package rpc

import (
	"reflect"

	"git.loafle.net/commons_go/rpc/protocol"
)

/**

Network connection
	Handshake(1..n)
		Send request
			HTTP


*/

// NewRPCRegistry returns a new RPC registry.
func NewRegistry() Registry {
	return &rpcRegistry{
		services: new(serviceMap),
	}
}

type Registry interface {
	RegisterService(receiver interface{}, name string) error
	HasMethod(method string) bool
	Invoke(codec protocol.RegistryCodec) (result interface{}, err error)
}

// RPCRegistry serves registered RPC services using registered codecs.
type rpcRegistry struct {
	services *serviceMap
}

// 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 *rpcRegistry) RegisterService(receiver interface{}, name string) error {
	return rr.services.register(receiver, name)
}

// HasMethod returns true if the given method is registered.
//
// The method uses a dotted notation as in "Service.Method".
func (rr *rpcRegistry) HasMethod(method string) bool {
	if _, _, err := rr.services.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 *rpcRegistry) Invoke(codec protocol.RegistryCodec) (result interface{}, err error) {
	serviceSpec, methodSpec, errGet := rr.services.get(codec.Method())
	if errGet != nil {
		return nil, errGet
	}
	// Decode the args.
	args := reflect.New(methodSpec.argsType)
	if errRead := codec.ReadParams(args.Interface()); errRead != nil {
		return nil, errRead
	}
	// Call the service method.
	reply := reflect.New(methodSpec.replyType)
	errValue := methodSpec.method.Func.Call([]reflect.Value{
		serviceSpec.rcvr,
		args,
		reply,
	})

	// Cast the result to error if needed.
	var errResult error
	errInter := errValue[0].Interface()
	if errInter != nil {
		errResult = errInter.(error)
	}

	if errResult != nil {
		return nil, errResult
	}

	return reply.Interface(), nil
}