// Copyright 2018 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 impl

import (

	"fmt"

	"reflect"

	"strings"

	"sync"

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

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

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

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

)

// legacyEnumName returns the name of enums used in legacy code.

// It is neither the protobuf full name nor the qualified Go name,

// but rather an odd hybrid of both.

func legacyEnumName(ed pref.EnumDescriptor) string {

	var protoPkg string

	enumName := string(ed.FullName())

	if fd := ed.ParentFile(); fd != nil {

		protoPkg = string(fd.Package())

		enumName = strings.TrimPrefix(enumName, protoPkg+".")

	}

	if protoPkg == "" {

		return strs.GoCamelCase(enumName)

	}

	return protoPkg + "." + strs.GoCamelCase(enumName)

}

// legacyWrapEnum wraps v as a protoreflect.Enum,

// where v must be a int32 kind and not implement the v2 API already.

func legacyWrapEnum(v reflect.Value) pref.Enum {

	et := legacyLoadEnumType(v.Type())

	return et.New(pref.EnumNumber(v.Int()))

}

var legacyEnumTypeCache sync.Map // map[reflect.Type]protoreflect.EnumType

// legacyLoadEnumType dynamically loads a protoreflect.EnumType for t,

// where t must be an int32 kind and not implement the v2 API already.

func legacyLoadEnumType(t reflect.Type) pref.EnumType {

	// Fast-path: check if a EnumType is cached for this concrete type.

	if et, ok := legacyEnumTypeCache.Load(t); ok {

		return et.(pref.EnumType)

	}

	// Slow-path: derive enum descriptor and initialize EnumType.

	var et pref.EnumType

	ed := LegacyLoadEnumDesc(t)

	et = &legacyEnumType{

		desc:   ed,

		goType: t,

	}

	if et, ok := legacyEnumTypeCache.LoadOrStore(t, et); ok {

		return et.(pref.EnumType)

	}

	return et

}

type legacyEnumType struct {

	desc   pref.EnumDescriptor

	goType reflect.Type

	m      sync.Map // map[protoreflect.EnumNumber]proto.Enum

}

func (t *legacyEnumType) New(n pref.EnumNumber) pref.Enum {

	if e, ok := t.m.Load(n); ok {

		return e.(pref.Enum)

	}

	e := &legacyEnumWrapper{num: n, pbTyp: t, goTyp: t.goType}

	t.m.Store(n, e)

	return e

}

func (t *legacyEnumType) Descriptor() pref.EnumDescriptor {

	return t.desc

}

type legacyEnumWrapper struct {

	num   pref.EnumNumber

	pbTyp pref.EnumType

	goTyp reflect.Type

}

func (e *legacyEnumWrapper) Descriptor() pref.EnumDescriptor {

	return e.pbTyp.Descriptor()

}

func (e *legacyEnumWrapper) Type() pref.EnumType {

	return e.pbTyp

}

func (e *legacyEnumWrapper) Number() pref.EnumNumber {

	return e.num

}

func (e *legacyEnumWrapper) ProtoReflect() pref.Enum {

	return e

}

func (e *legacyEnumWrapper) protoUnwrap() interface{} {

	v := reflect.New(e.goTyp).Elem()

	v.SetInt(int64(e.num))

	return v.Interface()

}

var (

	_ pref.Enum = (*legacyEnumWrapper)(nil)

	_ unwrapper = (*legacyEnumWrapper)(nil)

)

var legacyEnumDescCache sync.Map // map[reflect.Type]protoreflect.EnumDescriptor

// LegacyLoadEnumDesc returns an EnumDescriptor derived from the Go type,

// which must be an int32 kind and not implement the v2 API already.

