conversion_generator.go

/*
Copyright 2015 The Kubernetes Authors All rights reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package runtime

import (
	"fmt"
	"io"
	"log"
	"path"
	"reflect"
	goruntime "runtime"
	"sort"
	"strings"

	"k8s.io/kubernetes/pkg/api/unversioned"
	"k8s.io/kubernetes/pkg/util/sets"
)

type ConversionGenerator interface {
	GenerateConversionsForType(groupVersion unversioned.GroupVersion, reflection reflect.Type) error
	WriteConversionFunctions(w io.Writer) error
	RegisterConversionFunctions(w io.Writer, pkg string) error
	AddImport(pkg string) string
	RepackImports(exclude sets.String)
	WriteImports(w io.Writer) error
	OverwritePackage(pkg, overwrite string)
	AssumePrivateConversions()
}

func NewConversionGenerator(scheme *Scheme, targetPkg string) ConversionGenerator {
	g := &conversionGenerator{
		scheme: scheme,

		nameFormat:          "Convert_%s_%s_To_%s_%s",
		generatedNamePrefix: "auto",
		targetPkg:           targetPkg,

		publicFuncs:   make(map[typePair]functionName),
		convertibles:  make(map[reflect.Type]reflect.Type),
		overridden:    make(map[reflect.Type]bool),
		pkgOverwrites: make(map[string]string),
		imports:       make(map[string]string),
		shortImports:  make(map[string]string),
	}
	g.targetPackage(targetPkg)
	g.AddImport("reflect")
	g.AddImport("k8s.io/kubernetes/pkg/conversion")
	return g
}

var complexTypes []reflect.Kind = []reflect.Kind{reflect.Map, reflect.Ptr, reflect.Slice, reflect.Interface, reflect.Struct}

type functionName struct {
	name        string
	packageName string
}

type conversionGenerator struct {
	scheme *Scheme

	nameFormat          string
	generatedNamePrefix string
	targetPkg           string

	publicFuncs  map[typePair]functionName
	convertibles map[reflect.Type]reflect.Type
	overridden   map[reflect.Type]bool
	// If pkgOverwrites is set for a given package name, that package name
	// will be replaced while writing conversion function. If empty, package
	// name will be omitted.
	pkgOverwrites map[string]string
	// map of package names to shortname
	imports map[string]string
	// map of short names to package names
	shortImports map[string]string

	// A buffer that is used for storing lines that needs to be written.
	linesToPrint []string

	// if true, we assume conversions on the scheme are not available to us in the current package
	assumePrivateConversions bool
}

func (g *conversionGenerator) AssumePrivateConversions() {
	g.assumePrivateConversions = true
}

func (g *conversionGenerator) AddImport(pkg string) string {
	return g.addImportByPath(pkg)
}

func (g *conversionGenerator) GenerateConversionsForType(gv unversioned.GroupVersion, reflection reflect.Type) error {
	kind := reflection.Name()
	// TODO this is equivalent to what it did before, but it needs to be fixed for the proper group
	internalVersion := gv
	internalVersion.Version = APIVersionInternal

	internalObj, err := g.scheme.New(internalVersion.WithKind(kind))
	if err != nil {
		return fmt.Errorf("cannot create an object of type %v in internal version", kind)
	}
	internalObjType := reflect.TypeOf(internalObj)
	if internalObjType.Kind() != reflect.Ptr {
		return fmt.Errorf("created object should be of type Ptr: %v", internalObjType.Kind())
	}
	inErr := g.generateConversionsBetween(reflection, internalObjType.Elem())
	outErr := g.generateConversionsBetween(internalObjType.Elem(), reflection)
	if inErr != nil || outErr != nil {
		return fmt.Errorf("errors: %v, %v", inErr, outErr)
	}
	return nil
}

// primitiveConversion returns true if the two types can be converted via a cast.
func primitiveConversion(inType, outType reflect.Type) (string, bool) {
	switch inType.Kind() {
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
		reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64,
		reflect.Float32, reflect.Float64:
		switch outType.Kind() {
		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
			reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64,
			reflect.Float32, reflect.Float64:
			return outType.Name(), true
		}
	}
	return "", false
}

func (g *conversionGenerator) generateConversionsBetween(inType, outType reflect.Type) error {
	existingConversion := g.scheme.Converter().HasConversionFunc(inType, outType) && g.scheme.Converter().HasConversionFunc(outType, inType)

