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.

	var in []reflect.Value
	paramValues, paramInstances := methodSpec.getParams()
	if nil != paramValues {
		in = make([]reflect.Value, len(paramValues)+1)
		if errRead := codec.ReadParams(paramInstances); errRead != nil {
			return nil, errRead
		}
		for indexI := 0; indexI < len(paramValues); indexI++ {
			in[indexI+1] = paramValues[indexI]
		}
	} else {
		in = make([]reflect.Value, 1)
	}
	in[0] = serviceSpec.rcvr

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

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

	return
}