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peerplays-fc/include/fc/rpc/api_connection.hpp
theoreticalbts 5c1bb56177 Implement modular API support 
- Create class `api_base` to be base class of `api<T>`, and `typedef shared_ptr<api_base> api_ptr`
- Create function `api_base::as<T>()` to allow simple downcast to `api<T>`
- Create class `any_api` to contain an API which has been returned from the remote end, but not yet cast with `as<T>`
- `to_generic()` override allowing remote API to return `api_ptr`, thus we need not know the type of the returned API at compile time
- Allow API's to be referenced by name, if we call with a string API name in the JSON the framework calls get_api_by_name on API 1 to determine the API ID
2016-04-04 00:50:56 -04:00

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#pragma once
#include <fc/variant.hpp>
#include <fc/optional.hpp>
#include <fc/api.hpp>
#include <fc/any.hpp>
#include <memory>
#include <vector>
#include <functional>
#include <utility>
#include <fc/signals.hpp>
//#include <fc/rpc/json_connection.hpp>
namespace fc {
class api_connection;
namespace detail {
template<typename Signature>
class callback_functor
{
public:
typedef typename std::function<Signature>::result_type result_type;
callback_functor( std::weak_ptr< fc::api_connection > con, uint64_t id )
:_callback_id(id),_api_connection(con){}
template<typename... Args>
result_type operator()( Args... args )const;
private:
uint64_t _callback_id;
std::weak_ptr< fc::api_connection > _api_connection;
};
template<typename R, typename Arg0, typename ... Args>
std::function<R(Args...)> bind_first_arg( const std::function<R(Arg0,Args...)>& f, Arg0 a0 )
{
return [=]( Args... args ) { return f( a0, args... ); };
}
template<typename R>
R call_generic( const std::function<R()>& f, variants::const_iterator a0, variants::const_iterator e )
{
return f();
}
template<typename R, typename Arg0, typename ... Args>
R call_generic( const std::function<R(Arg0,Args...)>& f, variants::const_iterator a0, variants::const_iterator e )
{
FC_ASSERT( a0 != e );
return call_generic<R,Args...>( bind_first_arg<R,Arg0,Args...>( f, a0->as< typename std::decay<Arg0>::type >() ), a0+1, e );
}
template<typename R, typename ... Args>
std::function<variant(const fc::variants&)> to_generic( const std::function<R(Args...)>& f )
{
return [=]( const variants& args ) {
return variant( call_generic( f, args.begin(), args.end() ) );
};
}
template<typename ... Args>
std::function<variant(const fc::variants&)> to_generic( const std::function<void(Args...)>& f )
{
return [=]( const variants& args ) {
call_generic( f, args.begin(), args.end() );
return variant();
};
}
/**
* If api<T> is returned from a remote method, the API is eagerly bound to api<T> of
* the correct type in api_visitor::from_variant(). This binding [1] needs a reference
* to the api_connection, which is made available to from_variant() as a parameter.
*
* However, in the case of a remote method which returns api_base which can subsequently
* be cast by the caller with as<T>, we need to keep track of the connection because
* the binding is done later (when the client code actually calls as<T>).
*
* [1] The binding actually happens in get_remote_api().
*/
class any_api : public api_base
{
public:
any_api( api_id_type api_id, const std::shared_ptr<fc::api_connection>& con )
: _api_id(api_id), _api_connection(con) {}
virtual uint64_t get_handle()const override
{ return _api_id; }
virtual api_id_type register_api( api_connection& conn )const override
{ FC_ASSERT( false ); return api_id_type(); }
api_id_type _api_id;
std::weak_ptr<fc::api_connection> _api_connection;
};
} // namespace detail
class generic_api
{
public:
template<typename Api>
generic_api( const Api& a, const std::shared_ptr<fc::api_connection>& c );
generic_api( const generic_api& cpy ) = delete;
variant call( const string& name, const variants& args )
{
auto itr = _by_name.find(name);
FC_ASSERT( itr != _by_name.end(), "no method with name '${name}'", ("name",name)("api",_by_name) );
return call( itr->second, args );
}
variant call( uint32_t method_id, const variants& args )
{
FC_ASSERT( method_id < _methods.size() );
return _methods[method_id](args);
}
std::weak_ptr< fc::api_connection > get_connection()
{
return _api_connection;
}
std::vector<std::string> get_method_names()const
{
std::vector<std::string> result;
result.reserve( _by_name.size() );
for( auto& m : _by_name ) result.push_back(m.first);
return result;
}
private:
friend struct api_visitor;
template<typename R, typename Arg0, typename ... Args>