	// Avoid processing the same type multiple times.
	if value, found := g.convertibles[inType]; found {
		if value != outType {
			return fmt.Errorf("multiple possible convertibles for %v", inType)
		}
		return nil
	}
	if inType == outType {
		switch inType.Kind() {
		case reflect.Ptr:
			return g.generateConversionsBetween(inType.Elem(), inType.Elem())
		case reflect.Struct:
			// pointers to structs invoke new(inType)
			if inType.PkgPath() != "k8s.io/kubernetes/pkg/util/intstr" {
				g.addImportByPath(inType.PkgPath())
			}
		}
		g.rememberConversionFunction(inType, inType, false)
		// Don't generate conversion methods for the same type.
		return nil
	}

	if _, ok := primitiveConversion(inType, outType); ok {
		return nil
	}

	if inType.Kind() != outType.Kind() {
		if existingConversion {
			g.rememberConversionFunction(inType, outType, false)
			g.rememberConversionFunction(outType, inType, false)
			return nil
		}
		return fmt.Errorf("cannot convert types of different kinds: %v %v", inType, outType)
	}

	g.addImportByPath(inType.PkgPath())
	g.addImportByPath(outType.PkgPath())

	// We should be able to generate conversions both sides.
	switch inType.Kind() {
	case reflect.Map:
		inErr := g.generateConversionsForMap(inType, outType)
		outErr := g.generateConversionsForMap(outType, inType)
		if !existingConversion && (inErr != nil || outErr != nil) {
			return inErr
		}
		// We don't add it to g.convertibles - maps should be handled correctly
		// inside appropriate conversion functions.
		return nil
	case reflect.Ptr:
		inErr := g.generateConversionsBetween(inType.Elem(), outType.Elem())
		outErr := g.generateConversionsBetween(outType.Elem(), inType.Elem())
		if !existingConversion && (inErr != nil || outErr != nil) {
			return inErr
		}
		// We don't add it to g.convertibles - maps should be handled correctly
		// inside appropriate conversion functions.
		return nil
	case reflect.Slice:
		inErr := g.generateConversionsForSlice(inType, outType)
		outErr := g.generateConversionsForSlice(outType, inType)
		if !existingConversion && (inErr != nil || outErr != nil) {
			return inErr
		}
		// We don't add it to g.convertibles - slices should be handled correctly
		// inside appropriate conversion functions.
		return nil
	case reflect.Interface:
		// TODO(wojtek-t): Currently we don't support converting interfaces.
		return fmt.Errorf("interfaces are not supported")
	case reflect.Struct:
		inErr := g.generateConversionsForStruct(inType, outType)
		outErr := g.generateConversionsForStruct(outType, inType)
		if !existingConversion && (inErr != nil || outErr != nil) {
			return inErr
		}
		g.rememberConversionFunction(inType, outType, true)
		if existingConversion {
			g.overridden[inType] = true
		}
		g.convertibles[inType] = outType
		return nil
	default:
		// All simple types should be handled correctly with default conversion.
		return nil
	}
}

func isComplexType(reflection reflect.Type) bool {
	for _, complexType := range complexTypes {
		if complexType == reflection.Kind() {
			return true
		}
	}
	return false
}

func (g *conversionGenerator) rememberConversionFunction(inType, outType reflect.Type, willGenerate bool) {
	if _, ok := g.publicFuncs[typePair{inType, outType}]; ok {
		return
	}

	if v, ok := g.scheme.Converter().ConversionFuncValue(inType, outType); ok {
		if fn := goruntime.FuncForPC(v.Pointer()); fn != nil {
			name := fn.Name()
			var p, n string
			if last := strings.LastIndex(name, "."); last != -1 {
				p = name[:last]
				n = name[last+1:]
			} else {
				n = name
			}
			if isPublic(n) {
				g.AddImport(p)
				g.publicFuncs[typePair{inType, outType}] = functionName{name: n, packageName: p}
			} else {
				log.Printf("WARNING: Cannot generate conversion %v -> %v, method %q is private", inType, outType, fn.Name())
			}
		} else {
			log.Printf("WARNING: Cannot generate conversion %v -> %v, method is not accessible", inType, outType)
		}
	} else if willGenerate {
		g.publicFuncs[typePair{inType, outType}] = functionName{name: g.conversionFunctionName(inType, outType)}
	}
}

