package dynamic

import (
	"context"
	"fmt"
	"github.com/gogf/gf/errors/gerror"
	"github.com/gogf/gf/frame/g"
	"github.com/smallnest/rpcx/log"
	"github.com/smallnest/rpcx/share"
	"reflect"
	"runtime"
	"sync"
	"unicode"
	"unicode/utf8"
)

var Invoker *InvokerImpl

func init() {
	Invoker = NewInvoker()
}

type InvokerImpl struct {
	classMapMu sync.RWMutex
	classMap   map[string]*service
}

func NewInvoker() *InvokerImpl {
	return &InvokerImpl{
		classMap: make(map[string]*service),
	}
}

var typeOfError = reflect.TypeOf((*error)(nil)).Elem()

var typeOfContext = reflect.TypeOf((*context.Context)(nil)).Elem()

type service struct {
	name   string                 // name of service
	rcvr   reflect.Value          // receiver of methods for the service
	typ    reflect.Type           // type of the receiver
	method map[string]*methodType // registered methods
}

type methodType struct {
	sync.Mutex // protects counters
	method     reflect.Method
	ArgType    reflect.Type
	ReplyType  reflect.Type
	// numCalls   uint
}

func isExported(name string) bool {
	rune, _ := utf8.DecodeRuneInString(name)
	return unicode.IsUpper(rune)
}

func isExportedOrBuiltinType(t reflect.Type) bool {
	for t.Kind() == reflect.Ptr {
		t = t.Elem()
	}

	return isExported(t.Name()) || t.PkgPath() == ""
}

func (s *InvokerImpl) Register(class interface{}) error {
	s.classMapMu.Lock()
	defer s.classMapMu.Unlock()
	service := new(service)
	service.typ = reflect.TypeOf(class)
	service.rcvr = reflect.ValueOf(class)
	sname := reflect.Indirect(service.rcvr).Type().Name() // Type
	if sname == "" {
		errorStr := "InvokerImpl.Register: no service name for type " + service.typ.String()
		g.Log().Error(errorStr)
		return gerror.New(errorStr)
	}
	if !isExported(sname) {
		errorStr := "InvokerImpl.Register: type " + sname + " is not exported"
		g.Log().Error(errorStr)
		return gerror.New(errorStr)
	}
	service.name = sname
	// Install the methods
	service.method = suitableMethods(service.typ, true)

	if len(service.method) == 0 {
		var errorStr string

		method := suitableMethods(reflect.PtrTo(service.typ), false)
		if len(method) != 0 {
			errorStr = "rpcx.Register: type " + sname + " has no exported methods of suitable type (hint: pass a pointer to value of that type)"
		} else {
			errorStr = "rpcx.Register: type " + sname + " has no exported methods of suitable type"
		}
		g.Log().Error(errorStr)
		return gerror.New(errorStr)
	}
	s.classMap[service.name] = service
	return nil
}

func suitableMethods(typ reflect.Type, reportErr bool) map[string]*methodType {
	methods := make(map[string]*methodType)
	for m := 0; m < typ.NumMethod(); m++ {
		method := typ.Method(m)
		mtype := method.Type
		mname := method.Name
		// Method must be exported.
		if method.PkgPath != "" {
			continue
		}
		// Method needs four ins: receiver, context.Context, *args, *reply.
		if mtype.NumIn() != 4 {
			if reportErr {
				log.Debug("method ", mname, " has wrong number of ins:", mtype.NumIn())
			}
			continue
		}
		// First arg must be context.Context
		ctxType := mtype.In(1)
		if !ctxType.Implements(typeOfContext) {
			if reportErr {
				log.Debug("method ", mname, " must use context.Context as the first parameter")
			}
			continue
		}

		// Second arg need not be a pointer.
		argType := mtype.In(2)
		if !isExportedOrBuiltinType(argType) {
			if reportErr {
				log.Info(mname, " parameter type not exported: ", argType)
			}
			continue
		}
		// Third arg must be a pointer.
		replyType := mtype.In(3)
		if replyType.Kind() != reflect.Ptr {
			if reportErr {
				log.Info("method", mname, " reply type not a pointer:", replyType)
			}
			continue
		}
		// Reply type must be exported.
		if !isExportedOrBuiltinType(replyType) {
			if reportErr {
				log.Info("method", mname, " reply type not exported:", replyType)
			}
			continue
		}
		// Method needs one out.
		if mtype.NumOut() != 1 {
			if reportErr {
				log.Info("method", mname, " has wrong number of outs:", mtype.NumOut())
			}
			continue
		}
		// The return type of the method must be error.
		if returnType := mtype.Out(0); returnType != typeOfError {
			if reportErr {
				log.Info("method", mname, " returns ", returnType.String(), " not error")
			}
			continue
		}
		methods[mname] = &methodType{method: method, ArgType: argType, ReplyType: replyType}

		reflectTypePools.Init(argType)
		reflectTypePools.Init(replyType)
	}
	return methods
}

func (s *InvokerImpl) HandleInvoker(ctx context.Context, req *Message) (res *Message, err error) {
	s.classMapMu.RLock()
	service := s.classMap[req.ClassName]
	if share.Trace {
		log.Debugf("server get service %+v for an request", service)
	}
	s.classMapMu.RUnlock()

	res = req.Clone()

	if service == nil {

	}
	mtype := service.method[req.MethodName]
	if mtype == nil {

	}

	args := reflectTypePools.Get(mtype.ArgType)

	if mtype.ArgType == reflect.TypeOf(req.Payload) {
		args = req.Payload
	}

	reply := reflectTypePools.Get(mtype.ReplyType)

	if mtype.ArgType.Kind() != reflect.Ptr {
		err = service.call(ctx, mtype, reflect.ValueOf(args).Elem(), reflect.ValueOf(reply))
	} else {
		err = service.call(ctx, mtype, reflect.ValueOf(args), reflect.ValueOf(reply))
	}
	reflectTypePools.Put(mtype.ArgType, args)

	if err != nil {
		if reply != nil {
			reflectTypePools.Put(mtype.ReplyType, reply)
			res.Payload = reply
		}
	} else {
		// return reply to object pool
		reflectTypePools.Put(mtype.ReplyType, reply)
		res.Payload = reply
	}

	return res, nil
}

func (s *service) call(ctx context.Context, mtype *methodType, args, reply reflect.Value) (err error) {
	defer func() {
		if r := recover(); r != nil {
			buf := make([]byte, 4096)
			n := runtime.Stack(buf, false)
			buf = buf[:n]

			err = fmt.Errorf("[service internal error]: %v, method: %s, args: %+v, stack: %s",
				r, mtype.method.Name, args.Interface(), buf)
			log.Error(err)
		}
	}()

	function := mtype.method.Func
	// Invoke the method, providing a new value for the reply.
	returnValues := function.Call([]reflect.Value{s.rcvr, reflect.ValueOf(ctx), args, reply})
	// The return value for the method is an error.
	errInter := returnValues[0].Interface()
	if errInter != nil {
		return errInter.(error)
	}

	return nil
}

type Message struct {
	ClassName  string
	MethodName string
	Metadata   map[string]string
	Payload    interface{}
}

// Clone clones from an message.
func (m Message) Clone() *Message {
	return &Message{
		ClassName:  m.ClassName,
		MethodName: m.MethodName,
		Metadata:   m.Metadata,
	}
}