// Protocol Buffers for Go with Gadgets
//
// Copyright (c) 2013, The GoGo Authors. All rights reserved.
// http://github.com/gogo/protobuf
//
// Go support for Protocol Buffers - Google's data interchange format
//
// Copyright 2010 The Go Authors.  All rights reserved.
// https://github.com/golang/protobuf
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

/*
	The code generator for the plugin for the Google protocol buffer compiler.
	It generates Go code from the protocol buffer description files read by the
	main routine.
*/
package generator

import (
	"bytes"
	"fmt"
	"log"
	"os"
	"path"
	"strconv"
	"strings"
	"unicode"
	"unicode/utf8"

	"github.com/gogo/protobuf/gogoproto"
	"github.com/gogo/protobuf/protoc-gen-gogo/descriptor"
	plugin "github.com/gogo/protobuf/protoc-gen-gogo/plugin"
)

// generatedCodeVersion indicates a version of the generated code.
// It is incremented whenever an incompatibility between the generated code and
// proto package is introduced; the generated code references
// a constant, proto.ProtoPackageIsVersionN (where N is generatedCodeVersion).
const generatedCodeVersion = 2

// A Plugin provides functionality to add to the output during Go code generation,
// such as to produce RPC stubs.
type Plugin interface {
	// Name identifies the plugin.
	Name() string
	// Init is called once after data structures are built but before
	// code generation begins.
	Init(g *Generator)
	// Generate produces the code generated by the plugin for this file,
	// except for the imports, by calling the generator's methods P, In, and Out.
	Generate(file *FileDescriptor)
	// GenerateImports produces the import declarations for this file.
	// It is called after Generate.
	GenerateImports(file *FileDescriptor)
}

// Each type we import as a protocol buffer (other than FileDescriptorProto) needs
// a pointer to the FileDescriptorProto that represents it.  These types achieve that
// wrapping by placing each Proto inside a struct with the pointer to its File. The
// structs have the same names as their contents, with "Proto" removed.
// FileDescriptor is used to store the things that it points to.

// The file and package name method are common to messages and enums.
type common struct {
	file *descriptor.FileDescriptorProto // File this object comes from.
}

// PackageName is name in the package clause in the generated file.
func (c *common) PackageName() string { return uniquePackageOf(c.file) }

func (c *common) File() *descriptor.FileDescriptorProto { return c.file }

func fileIsProto3(file *descriptor.FileDescriptorProto) bool {
	return file.GetSyntax() == "proto3"
}

func (c *common) proto3() bool { return fileIsProto3(c.file) }

// Descriptor represents a protocol buffer message.
type Descriptor struct {
	common
	*descriptor.DescriptorProto
	parent   *Descriptor            // The containing message, if any.
	nested   []*Descriptor          // Inner messages, if any.
	enums    []*EnumDescriptor      // Inner enums, if any.
	ext      []*ExtensionDescriptor // Extensions, if any.
	typename []string               // Cached typename vector.
	index    int                    // The index into the container, whether the file or another message.
	path     string                 // The SourceCodeInfo path as comma-separated integers.
	group    bool
}

// TypeName returns the elements of the dotted type name.
// The package name is not part of this name.
func (d *Descriptor) TypeName() []string {
	if d.typename != nil {
		return d.typename
	}
	n := 0
	for parent := d; parent != nil; parent = parent.parent {
		n++
	}
	s := make([]string, n, n)
	for parent := d; parent != nil; parent = parent.parent {
		n--
		s[n] = parent.GetName()
	}
	d.typename = s
	return s
}

func (d *Descriptor) allowOneof() bool {
	return true
}

// EnumDescriptor describes an enum. If it's at top level, its parent will be nil.
// Otherwise it will be the descriptor of the message in which it is defined.
type EnumDescriptor struct {
	common
	*descriptor.EnumDescriptorProto
	parent   *Descriptor // The containing message, if any.
	typename []string    // Cached typename vector.
	index    int         // The index into the container, whether the file or a message.
	path     string      // The SourceCodeInfo path as comma-separated integers.
}

// TypeName returns the elements of the dotted type name.
// The package name is not part of this name.
func (e *EnumDescriptor) TypeName() (s []string) {
	if e.typename != nil {
		return e.typename
	}
	name := e.GetName()
	if e.parent == nil {
		s = make([]string, 1)
	} else {
		pname := e.parent.TypeName()
		s = make([]string, len(pname)+1)
		copy(s, pname)
	}
	s[len(s)-1] = name
	e.typename = s
	return s
}

// alias provides the TypeName corrected for the application of any naming
// extensions on the enum type. It should be used for generating references to
// the Go types and for calculating prefixes.
func (e *EnumDescriptor) alias() (s []string) {
	s = e.TypeName()
	if gogoproto.IsEnumCustomName(e.EnumDescriptorProto) {
		s[len(s)-1] = gogoproto.GetEnumCustomName(e.EnumDescriptorProto)
	}

	return
}

// Everything but the last element of the full type name, CamelCased.
// The values of type Foo.Bar are call Foo_value1... not Foo_Bar_value1... .
func (e *EnumDescriptor) prefix() string {
	typeName := e.alias()
	if e.parent == nil {
		// If the enum is not part of a message, the prefix is just the type name.
		return CamelCase(typeName[len(typeName)-1]) + "_"
	}
	return CamelCaseSlice(typeName[0:len(typeName)-1]) + "_"
}

// The integer value of the named constant in this enumerated type.
func (e *EnumDescriptor) integerValueAsString(name string) string {
	for _, c := range e.Value {
		if c.GetName() == name {
			return fmt.Sprint(c.GetNumber())
		}
	}
	log.Fatal("cannot find value for enum constant")
	return ""
}

// ExtensionDescriptor describes an extension. If it's at top level, its parent will be nil.
// Otherwise it will be the descriptor of the message in which it is defined.
type ExtensionDescriptor struct {
	common
	*descriptor.FieldDescriptorProto
	parent *Descriptor // The containing message, if any.
}

// TypeName returns the elements of the dotted type name.
// The package name is not part of this name.
func (e *ExtensionDescriptor) TypeName() (s []string) {
	name := e.GetName()
	if e.parent == nil {
		// top-level extension
		s = make([]string, 1)
	} else {
		pname := e.parent.TypeName()
		s = make([]string, len(pname)+1)
		copy(s, pname)
	}
	s[len(s)-1] = name
	return s
}

// DescName returns the variable name used for the generated descriptor.
func (e *ExtensionDescriptor) DescName() string {
	// The full type name.
	typeName := e.TypeName()
	// Each scope of the extension is individually CamelCased, and all are joined with "_" with an "E_" prefix.
	for i, s := range typeName {
		typeName[i] = CamelCase(s)
	}
	return "E_" + strings.Join(typeName, "_")
}

// ImportedDescriptor describes a type that has been publicly imported from another file.
type ImportedDescriptor struct {
	common
	o Object
}

func (id *ImportedDescriptor) TypeName() []string { return id.o.TypeName() }

// FileDescriptor describes an protocol buffer descriptor file (.proto).
// It includes slices of all the messages and enums defined within it.
// Those slices are constructed by WrapTypes.
type FileDescriptor struct {
	*descriptor.FileDescriptorProto
	desc []*Descriptor          // All the messages defined in this file.
	enum []*EnumDescriptor      // All the enums defined in this file.
	ext  []*ExtensionDescriptor // All the top-level extensions defined in this file.
	imp  []*ImportedDescriptor  // All types defined in files publicly imported by this file.