func isPublic(name string) bool {
	return strings.ToUpper(name[:1]) == name[:1]
}

func (g *conversionGenerator) generateConversionsForMap(inType, outType reflect.Type) error {
	inKey := inType.Key()
	outKey := outType.Key()
	g.addImportByPath(inKey.PkgPath())
	g.addImportByPath(outKey.PkgPath())
	if err := g.generateConversionsBetween(inKey, outKey); err != nil {
		return err
	}
	inValue := inType.Elem()
	outValue := outType.Elem()
	g.addImportByPath(inValue.PkgPath())
	g.addImportByPath(outValue.PkgPath())
	if err := g.generateConversionsBetween(inValue, outValue); err != nil {
		return err
	}
	return nil
}

func (g *conversionGenerator) generateConversionsForSlice(inType, outType reflect.Type) error {
	inElem := inType.Elem()
	outElem := outType.Elem()
	// slice conversion requires the package for the destination type in order to instantiate the map
	g.addImportByPath(outElem.PkgPath())
	if err := g.generateConversionsBetween(inElem, outElem); err != nil {
		return err
	}
	return nil
}

func (g *conversionGenerator) generateConversionsForStruct(inType, outType reflect.Type) error {
	errs := []string{}
	for i := 0; i < inType.NumField(); i++ {
		inField := inType.Field(i)
		outField, found := outType.FieldByName(inField.Name)
		if !found {
			// aggregate the errors so we can return them at the end but still provide
			// best effort for generation for other fields in this type
			errs = append(errs, fmt.Sprintf("couldn't find a corresponding field %v in %v", inField.Name, outType))
			continue
		}
		if isComplexType(inField.Type) {
			if err := g.generateConversionsBetween(inField.Type, outField.Type); err != nil {
				return err
			}
		}
	}

	if len(errs) == 0 {
		return nil
	}
	return fmt.Errorf(strings.Join(errs, ","))
}

// A buffer of lines that will be written.
type bufferedLine struct {
	line        string
	indentation int
}

type buffer struct {
	lines []bufferedLine
}

func newBuffer() *buffer {
	return &buffer{
		lines: make([]bufferedLine, 0),
	}
}

func (b *buffer) addLine(line string, indent int) {
	b.lines = append(b.lines, bufferedLine{line, indent})
}

func (b *buffer) flushLines(w io.Writer) error {
	for _, line := range b.lines {
		indentation := strings.Repeat("\t", line.indentation)
		fullLine := fmt.Sprintf("%s%s", indentation, line.line)
		if _, err := io.WriteString(w, fullLine); err != nil {
			return err
		}
	}
	return nil
}

type byName []reflect.Type

func (s byName) Len() int {
	return len(s)
}

func (s byName) Less(i, j int) bool {
	fullNameI := s[i].PkgPath() + "/" + s[i].Name()
	fullNameJ := s[j].PkgPath() + "/" + s[j].Name()
	return fullNameI < fullNameJ
}

func (s byName) Swap(i, j int) {
	s[i], s[j] = s[j], s[i]
}

func (g *conversionGenerator) targetPackage(pkg string) {
	g.imports[pkg] = ""
	g.shortImports[""] = pkg
}

func (g *conversionGenerator) RepackImports(exclude sets.String) {
	var packages []string
	for key := range g.imports {
		packages = append(packages, key)
	}
	sort.Strings(packages)
	g.imports = make(map[string]string)
	g.shortImports = make(map[string]string)
	g.targetPackage(g.targetPkg)
	for _, pkg := range packages {
		if !exclude.Has(pkg) {
			g.addImportByPath(pkg)
		}
	}
}

func (g *conversionGenerator) WriteImports(w io.Writer) error {
	var packages []string
	for key := range g.imports {
		packages = append(packages, key)
	}
	sort.Strings(packages)

	buffer := newBuffer()
	indent := 0
	buffer.addLine("import (\n", indent)
	for _, importPkg := range packages {
		if len(importPkg) == 0 {
			continue
		}
		if len(g.imports[importPkg]) == 0 {
			continue
		}
		buffer.addLine(fmt.Sprintf("%s \"%s\"\n", g.imports[importPkg], importPkg), indent+1)
	}
	buffer.addLine(")\n", indent)
	buffer.addLine("\n", indent)
	if err := buffer.flushLines(w); err != nil {
		return err
	}
	return nil
}

