feat: add initial support for mutation trees

pkg/engine/mutate/expression.go

@@ -0,0 +1,65 @@
+package mutate
+
+import (
+	"context"
+	"reflect"
+	"regexp"
+
+	reflectutils "github.com/kyverno/kyverno-json/pkg/utils/reflect"
+)
+
+var (
+	foreachRegex = regexp.MustCompile(`^~(\w+)?\.(.*)`)
+	bindingRegex = regexp.MustCompile(`(.*)\s*->\s*(\w+)$`)
+	escapeRegex  = regexp.MustCompile(`^\\(.+)\\$`)
+	engineRegex  = regexp.MustCompile(`^\((?:(\w+):)?(.+)\)$`)
+)
+
+type expression struct {
+	foreach     bool
+	foreachName string
+	statement   string
+	binding     string
+	engine      string
+}
+
+func parseExpressionRegex(ctx context.Context, in string) *expression {
+	expression := &expression{}
+	// 1. match foreach
+	if match := foreachRegex.FindStringSubmatch(in); match != nil {
+		expression.foreach = true
+		expression.foreachName = match[1]
+		in = match[2]
+	}
+	// 2. match binding
+	if match := bindingRegex.FindStringSubmatch(in); match != nil {
+		expression.binding = match[2]
+		in = match[1]
+	}
+	// 3. match escape, if there's no escaping then match engine
+	if match := escapeRegex.FindStringSubmatch(in); match != nil {
+		in = match[1]
+	} else {
+		if match := engineRegex.FindStringSubmatch(in); match != nil {
+			expression.engine = match[1]
+			// account for default engine
+			if expression.engine == "" {
+				expression.engine = "jp"
+			}
+			in = match[2]
+		}
+	}
+	// parse statement
+	expression.statement = in
+	if expression.statement == "" {
+		return nil
+	}
+	return expression
+}
+
+func parseExpression(ctx context.Context, value any) *expression {
+	if reflectutils.GetKind(value) != reflect.String {
+		return nil
+	}
+	return parseExpressionRegex(ctx, reflect.ValueOf(value).String())
+}

pkg/engine/mutate/mutate.go

@@ -0,0 +1,13 @@
+package mutate
+
+import (
+	"context"
+
+	"github.com/jmespath-community/go-jmespath/pkg/binding"
+	"github.com/kyverno/kyverno-json/pkg/engine/template"
+	"k8s.io/apimachinery/pkg/util/validation/field"
+)
+
+func Mutate(ctx context.Context, path *field.Path, mutation Mutation, value any, bindings binding.Bindings, opts ...template.Option) (any, error) {
+	return mutation.mutate(ctx, path, value, bindings, opts...)
+}

pkg/engine/mutate/mutation.go

@@ -0,0 +1,13 @@
+package mutate
+
+import (
+	"context"
+
+	"github.com/jmespath-community/go-jmespath/pkg/binding"
+	"github.com/kyverno/kyverno-json/pkg/engine/template"
+	"k8s.io/apimachinery/pkg/util/validation/field"
+)
+
+type Mutation interface {
+	mutate(context.Context, *field.Path, any, binding.Bindings, ...template.Option) (any, error)
+}

