// Copyright 2019 The Go Authors. All rights reserved.

// Use of this source code is governed by a BSD-style

// license that can be found in the LICENSE file.

package protodesc

import (

	"google.golang.org/protobuf/internal/encoding/defval"

	"google.golang.org/protobuf/internal/errors"

	"google.golang.org/protobuf/internal/filedesc"

	"google.golang.org/protobuf/reflect/protoreflect"

	"google.golang.org/protobuf/reflect/protoregistry"

	"google.golang.org/protobuf/types/descriptorpb"

)

// resolver is a wrapper around a local registry of declarations within the file

// and the remote resolver. The remote resolver is restricted to only return

// descriptors that have been imported.

type resolver struct {

	local   descsByName

	remote  Resolver

	imports importSet

	allowUnresolvable bool

}

func (r *resolver) resolveMessageDependencies(ms []filedesc.Message, mds []*descriptorpb.DescriptorProto) (err error) {

	for i, md := range mds {

		m := &ms[i]

		for j, fd := range md.GetField() {

			f := &m.L2.Fields.List[j]

			if f.L1.Cardinality == protoreflect.Required {

				m.L2.RequiredNumbers.List = append(m.L2.RequiredNumbers.List, f.L1.Number)

			}

			if fd.OneofIndex != nil {

				k := int(fd.GetOneofIndex())

				if !(0 <= k && k < len(md.GetOneofDecl())) {

					return errors.New("message field %q has an invalid oneof index: %d", f.FullName(), k)

				}

				o := &m.L2.Oneofs.List[k]

				f.L1.ContainingOneof = o

				o.L1.Fields.List = append(o.L1.Fields.List, f)

			}

			if f.L1.Kind, f.L1.Enum, f.L1.Message, err = r.findTarget(f.Kind(), f.Parent().FullName(), partialName(fd.GetTypeName()), f.IsWeak()); err != nil {

				return errors.New("message field %q cannot resolve type: %v", f.FullName(), err)

			}

			if fd.DefaultValue != nil {

				v, ev, err := unmarshalDefault(fd.GetDefaultValue(), f, r.allowUnresolvable)

				if err != nil {

					return errors.New("message field %q has invalid default: %v", f.FullName(), err)

				}

				f.L1.Default = filedesc.DefaultValue(v, ev)

			}

		}

		if err := r.resolveMessageDependencies(m.L1.Messages.List, md.GetNestedType()); err != nil {

			return err

		}

		if err := r.resolveExtensionDependencies(m.L1.Extensions.List, md.GetExtension()); err != nil {

			return err

		}

	}

	return nil

}

func (r *resolver) resolveExtensionDependencies(xs []filedesc.Extension, xds []*descriptorpb.FieldDescriptorProto) (err error) {

	for i, xd := range xds {

		x := &xs[i]

		if x.L1.Extendee, err = r.findMessageDescriptor(x.Parent().FullName(), partialName(xd.GetExtendee()), false); err != nil {

			return errors.New("extension field %q cannot resolve extendee: %v", x.FullName(), err)

		}

		if x.L1.Kind, x.L2.Enum, x.L2.Message, err = r.findTarget(x.Kind(), x.Parent().FullName(), partialName(xd.GetTypeName()), false); err != nil {

			return errors.New("extension field %q cannot resolve type: %v", x.FullName(), err)

		}

		if xd.DefaultValue != nil {

			v, ev, err := unmarshalDefault(xd.GetDefaultValue(), x, r.allowUnresolvable)

			if err != nil {

				return errors.New("extension field %q has invalid default: %v", x.FullName(), err)

			}

			x.L2.Default = filedesc.DefaultValue(v, ev)

		}

	}

	return nil

}

func (r *resolver) resolveServiceDependencies(ss []filedesc.Service, sds []*descriptorpb.ServiceDescriptorProto) (err error) {

	for i, sd := range sds {

		s := &ss[i]

		for j, md := range sd.GetMethod() {

			m := &s.L2.Methods.List[j]

			m.L1.Input, err = r.findMessageDescriptor(m.Parent().FullName(), partialName(md.GetInputType()), false)

			if err != nil {

				return errors.New("service method %q cannot resolve input: %v", m.FullName(), err)

			}

			m.L1.Output, err = r.findMessageDescriptor(s.FullName(), partialName(md.GetOutputType()), false)

			if err != nil {

				return errors.New("service method %q cannot resolve output: %v", m.FullName(), err)

			}

		}

	}

	return nil

}

// findTarget finds an enum or message descriptor if k is an enum, message,

// group, or unknown. If unknown, and the name could be resolved, the kind

// returned kind is set based on the type of the resolved descriptor.

func (r *resolver) findTarget(k protoreflect.Kind, scope protoreflect.FullName, ref partialName, isWeak bool) (protoreflect.Kind, protoreflect.EnumDescriptor, protoreflect.MessageDescriptor, error) {

	switch k {

	case protoreflect.EnumKind:

		ed, err := r.findEnumDescriptor(scope, ref, isWeak)

		if err != nil {

			return 0, nil, nil, err

		}

		return k, ed, nil, nil

	case protoreflect.MessageKind, protoreflect.GroupKind:

		md, err := r.findMessageDescriptor(scope, ref, isWeak)

		if err != nil {

			return 0, nil, nil, err

		}

		return k, nil, md, nil

	case 0:

		// Handle unspecified kinds (possible with parsers that operate

		// on a per-file basis without knowledge of dependencies).

		d, err := r.findDescriptor(scope, ref)

		if err == protoregistry.NotFound && (r.allowUnresolvable || isWeak) {

			return k, filedesc.PlaceholderEnum(ref.FullName()), filedesc.PlaceholderMessage(ref.FullName()), nil

		} else if err == protoregistry.NotFound {

			return 0, nil, nil, errors.New("%q not found", ref.FullName())

		} else if err != nil {

			return 0, nil, nil, err

		}

		switch d := d.(type) {

		case protoreflect.EnumDescriptor:

			return protoreflect.EnumKind, d, nil, nil

		case protoreflect.MessageDescriptor:

			return protoreflect.MessageKind, nil, d, nil

		default:

			return 0, nil, nil, errors.New("unknown kind")

		}

	default:

		if ref != "" {

			return 0, nil, nil, errors.New("target name cannot be specified for %v", k)

		}

		if !k.IsValid() {

			return 0, nil, nil, errors.New("invalid kind: %d", k)

		}

		return k, nil, nil, nil

	}

}

// findDescriptor finds the descriptor by name,

// which may be a relative name within some scope.