func (g *conversionGenerator) WriteConversionFunctions(w io.Writer) error {
	// It's desired to print conversion functions always in the same order
	// (e.g. for better tracking of what has really been added).
	var keys []reflect.Type
	for key := range g.convertibles {
		keys = append(keys, key)
	}
	sort.Sort(byName(keys))

	buffer := newBuffer()
	indent := 0
	for _, inType := range keys {
		outType := g.convertibles[inType]
		// All types in g.convertibles are structs.
		if inType.Kind() != reflect.Struct {
			return fmt.Errorf("non-struct conversions are not-supported")
		}
		if err := g.writeConversionForType(buffer, inType, outType, indent); err != nil {
			return err
		}
	}
	if err := buffer.flushLines(w); err != nil {
		return err
	}
	return nil
}

func (g *conversionGenerator) writeRegisterHeader(b *buffer, pkg string, indent int) {
	b.addLine("func init() {\n", indent)
	b.addLine(fmt.Sprintf("err := %s.AddGeneratedConversionFuncs(\n", pkg), indent+1)
}

func (g *conversionGenerator) writeRegisterFooter(b *buffer, indent int) {
	b.addLine(")\n", indent+1)
	b.addLine("if err != nil {\n", indent+1)
	b.addLine("// If one of the conversion functions is malformed, detect it immediately.\n", indent+2)
	b.addLine("panic(err)\n", indent+2)
	b.addLine("}\n", indent+1)
	b.addLine("}\n", indent)
	b.addLine("\n", indent)
}

func (g *conversionGenerator) RegisterConversionFunctions(w io.Writer, pkg string) error {
	// Write conversion function names alphabetically ordered.
	var names []string
	for inType, outType := range g.convertibles {
		names = append(names, g.generatedFunctionName(inType, outType))
	}
	sort.Strings(names)

	buffer := newBuffer()
	indent := 0
	g.writeRegisterHeader(buffer, pkg, indent)
	for _, name := range names {
		buffer.addLine(fmt.Sprintf("%s,\n", name), indent+2)
	}
	g.writeRegisterFooter(buffer, indent)
	if err := buffer.flushLines(w); err != nil {
		return err
	}
	return nil
}

func (g *conversionGenerator) addImportByPath(pkg string) string {
	if name, ok := g.imports[pkg]; ok {
		return name
	}
	name := path.Base(pkg)
	if _, ok := g.shortImports[name]; !ok {
		g.imports[pkg] = name
		g.shortImports[name] = pkg
		return name
	}
	if dirname := path.Base(path.Dir(pkg)); len(dirname) > 0 {
		name = dirname + name
		if _, ok := g.shortImports[name]; !ok {
			g.imports[pkg] = name
			g.shortImports[name] = pkg
			return name
		}
		if subdirname := path.Base(path.Dir(path.Dir(pkg))); len(subdirname) > 0 {
			name = subdirname + name
			if _, ok := g.shortImports[name]; !ok {
				g.imports[pkg] = name
				g.shortImports[name] = pkg
				return name
			}
		}
	}
	for i := 2; i < 100; i++ {
		generatedName := fmt.Sprintf("%s%d", name, i)
		if _, ok := g.shortImports[generatedName]; !ok {
			g.imports[pkg] = generatedName
			g.shortImports[generatedName] = pkg
			return generatedName
		}
	}
	panic(fmt.Sprintf("unable to find a unique name for the package path %q: %v", pkg, g.shortImports))
}

func (g *conversionGenerator) typeName(inType reflect.Type) string {
	switch inType.Kind() {
	case reflect.Slice:
		return fmt.Sprintf("[]%s", g.typeName(inType.Elem()))
	case reflect.Ptr:
		return fmt.Sprintf("*%s", g.typeName(inType.Elem()))
	case reflect.Map:
		if len(inType.Name()) == 0 {
			return fmt.Sprintf("map[%s]%s", g.typeName(inType.Key()), g.typeName(inType.Elem()))
		}
		fallthrough
	default:
		pkg, name := inType.PkgPath(), inType.Name()
		if len(name) == 0 && inType.Kind() == reflect.Struct {
			return "struct{}"
		}
		if len(pkg) == 0 {
			// Default package.
			return name
		}
		if val, found := g.pkgOverwrites[pkg]; found {
			pkg = val
		}
		if len(pkg) == 0 {
			return name
		}
		short := g.addImportByPath(pkg)
		if len(short) > 0 {
			return fmt.Sprintf("%s.%s", short, name)
		}
		return name
	}
}

