New RPC integration

rpc.md

Introduce a new type Api in the rpc package:

// Api describes the set of methods offered over the RPC interface
type Api struct {
  Namespace string     // namespace under which the rpc methods of Service are exposed
  Version string       // api version for DApp's
  Service interface{}  // receiver instance which holds the methods
  Public bool          // indication if the methods must be considered safe for public use
}

Extend the node.Service interface with a new method:

// Api retrieves the list of RPC methods the service provides 
Api() []*rpc.Api

When the node stack is started a new rpc.Server instance is created and available API's are registered.

ipcServer := rpc.NewServer()
httpServer := rpc.NewServer()

for _, api := range apis {
  if mustOffer(api, rpc.IPC) {
    ipcServer.register(api)
  }
  if mustOffer(api, rpc.HTTP) {
    httpServer.register(api)
  }
}

// mustOffer indicates if the API must be offered for the given rpc type (IPC, HTTP, WS?...)
func mustOffer(api *Api, type rpc.Type) bool {
  // use defaults, all over IPC and only public over HTTP
  // or use user overriden settings
}

An example implementation for the Api() call:

// BlockServer offers a public block API
type BlockService struct {}
func (*s BlockService) Get(...) ... {}

// BlockManagementService offers a private block API
type BlockManagementService struct {}
func (s *BlockService) Delete(...) ... {}

func (s *MyService) Apis() []*Api {
  return []*Api{
    &Api{
      Namespace: "eth",
      Version: "1.0",
      Public: true,
      Service: new(BlockService),
    },
    &Api{
    Namespace: "eth",
      Version: "1.0",
      Public: false,
      Service: new(BlockManagementService),
    },
  }
}