	// Comments, stored as a map of path (comma-separated integers) to the comment.
	comments map[string]*descriptor.SourceCodeInfo_Location

	// The full list of symbols that are exported,
	// as a map from the exported object to its symbols.
	// This is used for supporting public imports.
	exported map[Object][]symbol

	index int // The index of this file in the list of files to generate code for

	proto3 bool // whether to generate proto3 code for this file

	suffix string // filename suffix
}

// PackageName is the package name we'll use in the generated code to refer to this file.
func (d *FileDescriptor) PackageName() string { return uniquePackageOf(d.FileDescriptorProto) }

// VarName is the variable name we'll use in the generated code to refer
// to the compressed bytes of this descriptor. It is not exported, so
// it is only valid inside the generated package.
func (d *FileDescriptor) VarName() string { return fmt.Sprintf("fileDescriptor%v", FileName(d)) }

// goPackageOption interprets the file's go_package option.
// If there is no go_package, it returns ("", "", false).
// If there's a simple name, it returns ("", pkg, true).
// If the option implies an import path, it returns (impPath, pkg, true).
func (d *FileDescriptor) goPackageOption() (impPath, pkg string, ok bool) {
	pkg = d.GetOptions().GetGoPackage()
	if pkg == "" {
		return
	}
	ok = true
	// The presence of a slash implies there's an import path.
	slash := strings.LastIndex(pkg, "/")
	if slash < 0 {
		return
	}
	impPath, pkg = pkg, pkg[slash+1:]
	// A semicolon-delimited suffix overrides the package name.
	sc := strings.IndexByte(impPath, ';')
	if sc < 0 {
		return
	}
	impPath, pkg = impPath[:sc], impPath[sc+1:]
	return
}

// goPackageName returns the Go package name to use in the
// generated Go file.  The result explicit reports whether the name
// came from an option go_package statement.  If explicit is false,
// the name was derived from the protocol buffer's package statement
// or the input file name.
func (d *FileDescriptor) goPackageName() (name string, explicit bool) {
	// Does the file have a "go_package" option?
	if _, pkg, ok := d.goPackageOption(); ok {
		return pkg, true
	}

	// Does the file have a package clause?
	if pkg := d.GetPackage(); pkg != "" {
		return pkg, false
	}
	// Use the file base name.
	return baseName(d.GetName()), false
}

// goFileName returns the output name for the generated Go file.
func (d *FileDescriptor) goFileName() string {
	name := *d.Name
	if ext := path.Ext(name); ext == ".proto" || ext == ".protodevel" {
		name = name[:len(name)-len(ext)]
	}
	name += d.suffix

	// Does the file have a "go_package" option?
	// If it does, it may override the filename.
	if impPath, _, ok := d.goPackageOption(); ok && impPath != "" {
		// Replace the existing dirname with the declared import path.
		_, name = path.Split(name)
		name = path.Join(impPath, name)
		return name
	}

	return name
}

func (d *FileDescriptor) addExport(obj Object, sym symbol) {
	d.exported[obj] = append(d.exported[obj], sym)
}

// symbol is an interface representing an exported Go symbol.
type symbol interface {
	// GenerateAlias should generate an appropriate alias
	// for the symbol from the named package.
	GenerateAlias(g *Generator, pkg string)
}

// Object is an interface abstracting the abilities shared by enums, messages, extensions and imported objects.
type Object interface {
	PackageName() string // The name we use in our output (a_b_c), possibly renamed for uniqueness.
	TypeName() []string
	File() *descriptor.FileDescriptorProto
}

// Each package name we generate must be unique. The package we're generating
// gets its own name but every other package must have a unique name that does
// not conflict in the code we generate.  These names are chosen globally (although
// they don't have to be, it simplifies things to do them globally).
func uniquePackageOf(fd *descriptor.FileDescriptorProto) string {
	s, ok := uniquePackageName[fd]
	if !ok {
		log.Fatal("internal error: no package name defined for " + fd.GetName())
	}
	return s
}

// Generator is the type whose methods generate the output, stored in the associated response structure.
type Generator struct {
	*bytes.Buffer

	Request  *plugin.CodeGeneratorRequest  // The input.
	Response *plugin.CodeGeneratorResponse // The output.
	Suffix   string                        // Filename suffix

	Param             map[string]string // Command-line parameters.
	PackageImportPath string            // Go import path of the package we're generating code for
	ImportPrefix      string            // String to prefix to imported package file names.
	ImportMap         map[string]string // Mapping from .proto file name to import path

	Pkg map[string]string // The names under which we import support packages

	packageName      string                     // What we're calling ourselves.
	allFiles         []*FileDescriptor          // All files in the tree
	allFilesByName   map[string]*FileDescriptor // All files by filename.
	genFiles         []*FileDescriptor          // Those files we will generate output for.
	file             *FileDescriptor            // The file we are compiling now.
	usedPackages     map[string]bool            // Names of packages used in current file.
	typeNameToObject map[string]Object          // Key is a fully-qualified name in input syntax.
	init             []string                   // Lines to emit in the init function.
	indent           string
	writeOutput      bool

	customImports  []string
	writtenImports map[string]bool // For de-duplicating written imports
}

// New creates a new generator and allocates the request and response protobufs.
func New() *Generator {
	g := new(Generator)
	g.Buffer = new(bytes.Buffer)
	g.Request = new(plugin.CodeGeneratorRequest)
	g.Response = new(plugin.CodeGeneratorResponse)
	g.Suffix = ".pb.go"
	g.writtenImports = make(map[string]bool)
	uniquePackageName = make(map[*descriptor.FileDescriptorProto]string)
	pkgNamesInUse = make(map[string][]*FileDescriptor)
	return g
}

// Error reports a problem, including an error, and exits the program.
func (g *Generator) Error(err error, msgs ...string) {
	s := strings.Join(msgs, " ") + ":" + err.Error()
	log.Print("protoc-gen-yarpc: error:", s)
	os.Exit(1)
}

// Fail reports a problem and exits the program.
func (g *Generator) Fail(msgs ...string) {
	s := strings.Join(msgs, " ")
	log.Print("protoc-gen-yarpc: error:", s)
	os.Exit(1)
}

// CommandLineParameters breaks the comma-separated list of key=value pairs
// in the parameter (a member of the request protobuf) into a key/value map.
// It then sets file name mappings defined by those entries.
func (g *Generator) CommandLineParameters(parameter string) {
	g.Param = make(map[string]string)
	for _, p := range strings.Split(parameter, ",") {
		if i := strings.Index(p, "="); i < 0 {
			g.Param[p] = ""
		} else {
			g.Param[p[0:i]] = p[i+1:]
		}
	}

	g.ImportMap = make(map[string]string)
	for k, v := range g.Param {
		switch k {
		case "import_prefix":
			g.ImportPrefix = v
		case "import_path":
			g.PackageImportPath = v
		default:
			if len(k) > 0 && k[0] == 'M' {
				g.ImportMap[k[1:]] = v
			}
		}
	}
}

