package internalgengo

import (
	"fmt"
	"sort"
	"strconv"
	"strings"

	"google.golang.org/protobuf/compiler/protogen"
	"google.golang.org/protobuf/reflect/protoreflect"
)

var (
	strconvPackage   = protogen.GoImportPath("strconv")
	fmtPackage       = protogen.GoImportPath("fmt")
	jsonPackage      = protogen.GoImportPath("encoding/json")
	easyprotoPackage = protogen.GoImportPath("github.com/VictoriaMetrics/easyproto")
	mpPackage        = protogen.GoImportPath("git.frostfs.info/TrueCloudLab/frostfs-api-go/v2/util/pool")
	protoPackage     = protogen.GoImportPath("git.frostfs.info/TrueCloudLab/frostfs-api-go/v2/util/proto")
	encodingPackage  = protogen.GoImportPath("git.frostfs.info/TrueCloudLab/frostfs-api-go/v2/util/proto/encoding")

	mp = mpPackage.Ident("MarshalerPool")
)

// GenerateFile generates a *.pb.go file enforcing field-order serialization.
func GenerateFile(gen *protogen.Plugin, file *protogen.File) *protogen.GeneratedFile {
	filename := file.GeneratedFilenamePrefix + "_frostfs.pb.go"
	g := gen.NewGeneratedFile(filename, file.GoImportPath)

	g.P("// Code generated by protoc-gen-go-frostfs. DO NOT EDIT.")
	g.P()
	g.P("package ", file.GoPackageName)
	g.P()
	g.Import(encodingPackage)

	// Doesn't work for multiple files in a single package, use external pool.
	// g.P("var mp ", easyprotoPackage.Ident("MarshalerPool"))

	for _, e := range file.Enums {
		emitEnum(g, e)
	}
	for _, msg := range file.Messages {
		emitEasyProto(g, msg)
	}
	return g
}

func emitEnum(g *protogen.GeneratedFile, e *protogen.Enum) {
	g.P("type " + e.GoIdent.GoName + " int32")
	g.P("const (")
	for _, ev := range e.Values {
		g.P(ev.GoIdent.GoName, " ", e.GoIdent.GoName, " = ", ev.Desc.Number())
	}
	g.P(")")

	g.P("var (")
	g.P(e.GoIdent.GoName+"_name", " = map[int32]string{")
	for _, value := range e.Values {
		g.P(value.Desc.Number(), ": ", strconv.Quote(string(value.Desc.Name())), ",")
	}
	g.P("}")
	g.P(e.GoIdent.GoName+"_value", " = map[string]int32{")
	for _, value := range e.Values {
		g.P(strconv.Quote(string(value.Desc.Name())), ": ", value.Desc.Number(), ",")
	}
	g.P("}")
	g.P(")")
	g.P()

	g.P("func (x ", e.GoIdent.GoName, ") String() string {")
	g.P("if v, ok := ", e.GoIdent.GoName+"_name[int32(x)]; ok {")
	g.P("return v")
	g.P("}")
	g.P("return ", strconvPackage.Ident("FormatInt"), "(int64(x), 10)")
	g.P("}")

	g.P("func (x *", e.GoIdent.GoName, ") FromString(s string) bool {")
	g.P("if v, ok := ", e.GoIdent.GoName+"_value[s]; ok {")
	g.P("*x = ", e.GoIdent.GoName, "(v)")
	g.P("return true")
	g.P("}")
	g.P("return false")
	g.P("}")
}

func emitEasyProto(g *protogen.GeneratedFile, msg *protogen.Message) {
	for _, e := range msg.Enums {
		emitEnum(g, e)
	}
	for _, m := range msg.Messages {
		emitEasyProto(g, m)
	}

	g.P("type " + msg.GoIdent.GoName + " struct {")
	emitMessageFields(g, msg)
	g.P("}")

	g.P("var (")
	g.P("_ ", encodingPackage.Ident("ProtoMarshaler"), " = (*", msg.GoIdent.GoName, ")(nil)")
	g.P("_ ", encodingPackage.Ident("ProtoUnmarshaler"), " = (*", msg.GoIdent.GoName, ")(nil)")
	g.P("_ ", jsonPackage.Ident("Marshaler"), " = (*", msg.GoIdent.GoName, ")(nil)")
	g.P("_ ", jsonPackage.Ident("Unmarshaler"), " = (*", msg.GoIdent.GoName, ")(nil)")
	g.P(")")

	emitStableSize(g, msg)
	if strings.HasSuffix(msg.GoIdent.GoName, "Request") || strings.HasSuffix(msg.GoIdent.GoName, "Response") {
		emitSignatureMethods(g, msg)
	}

	emitProtoMethods(g, msg)
	emitGettersSetters(g, msg)
	emitJSONMethods(g, msg)