func (g *conversionGenerator) writeDefaultingFunc(b *buffer, inType reflect.Type, indent int) error {
	getStmt := "if defaulting, found := s.DefaultingInterface(reflect.TypeOf(*in)); found {\n"
	b.addLine(getStmt, indent)
	callFormat := "defaulting.(func(*%s))(in)\n"
	callStmt := fmt.Sprintf(callFormat, g.typeName(inType))
	b.addLine(callStmt, indent+1)
	b.addLine("}\n", indent)
	return nil
}

func packageForName(inType reflect.Type) string {
	if inType.PkgPath() == "" {
		return ""
	}
	slices := strings.Split(inType.PkgPath(), "/")
	return slices[len(slices)-1]
}

func (g *conversionGenerator) conversionFunctionName(inType, outType reflect.Type) string {
	funcNameFormat := g.nameFormat
	inPkg := packageForName(inType)
	outPkg := packageForName(outType)
	funcName := fmt.Sprintf(funcNameFormat, inPkg, inType.Name(), outPkg, outType.Name())
	return funcName
}

func (g *conversionGenerator) conversionFunctionCall(inType, outType reflect.Type, scopeName string, args ...string) string {
	if named, ok := g.publicFuncs[typePair{inType, outType}]; ok {
		args[len(args)-1] = scopeName
		name := named.name
		localPackageName, ok := g.imports[named.packageName]
		if !ok {
			panic(fmt.Sprintf("have not defined an import for %s", named.packageName))
		}
		if len(named.packageName) > 0 && len(localPackageName) > 0 {
			name = localPackageName + "." + name
		}
		return fmt.Sprintf("%s(%s)", name, strings.Join(args, ", "))
	}
	log.Printf("WARNING: Using reflection to convert %v -> %v (no public conversion)", inType, outType)
	return fmt.Sprintf("%s.Convert(%s)", scopeName, strings.Join(args, ", "))
}

func (g *conversionGenerator) generatedFunctionName(inType, outType reflect.Type) string {
	return g.generatedNamePrefix + g.conversionFunctionName(inType, outType)
}

func (g *conversionGenerator) writeHeader(b *buffer, name, inType, outType string, indent int) {
	format := "func %s(in *%s, out *%s, s conversion.Scope) error {\n"
	stmt := fmt.Sprintf(format, name, inType, outType)
	b.addLine(stmt, indent)
}

func (g *conversionGenerator) writeFooter(b *buffer, indent int) {
	b.addLine("return nil\n", indent+1)
	b.addLine("}\n", indent)
}

func (g *conversionGenerator) writeConversionForMap(b *buffer, inField, outField reflect.StructField, indent int) error {
	ifFormat := "if in.%s != nil {\n"
	ifStmt := fmt.Sprintf(ifFormat, inField.Name)
	b.addLine(ifStmt, indent)
	makeFormat := "out.%s = make(%s)\n"
	makeStmt := fmt.Sprintf(makeFormat, outField.Name, g.typeName(outField.Type))
	b.addLine(makeStmt, indent+1)
	forFormat := "for key, val := range in.%s {\n"
	forStmt := fmt.Sprintf(forFormat, inField.Name)
	b.addLine(forStmt, indent+1)