// DefaultPackageName returns the package name printed for the object.
// If its file is in a different package, it returns the package name we're using for this file, plus ".".
// Otherwise it returns the empty string.
func (g *Generator) DefaultPackageName(obj Object) string {
	pkg := obj.PackageName()
	if pkg == g.packageName {
		return ""
	}
	return pkg + "."
}

// For each input file, the unique package name to use, underscored.
var uniquePackageName = make(map[*descriptor.FileDescriptorProto]string)

// Package names already registered.  Key is the name from the .proto file;
// value is the name that appears in the generated code.
var pkgNamesInUse = make(map[string][]*FileDescriptor)

// Create and remember a guaranteed unique package name for this file descriptor.
// Pkg is the candidate name.  If f is nil, it's a builtin package like "proto" and
// has no file descriptor.
func RegisterUniquePackageName(pkg string, f *FileDescriptor) string {
	// Convert dots to underscores before finding a unique alias.
	pkg = strings.Map(badToUnderscore, pkg)

	var i = -1
	var ptr *FileDescriptor = nil
	for i, ptr = range pkgNamesInUse[pkg] {
		if ptr == f {
			if i == 0 {
				return pkg
			}
			return pkg + strconv.Itoa(i)
		}
	}

	pkgNamesInUse[pkg] = append(pkgNamesInUse[pkg], f)
	i += 1

	if i > 0 {
		pkg = pkg + strconv.Itoa(i)
	}

	if f != nil {
		uniquePackageName[f.FileDescriptorProto] = pkg
	}
	return pkg
}

var isGoKeyword = map[string]bool{
	"break":       true,
	"case":        true,
	"chan":        true,
	"const":       true,
	"continue":    true,
	"default":     true,
	"else":        true,
	"defer":       true,
	"fallthrough": true,
	"for":         true,
	"func":        true,
	"go":          true,
	"goto":        true,
	"if":          true,
	"import":      true,
	"interface":   true,
	"map":         true,
	"package":     true,
	"range":       true,
	"return":      true,
	"select":      true,
	"struct":      true,
	"switch":      true,
	"type":        true,
	"var":         true,
}

// defaultGoPackage returns the package name to use,
// derived from the import path of the package we're building code for.
func (g *Generator) defaultGoPackage() string {
	p := g.PackageImportPath
	if i := strings.LastIndex(p, "/"); i >= 0 {
		p = p[i+1:]
	}
	if p == "" {
		return ""
	}

	p = strings.Map(badToUnderscore, p)
	// Identifier must not be keyword: insert _.
	if isGoKeyword[p] {
		p = "_" + p
	}
	// Identifier must not begin with digit: insert _.
	if r, _ := utf8.DecodeRuneInString(p); unicode.IsDigit(r) {
		p = "_" + p
	}
	return p
}

// SetPackageNames sets the package name for this run.
// The package name must agree across all files being generated.
// It also defines unique package names for all imported files.
func (g *Generator) SetPackageNames() {
	// Register the name for this package.  It will be the first name
	// registered so is guaranteed to be unmodified.
	pkg, explicit := g.genFiles[0].goPackageName()

	// Check all files for an explicit go_package option.
	for _, f := range g.genFiles {
		thisPkg, thisExplicit := f.goPackageName()
		if thisExplicit {
			if !explicit {
				// Let this file's go_package option serve for all input files.
				pkg, explicit = thisPkg, true
			} else if thisPkg != pkg {
				g.Fail("inconsistent package names:", thisPkg, pkg)
			}
		}
	}

	// If we don't have an explicit go_package option but we have an
	// import path, use that.
	if !explicit {
		p := g.defaultGoPackage()
		if p != "" {
			pkg, explicit = p, true
		}
	}

	// If there was no go_package and no import path to use,
	// double-check that all the inputs have the same implicit
	// Go package name.
	if !explicit {
		for _, f := range g.genFiles {
			thisPkg, _ := f.goPackageName()
			if thisPkg != pkg {
				g.Fail("inconsistent package names:", thisPkg, pkg)
			}
		}
	}

	g.packageName = RegisterUniquePackageName(pkg, g.genFiles[0])

	// Register the support package names. They might collide with the
	// name of a package we import.
	g.Pkg = map[string]string{
		"fmt":          RegisterUniquePackageName("fmt", nil),
		"math":         RegisterUniquePackageName("math", nil),
		"proto":        RegisterUniquePackageName("proto", nil),
		"golang_proto": RegisterUniquePackageName("golang_proto", nil),
	}

AllFiles:
	for _, f := range g.allFiles {
		for _, genf := range g.genFiles {
			if f == genf {
				// In this package already.
				uniquePackageName[f.FileDescriptorProto] = g.packageName
				continue AllFiles
			}
		}
		// The file is a dependency, so we want to ignore its go_package option
		// because that is only relevant for its specific generated output.
		pkg := f.GetPackage()
		if pkg == "" {
			pkg = baseName(*f.Name)
		}
		RegisterUniquePackageName(pkg, f)
	}
}

// WrapTypes walks the incoming data, wrapping DescriptorProtos, EnumDescriptorProtos
// and FileDescriptorProtos into file-referenced objects within the Generator.
// It also creates the list of files to generate and so should be called before GenerateAllFiles.
func (g *Generator) WrapTypes() {
	g.allFiles = make([]*FileDescriptor, 0, len(g.Request.ProtoFile))
	g.allFilesByName = make(map[string]*FileDescriptor, len(g.allFiles))
	for _, f := range g.Request.ProtoFile {
		// We must wrap the descriptors before we wrap the enums
		descs := wrapDescriptors(f)
		g.buildNestedDescriptors(descs)
		enums := wrapEnumDescriptors(f, descs)
		g.buildNestedEnums(descs, enums)
		exts := wrapExtensions(f)
		fd := &FileDescriptor{
			FileDescriptorProto: f,
			desc:                descs,
			enum:                enums,
			ext:                 exts,
			exported:            make(map[Object][]symbol),
			proto3:              fileIsProto3(f),
			suffix:              g.Suffix,
		}
		extractComments(fd)
		g.allFiles = append(g.allFiles, fd)
		g.allFilesByName[f.GetName()] = fd
	}
	for _, fd := range g.allFiles {
		fd.imp = wrapImported(fd.FileDescriptorProto, g)
	}

	g.genFiles = make([]*FileDescriptor, 0, len(g.Request.FileToGenerate))
	for _, fileName := range g.Request.FileToGenerate {
		fd := g.allFilesByName[fileName]
		if fd == nil {
			g.Fail("could not find file named", fileName)
		}
		fd.index = len(g.genFiles)
		g.genFiles = append(g.genFiles, fd)
	}
}

// Scan the descriptors in this file.  For each one, build the slice of nested descriptors
func (g *Generator) buildNestedDescriptors(descs []*Descriptor) {
	for _, desc := range descs {
		if len(desc.NestedType) != 0 {
			for _, nest := range descs {
				if nest.parent == desc {
					desc.nested = append(desc.nested, nest)
				}
			}
			if len(desc.nested) != len(desc.NestedType) {
				g.Fail("internal error: nesting failure for", desc.GetName())
			}
		}
	}
}

func (g *Generator) buildNestedEnums(descs []*Descriptor, enums []*EnumDescriptor) {
	for _, desc := range descs {
		if len(desc.EnumType) != 0 {
			for _, enum := range enums {
				if enum.parent == desc {
					desc.enums = append(desc.enums, enum)
				}
			}
			if len(desc.enums) != len(desc.EnumType) {
				g.Fail("internal error: enum nesting failure for", desc.GetName())
			}
		}
	}
}

