composite_generic_list.go

package protopath

import (
	"strconv"

	"github.com/daishe/protoreflectextra"
	"google.golang.org/protobuf/reflect/protoreflect"
)

// listIndex parses the provided name as a list index. It also reports if the provided name was parsed successfully. In case of parsing failure, it returns 0 and false.
func listIndex(name string) (int, bool) {
	i, err := strconv.ParseInt(name, 10, 0)
	if err != nil {
		return 0, false
	}
	return int(i), true
}

// listIndexNormalized normalizes the provided list index, by ensuring it will have a non negative value assuming it points to an element in a list with the given length. It reports if the provided index was normalized successfully. In case of failure, it returns 0 and false.
func listIndexNormalized(len, index int) (int, bool) {
	if index < -len || index >= len {
		return 0, false
	}
	if index < 0 {
		index = len + index
	}
	return index, true
}

func listIndexInListOrError(list protoreflectextra.List, name string) (int, error) {
	if !list.IsMutable() {
		return 0, &ErrNotFound{Kind: "index", Value: name}
	}
	index, ok := listIndex(name)
	if !ok {
		return 0, &ErrNotFound{Kind: "index", Value: name}
	}
	index, ok = listIndexNormalized(list.Len(), index)
	if !ok {
		return 0, &ErrNotFound{Kind: "index", Value: name}
	}
	return index, nil
}

func interfaceOfListItem(field protoreflect.FieldDescriptor, value protoreflect.Value) any {
	if field.Kind() == protoreflect.EnumKind {
		return protoreflectextra.NewEnum(field.Enum(), value.Enum())
	}
	return value.Interface()
}

type genericListComposite struct {
	List protoreflectextra.List
}

func newGenericListComposite(li protoreflectextra.List) genericListComposite {
	return genericListComposite{List: li}
}

func (c genericListComposite) IsReadOnly() bool {
	return !c.List.IsMutable()
}

func (c genericListComposite) Self() any {
	return c.List
}

func (c genericListComposite) Get(s Segment) (any, error) {
	idx, err := listIndexInListOrError(c.List, s.Value())
	if err != nil {
		return nil, err
	}
	return interfaceOfListItem(c.List.Descriptor().ListElement(), c.List.Get(idx)), nil
}

func (c genericListComposite) Mutable(s Segment) (any, error) {
	if !c.List.IsMutable() {
		return nil, ErrMutationOfReadOnlyValue
	}
	return c.Get(s)
}

func (c genericListComposite) Access(s Segment) (any, error) {
	idx, err := listIndexInListOrError(c.List, s.Value())
	if err != nil {
		return nil, err
	}
	if c.List.Descriptor().ListElement().Kind() != protoreflect.MessageKind {
		return nil, newErrInSegment(s, ErrAccessToNonCompositeType)
	}
	return c.List.Get(idx).Message(), nil
}

func (c genericListComposite) AccessMutable(s Segment) (any, error) {
	if !c.List.IsMutable() {
		return nil, ErrMutationOfReadOnlyValue
	}
	idx, err := listIndexInListOrError(c.List, s.Value())
	if err != nil {
		return nil, err
	}
	if c.List.Descriptor().ListElement().Kind() != protoreflect.MessageKind {
		return nil, newErrInSegment(s, ErrAccessToNonCompositeType)
	}
	return c.List.Get(idx).Message(), nil
}