	for _, f := range msg.Fields {
		if isFirstOneof(f) {
			genOneof(g, f)
		}
	}
}

func isFirstOneof(f *protogen.Field) bool {
	return f.Oneof != nil && f == f.Oneof.Fields[0]
}

func emitOneofGettersSetters(g *protogen.GeneratedFile, msg *protogen.Message, ff *protogen.Field) {
	// For some reason protoc generates different code for oneof message/non-message fields:
	// 1. For message we have 2 level struct wrapping and setters use inner type.
	// 2. For other types we also have 2 level wrapping, but setters use outer type.
	ft := fieldType(g, ff)

	g.P("func (x *", msg.GoIdent.GoName, ") Get", ff.GoName, "() ", ft, " {")
	g.P("if xx, ok := x.Get", ff.Oneof.GoName, "().(*", ff.GoIdent, "); ok { return xx.", ff.GoName, " }")
	g.P("return ", fieldDefaultValue(ff))
	g.P("}")

	if ff.Desc.Kind() == protoreflect.MessageKind {
		g.P("func (x *", msg.GoIdent.GoName, ") Set", ff.GoName, "(v ", ft, ") {")
		g.P("x.", ff.Oneof.GoName, " = &", ff.GoIdent, "{", ff.GoName, ": v}")
		g.P("}")
	} else {
		g.P("func (x *", msg.GoIdent.GoName, ") Set", ff.GoName, "(v *", ff.GoIdent, ") {")
		g.P("x.", ff.Oneof.GoName, " = v")
		g.P("}")

		ft := fieldType(g, ff)
		emitGetterSetter(g, ff.GoIdent.GoName, ff.GoName, ft.String(), fieldDefaultValue(ff))
	}
}

func emitGettersSetters(g *protogen.GeneratedFile, msg *protogen.Message) {
	for _, f := range msg.Fields {
		if f.Oneof != nil {
			if f.Oneof.Fields[0] == f {
				emitGetterSetter(g, msg.GoIdent.GoName, f.Oneof.GoName, oneOfDescriptor(f.Oneof), "nil")
				for _, ff := range f.Oneof.Fields {
					emitOneofGettersSetters(g, msg, ff)
				}
			}
			continue
		}

		ft := fieldType(g, f)
		emitGetterSetter(g, msg.GoIdent.GoName, f.GoName, ft.String(), fieldDefaultValue(f))
	}
}

func emitMessageFields(g *protogen.GeneratedFile, msg *protogen.Message) {
	for _, field := range msg.Fields {
		genMessageField(g, field)
	}
}

func genMessageField(g *protogen.GeneratedFile, field *protogen.Field) {
	if field.Oneof != nil {
		if field.Oneof.Fields[0] == field {
			g.P(field.Oneof.GoName, " ", oneOfDescriptor(field.Oneof))
		}
		return
	}

	typ := fieldType(g, field)
	g.P(field.GoName, " ", typ, fmt.Sprintf(" `json:%q`", fieldJSONName(field)))
}

func oneOfDescriptor(oneof *protogen.Oneof) string {
	return "is" + oneof.GoIdent.GoName
}

func genOneof(g *protogen.GeneratedFile, field *protogen.Field) {
	ifName := oneOfDescriptor(field.Oneof)
	g.P("type ", ifName, " interface {")
	g.P(ifName, "()")
	g.P("}")
	g.P()
	for _, field := range field.Oneof.Fields {
		g.P("type ", field.GoIdent, " struct {")

		ft := fieldType(g, field)
		g.P(field.GoName, " ", ft)
		g.P("}")
		g.P()
	}
	for _, field := range field.Oneof.Fields {
		g.P("func (*", field.GoIdent, ") ", ifName, "() {}")
		g.P()
	}
}

func fieldDefaultValue(field *protogen.Field) string {
	if field.Desc.Cardinality() == protoreflect.Repeated {
		return "nil"
	}

	switch field.Desc.Kind() {
	case protoreflect.MessageKind, protoreflect.BytesKind:
		return "nil"
	case protoreflect.BoolKind:
		return "false"
	case protoreflect.StringKind:
		return `""`
	default:
		return "0"
	}
}

func castFieldName(f *protogen.Field) string {
	if f.Oneof != nil {
		return "x." + f.Oneof.GoName
	}

	name := "x." + f.GoName
	if f.Desc.Kind() != protoreflect.EnumKind {
		return name
	}
	return "int32(" + name + ")"
}

func sortFields(fs []*protogen.Field) []*protogen.Field {
	res := make([]*protogen.Field, len(fs))
	copy(res, fs)
	sort.Slice(res, func(i, j int) bool {
		return res[i].Desc.Number() < res[j].Desc.Number()
	})
	return res
}