// Construct the Descriptor
func newDescriptor(desc *descriptor.DescriptorProto, parent *Descriptor, file *descriptor.FileDescriptorProto, index int) *Descriptor {
	d := &Descriptor{
		common:          common{file},
		DescriptorProto: desc,
		parent:          parent,
		index:           index,
	}
	if parent == nil {
		d.path = fmt.Sprintf("%d,%d", messagePath, index)
	} else {
		d.path = fmt.Sprintf("%s,%d,%d", parent.path, messageMessagePath, index)
	}

	// The only way to distinguish a group from a message is whether
	// the containing message has a TYPE_GROUP field that matches.
	if parent != nil {
		parts := d.TypeName()
		if file.Package != nil {
			parts = append([]string{*file.Package}, parts...)
		}
		exp := "." + strings.Join(parts, ".")
		for _, field := range parent.Field {
			if field.GetType() == descriptor.FieldDescriptorProto_TYPE_GROUP && field.GetTypeName() == exp {
				d.group = true
				break
			}
		}
	}

	for _, field := range desc.Extension {
		d.ext = append(d.ext, &ExtensionDescriptor{common{file}, field, d})
	}

	return d
}

// Return a slice of all the Descriptors defined within this file
func wrapDescriptors(file *descriptor.FileDescriptorProto) []*Descriptor {
	sl := make([]*Descriptor, 0, len(file.MessageType)+10)
	for i, desc := range file.MessageType {
		sl = wrapThisDescriptor(sl, desc, nil, file, i)
	}
	return sl
}

// Wrap this Descriptor, recursively
func wrapThisDescriptor(sl []*Descriptor, desc *descriptor.DescriptorProto, parent *Descriptor, file *descriptor.FileDescriptorProto, index int) []*Descriptor {
	sl = append(sl, newDescriptor(desc, parent, file, index))
	me := sl[len(sl)-1]
	for i, nested := range desc.NestedType {
		sl = wrapThisDescriptor(sl, nested, me, file, i)
	}
	return sl
}

// Construct the EnumDescriptor
func newEnumDescriptor(desc *descriptor.EnumDescriptorProto, parent *Descriptor, file *descriptor.FileDescriptorProto, index int) *EnumDescriptor {
	ed := &EnumDescriptor{
		common:              common{file},
		EnumDescriptorProto: desc,
		parent:              parent,
		index:               index,
	}
	if parent == nil {
		ed.path = fmt.Sprintf("%d,%d", enumPath, index)
	} else {
		ed.path = fmt.Sprintf("%s,%d,%d", parent.path, messageEnumPath, index)
	}
	return ed
}

// Return a slice of all the EnumDescriptors defined within this file
func wrapEnumDescriptors(file *descriptor.FileDescriptorProto, descs []*Descriptor) []*EnumDescriptor {
	sl := make([]*EnumDescriptor, 0, len(file.EnumType)+10)
	// Top-level enums.
	for i, enum := range file.EnumType {
		sl = append(sl, newEnumDescriptor(enum, nil, file, i))
	}
	// Enums within messages. Enums within embedded messages appear in the outer-most message.
	for _, nested := range descs {
		for i, enum := range nested.EnumType {
			sl = append(sl, newEnumDescriptor(enum, nested, file, i))
		}
	}
	return sl
}

// Return a slice of all the top-level ExtensionDescriptors defined within this file.
func wrapExtensions(file *descriptor.FileDescriptorProto) []*ExtensionDescriptor {
	var sl []*ExtensionDescriptor
	for _, field := range file.Extension {
		sl = append(sl, &ExtensionDescriptor{common{file}, field, nil})
	}
	return sl
}

// Return a slice of all the types that are publicly imported into this file.
func wrapImported(file *descriptor.FileDescriptorProto, g *Generator) (sl []*ImportedDescriptor) {
	for _, index := range file.PublicDependency {
		df := g.fileByName(file.Dependency[index])
		for _, d := range df.desc {
			if d.GetOptions().GetMapEntry() {
				continue
			}
			sl = append(sl, &ImportedDescriptor{common{file}, d})
		}
		for _, e := range df.enum {
			sl = append(sl, &ImportedDescriptor{common{file}, e})
		}
		for _, ext := range df.ext {
			sl = append(sl, &ImportedDescriptor{common{file}, ext})
		}
	}
	return
}

func extractComments(file *FileDescriptor) {
	file.comments = make(map[string]*descriptor.SourceCodeInfo_Location)
	for _, loc := range file.GetSourceCodeInfo().GetLocation() {
		if loc.LeadingComments == nil {
			continue
		}
		var p []string
		for _, n := range loc.Path {
			p = append(p, strconv.Itoa(int(n)))
		}
		file.comments[strings.Join(p, ",")] = loc
	}
}

// BuildTypeNameMap builds the map from fully qualified type names to objects.
// The key names for the map come from the input data, which puts a period at the beginning.
// It should be called after SetPackageNames and before GenerateAllFiles.
func (g *Generator) BuildTypeNameMap() {
	g.typeNameToObject = make(map[string]Object)
	for _, f := range g.allFiles {
		// The names in this loop are defined by the proto world, not us, so the
		// package name may be empty.  If so, the dotted package name of X will
		// be ".X"; otherwise it will be ".pkg.X".
		dottedPkg := "." + f.GetPackage()
		if dottedPkg != "." {
			dottedPkg += "."
		}
		for _, enum := range f.enum {
			name := dottedPkg + dottedSlice(enum.TypeName())
			g.typeNameToObject[name] = enum
		}
		for _, desc := range f.desc {
			name := dottedPkg + dottedSlice(desc.TypeName())
			g.typeNameToObject[name] = desc
		}
	}
}

// ObjectNamed, given a fully-qualified input type name as it appears in the input data,
// returns the descriptor for the message or enum with that name.
func (g *Generator) ObjectNamed(typeName string) Object {
	o, ok := g.typeNameToObject[typeName]
	if !ok {
		g.Fail("can't find object with type", typeName)
	}

	// If the file of this object isn't a direct dependency of the current file,
	// or in the current file, then this object has been publicly imported into
	// a dependency of the current file.
	// We should return the ImportedDescriptor object for it instead.
	direct := *o.File().Name == *g.file.Name
	if !direct {
		for _, dep := range g.file.Dependency {
			if *g.fileByName(dep).Name == *o.File().Name {
				direct = true
				break
			}
		}
	}
	if !direct {
		found := false
	Loop:
		for _, dep := range g.file.Dependency {
			df := g.fileByName(*g.fileByName(dep).Name)
			for _, td := range df.imp {
				if td.o == o {
					// Found it!
					o = td
					found = true
					break Loop
				}
			}
		}
		if !found {
			log.Printf("protoc-gen-yarpc: WARNING: failed finding publicly imported dependency for %v, used in %v", typeName, *g.file.Name)
		}
	}

	return o
}

// P prints the arguments to the generated output.  It handles strings and int32s, plus
// handling indirections because they may be *string, etc.
func (g *Generator) P(str ...interface{}) {
	if !g.writeOutput {
		return
	}
	g.WriteString(g.indent)
	for _, v := range str {
		switch s := v.(type) {
		case string:
			g.WriteString(s)
		case *string:
			g.WriteString(*s)
		case bool:
			fmt.Fprintf(g, "%t", s)
		case *bool:
			fmt.Fprintf(g, "%t", *s)
		case int:
			fmt.Fprintf(g, "%d", s)
		case *int32:
			fmt.Fprintf(g, "%d", *s)
		case *int64:
			fmt.Fprintf(g, "%d", *s)
		case float64:
			fmt.Fprintf(g, "%g", s)
		case *float64:
			fmt.Fprintf(g, "%g", *s)
		default:
			g.Fail(fmt.Sprintf("unknown type in printer: %T", v))
		}
	}
	g.WriteByte('\n')
}

