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// Copyright 2023 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package ext
import (
"math"
"github.com/google/cel-go/cel"
"github.com/google/cel-go/checker"
"github.com/google/cel-go/common/types"
"github.com/google/cel-go/common/types/ref"
"github.com/google/cel-go/common/types/traits"
"github.com/google/cel-go/interpreter"
)
// Sets returns a cel.EnvOption to configure namespaced set relationship
// functions.
//
// There is no set type within CEL, and while one may be introduced in the
// future, there are cases where a `list` type is known to behave like a set.
// For such cases, this library provides some basic functionality for
// determining set containment, equivalence, and intersection.
//
// # Sets.Contains
//
// Returns whether the first list argument contains all elements in the second
// list argument. The list may contain elements of any type and standard CEL
// equality is used to determine whether a value exists in both lists. If the
// second list is empty, the result will always return true.
//
// sets.contains(list(T), list(T)) -> bool
//
// Examples:
//
// sets.contains([], []) // true
// sets.contains([], [1]) // false
// sets.contains([1, 2, 3, 4], [2, 3]) // true
// sets.contains([1, 2.0, 3u], [1.0, 2u, 3]) // true
//
// # Sets.Equivalent
//
// Returns whether the first and second list are set equivalent. Lists are set
// equivalent if for every item in the first list, there is an element in the
// second which is equal. The lists may not be of the same size as they do not
// guarantee the elements within them are unique, so size does not factor into
// the computation.
//
// Examples:
//
// sets.equivalent([], []) // true
// sets.equivalent([1], [1, 1]) // true
// sets.equivalent([1], [1u, 1.0]) // true
// sets.equivalent([1, 2, 3], [3u, 2.0, 1]) // true
//
// # Sets.Intersects
//
// Returns whether the first list has at least one element whose value is equal
// to an element in the second list. If either list is empty, the result will
// be false.
//
// Examples:
//
// sets.intersects([1], []) // false
// sets.intersects([1], [1, 2]) // true
// sets.intersects([[1], [2, 3]], [[1, 2], [2, 3.0]]) // true
func Sets() cel.EnvOption {
return cel.Lib(setsLib{})
}
type setsLib struct{}
// LibraryName implements the SingletonLibrary interface method.
func (setsLib) LibraryName() string {
return "cel.lib.ext.sets"
}
// CompileOptions implements the Library interface method.
func (setsLib) CompileOptions() []cel.EnvOption {
listType := cel.ListType(cel.TypeParamType("T"))
return []cel.EnvOption{
cel.Function("sets.contains",
cel.Overload("list_sets_contains_list", []*cel.Type{listType, listType}, cel.BoolType,
cel.BinaryBinding(setsContains))),
cel.Function("sets.equivalent",
cel.Overload("list_sets_equivalent_list", []*cel.Type{listType, listType}, cel.BoolType,
cel.BinaryBinding(setsEquivalent))),
cel.Function("sets.intersects",
cel.Overload("list_sets_intersects_list", []*cel.Type{listType, listType}, cel.BoolType,
cel.BinaryBinding(setsIntersects))),
cel.CostEstimatorOptions(
checker.OverloadCostEstimate("list_sets_contains_list", estimateSetsCost(1)),
checker.OverloadCostEstimate("list_sets_intersects_list", estimateSetsCost(1)),
// equivalence requires potentially two m*n comparisons to ensure each list is contained by the other
checker.OverloadCostEstimate("list_sets_equivalent_list", estimateSetsCost(2)),
),
}
}
// ProgramOptions implements the Library interface method.
func (setsLib) ProgramOptions() []cel.ProgramOption {
return []cel.ProgramOption{
cel.CostTrackerOptions(
interpreter.OverloadCostTracker("list_sets_contains_list", trackSetsCost(1)),
interpreter.OverloadCostTracker("list_sets_intersects_list", trackSetsCost(1)),
interpreter.OverloadCostTracker("list_sets_equivalent_list", trackSetsCost(2)),
),
}
}
func setsIntersects(listA, listB ref.Val) ref.Val {
lA := listA.(traits.Lister)
lB := listB.(traits.Lister)
it := lA.Iterator()
for it.HasNext() == types.True {
exists := lB.Contains(it.Next())
if exists == types.True {
return types.True
}
}
return types.False
}
func setsContains(list, sublist ref.Val) ref.Val {
l := list.(traits.Lister)
sub := sublist.(traits.Lister)
it := sub.Iterator()
for it.HasNext() == types.True {
exists := l.Contains(it.Next())
if exists != types.True {
return exists
}
}
return types.True
}
func setsEquivalent(listA, listB ref.Val) ref.Val {
aContainsB := setsContains(listA, listB)
if aContainsB != types.True {
return aContainsB
}
return setsContains(listB, listA)
}
func estimateSetsCost(costFactor float64) checker.FunctionEstimator {
return func(estimator checker.CostEstimator, target *checker.AstNode, args []checker.AstNode) *checker.CallEstimate {
if len(args) == 2 {
arg0Size := estimateSize(estimator, args[0])
arg1Size := estimateSize(estimator, args[1])
costEstimate := arg0Size.Multiply(arg1Size).MultiplyByCostFactor(costFactor).Add(callCostEstimate)
return &checker.CallEstimate{CostEstimate: costEstimate}
}
return nil
}
}
func estimateSize(estimator checker.CostEstimator, node checker.AstNode) checker.SizeEstimate {
if l := node.ComputedSize(); l != nil {
return *l
}
if l := estimator.EstimateSize(node); l != nil {
return *l
}
return checker.SizeEstimate{Min: 0, Max: math.MaxUint64}
}
func trackSetsCost(costFactor float64) interpreter.FunctionTracker {
return func(args []ref.Val, _ ref.Val) *uint64 {
lhsSize := actualSize(args[0])
rhsSize := actualSize(args[1])
cost := callCost + uint64(float64(lhsSize*rhsSize)*costFactor)
return &cost
}
}
func actualSize(value ref.Val) uint64 {
if sz, ok := value.(traits.Sizer); ok {
return uint64(sz.Size().(types.Int))
}
return 1
}
var (
callCostEstimate = checker.CostEstimate{Min: 1, Max: 1}
callCost = uint64(1)
)
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