pkg/engine/mutate/parse.go

@@ -0,0 +1,156 @@
+package mutate
+
+import (
+	"context"
+	"fmt"
+	"reflect"
+
+	"github.com/jmespath-community/go-jmespath/pkg/binding"
+	"github.com/kyverno/kyverno-json/pkg/engine/template"
+	reflectutils "github.com/kyverno/kyverno-json/pkg/utils/reflect"
+	"k8s.io/apimachinery/pkg/util/validation/field"
+)
+
+func Parse(ctx context.Context, mutation any) Mutation {
+	switch reflectutils.GetKind(mutation) {
+	case reflect.Slice:
+		node := sliceNode{}
+		valueOf := reflect.ValueOf(mutation)
+		for i := 0; i < valueOf.Len(); i++ {
+			node = append(node, Parse(ctx, valueOf.Index(i).Interface()))
+		}
+		return node
+	case reflect.Map:
+		node := mapNode{}
+		iter := reflect.ValueOf(mutation).MapRange()
+		for iter.Next() {
+			node[iter.Key().Interface()] = Parse(ctx, iter.Value().Interface())
+		}
+		return node
+	default:
+		return &scalarNode{rhs: mutation}
+	}
+}
+
+// mapNode is the mutation type represented by a map.
+// it is responsible for projecting the analysed resource and passing the result to the descendant
+type mapNode map[any]Mutation
+
+func (n mapNode) mutate(ctx context.Context, path *field.Path, value any, bindings binding.Bindings, opts ...template.Option) (any, error) {
+	out := map[any]any{}
+	for k, v := range n {
+		// TODO: very simple implementation
+		mapValue := reflect.ValueOf(value).MapIndex(reflect.ValueOf(k))
+		if !mapValue.IsValid() {
+			continue
+		}
+		value := mapValue.Interface()
+		// TODO: does it make sense to take valueOf.Index(i).Interface() here ?
+		if inner, err := v.mutate(ctx, path.Child(fmt.Sprint(k)), value, bindings, opts...); err != nil {
+			return nil, err
+		} else {
+			out[k] = inner
+		}
+		// projection, err := project(ctx, k, value, bindings, opts...)
+		// if err != nil {
+		// 	return nil, field.InternalError(path.Child(fmt.Sprint(k)), err)
+		// } else {
+		// 	if projection.binding != "" {
+		// 		bindings = bindings.Register("$"+projection.binding, jpbinding.NewBinding(projection.result))
+		// 	}
+		// 	if projection.foreach {
+		// 		projectedKind := reflectutils.GetKind(projection.result)
+		// 		if projectedKind == reflect.Slice {
+		// 			valueOf := reflect.ValueOf(projection.result)
+		// 			for i := 0; i < valueOf.Len(); i++ {
+		// 				bindings := bindings
+		// 				if projection.foreachName != "" {
+		// 					bindings = bindings.Register("$"+projection.foreachName, jpbinding.NewBinding(i))
+		// 				}
+		// 				if _errs, err := v.mutate(ctx, path.Child(fmt.Sprint(k)).Index(i), valueOf.Index(i).Interface(), bindings, opts...); err != nil {
+		// 					return nil, err
+		// 				} else {
+		// 					errs = append(errs, _errs...)
+		// 				}
+		// 			}
+		// 		} else if projectedKind == reflect.Map {
+		// 			iter := reflect.ValueOf(projection.result).MapRange()
+		// 			for iter.Next() {
+		// 				key := iter.Key().Interface()
+		// 				bindings := bindings
+		// 				if projection.foreachName != "" {
+		// 					bindings = bindings.Register("$"+projection.foreachName, jpbinding.NewBinding(key))
+		// 				}
+		// 				if _errs, err := v.mutate(ctx, path.Child(fmt.Sprint(k)).Key(fmt.Sprint(key)), iter.Value().Interface(), bindings, opts...); err != nil {
+		// 					return nil, err
+		// 				} else {
+		// 					errs = append(errs, _errs...)
+		// 				}
+		// 			}
+		// 		} else {
+		// 			return nil, field.TypeInvalid(path.Child(fmt.Sprint(k)), projection.result, "expected a slice or a map")
+		// 		}
+		// 	} else {
+		// 		if _errs, err := v.mutate(ctx, path.Child(fmt.Sprint(k)), projection.result, bindings, opts...); err != nil {
+		// 			return nil, err
+		// 		} else {
+		// 			errs = append(errs, _errs...)
+		// 		}
+		// 	}
+		// }
+	}
+	return out, nil
+}
+
+// sliceNode is the mutation type represented by a slice.
+// it first compares the length of the analysed resource with the length of the descendants.
+// if lengths match all descendants are evaluated with their corresponding items.
+type sliceNode []Mutation
+
+func (n sliceNode) mutate(ctx context.Context, path *field.Path, value any, bindings binding.Bindings, opts ...template.Option) (any, error) {
+	if value == nil {
+		return nil, nil
+	} else if reflectutils.GetKind(value) != reflect.Slice {
+		return nil, field.TypeInvalid(path, value, "expected a slice")
+	} else {
+		var out []any
+		valueOf := reflect.ValueOf(value)
+		for i := range n {
+			// TODO: does it make sense to take valueOf.Index(i).Interface() here ?
+			if inner, err := n[i].mutate(ctx, path.Index(i), valueOf.Index(i).Interface(), bindings, opts...); err != nil {
+				return nil, err
+			} else {
+				out = append(out, inner)
+			}
+		}
+		return out, nil
+	}
+}
+
+// scalarNode is a terminal type of mutation.
+// it receives a value and compares it with an expected value.
+// the expected value can be the result of an expression.
+type scalarNode struct {
+	rhs any
+}
+
+func (n *scalarNode) mutate(ctx context.Context, path *field.Path, value any, bindings binding.Bindings, opts ...template.Option) (any, error) {
+	rhs := n.rhs
+	expression := parseExpression(ctx, rhs)
+	// we only project if the expression uses the engine syntax
+	// this is to avoid the case where the value is a map and the RHS is a string
+	if expression != nil && expression.engine != "" {
+		if expression.foreachName != "" {
+			return nil, field.Invalid(path, rhs, "foreach is not supported on the RHS")
+		}
+		if expression.binding != "" {
+			return nil, field.Invalid(path, rhs, "binding is not supported on the RHS")
+		}
+		projected, err := template.Execute(ctx, expression.statement, value, bindings, opts...)
+		if err != nil {
+			return nil, field.InternalError(path, err)
+		}
+		rhs = projected
+	}
+	return rhs, nil
+}