// addInitf stores the given statement to be printed inside the file's init function.
// The statement is given as a format specifier and arguments.
func (g *Generator) addInitf(stmt string, a ...interface{}) {
	g.init = append(g.init, fmt.Sprintf(stmt, a...))
}

func (g *Generator) PrintImport(alias, pkg string) {
	statement := "import " + alias + " " + strconv.Quote(pkg)
	if g.writtenImports[statement] {
		return
	}
	g.P(statement)
	g.writtenImports[statement] = true
}

// In Indents the output one tab stop.
func (g *Generator) In() { g.indent += "\t" }

// Out unindents the output one tab stop.
func (g *Generator) Out() {
	if len(g.indent) > 0 {
		g.indent = g.indent[1:]
	}
}

// FileOf return the FileDescriptor for this FileDescriptorProto.
func (g *Generator) FileOf(fd *descriptor.FileDescriptorProto) *FileDescriptor {
	for _, file := range g.allFiles {
		if file.FileDescriptorProto == fd {
			return file
		}
	}
	g.Fail("could not find file in table:", fd.GetName())
	return nil
}

// Generate the header, including package definition
func (g *Generator) generateHeader() {
	g.P("// Code generated by protoc-gen-yarpc. DO NOT EDIT.")
	g.P("// source: ", *g.file.Name)
	g.P()

	name := g.file.PackageName()

	if g.file.index == 0 {
		// Generate package docs for the first file in the package.
		g.P("/*")
		g.P("Package ", name, " is a generated protocol buffer package.")
		g.P()
		if loc, ok := g.file.comments[strconv.Itoa(packagePath)]; ok {
			// not using g.PrintComments because this is a /* */ comment block.
			text := strings.TrimSuffix(loc.GetLeadingComments(), "\n")
			for _, line := range strings.Split(text, "\n") {
				line = strings.TrimPrefix(line, " ")
				// ensure we don't escape from the block comment
				line = strings.Replace(line, "*/", "* /", -1)
				g.P(line)
			}
			g.P()
		}
		var topMsgs []string
		g.P("It is generated from these files:")
		for _, f := range g.genFiles {
			g.P("\t", f.Name)
			for _, msg := range f.desc {
				if msg.parent != nil {
					continue
				}
				topMsgs = append(topMsgs, CamelCaseSlice(msg.TypeName()))
			}
		}
		g.P()
		g.P("It has these top-level messages:")
		for _, msg := range topMsgs {
			g.P("\t", msg)
		}
		g.P("*/")
	}

	g.P("package ", name)
	g.P()
}

// PrintComments prints any comments from the source .proto file.
// The path is a comma-separated list of integers.
// It returns an indication of whether any comments were printed.
// See descriptor.proto for its format.
func (g *Generator) PrintComments(path string) bool {
	if !g.writeOutput {
		return false
	}
	if loc, ok := g.file.comments[path]; ok {
		text := strings.TrimSuffix(loc.GetLeadingComments(), "\n")
		for _, line := range strings.Split(text, "\n") {
			g.P("// ", strings.TrimPrefix(line, " "))
		}
		return true
	}
	return false
}

// Comments returns any comments from the source .proto file and empty string if comments not found.
// The path is a comma-separated list of intergers.
// See descriptor.proto for its format.
func (g *Generator) Comments(path string) string {
	loc, ok := g.file.comments[path]
	if !ok {
		return ""
	}
	text := strings.TrimSuffix(loc.GetLeadingComments(), "\n")
	return text
}

func (g *Generator) fileByName(filename string) *FileDescriptor {
	return g.allFilesByName[filename]
}

// weak returns whether the ith import of the current file is a weak import.
func (g *Generator) weak(i int32) bool {
	for _, j := range g.file.WeakDependency {
		if j == i {
			return true
		}
	}
	return false
}

// Generate the imports
func (g *Generator) generateImports() {
	// We almost always need a proto import.  Rather than computing when we
	// do, which is tricky when there's a plugin, just import it and
	// reference it later. The same argument applies to the fmt and math packages.
	if gogoproto.ImportsGoGoProto(g.file.FileDescriptorProto) {
		g.PrintImport(g.Pkg["proto"], g.ImportPrefix+"github.com/gogo/protobuf/proto")
		if gogoproto.RegistersGolangProto(g.file.FileDescriptorProto) {
			g.PrintImport(g.Pkg["golang_proto"], g.ImportPrefix+"github.com/golang/protobuf/proto")
		}
	} else {
		g.PrintImport(g.Pkg["proto"], g.ImportPrefix+"github.com/golang/protobuf/proto")
	}
	g.PrintImport(g.Pkg["fmt"], "fmt")
	g.PrintImport(g.Pkg["math"], "math")

	for i, s := range g.file.Dependency {
		fd := g.fileByName(s)
		// Do not import our own package.
		if fd.PackageName() == g.packageName {
			continue
		}
		filename := fd.goFileName()
		// By default, import path is the dirname of the Go filename.
		importPath := path.Dir(filename)
		if substitution, ok := g.ImportMap[s]; ok {
			importPath = substitution
		}
		importPath = g.ImportPrefix + importPath
		// Skip weak imports.
		if g.weak(int32(i)) {
			g.P("// skipping weak import ", fd.PackageName(), " ", strconv.Quote(importPath))
			continue
		}
		// We need to import all the dependencies, even if we don't reference them,
		// because other code and tools depend on having the full transitive closure
		// of protocol buffer types in the binary.
		if _, ok := g.usedPackages[fd.PackageName()]; ok {
			g.PrintImport(fd.PackageName(), importPath)
		} else {
			g.P("import _ ", strconv.Quote(importPath))
		}
	}
	g.P()
	for _, s := range g.customImports {
		s1 := strings.Map(badToUnderscore, s)
		g.PrintImport(s1, s)
	}
	g.P()
	g.P("// Reference imports to suppress errors if they are not otherwise used.")
	g.P("var _ = ", g.Pkg["proto"], ".Marshal")
	if gogoproto.ImportsGoGoProto(g.file.FileDescriptorProto) && gogoproto.RegistersGolangProto(g.file.FileDescriptorProto) {
		g.P("var _ = ", g.Pkg["golang_proto"], ".Marshal")
	}
	g.P("var _ = ", g.Pkg["fmt"], ".Errorf")
	g.P("var _ = ", g.Pkg["math"], ".Inf")
	for _, cimport := range g.customImports {
		if cimport == "time" {
			g.P("var _ = time.Kitchen")
			break
		}
	}
	g.P()
}