//

// This is exported for testing purposes.

func LegacyLoadEnumDesc(t reflect.Type) pref.EnumDescriptor {

	// Fast-path: check if an EnumDescriptor is cached for this concrete type.

	if ed, ok := legacyEnumDescCache.Load(t); ok {

		return ed.(pref.EnumDescriptor)

	}

	// Slow-path: initialize EnumDescriptor from the raw descriptor.

	ev := reflect.Zero(t).Interface()

	if _, ok := ev.(pref.Enum); ok {

		panic(fmt.Sprintf("%v already implements proto.Enum", t))

	}

	edV1, ok := ev.(enumV1)

	if !ok {

		return aberrantLoadEnumDesc(t)

	}

	b, idxs := edV1.EnumDescriptor()

	var ed pref.EnumDescriptor

	if len(idxs) == 1 {

		ed = legacyLoadFileDesc(b).Enums().Get(idxs[0])

	} else {

		md := legacyLoadFileDesc(b).Messages().Get(idxs[0])

		for _, i := range idxs[1 : len(idxs)-1] {

			md = md.Messages().Get(i)

		}

		ed = md.Enums().Get(idxs[len(idxs)-1])

	}

	if ed, ok := legacyEnumDescCache.LoadOrStore(t, ed); ok {

		return ed.(protoreflect.EnumDescriptor)

	}

	return ed

}

var aberrantEnumDescCache sync.Map // map[reflect.Type]protoreflect.EnumDescriptor

// aberrantLoadEnumDesc returns an EnumDescriptor derived from the Go type,

// which must not implement protoreflect.Enum or enumV1.

//

// If the type does not implement enumV1, then there is no reliable

// way to derive the original protobuf type information.

// We are unable to use the global enum registry since it is

// unfortunately keyed by the protobuf full name, which we also do not know.

// Thus, this produces some bogus enum descriptor based on the Go type name.

func aberrantLoadEnumDesc(t reflect.Type) pref.EnumDescriptor {

	// Fast-path: check if an EnumDescriptor is cached for this concrete type.

	if ed, ok := aberrantEnumDescCache.Load(t); ok {

		return ed.(pref.EnumDescriptor)

	}

	// Slow-path: construct a bogus, but unique EnumDescriptor.

	ed := &filedesc.Enum{L2: new(filedesc.EnumL2)}

	ed.L0.FullName = AberrantDeriveFullName(t) // e.g., github_com.user.repo.MyEnum

	ed.L0.ParentFile = filedesc.SurrogateProto3

	ed.L2.Values.List = append(ed.L2.Values.List, filedesc.EnumValue{})

	// TODO: Use the presence of a UnmarshalJSON method to determine proto2?

	vd := &ed.L2.Values.List[0]

	vd.L0.FullName = ed.L0.FullName + "_UNKNOWN" // e.g., github_com.user.repo.MyEnum_UNKNOWN

	vd.L0.ParentFile = ed.L0.ParentFile

	vd.L0.Parent = ed

	// TODO: We could use the String method to obtain some enum value names by

	// starting at 0 and print the enum until it produces invalid identifiers.

	// An exhaustive query is clearly impractical, but can be best-effort.

	if ed, ok := aberrantEnumDescCache.LoadOrStore(t, ed); ok {

		return ed.(pref.EnumDescriptor)

	}

	return ed

}

// AberrantDeriveFullName derives a fully qualified protobuf name for the given Go type

// The provided name is not guaranteed to be stable nor universally unique.

// It should be sufficiently unique within a program.

//

// This is exported for testing purposes.

func AberrantDeriveFullName(t reflect.Type) pref.FullName {

	sanitize := func(r rune) rune {

		switch {

		case r == '/':

			return '.'

		case 'a' <= r && r <= 'z', 'A' <= r && r <= 'Z', '0' <= r && r <= '9':

			return r

		default:

			return '_'

		}

	}

	prefix := strings.Map(sanitize, t.PkgPath())

	suffix := strings.Map(sanitize, t.Name())

	if suffix == "" {

		suffix = fmt.Sprintf("UnknownX%X", reflect.ValueOf(t).Pointer())

	}

	ss := append(strings.Split(prefix, "."), suffix)

	for i, s := range ss {

		if s == "" || ('0' <= s[0] && s[0] <= '9') {

			ss[i] = "x" + s

		}

	}

	return pref.FullName(strings.Join(ss, "."))

}