pkg/engine/mutate/project.go

@@ -0,0 +1,63 @@
+package mutate
+
+// import (
+// 	"context"
+// 	"reflect"
+
+// 	"github.com/jmespath-community/go-jmespath/pkg/binding"
+// 	"github.com/kyverno/kyverno-json/pkg/engine/template"
+// 	reflectutils "github.com/kyverno/kyverno-json/pkg/utils/reflect"
+// )
+
+// type projection struct {
+// 	foreach     bool
+// 	foreachName string
+// 	binding     string
+// 	result      any
+// }
+
+// func project(ctx context.Context, key any, value any, bindings binding.Bindings, opts ...template.Option) (*projection, error) {
+// 	expression := parseExpression(ctx, key)
+// 	if expression != nil {
+// 		if expression.engine != "" {
+// 			projected, err := template.Execute(ctx, expression.statement, value, bindings, opts...)
+// 			if err != nil {
+// 				return nil, err
+// 			}
+// 			return &projection{
+// 				foreach:     expression.foreach,
+// 				foreachName: expression.foreachName,
+// 				binding:     expression.binding,
+// 				result:      projected,
+// 			}, nil
+// 		} else {
+// 			if reflectutils.GetKind(value) == reflect.Map {
+// 				mapValue := reflect.ValueOf(value).MapIndex(reflect.ValueOf(expression.statement))
+// 				var value any
+// 				if mapValue.IsValid() {
+// 					value = mapValue.Interface()
+// 				}
+// 				return &projection{
+// 					foreach:     expression.foreach,
+// 					foreachName: expression.foreachName,
+// 					binding:     expression.binding,
+// 					result:      value,
+// 				}, nil
+// 			}
+// 		}
+// 	}
+// 	if reflectutils.GetKind(value) == reflect.Map {
+// 		mapValue := reflect.ValueOf(value).MapIndex(reflect.ValueOf(key))
+// 		var value any
+// 		if mapValue.IsValid() {
+// 			value = mapValue.Interface()
+// 		}
+// 		return &projection{
+// 			result: value,
+// 		}, nil
+// 	}
+// 	// TODO is this an error ?
+// 	return &projection{
+// 		result: value,
+// 	}, nil
+// }