	// Whether we need to explicitly create a new value.
	newValue := false
	if isComplexType(inField.Type.Elem()) || !inField.Type.Elem().ConvertibleTo(outField.Type.Elem()) {
		newValue = true
		newFormat := "newVal := %s{}\n"
		newStmt := fmt.Sprintf(newFormat, g.typeName(outField.Type.Elem()))
		b.addLine(newStmt, indent+2)
		call := g.conversionFunctionCall(inField.Type.Elem(), outField.Type.Elem(), "s", "&val", "&newVal", "0")
		convertStmt := fmt.Sprintf("if err := %s; err != nil {\n", call)
		b.addLine(convertStmt, indent+2)
		b.addLine("return err\n", indent+3)
		b.addLine("}\n", indent+2)
	}
	if inField.Type.Key().ConvertibleTo(outField.Type.Key()) {
		value := "val"
		if newValue {
			value = "newVal"
		}
		assignStmt := ""
		if inField.Type.Key().AssignableTo(outField.Type.Key()) {
			assignStmt = fmt.Sprintf("out.%s[key] = %s\n", outField.Name, value)
		} else {
			assignStmt = fmt.Sprintf("out.%s[%s(key)] = %s\n", outField.Name, g.typeName(outField.Type.Key()), value)
		}
		b.addLine(assignStmt, indent+2)
	} else {
		// TODO(wojtek-t): Support maps with keys that are non-convertible to each other.
		return fmt.Errorf("conversions between unconvertible keys in map are not supported.")
	}
	b.addLine("}\n", indent+1)
	b.addLine("} else {\n", indent)
	nilFormat := "out.%s = nil\n"
	nilStmt := fmt.Sprintf(nilFormat, outField.Name)
	b.addLine(nilStmt, indent+1)
	b.addLine("}\n", indent)
	return nil
}

func (g *conversionGenerator) writeConversionForSlice(b *buffer, inField, outField reflect.StructField, indent int) error {
	ifFormat := "if in.%s != nil {\n"
	ifStmt := fmt.Sprintf(ifFormat, inField.Name)
	b.addLine(ifStmt, indent)
	makeFormat := "out.%s = make(%s, len(in.%s))\n"
	makeStmt := fmt.Sprintf(makeFormat, outField.Name, g.typeName(outField.Type), inField.Name)
	b.addLine(makeStmt, indent+1)
	forFormat := "for i := range in.%s {\n"
	forStmt := fmt.Sprintf(forFormat, inField.Name)
	b.addLine(forStmt, indent+1)

	assigned := false
	switch inField.Type.Elem().Kind() {
	case reflect.Map, reflect.Ptr, reflect.Slice, reflect.Interface, reflect.Struct:
		// Don't copy these via assignment/conversion!
	default:
		// This should handle all simple types.
		if inField.Type.Elem().AssignableTo(outField.Type.Elem()) {
			assignFormat := "out.%s[i] = in.%s[i]\n"
			assignStmt := fmt.Sprintf(assignFormat, outField.Name, inField.Name)
			b.addLine(assignStmt, indent+2)
			assigned = true
		} else if inField.Type.Elem().ConvertibleTo(outField.Type.Elem()) {
			assignFormat := "out.%s[i] = %s(in.%s[i])\n"
			assignStmt := fmt.Sprintf(assignFormat, outField.Name, g.typeName(outField.Type.Elem()), inField.Name)
			b.addLine(assignStmt, indent+2)
			assigned = true
		}
	}
	if !assigned {
		call := g.conversionFunctionCall(inField.Type.Elem(), outField.Type.Elem(), "s", "&in."+inField.Name+"[i]", "&out."+outField.Name+"[i]", "0")
		assignStmt := fmt.Sprintf("if err := %s; err != nil {\n", call)
		b.addLine(assignStmt, indent+2)
		b.addLine("return err\n", indent+3)
		b.addLine("}\n", indent+2)
	}
	b.addLine("}\n", indent+1)
	b.addLine("} else {\n", indent)
	nilFormat := "out.%s = nil\n"
	nilStmt := fmt.Sprintf(nilFormat, outField.Name)
	b.addLine(nilStmt, indent+1)
	b.addLine("}\n", indent)
	return nil
}