func (g *Generator) generateImported(id *ImportedDescriptor) {
	// Don't generate public import symbols for files that we are generating
	// code for, since those symbols will already be in this package.
	// We can't simply avoid creating the ImportedDescriptor objects,
	// because g.genFiles isn't populated at that stage.
	tn := id.TypeName()
	sn := tn[len(tn)-1]
	df := g.FileOf(id.o.File())
	filename := *df.Name
	for _, fd := range g.genFiles {
		if *fd.Name == filename {
			g.P("// Ignoring public import of ", sn, " from ", filename)
			g.P()
			return
		}
	}
	g.P("// ", sn, " from public import ", filename)
	g.usedPackages[df.PackageName()] = true

	for _, sym := range df.exported[id.o] {
		sym.GenerateAlias(g, df.PackageName())
	}

	g.P()
}

// The tag is a string like "varint,2,opt,name=fieldname,def=7" that
// identifies details of the field for the protocol buffer marshaling and unmarshaling
// code.  The fields are:
//	wire encoding
//	protocol tag number
//	opt,req,rep for optional, required, or repeated
//	packed whether the encoding is "packed" (optional; repeated primitives only)
//	name= the original declared name
//	enum= the name of the enum type if it is an enum-typed field.
//	proto3 if this field is in a proto3 message
//	def= string representation of the default value, if any.
// The default value must be in a representation that can be used at run-time
// to generate the default value. Thus bools become 0 and 1, for instance.
func (g *Generator) goTag(message *Descriptor, field *descriptor.FieldDescriptorProto, wiretype string) string {
	optrepreq := ""
	switch {
	case isOptional(field):
		optrepreq = "opt"
	case isRequired(field):
		optrepreq = "req"
	case isRepeated(field):
		optrepreq = "rep"
	}
	var defaultValue string
	if dv := field.DefaultValue; dv != nil { // set means an explicit default
		defaultValue = *dv
		// Some types need tweaking.
		switch *field.Type {
		case descriptor.FieldDescriptorProto_TYPE_BOOL:
			if defaultValue == "true" {
				defaultValue = "1"
			} else {
				defaultValue = "0"
			}
		case descriptor.FieldDescriptorProto_TYPE_STRING,
			descriptor.FieldDescriptorProto_TYPE_BYTES:
			// Nothing to do. Quoting is done for the whole tag.
		case descriptor.FieldDescriptorProto_TYPE_ENUM:
			// For enums we need to provide the integer constant.
			obj := g.ObjectNamed(field.GetTypeName())
			if id, ok := obj.(*ImportedDescriptor); ok {
				// It is an enum that was publicly imported.
				// We need the underlying type.
				obj = id.o
			}
			enum, ok := obj.(*EnumDescriptor)
			if !ok {
				log.Printf("obj is a %T", obj)
				if id, ok := obj.(*ImportedDescriptor); ok {
					log.Printf("id.o is a %T", id.o)
				}
				g.Fail("unknown enum type", CamelCaseSlice(obj.TypeName()))
			}
			defaultValue = enum.integerValueAsString(defaultValue)
		}
		defaultValue = ",def=" + defaultValue
	}
	enum := ""
	if *field.Type == descriptor.FieldDescriptorProto_TYPE_ENUM {
		// We avoid using obj.PackageName(), because we want to use the
		// original (proto-world) package name.
		obj := g.ObjectNamed(field.GetTypeName())
		if id, ok := obj.(*ImportedDescriptor); ok {
			obj = id.o
		}
		enum = ",enum="
		if pkg := obj.File().GetPackage(); pkg != "" {
			enum += pkg + "."
		}
		enum += CamelCaseSlice(obj.TypeName())
	}
	packed := ""
	if (field.Options != nil && field.Options.GetPacked()) ||
		// Per https://developers.google.com/protocol-buffers/docs/proto3#simple:
		// "In proto3, repeated fields of scalar numeric types use packed encoding by default."
		(message.proto3() && (field.Options == nil || field.Options.Packed == nil) &&
			isRepeated(field) && IsScalar(field)) {
		packed = ",packed"
	}
	fieldName := field.GetName()
	name := fieldName
	if *field.Type == descriptor.FieldDescriptorProto_TYPE_GROUP {
		// We must use the type name for groups instead of
		// the field name to preserve capitalization.
		// type_name in FieldDescriptorProto is fully-qualified,
		// but we only want the local part.
		name = *field.TypeName
		if i := strings.LastIndex(name, "."); i >= 0 {
			name = name[i+1:]
		}
	}
	if json := field.GetJsonName(); json != "" && json != name {
		// TODO: escaping might be needed, in which case
		// perhaps this should be in its own "json" tag.
		name += ",json=" + json
	}
	name = ",name=" + name

	embed := ""
	if gogoproto.IsEmbed(field) {
		embed = ",embedded=" + fieldName
	}

	ctype := ""
	if gogoproto.IsCustomType(field) {
		ctype = ",customtype=" + gogoproto.GetCustomType(field)
	}

	casttype := ""
	if gogoproto.IsCastType(field) {
		casttype = ",casttype=" + gogoproto.GetCastType(field)
	}

	castkey := ""
	if gogoproto.IsCastKey(field) {
		castkey = ",castkey=" + gogoproto.GetCastKey(field)
	}

	castvalue := ""
	if gogoproto.IsCastValue(field) {
		castvalue = ",castvalue=" + gogoproto.GetCastValue(field)
		// record the original message type for jsonpb reconstruction
		desc := g.ObjectNamed(field.GetTypeName())
		if d, ok := desc.(*Descriptor); ok && d.GetOptions().GetMapEntry() {
			valueField := d.Field[1]
			if valueField.IsMessage() {
				castvalue += ",castvaluetype=" + strings.TrimPrefix(valueField.GetTypeName(), ".")
			}
		}
	}

	if message.proto3() {
		// We only need the extra tag for []byte fields;
		// no need to add noise for the others.
		if *field.Type != descriptor.FieldDescriptorProto_TYPE_MESSAGE &&
			*field.Type != descriptor.FieldDescriptorProto_TYPE_GROUP &&
			!field.IsRepeated() {
			name += ",proto3"
		}
	}
	oneof := ""
	if field.OneofIndex != nil {
		oneof = ",oneof"
	}
	stdtime := ""
	if gogoproto.IsStdTime(field) {
		stdtime = ",stdtime"
	}
	stdduration := ""
	if gogoproto.IsStdDuration(field) {
		stdduration = ",stdduration"
	}
	return strconv.Quote(fmt.Sprintf("%s,%d,%s%s%s%s%s%s%s%s%s%s%s%s%s",
		wiretype,
		field.GetNumber(),
		optrepreq,
		packed,
		name,
		enum,
		oneof,
		defaultValue,
		embed,
		ctype,
		casttype,
		castkey,
		castvalue,
		stdtime,
		stdduration))
}

func needsStar(field *descriptor.FieldDescriptorProto, proto3 bool, allowOneOf bool) bool {
	if isRepeated(field) &&
		(*field.Type != descriptor.FieldDescriptorProto_TYPE_MESSAGE || gogoproto.IsCustomType(field)) &&
		(*field.Type != descriptor.FieldDescriptorProto_TYPE_GROUP) {
		return false
	}
	if *field.Type == descriptor.FieldDescriptorProto_TYPE_BYTES && !gogoproto.IsCustomType(field) {
		return false
	}
	if !gogoproto.IsNullable(field) {
		return false
	}
	if field.OneofIndex != nil && allowOneOf &&
		(*field.Type != descriptor.FieldDescriptorProto_TYPE_MESSAGE) &&
		(*field.Type != descriptor.FieldDescriptorProto_TYPE_GROUP) {
		return false
	}
	if proto3 &&
		(*field.Type != descriptor.FieldDescriptorProto_TYPE_MESSAGE) &&
		(*field.Type != descriptor.FieldDescriptorProto_TYPE_GROUP) &&
		!gogoproto.IsCustomType(field) {
		return false
	}
	return true
}

