(predicate_result::null_optional);
      return (*this)(*f, a);
   }
};

// List contains none of list predicate
template<typename C1, typename C2, typename = void> struct predicate_has_none : predicate_invalid<C1, C2> {};
template<typename FieldElement, typename ArgumentElement>
struct predicate_has_none<flat_set<FieldElement>, flat_set<ArgumentElement>,
                          std::enable_if_t<comparable_types<FieldElement, ArgumentElement>>> {
   // Field is already flat_set
   constexpr static bool valid = true;
   bool operator()(const flat_set<FieldElement>& f, const flat_set<ArgumentElement>& a) const {
      flat_set<FieldElement> intersection;
      std::set_intersection(f.begin(), f.end(), a.begin(), a.end(),
                            std::inserter(intersection, intersection.begin()));
      return intersection.empty();
   }
};
template<typename FieldContainer, typename ArgumentElement>
struct predicate_has_none<FieldContainer, flat_set<ArgumentElement>,
                          std::enable_if_t<is_container<FieldContainer> && !is_flat_set<FieldContainer> &&
                                           comparable_types<typename FieldContainer::value_type, ArgumentElement>>> {
   // Field is other container
   constexpr static bool valid = true;
   bool operator()(const FieldContainer& f, const flat_set<ArgumentElement>& a) const {
      return !std::any_of(f.begin(), f.end(), [&a](const auto& fe) { return a.count(fe) > 0; });
   }
};
template<typename OptionalType, typename Argument>
struct predicate_has_none<fc::optional<OptionalType>, Argument, void> : predicate_has_all<OptionalType, Argument> {
   // Field is optional container
   bool operator()(const fc::optional<OptionalType>& f, const Argument& a) const {
      if (!f.valid()) return predicate_result::Rejection(predicate_result::null_optional);
      return (*this)(*f, a);
   }
};

// Forward declaration of restrictions_to_predicate, because attribute assertions and logical ORs recurse into it
template<typename Object> object_restriction_predicate<Object> restrictions_to_predicate(vector<restriction>, bool);

template<typename Field>
struct attribute_assertion {
   static object_restriction_predicate<Field> create(vector<restriction>&& rs) {
      return restrictions_to_predicate<Field>(std::move(rs), false);
   }
};
template<typename Field>
struct attribute_assertion<fc::optional<Field>> {
   static object_restriction_predicate<fc::optional<Field>> create(vector<restriction>&& rs) {
      return [p=restrictions_to_predicate<Field>(std::move(rs), false)](const fc::optional<Field>& f) {
         if (!f.valid()) return predicate_result::Rejection(predicate_result::null_optional);
         return p(*f);
      };
   }
};
template<typename Extension>
struct attribute_assertion<extension<Extension>> {
   static object_restriction_predicate<extension<Extension>> create(vector<restriction>&& rs) {
      return [p=restrictions_to_predicate<Extension>(std::move(rs), false)](const extension<Extension>& x) {
         return p(x.value);
      };
   }
};

template<typename Variant>
struct variant_assertion {
   static object_restriction_predicate<Variant> create(restriction::variant_assert_argument_type&&) {
      FC_THROW_EXCEPTION(fc::assert_exception, "Invalid variant assertion on non-variant field",
                         ("Field", fc::get_typename<Variant>::name()));
   }
};
template<typename... Types>
struct variant_assertion<static_variant<Types...>> {
   using Variant = static_variant<Types...>;

