text: // Copyright (c) 2013-2014 Sandstorm Development Group, Inc. and contributors
  // Licensed under the MIT License:
  //
  // Permission is hereby granted, free of charge, to any person obtaining a copy
  // of this software and associated documentation files (the "Software"), to deal
  // in the Software without restriction, including without limitation the rights
  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  // copies of the Software, and to permit persons to whom the Software is
  // furnished to do so, subject to the following conditions:
  //
  // The above copyright notice and this permission notice shall be included in
  // all copies or substantial portions of the Software.
  //
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  // THE SOFTWARE.
  
  #ifndef CAPNP_EZ_RPC_H_
  #define CAPNP_EZ_RPC_H_
  
  #if defined(__GNUC__) && !CAPNP_HEADER_WARNINGS
  #pragma GCC system_header
  #endif
  
  #include "rpc.h"
  #include "message.h"
  
  struct sockaddr;
  
  namespace kj { class AsyncIoProvider; class LowLevelAsyncIoProvider; }
  
  namespace capnp {
  
  class EzRpcContext;
  
  class EzRpcClient {
    // Super-simple interface for setting up a Cap'n Proto RPC client.  Example:
    //
    //     # Cap'n Proto schema
    //     interface Adder {
    //       add @0 (left :Int32, right :Int32) -> (value :Int32);
    //     }
    //
    //     // C++ client
    //     int main() {
    //       capnp::EzRpcClient client("localhost:3456");
    //       Adder::Client adder = client.getMain<Adder>();
    //       auto request = adder.addRequest();
    //       request.setLeft(12);
    //       request.setRight(34);
    //       auto response = request.send().wait(client.getWaitScope());
    //       assert(response.getValue() == 46);
    //       return 0;
    //     }
    //
    //     // C++ server
    //     class AdderImpl final: public Adder::Server {
    //     public:
    //       kj::Promise<void> add(AddContext context) override {
    //         auto params = context.getParams();
    //         context.getResults().setValue(params.getLeft() + params.getRight());
    //         return kj::READY_NOW;
    //       }
    //     };
    //
    //     int main() {
    //       capnp::EzRpcServer server(kj::heap<AdderImpl>(), "*:3456");
    //       kj::NEVER_DONE.wait(server.getWaitScope());
    //     }
    //
    // This interface is easy, but it hides a lot of useful features available from the lower-level
    // classes:
    // - The server can only export a small set of public, singleton capabilities under well-known
    //   string names.  This is fine for transient services where no state needs to be kept between
    //   connections, but hides the power of Cap'n Proto when it comes to long-lived resources.
    // - EzRpcClient/EzRpcServer automatically set up a `kj::EventLoop` and make it current for the
    //   thread.  Only one `kj::EventLoop` can exist per thread, so you cannot use these interfaces
    //   if you wish to set up your own event loop.  (However, you can safely create multiple
    //   EzRpcClient / EzRpcServer objects in a single thread; they will make sure to make no more
    //   than one EventLoop.)
    // - These classes only support simple two-party connections, not multilateral VatNetworks.
    // - These classes only support communication over a raw, unencrypted socket.  If you want to
    //   build on an abstract stream (perhaps one which supports encryption), you must use the
    //   lower-level interfaces.
    //
    // Some of these restrictions will probably be lifted in future versions, but some things will
    // always require using the low-level interfaces directly.  If you are interested in working
    // at a lower level, start by looking at these interfaces:
    // - `kj::startAsyncIo()` in `kj/async-io.h`.
    // - `RpcSystem` in `capnp/rpc.h`.
    // - `TwoPartyVatNetwork` in `capnp/rpc-twoparty.h`.
  
  public:
    explicit EzRpcClient(kj::StringPtr serverAddress, uint defaultPort = 0,
                         ReaderOptions readerOpts = ReaderOptions());
    // Construct a new EzRpcClient and connect to the given address.  The connection is formed in
    // the background -- if it fails, calls to capabilities returned by importCap() will fail with an
    // appropriate exception.
    //
    // `defaultPort` is the IP port number to use if `serverAddress` does not include it explicitly.
    // If unspecified, the port is required in `serverAddress`.
    //
    // The address is parsed by `kj::Network` in `kj/async-io.h`.  See that interface for more info
    // on the address format, but basically it's what you'd expect.
    //
    // `readerOpts` is the ReaderOptions structure used to read each incoming message on the
    // connection. Setting this may be necessary if you need to receive very large individual
    // messages or messages. However, it is recommended that you instead think about how to change
    // your protocol to send large data blobs in multiple small chunks -- this is much better for
    // both security and performance. See `ReaderOptions` in `message.h` for more details.
  
    EzRpcClient(const struct sockaddr* serverAddress, uint addrSize,
                ReaderOptions readerOpts = ReaderOptions());
    // Like the above constructor, but connects to an already-resolved socket address.  Any address
    // format supported by `kj::Network` in `kj/async-io.h` is accepted.
  
    explicit EzRpcClient(int socketFd, ReaderOptions readerOpts = ReaderOptions());
    // Create a client on top of an already-connected socket.
    // `readerOpts` acts as in the first constructor.
  