// TypeName is the printed name appropriate for an item. If the object is in the current file,
// TypeName drops the package name and underscores the rest.
// Otherwise the object is from another package; and the result is the underscored
// package name followed by the item name.
// The result always has an initial capital.
func (g *Generator) TypeName(obj Object) string {
	return g.DefaultPackageName(obj) + CamelCaseSlice(obj.TypeName())
}

// TypeNameWithPackage is like TypeName, but always includes the package
// name even if the object is in our own package.
func (g *Generator) TypeNameWithPackage(obj Object) string {
	return obj.PackageName() + CamelCaseSlice(obj.TypeName())
}

// GoType returns a string representing the type name, and the wire type
func (g *Generator) GoType(message *Descriptor, field *descriptor.FieldDescriptorProto) (typ string, wire string) {
	// TODO: Options.
	switch *field.Type {
	case descriptor.FieldDescriptorProto_TYPE_DOUBLE:
		typ, wire = "float64", "fixed64"
	case descriptor.FieldDescriptorProto_TYPE_FLOAT:
		typ, wire = "float32", "fixed32"
	case descriptor.FieldDescriptorProto_TYPE_INT64:
		typ, wire = "int64", "varint"
	case descriptor.FieldDescriptorProto_TYPE_UINT64:
		typ, wire = "uint64", "varint"
	case descriptor.FieldDescriptorProto_TYPE_INT32:
		typ, wire = "int32", "varint"
	case descriptor.FieldDescriptorProto_TYPE_UINT32:
		typ, wire = "uint32", "varint"
	case descriptor.FieldDescriptorProto_TYPE_FIXED64:
		typ, wire = "uint64", "fixed64"
	case descriptor.FieldDescriptorProto_TYPE_FIXED32:
		typ, wire = "uint32", "fixed32"
	case descriptor.FieldDescriptorProto_TYPE_BOOL:
		typ, wire = "bool", "varint"
	case descriptor.FieldDescriptorProto_TYPE_STRING:
		typ, wire = "string", "bytes"
	case descriptor.FieldDescriptorProto_TYPE_GROUP:
		desc := g.ObjectNamed(field.GetTypeName())
		typ, wire = g.TypeName(desc), "group"
	case descriptor.FieldDescriptorProto_TYPE_MESSAGE:
		desc := g.ObjectNamed(field.GetTypeName())
		typ, wire = g.TypeName(desc), "bytes"
	case descriptor.FieldDescriptorProto_TYPE_BYTES:
		typ, wire = "[]byte", "bytes"
	case descriptor.FieldDescriptorProto_TYPE_ENUM:
		desc := g.ObjectNamed(field.GetTypeName())
		typ, wire = g.TypeName(desc), "varint"
	case descriptor.FieldDescriptorProto_TYPE_SFIXED32:
		typ, wire = "int32", "fixed32"
	case descriptor.FieldDescriptorProto_TYPE_SFIXED64:
		typ, wire = "int64", "fixed64"
	case descriptor.FieldDescriptorProto_TYPE_SINT32:
		typ, wire = "int32", "zigzag32"
	case descriptor.FieldDescriptorProto_TYPE_SINT64:
		typ, wire = "int64", "zigzag64"
	default:
		g.Fail("unknown type for", field.GetName())
	}
	switch {
	case gogoproto.IsCustomType(field) && gogoproto.IsCastType(field):
		g.Fail(field.GetName() + " cannot be custom type and cast type")
	case gogoproto.IsCustomType(field):
		var packageName string
		var err error
		packageName, typ, err = getCustomType(field)
		if err != nil {
			g.Fail(err.Error())
		}
		if len(packageName) > 0 {
			g.customImports = append(g.customImports, packageName)
		}
	case gogoproto.IsCastType(field):
		var packageName string
		var err error
		packageName, typ, err = getCastType(field)
		if err != nil {
			g.Fail(err.Error())
		}
		if len(packageName) > 0 {
			g.customImports = append(g.customImports, packageName)
		}
	case gogoproto.IsStdTime(field):
		g.customImports = append(g.customImports, "time")
		typ = "time.Time"
	case gogoproto.IsStdDuration(field):
		g.customImports = append(g.customImports, "time")
		typ = "time.Duration"
	}
	if needsStar(field, g.file.proto3 && field.Extendee == nil, message != nil && message.allowOneof()) {
		typ = "*" + typ
	}
	if isRepeated(field) {
		typ = "[]" + typ
	}
	return
}

// GoMapDescriptor is a full description of the map output struct.
type GoMapDescriptor struct {
	GoType string

	KeyField      *descriptor.FieldDescriptorProto
	KeyAliasField *descriptor.FieldDescriptorProto
	KeyTag        string

	ValueField      *descriptor.FieldDescriptorProto
	ValueAliasField *descriptor.FieldDescriptorProto
	ValueTag        string
}

func (g *Generator) GoMapType(d *Descriptor, field *descriptor.FieldDescriptorProto) *GoMapDescriptor {
	if d == nil {
		byName := g.ObjectNamed(field.GetTypeName())
		desc, ok := byName.(*Descriptor)
		if byName == nil || !ok || !desc.GetOptions().GetMapEntry() {
			g.Fail(fmt.Sprintf("field %s is not a map", field.GetTypeName()))
			return nil
		}
		d = desc
	}

	m := &GoMapDescriptor{
		KeyField:   d.Field[0],
		ValueField: d.Field[1],
	}

	// Figure out the Go types and tags for the key and value types.
	m.KeyAliasField, m.ValueAliasField = g.GetMapKeyField(field, m.KeyField), g.GetMapValueField(field, m.ValueField)
	keyType, keyWire := g.GoType(d, m.KeyAliasField)
	valType, valWire := g.GoType(d, m.ValueAliasField)

	m.KeyTag, m.ValueTag = g.goTag(d, m.KeyField, keyWire), g.goTag(d, m.ValueField, valWire)

	if gogoproto.IsCastType(field) {
		var packageName string
		var err error
		packageName, typ, err := getCastType(field)
		if err != nil {
			g.Fail(err.Error())
		}
		if len(packageName) > 0 {
			g.customImports = append(g.customImports, packageName)
		}
		m.GoType = typ
		return m
	}