   template<typename Value>
   static auto make_predicate(vector<restriction>&& rs) {
      return [p=restrictions_to_predicate<Value>(std::move(rs), true)](const Variant& v) {
         if (v.which() == Variant::template tag<Value>::value)
            return p(v.template get<Value>());
         return predicate_result::Rejection(predicate_result::incorrect_variant_type);
      };
   }
   static object_restriction_predicate<Variant> create(restriction::variant_assert_argument_type&& arg) {
      return typelist::runtime::dispatch(typelist::list<Types...>(), arg.first,
                                         [&arg](auto t) -> object_restriction_predicate<Variant> {
         using Value = typename decltype(t)::type;
         return variant_assertion::make_predicate<Value>(std::move(arg.second));
      });
   }
};
template<typename... Types>
struct variant_assertion<fc::optional<static_variant<Types...>>> {
   using Variant = static_variant<Types...>;
   using Optional = fc::optional<Variant>;
   static object_restriction_predicate<Optional> create(restriction::variant_assert_argument_type&& arg) {
      return typelist::runtime::dispatch(typelist::list<Types...>(), arg.first,
                                         [&arg](auto t) -> object_restriction_predicate<Optional> {
         using Value = typename decltype(t)::type;
         auto pred = variant_assertion<Variant>::template make_predicate<Value>(std::move(arg.second));
         return [p=std::move(pred)](const Optional& opt) {
            if (!opt.valid()) return predicate_result::Rejection(predicate_result::null_optional);
            return p(*opt);
         };
      });
   }
};

// Embed the argument into the predicate functor
template<typename F, typename P, typename A, typename = std::enable_if_t<P::valid>>
object_restriction_predicate<F> embed_argument(P p, A a, short) {
   return [p=std::move(p), a=std::move(a)](const F& f) {
      if (p(f, a)) return predicate_result::Success();
      return predicate_result::Rejection(predicate_result::predicate_was_false);
   };
}
template<typename F, typename P, typename A>
object_restriction_predicate<F> embed_argument(P, A, long) {
   FC_THROW_EXCEPTION(fc::assert_exception, "Invalid types for predicate");
}

// Resolve the argument type and make a predicate for it
template<template<typename...> class Predicate, typename Field, typename ArgVariant>
object_restriction_predicate<Field> make_predicate(ArgVariant arg) {
   return typelist::runtime::dispatch(typename ArgVariant::list(), arg.which(),
                                      [&arg](auto t) mutable -> object_restriction_predicate<Field> {
      using Arg = typename decltype(t)::type;
      return embed_argument<Field>(Predicate<Field, Arg>(), std::move(arg.template get<Arg>()), short());
   });
}

template<typename Field>
object_restriction_predicate<Field> create_predicate_function(restriction_function func, restriction_argument arg) {
   try {
      switch(func) {
      case restriction::func_eq:
         return make_predicate<predicate_eq, Field>(static_variant<equality_types_list>::import_from(std::move(arg)));
      case restriction::func_ne:
         return make_predicate<predicate_ne, Field>(static_variant<equality_types_list>::import_from(std::move(arg)));
      case restriction::func_lt:
         return make_predicate<predicate_lt, Field>(static_variant<comparable_types_list>
                                                    ::import_from(std::move(arg)));
      case restriction::func_le:
         return make_predicate<predicate_le, Field>(static_variant<comparable_types_list>
                                                    ::import_from(std::move(arg)));
      case restriction::func_gt:
         return make_predicate<predicate_gt, Field>(static_variant<comparable_types_list>
                                                    ::import_from(std::move(arg)));
      case restriction::func_ge:
         return make_predicate<predicate_ge, Field>(static_variant<comparable_types_list>
                                                    ::import_from(std::move(arg)));
      case restriction::func_in:
         return make_predicate<predicate_in, Field>(static_variant<list_types_list>::import_from(std::move(arg)));
      case restriction::func_not_in:
         return make_predicate<predicate_not_in, Field>(static_variant<list_types_list>
                                                        ::import_from(std::move(arg)));
      case restriction::func_has_all:
         return make_predicate<predicate_has_all, Field>(static_variant<list_types_list>
                                                         ::import_from(std::move(arg)));
      case restriction::func_has_none:
         return make_predicate<predicate_has_none, Field>(static_variant<list_types_list>
                                                          ::import_from(std::move(arg)));
      case restriction::func_attr:
         FC_ASSERT(arg.which() == restriction_argument::tag<vector<restriction>>::value,
                   "Argument type for attribute assertion must be restriction list");
         return attribute_assertion<Field>::create(std::move(arg.get<vector<restriction>>()));
      case restriction::func_variant_assert:
         FC_ASSERT(arg.which() == restriction_argument::tag<restriction::variant_assert_argument_type>::value,
                   "Argument type for attribute assertion must be pair of variant tag and restriction list");
         return variant_assertion<Field>::create(std::move(arg.get<restriction::variant_assert_argument_type>()));
      default:
          FC_THROW_EXCEPTION(fc::assert_exception, "Invalid function type on restriction");
      }
   } FC_CAPTURE_AND_RETHROW( (fc::get_typename<Field>::name())(func)(arg) )
}