func (g *conversionGenerator) writeConversionForPtr(b *buffer, inField, outField reflect.StructField, indent int) error {
	switch inField.Type.Elem().Kind() {
	case reflect.Map, reflect.Ptr, reflect.Slice, reflect.Interface, reflect.Struct:
		// Don't copy these via assignment/conversion!
	default:
		// This should handle pointers to all simple types.
		assignable := inField.Type.Elem().AssignableTo(outField.Type.Elem())
		convertible := inField.Type.Elem().ConvertibleTo(outField.Type.Elem())
		if assignable || convertible {
			ifFormat := "if in.%s != nil {\n"
			ifStmt := fmt.Sprintf(ifFormat, inField.Name)
			b.addLine(ifStmt, indent)
			newFormat := "out.%s = new(%s)\n"
			newStmt := fmt.Sprintf(newFormat, outField.Name, g.typeName(outField.Type.Elem()))
			b.addLine(newStmt, indent+1)
		}
		if assignable {
			assignFormat := "*out.%s = *in.%s\n"
			assignStmt := fmt.Sprintf(assignFormat, outField.Name, inField.Name)
			b.addLine(assignStmt, indent+1)
		} else if convertible {
			assignFormat := "*out.%s = %s(*in.%s)\n"
			assignStmt := fmt.Sprintf(assignFormat, outField.Name, g.typeName(outField.Type.Elem()), inField.Name)
			b.addLine(assignStmt, indent+1)
		}
		if assignable || convertible {
			b.addLine("} else {\n", indent)
			nilFormat := "out.%s = nil\n"
			nilStmt := fmt.Sprintf(nilFormat, outField.Name)
			b.addLine(nilStmt, indent+1)
			b.addLine("}\n", indent)
			return nil
		}
	}

	b.addLine(fmt.Sprintf("// unable to generate simple pointer conversion for %v -> %v\n", inField.Type.Elem(), outField.Type.Elem()), indent)
	ifFormat := "if in.%s != nil {\n"
	ifStmt := fmt.Sprintf(ifFormat, inField.Name)
	b.addLine(ifStmt, indent)
	assignStmt := ""
	if _, ok := g.publicFuncs[typePair{inField.Type.Elem(), outField.Type.Elem()}]; ok {
		newFormat := "out.%s = new(%s)\n"
		newStmt := fmt.Sprintf(newFormat, outField.Name, g.typeName(outField.Type.Elem()))
		b.addLine(newStmt, indent+1)
		call := g.conversionFunctionCall(inField.Type.Elem(), outField.Type.Elem(), "s", "in."+inField.Name, "out."+outField.Name, "0")
		assignStmt = fmt.Sprintf("if err := %s; err != nil {\n", call)
	} else {
		call := g.conversionFunctionCall(inField.Type.Elem(), outField.Type.Elem(), "s", "&in."+inField.Name, "&out."+outField.Name, "0")
		assignStmt = fmt.Sprintf("if err := %s; err != nil {\n", call)
	}
	b.addLine(assignStmt, indent+1)
	b.addLine("return err\n", indent+2)
	b.addLine("}\n", indent+1)
	b.addLine("} else {\n", indent)
	nilFormat := "out.%s = nil\n"
	nilStmt := fmt.Sprintf(nilFormat, outField.Name)
	b.addLine(nilStmt, indent+1)
	b.addLine("}\n", indent)
	return nil
}

func (g *conversionGenerator) canTryConversion(b *buffer, inType reflect.Type, inField, outField reflect.StructField, indent int) (bool, error) {
	if inField.Type.Kind() != outField.Type.Kind() {
		if !g.overridden[inType] {
			return false, fmt.Errorf("input %s.%s (%s) does not match output (%s) and conversion is not overridden", inType, inField.Name, inField.Type.Kind(), outField.Type.Kind())
		}
		b.addLine(fmt.Sprintf("// in.%s has no peer in out\n", inField.Name), indent)
		return false, nil
	}
	return true, nil
}

func (g *conversionGenerator) writeConversionForStruct(b *buffer, inType, outType reflect.Type, indent int) error {
	for i := 0; i < inType.NumField(); i++ {
		inField := inType.Field(i)
		outField, found := outType.FieldByName(inField.Name)
		if !found {
			if !g.overridden[inType] {
				return fmt.Errorf("input %s.%s has no peer in output %s and conversion is not overridden", inType, inField.Name, outType)
			}
			b.addLine(fmt.Sprintf("// in.%s has no peer in out\n", inField.Name), indent)
			continue
		}

		if g.scheme.Converter().IsConversionIgnored(inField.Type, outField.Type) {
			continue
		}

