composite.go

package protopath

import (
	"github.com/daishe/protoreflectextra"
	"google.golang.org/protobuf/proto"
	"google.golang.org/protobuf/reflect/protoreflect"

	"github.com/daishe/protopath/internal/genid"
)

// composite is a wrapper of any composite protocol buffer type (message, list or map) allowing easy traversal and operations.
type composite interface {
	// IsReadOnly reports wether underlying composite value is read only.
	IsReadOnly() bool

	// Self returns underlying composite value. For messages it returns its protoreflect.Message value. For lists and maps it returns List and Map interfaces accordingly.
	Self() any

	// Get returns value associated with the given field / index / key. It returns error if the field / index / key is not found. For scalar types and messages it returns its value. For lists and maps it returns List and Map interfaces accordingly.
	Get(s Segment) (any, error)

	// Mutable is a mutable variant of Get method - it returns value associated with the given field / index / key. It returns error if the underlying composite value is read-only or the field / index / key is not found. For scalar types and messages it returns its value. For lists and maps it returns List and Map interfaces accordingly.
	Mutable(s Segment) (any, error)

	// Access descends into the given field / index / key and returns that value. It returns error if the field / index / key is not found or is not associated with a composite type.
	Access(s Segment) (any, error)

	// AccessMutable is a mutable variant of Access method - it descends into the given field / index / key and returns that value. It returns error if the underlying composite value is read-only, if the field / index / key is not found or is not associated with a composite type.
	AccessMutable(s Segment) (any, error)
}

func newComposite(x any) composite {
	switch x := x.(type) {
	case protoreflectextra.List:
		return newGenericListComposite(x)
	case protoreflectextra.Map:
		return newGenericMapComposite(x)
	case proto.Message:
		return newMessageComposite(x.ProtoReflect())
	case protoreflect.Message:
		return newMessageComposite(x)
	}
	return nil
}

func newMessageComposite(m protoreflect.Message) composite {
	switch m.Descriptor().FullName() { // must have a case for each massage based composite implementation
	case genid.Value_message_fullname:
		return newValueComposite(m)
	case genid.Struct_message_fullname:
		return newStructComposite(m)
	case genid.ListValue_message_fullname:
		return newListValueComposite(m)
	default: // generic proto message
		return newGenericMessageComposite(m)
	}
}