#include "create_predicate_fwd.hxx"

template<typename Object,
         typename = std::enable_if_t<typelist::length<typename fc::reflector<Object>::native_members>() != 0>>
object_restriction_predicate<Object> create_field_predicate(restriction&& r, short) {
   using member_list = typename fc::reflector<Object>::native_members;
   FC_ASSERT( r.member_index < static_cast<uint64_t>(typelist::length<member_list>()),
              "Invalid member index ${I} for object ${O}",
              ("I", r.member_index)("O", fc::get_typename<Object>::name()) );
   auto predicator = [f=r.restriction_type, a=std::move(r.argument)](auto t) -> object_restriction_predicate<Object> {
      using FieldReflection = typename decltype(t)::type;
      using Field = typename FieldReflection::type;
      auto p = create_predicate_function<Field>(static_cast<restriction_function>(f), std::move(a));
      return [p=std::move(p)](const Object& o) { return p(FieldReflection::get(o)); };
   };
   return typelist::runtime::dispatch(member_list(), static_cast<size_t>(r.member_index.value), predicator);
}
template<typename Object>
object_restriction_predicate<Object> create_field_predicate(restriction&&, long) {
   FC_THROW_EXCEPTION(fc::assert_exception, "Invalid restriction references member of non-object type: ${O}",
                      ("O", fc::get_typename<Object>::name()));
}

template<typename Object>
object_restriction_predicate<Object> create_logical_or_predicate(vector<vector<restriction>> rs) {
   FC_ASSERT(rs.size() > 1, "Logical OR must have at least two branches");
   auto to_predicate = std::bind(restrictions_to_predicate<Object>, std::placeholders::_1, false);

   vector<object_restriction_predicate<Object>> predicates;
   std::transform(std::make_move_iterator(rs.begin()), std::make_move_iterator(rs.end()),
                  std::back_inserter(predicates), to_predicate);

   return [predicates=std::move(predicates)](const Object& obj) {
      vector<predicate_result> rejections;
      bool success = std::any_of(predicates.begin(), predicates.end(),
                                 [o=std::cref(obj), &rejections](const auto& p) {
         auto result = p(o);
         if (!result) rejections.push_back(std::move(result));
         return !!result;
      });
      if (success) return predicate_result::Success();
      return predicate_result::Rejection(std::move(rejections));
   };
}

template<typename Object>
object_restriction_predicate<Object> restrictions_to_predicate(vector<restriction> rs, bool allow_empty) {
   if (!allow_empty)
      FC_ASSERT(!rs.empty(), "Empty attribute assertions and logical OR branches are not permitted");

   vector<object_restriction_predicate<Object>> predicates;
   std::transform(std::make_move_iterator(rs.begin()), std::make_move_iterator(rs.end()),
                  std::back_inserter(predicates), [](restriction&& r) {
      if (r.restriction_type.value == restriction::func_logical_or) {
          FC_ASSERT(r.argument.which() == restriction_argument::tag<vector<vector<restriction>>>::value,
                    "Restriction argument for logical OR function type must be list of restriction lists.");
          return create_logical_or_predicate<Object>(std::move(r.argument.get<vector<vector<restriction>>>()));
      }
      return create_field_predicate<Object>(std::move(r), short());
   });

   return [predicates=std::move(predicates)](const Object& obj) {
      for (size_t i = 0; i < predicates.size(); ++i) {
         auto result = predicates[i](obj);
         if (!result) {
            result.rejection_path.push_back(i);
            return result;
         }
      }
      return predicate_result::Success();
   };
}

} } // namespace graphene::protocol