	// We don't use stars, except for message-typed values.
	// Message and enum types are the only two possibly foreign types used in maps,
	// so record their use. They are not permitted as map keys.
	keyType = strings.TrimPrefix(keyType, "*")
	switch *m.ValueAliasField.Type {
	case descriptor.FieldDescriptorProto_TYPE_ENUM:
		valType = strings.TrimPrefix(valType, "*")
		g.RecordTypeUse(m.ValueAliasField.GetTypeName())
	case descriptor.FieldDescriptorProto_TYPE_MESSAGE:
		if !gogoproto.IsNullable(m.ValueAliasField) {
			valType = strings.TrimPrefix(valType, "*")
		}
		if !gogoproto.IsStdTime(field) && !gogoproto.IsStdDuration(field) {
			g.RecordTypeUse(m.ValueAliasField.GetTypeName())
		}
	default:
		if gogoproto.IsCustomType(m.ValueAliasField) {
			if !gogoproto.IsNullable(m.ValueAliasField) {
				valType = strings.TrimPrefix(valType, "*")
			}
			g.RecordTypeUse(m.ValueAliasField.GetTypeName())
		} else {
			valType = strings.TrimPrefix(valType, "*")
		}
	}

	m.GoType = fmt.Sprintf("map[%s]%s", keyType, valType)
	return m
}

func (g *Generator) RecordTypeUse(t string) {
	if obj, ok := g.typeNameToObject[t]; ok {
		// Call ObjectNamed to get the true object to record the use.
		obj = g.ObjectNamed(t)
		g.usedPackages[obj.PackageName()] = true
	}
}

// Method names that may be generated.  Fields with these names get an
// underscore appended. Any change to this set is a potential incompatible
// API change because it changes generated field names.
var methodNames = [...]string{
	"Reset",
	"String",
	"ProtoMessage",
	"Marshal",
	"Unmarshal",
	"ExtensionRangeArray",
	"ExtensionMap",
	"Descriptor",
	"MarshalTo",
	"Equal",
	"VerboseEqual",
	"GoString",
	"ProtoSize",
}

func (g *Generator) generateInitFunction() {
	if len(g.init) == 0 {
		return
	}
	g.P("func init() {")
	g.In()
	for _, l := range g.init {
		g.P(l)
	}
	g.Out()
	g.P("}")
	g.init = nil
}

// And now lots of helper functions.

// Is c an ASCII lower-case letter?
func isASCIILower(c byte) bool {
	return 'a' <= c && c <= 'z'
}

// Is c an ASCII digit?
func isASCIIDigit(c byte) bool {
	return '0' <= c && c <= '9'
}

// CamelCase returns the CamelCased name.
// If there is an interior underscore followed by a lower case letter,
// drop the underscore and convert the letter to upper case.
// There is a remote possibility of this rewrite causing a name collision,
// but it's so remote we're prepared to pretend it's nonexistent - since the
// C++ generator lowercases names, it's extremely unlikely to have two fields
// with different capitalizations.
// In short, _my_field_name_2 becomes XMyFieldName_2.
func CamelCase(s string) string {
	if s == "" {
		return ""
	}
	t := make([]byte, 0, 32)
	i := 0
	if s[0] == '_' {
		// Need a capital letter; drop the '_'.
		t = append(t, 'X')
		i++
	}
	// Invariant: if the next letter is lower case, it must be converted
	// to upper case.
	// That is, we process a word at a time, where words are marked by _ or
	// upper case letter. Digits are treated as words.
	for ; i < len(s); i++ {
		c := s[i]
		if c == '_' && i+1 < len(s) && isASCIILower(s[i+1]) {
			continue // Skip the underscore in s.
		}
		if isASCIIDigit(c) {
			t = append(t, c)
			continue
		}
		// Assume we have a letter now - if not, it's a bogus identifier.
		// The next word is a sequence of characters that must start upper case.
		if isASCIILower(c) {
			c ^= ' ' // Make it a capital letter.
		}
		t = append(t, c) // Guaranteed not lower case.
		// Accept lower case sequence that follows.
		for i+1 < len(s) && isASCIILower(s[i+1]) {
			i++
			t = append(t, s[i])
		}
	}
	return string(t)
}

// CamelCaseSlice is like CamelCase, but the argument is a slice of strings to
// be joined with "_".
func CamelCaseSlice(elem []string) string { return CamelCase(strings.Join(elem, "_")) }

// dottedSlice turns a sliced name into a dotted name.
func dottedSlice(elem []string) string { return strings.Join(elem, ".") }

// Is this field optional?
func isOptional(field *descriptor.FieldDescriptorProto) bool {
	return field.Label != nil && *field.Label == descriptor.FieldDescriptorProto_LABEL_OPTIONAL
}

// Is this field required?
func isRequired(field *descriptor.FieldDescriptorProto) bool {
	return field.Label != nil && *field.Label == descriptor.FieldDescriptorProto_LABEL_REQUIRED
}

// Is this field repeated?
func isRepeated(field *descriptor.FieldDescriptorProto) bool {
	return field.Label != nil && *field.Label == descriptor.FieldDescriptorProto_LABEL_REPEATED
}

// Is this field a scalar numeric type?
func IsScalar(field *descriptor.FieldDescriptorProto) bool {
	if field.Type == nil {
		return false
	}
	switch *field.Type {
	case descriptor.FieldDescriptorProto_TYPE_DOUBLE,
		descriptor.FieldDescriptorProto_TYPE_FLOAT,
		descriptor.FieldDescriptorProto_TYPE_INT64,
		descriptor.FieldDescriptorProto_TYPE_UINT64,
		descriptor.FieldDescriptorProto_TYPE_INT32,
		descriptor.FieldDescriptorProto_TYPE_FIXED64,
		descriptor.FieldDescriptorProto_TYPE_FIXED32,
		descriptor.FieldDescriptorProto_TYPE_BOOL,
		descriptor.FieldDescriptorProto_TYPE_UINT32,
		descriptor.FieldDescriptorProto_TYPE_ENUM,
		descriptor.FieldDescriptorProto_TYPE_SFIXED32,
		descriptor.FieldDescriptorProto_TYPE_SFIXED64,
		descriptor.FieldDescriptorProto_TYPE_SINT32,
		descriptor.FieldDescriptorProto_TYPE_SINT64:
		return true
	default:
		return false
	}
}

// badToUnderscore is the mapping function used to generate Go names from package names,
// which can be dotted in the input .proto file.  It replaces non-identifier characters such as
// dot or dash with underscore.
func badToUnderscore(r rune) rune {
	if unicode.IsLetter(r) || unicode.IsDigit(r) || r == '_' {
		return r
	}
	return '_'
}

// baseName returns the last path element of the name, with the last dotted suffix removed.
func baseName(name string) string {
	// First, find the last element
	if i := strings.LastIndex(name, "/"); i >= 0 {
		name = name[i+1:]
	}
	// Now drop the suffix
	if i := strings.LastIndex(name, "."); i >= 0 {
		name = name[0:i]
	}
	return name
}

// The SourceCodeInfo message describes the location of elements of a parsed
// .proto file by way of a "path", which is a sequence of integers that
// describe the route from a FileDescriptorProto to the relevant submessage.
// The path alternates between a field number of a repeated field, and an index
// into that repeated field. The constants below define the field numbers that
// are used.
//
// See descriptor.proto for more information about this.
const (
	// tag numbers in FileDescriptorProto
	packagePath = 2 // package
	messagePath = 4 // message_type
	enumPath    = 5 // enum_type
	// tag numbers in DescriptorProto
	messageFieldPath   = 2 // field
	messageMessagePath = 3 // nested_type
	messageEnumPath    = 4 // enum_type
	messageOneofPath   = 8 // oneof_decl
	// tag numbers in EnumDescriptorProto
	enumValuePath = 2 // value
)