//

// Suppose the scope was "fizz.buzz" and the reference was "Foo.Bar",

// then the following full names are searched:

func (r *resolver) findDescriptor(scope protoreflect.FullName, ref partialName) (protoreflect.Descriptor, error) {

	if !ref.IsValid() {

		return nil, errors.New("invalid name reference: %q", ref)

	}

	if ref.IsFull() {

		scope, ref = "", ref[1:]

	}

	var foundButNotImported protoreflect.Descriptor

	for {

		// Derive the full name to search.

		s := protoreflect.FullName(ref)

		if scope != "" {

			s = scope + "." + s

		}

		// Check the current file for the descriptor.

		if d, ok := r.local[s]; ok {

			return d, nil

		}

		// Check the remote registry for the descriptor.

		d, err := r.remote.FindDescriptorByName(s)

		if err == nil {

			// Only allow descriptors covered by one of the imports.

			if r.imports[d.ParentFile().Path()] {

				return d, nil

			}

			foundButNotImported = d

		} else if err != protoregistry.NotFound {

			return nil, errors.Wrap(err, "%q", s)

		}

		// Continue on at a higher level of scoping.

		if scope == "" {

			if d := foundButNotImported; d != nil {

				return nil, errors.New("resolved %q, but %q is not imported", d.FullName(), d.ParentFile().Path())

			}

			return nil, protoregistry.NotFound

		}

		scope = scope.Parent()

	}

}

func (r *resolver) findEnumDescriptor(scope protoreflect.FullName, ref partialName, isWeak bool) (protoreflect.EnumDescriptor, error) {

	d, err := r.findDescriptor(scope, ref)

	if err == protoregistry.NotFound && (r.allowUnresolvable || isWeak) {

		return filedesc.PlaceholderEnum(ref.FullName()), nil

	} else if err == protoregistry.NotFound {

		return nil, errors.New("%q not found", ref.FullName())

	} else if err != nil {

		return nil, err

	}

	ed, ok := d.(protoreflect.EnumDescriptor)

	if !ok {

		return nil, errors.New("resolved %q, but it is not an enum", d.FullName())

	}

	return ed, nil

}

func (r *resolver) findMessageDescriptor(scope protoreflect.FullName, ref partialName, isWeak bool) (protoreflect.MessageDescriptor, error) {

	d, err := r.findDescriptor(scope, ref)

	if err == protoregistry.NotFound && (r.allowUnresolvable || isWeak) {

		return filedesc.PlaceholderMessage(ref.FullName()), nil

	} else if err == protoregistry.NotFound {

		return nil, errors.New("%q not found", ref.FullName())

	} else if err != nil {

		return nil, err

	}

	md, ok := d.(protoreflect.MessageDescriptor)

	if !ok {

		return nil, errors.New("resolved %q, but it is not an message", d.FullName())

	}

	return md, nil

}

// partialName is the partial name. A leading dot means that the name is full,

// otherwise the name is relative to some current scope.

// See google.protobuf.FieldDescriptorProto.type_name.

type partialName string

func (s partialName) IsFull() bool {

	return len(s) > 0 && s[0] == '.'

}

func (s partialName) IsValid() bool {

	if s.IsFull() {

		return protoreflect.FullName(s[1:]).IsValid()

	}

	return protoreflect.FullName(s).IsValid()

}

const unknownPrefix = "*."

// FullName converts the partial name to a full name on a best-effort basis.

// If relative, it creates an invalid full name, using a "*." prefix

// to indicate that the start of the full name is unknown.

func (s partialName) FullName() protoreflect.FullName {

	if s.IsFull() {

		return protoreflect.FullName(s[1:])

	}

	return protoreflect.FullName(unknownPrefix + s)

}

func unmarshalDefault(s string, fd protoreflect.FieldDescriptor, allowUnresolvable bool) (protoreflect.Value, protoreflect.EnumValueDescriptor, error) {

	var evs protoreflect.EnumValueDescriptors

	if fd.Enum() != nil {

		evs = fd.Enum().Values()

	}

	v, ev, err := defval.Unmarshal(s, fd.Kind(), evs, defval.Descriptor)

	if err != nil && allowUnresolvable && evs != nil && protoreflect.Name(s).IsValid() {

		v = protoreflect.ValueOfEnum(0)

		if evs.Len() > 0 {

			v = protoreflect.ValueOfEnum(evs.Get(0).Number())

		}

		ev = filedesc.PlaceholderEnumValue(fd.Enum().FullName().Parent().Append(protoreflect.Name(s)))

	} else if err != nil {

		return v, ev, err

	}

	if fd.Syntax() == protoreflect.Proto3 {

		return v, ev, errors.New("cannot be specified under proto3 semantics")

	}

	if fd.Kind() == protoreflect.MessageKind || fd.Kind() == protoreflect.GroupKind || fd.Cardinality() == protoreflect.Repeated {

		return v, ev, errors.New("cannot be specified on composite types")

	}

	return v, ev, nil

}