    ~EzRpcClient() noexcept(false);
  
    template <typename Type>
    typename Type::Client getMain();
    Capability::Client getMain();
    // Get the server's main (aka "bootstrap") interface.
  
    template <typename Type>
    typename Type::Client importCap(kj::StringPtr name)
        KJ_DEPRECATED("Change your server to export a main interface, then use getMain() instead.");
    Capability::Client importCap(kj::StringPtr name)
        KJ_DEPRECATED("Change your server to export a main interface, then use getMain() instead.");
    // ** DEPRECATED **
    //
    // Ask the sever for the capability with the given name.  You may specify a type to automatically
    // down-cast to that type.  It is up to you to specify the correct expected type.
    //
    // Named interfaces are deprecated. The new preferred usage pattern is for the server to export
    // a "main" interface which itself has methods for getting any other interfaces.
  
    kj::WaitScope& getWaitScope();
    // Get the `WaitScope` for the client's `EventLoop`, which allows you to synchronously wait on
    // promises.
  
    kj::AsyncIoProvider& getIoProvider();
    // Get the underlying AsyncIoProvider set up by the RPC system.  This is useful if you want
    // to do some non-RPC I/O in asynchronous fashion.
  
    kj::LowLevelAsyncIoProvider& getLowLevelIoProvider();
    // Get the underlying LowLevelAsyncIoProvider set up by the RPC system.  This is useful if you
    // want to do some non-RPC I/O in asynchronous fashion.
  
  private:
    struct Impl;
    kj::Own<Impl> impl;
  };
  
  class EzRpcServer {
    // The server counterpart to `EzRpcClient`.  See `EzRpcClient` for an example.
  
  public:
    explicit EzRpcServer(Capability::Client mainInterface, kj::StringPtr bindAddress,
                         uint defaultPort = 0, ReaderOptions readerOpts = ReaderOptions());
    // Construct a new `EzRpcServer` that binds to the given address.  An address of "*" means to
    // bind to all local addresses.
    //
    // `defaultPort` is the IP port number to use if `serverAddress` does not include it explicitly.
    // If unspecified, a port is chosen automatically, and you must call getPort() to find out what
    // it is.
    //
    // The address is parsed by `kj::Network` in `kj/async-io.h`.  See that interface for more info
    // on the address format, but basically it's what you'd expect.
    //
    // The server might not begin listening immediately, especially if `bindAddress` needs to be
    // resolved.  If you need to wait until the server is definitely up, wait on the promise returned
    // by `getPort()`.
    //
    // `readerOpts` is the ReaderOptions structure used to read each incoming message on the
    // connection. Setting this may be necessary if you need to receive very large individual
    // messages or messages. However, it is recommended that you instead think about how to change
    // your protocol to send large data blobs in multiple small chunks -- this is much better for
    // both security and performance. See `ReaderOptions` in `message.h` for more details.
  
    EzRpcServer(Capability::Client mainInterface, struct sockaddr* bindAddress, uint addrSize,
                ReaderOptions readerOpts = ReaderOptions());
    // Like the above constructor, but binds to an already-resolved socket address.  Any address
    // format supported by `kj::Network` in `kj/async-io.h` is accepted.
  
    EzRpcServer(Capability::Client mainInterface, int socketFd, uint port,
                ReaderOptions readerOpts = ReaderOptions());
    // Create a server on top of an already-listening socket (i.e. one on which accept() may be
    // called).  `port` is returned by `getPort()` -- it serves no other purpose.
    // `readerOpts` acts as in the other two above constructors.
  
    explicit EzRpcServer(kj::StringPtr bindAddress, uint defaultPort = 0,
                         ReaderOptions readerOpts = ReaderOptions())
        KJ_DEPRECATED("Please specify a main interface for your server.");
    EzRpcServer(struct sockaddr* bindAddress, uint addrSize,
                ReaderOptions readerOpts = ReaderOptions())
        KJ_DEPRECATED("Please specify a main interface for your server.");
    EzRpcServer(int socketFd, uint port, ReaderOptions readerOpts = ReaderOptions())
        KJ_DEPRECATED("Please specify a main interface for your server.");
  
    ~EzRpcServer() noexcept(false);
  
    void exportCap(kj::StringPtr name, Capability::Client cap);
    // Export a capability publicly under the given name, so that clients can import it.
    //
    // Keep in mind that you can implicitly convert `kj::Own<MyType::Server>&&` to
    // `Capability::Client`, so it's typical to pass something like
    // `kj::heap<MyImplementation>(<constructor params>)` as the second parameter.
  
    kj::Promise<uint> getPort();
    // Get the IP port number on which this server is listening.  This promise won't resolve until
    // the server is actually listening.  If the address was not an IP address (e.g. it was a Unix
    // domain socket) then getPort() resolves to zero.
  
    kj::WaitScope& getWaitScope();
    // Get the `WaitScope` for the client's `EventLoop`, which allows you to synchronously wait on
    // promises.
  
    kj::AsyncIoProvider& getIoProvider();
    // Get the underlying AsyncIoProvider set up by the RPC system.  This is useful if you want
    // to do some non-RPC I/O in asynchronous fashion.
  
    kj::LowLevelAsyncIoProvider& getLowLevelIoProvider();
    // Get the underlying LowLevelAsyncIoProvider set up by the RPC system.  This is useful if you
    // want to do some non-RPC I/O in asynchronous fashion.
  
  private:
    struct Impl;
    kj::Own<Impl> impl;
  };
  
  // =======================================================================================
  // inline implementation details
  
  template <typename Type>
  inline typename Type::Client EzRpcClient::getMain() {
    return getMain().castAs<Type>();
  }
  
  template <typename Type>
  inline typename Type::Client EzRpcClient::importCap(kj::StringPtr name) {
    return importCap(name).castAs<Type>();
  }
  
  }  // namespace capnp
  
  #endif  // CAPNP_EZ_RPC_H_
  