		existsConversion := g.scheme.Converter().HasConversionFunc(inField.Type, outField.Type)
		_, hasPublicConversion := g.publicFuncs[typePair{inField.Type, outField.Type}]
		// TODO: This allows a private conversion for a slice to take precedence over a public
		// conversion for the field, even though that is technically slower. We should report when
		// we generate an inefficient conversion.
		if existsConversion || hasPublicConversion {
			// Use the conversion method that is already defined.
			call := g.conversionFunctionCall(inField.Type, outField.Type, "s", "&in."+inField.Name, "&out."+outField.Name, "0")
			assignStmt := fmt.Sprintf("if err := %s; err != nil {\n", call)
			b.addLine(assignStmt, indent)
			b.addLine("return err\n", indent+1)
			b.addLine("}\n", indent)
			continue
		}

		switch inField.Type.Kind() {
		case reflect.Map:
			if try, err := g.canTryConversion(b, inType, inField, outField, indent); err != nil {
				return err
			} else if !try {
				continue
			}
			if err := g.writeConversionForMap(b, inField, outField, indent); err != nil {
				return err
			}
			continue
		case reflect.Ptr:
			if try, err := g.canTryConversion(b, inType, inField, outField, indent); err != nil {
				return err
			} else if !try {
				continue
			}
			if err := g.writeConversionForPtr(b, inField, outField, indent); err != nil {
				return err
			}
			continue
		case reflect.Slice:
			if try, err := g.canTryConversion(b, inType, inField, outField, indent); err != nil {
				return err
			} else if !try {
				continue
			}
			if err := g.writeConversionForSlice(b, inField, outField, indent); err != nil {
				return err
			}
			continue
		case reflect.Interface, reflect.Struct:
			// Don't copy these via assignment/conversion!
		default:
			// This should handle all simple types.
			if inField.Type.AssignableTo(outField.Type) {
				assignFormat := "out.%s = in.%s\n"
				assignStmt := fmt.Sprintf(assignFormat, outField.Name, inField.Name)
				b.addLine(assignStmt, indent)
				continue
			}
			if inField.Type.ConvertibleTo(outField.Type) {
				assignFormat := "out.%s = %s(in.%s)\n"
				assignStmt := fmt.Sprintf(assignFormat, outField.Name, g.typeName(outField.Type), inField.Name)
				b.addLine(assignStmt, indent)
				continue
			}
		}

		call := g.conversionFunctionCall(inField.Type, outField.Type, "s", "&in."+inField.Name, "&out."+outField.Name, "0")
		assignStmt := fmt.Sprintf("if err := %s; err != nil {\n", call)
		b.addLine(assignStmt, indent)
		b.addLine("return err\n", indent+1)
		b.addLine("}\n", indent)
	}
	return nil
}

func (g *conversionGenerator) writeConversionForType(b *buffer, inType, outType reflect.Type, indent int) error {
	// Always emit the auto-generated name.
	autoFuncName := g.generatedFunctionName(inType, outType)
	g.writeHeader(b, autoFuncName, g.typeName(inType), g.typeName(outType), indent)
	if err := g.writeDefaultingFunc(b, inType, indent+1); err != nil {
		return err
	}
	switch inType.Kind() {
	case reflect.Struct:
		if err := g.writeConversionForStruct(b, inType, outType, indent+1); err != nil {
			return err
		}
	default:
		return fmt.Errorf("type not supported: %v", inType)
	}
	g.writeFooter(b, indent)
	b.addLine("\n", 0)

	if !g.overridden[inType] {
		// Also emit the "user-facing" name.
		userFuncName := g.conversionFunctionName(inType, outType)
		g.writeHeader(b, userFuncName, g.typeName(inType), g.typeName(outType), indent)
		b.addLine(fmt.Sprintf("return %s(in, out, s)\n", autoFuncName), indent+1)
		b.addLine("}\n\n", 0)
	}

	return nil
}

func (g *conversionGenerator) existsConversionFunction(inType, outType reflect.Type) bool {
	if val, found := g.convertibles[inType]; found && val == outType {
		return true
	}
	if val, found := g.convertibles[outType]; found && val == inType {
		return true
	}
	return false
}

// TODO(wojtek-t): We should somehow change the conversion methods registered under:
// pkg/runtime/scheme.go to implement the naming convention for conversion functions
// and get rid of this hack.
type typePair struct {
	inType  reflect.Type
	outType reflect.Type
}

var defaultConversions []typePair = []typePair{}

func (g *conversionGenerator) OverwritePackage(pkg, overwrite string) {
	g.pkgOverwrites[pkg] = overwrite
}