package registry

import (
	"reflect"

	cuej "git.loafle.net/commons/util-go/encoding/json"
	cus "git.loafle.net/commons/util-go/service"
)

// NewRESTRegistry returns a new REST registry.
func NewRESTRegistry() RESTRegistry {
	return &restRegistry{
		serviceRegistry: new(cus.ServiceRegistry),
	}
}

type RESTRegistry interface {
	RESTInvoker
	GetService(name string) interface{}
	RegisterService(receiver interface{}, name string) error
	RegisterServices(receivers ...interface{}) error
	RegisterServiceMap(keysAndValues map[string]interface{}) error
}

// RESTRegistry serves registered REST services using registered codecs.
type restRegistry struct {
	serviceRegistry *cus.ServiceRegistry
}

// RegisterService adds a new service to the server.
//
// The name parameter is optional: if empty it will be inferred from
// the receiver type name.
//
// Methods from the receiver will be extracted if these rules are satisfied:
//
//    - The receiver is exported (begins with an upper case letter) or local
//      (defined in the package registering the service).
//    - The method name is exported.
//    - The method has two arguments: *args, *reply.
//    - All two arguments are pointers.
//    - The first and second arguments are exported or local.
//    - The method has return type error.
//
// All other methods are ignored.
func (rr *restRegistry) RegisterService(receiver interface{}, name string) error {
	return rr.serviceRegistry.Register(receiver, name)
}

func (rr *restRegistry) RegisterServices(receivers ...interface{}) error {
	if nil == receivers || 0 == len(receivers) {
		return nil
	}

	for _, receiver := range receivers {
		if err := rr.serviceRegistry.Register(receiver, ""); nil != err {
			return err
		}
	}
	return nil
}

func (rr *restRegistry) RegisterServiceMap(keysAndValues map[string]interface{}) error {
	if nil == keysAndValues || 0 == len(keysAndValues) {
		return nil
	}

	for name, receiver := range keysAndValues {
		if err := rr.serviceRegistry.Register(receiver, name); nil != err {
			return err
		}
	}
	return nil
}

func (rr *restRegistry) GetService(name string) interface{} {
	return rr.serviceRegistry.GetService(name)
}

// HasMethod returns true if the given method is registered.
//
// The method uses a dotted notation as in "Service.Method".
func (rr *restRegistry) HasMethod(method string) bool {
	if _, _, err := rr.serviceRegistry.Get(method); err == nil {
		return true
	}
	return false
}

// Invoke execute a method.
//
// Codecs are defined to process a given serialization scheme, e.g., JSON or
// XML. A codec is chosen based on the "Content-Type" header from the request,
// excluding the charset definition.
func (rr *restRegistry) Invoke(method string, params []string, leadingParams ...interface{}) (result interface{}, err error) {
	serviceSpec, methodSpec, errGet := rr.serviceRegistry.Get(method)
	if nil != errGet {
		return nil, errGet
	}
	// Decode the args.

	var in []reflect.Value
	pValues, pInstances := methodSpec.ParamValues()

	lParamLen := 0
	if nil != leadingParams {
		lParamLen = len(leadingParams)
	}

	if nil != pInstances && 0 < len(pInstances) {
		if err := cuej.SetValueWithJSONStringArray(params, pInstances[lParamLen:]); nil != err {
			return nil, err
		}

		pCount := len(pInstances)
		in = make([]reflect.Value, pCount+1)

		for indexI := lParamLen; indexI < pCount; indexI++ {
			if pValues[indexI].Type().Kind() == reflect.Ptr && pValues[indexI].Type().Elem().Kind() != reflect.Struct {
				in[indexI+1] = reflect.Indirect(pValues[indexI])
			} else {
				in[indexI+1] = pValues[indexI]
			}
		}
	} else {
		in = make([]reflect.Value, 1)
	}
	in[0] = serviceSpec.ReceiverValue()

	for indexI := 0; indexI < lParamLen; indexI++ {
		in[indexI+1] = reflect.ValueOf(leadingParams[indexI])
	}

	// Call the service method.
	returnValues := methodSpec.Call(in)

	if nil != methodSpec.ReturnType() {
		result = returnValues[0].Interface()
		if nil != returnValues[1].Interface() {
			err = returnValues[1].Interface().(error)
		}
	} else {
		if nil != returnValues[0].Interface() {
			err = returnValues[0].Interface().(error)
		}
	}

	return
}