std::function<R(Args...)> bind_first_arg( const std::function<R(Arg0,Args...)>& f, Arg0 a0 )const
{
return [=]( Args... args ) { return f( a0, args... ); };
}
template<typename R>
R call_generic( const std::function<R()>& f, variants::const_iterator a0, variants::const_iterator e )const
{
return f();
}
template<typename R, typename Signature, typename ... Args>
R call_generic( const std::function<R(std::function<Signature>,Args...)>& f, variants::const_iterator a0, variants::const_iterator e )
{
FC_ASSERT( a0 != e, "too few arguments passed to method" );
detail::callback_functor<Signature> arg0( get_connection(), a0->as<uint64_t>() );
return call_generic<R,Args...>( this->bind_first_arg<R,std::function<Signature>,Args...>( f, std::function<Signature>(arg0) ), a0+1, e );
}
template<typename R, typename Signature, typename ... Args>
R call_generic( const std::function<R(const std::function<Signature>&,Args...)>& f, variants::const_iterator a0, variants::const_iterator e )
{
FC_ASSERT( a0 != e, "too few arguments passed to method" );
detail::callback_functor<Signature> arg0( get_connection(), a0->as<uint64_t>() );
return call_generic<R,Args...>( this->bind_first_arg<R,const std::function<Signature>&,Args...>( f, arg0 ), a0+1, e );
}
template<typename R, typename Arg0, typename ... Args>
R call_generic( const std::function<R(Arg0,Args...)>& f, variants::const_iterator a0, variants::const_iterator e )
{
FC_ASSERT( a0 != e, "too few arguments passed to method" );
return call_generic<R,Args...>( this->bind_first_arg<R,Arg0,Args...>( f, a0->as< typename std::decay<Arg0>::type >() ), a0+1, e );
}
struct api_visitor
{
api_visitor( generic_api& a, const std::weak_ptr<fc::api_connection>& s ):api(a),_api_con(s){ }
template<typename Interface, typename Adaptor, typename ... Args>
std::function<variant(const fc::variants&)> to_generic( const std::function<api<Interface,Adaptor>(Args...)>& f )const;
template<typename Interface, typename Adaptor, typename ... Args>
std::function<variant(const fc::variants&)> to_generic( const std::function<fc::optional<api<Interface,Adaptor>>(Args...)>& f )const;
template<typename ... Args>
std::function<variant(const fc::variants&)> to_generic( const std::function<fc::api_ptr(Args...)>& f )const;
template<typename R, typename ... Args>
std::function<variant(const fc::variants&)> to_generic( const std::function<R(Args...)>& f )const;
template<typename ... Args>
std::function<variant(const fc::variants&)> to_generic( const std::function<void(Args...)>& f )const;
template<typename Result, typename... Args>
void operator()( const char* name, std::function<Result(Args...)>& memb )const {
api._methods.emplace_back( to_generic( memb ) );
api._by_name[name] = api._methods.size() - 1;
}
generic_api& api;
const std::weak_ptr<fc::api_connection>& _api_con;
};
std::weak_ptr<fc::api_connection> _api_connection;
fc::any _api;
std::map< std::string, uint32_t > _by_name;
std::vector< std::function<variant(const variants&)> > _methods;
}; // class generic_api
class api_connection : public std::enable_shared_from_this<fc::api_connection>
{
public:
api_connection(){}
virtual ~api_connection(){};
template<typename T>
api<T> get_remote_api( api_id_type api_id = 0 )
{
api<T> result;
result->visit( api_visitor( api_id, this->shared_from_this() ) );
return result;
}
/** makes calls to the remote server */
virtual variant send_call( api_id_type api_id, string method_name, variants args = variants() ) = 0;
virtual variant send_callback( uint64_t callback_id, variants args = variants() ) = 0;
virtual void send_notice( uint64_t callback_id, variants args = variants() ) = 0;
variant receive_call( api_id_type api_id, const string& method_name, const variants& args = variants() )const
{
FC_ASSERT( _local_apis.size() > api_id );
return _local_apis[api_id]->call( method_name, args );
}
variant receive_callback( uint64_t callback_id, const variants& args = variants() )const
{
FC_ASSERT( _local_callbacks.size() > callback_id );
return _local_callbacks[callback_id]( args );
}
void receive_notice( uint64_t callback_id, const variants& args = variants() )const
{
FC_ASSERT( _local_callbacks.size() > callback_id );
_local_callbacks[callback_id]( args );
}
template<typename Interface>
api_id_type register_api( const Interface& a )
{
auto handle = a.get_handle();
auto itr = _handle_to_id.find(handle);
if( itr != _handle_to_id.end() ) return itr->second;
_local_apis.push_back( std::unique_ptr<generic_api>( new generic_api(a, shared_from_this() ) ) );
_handle_to_id[handle] = _local_apis.size() - 1;
return _local_apis.size() - 1;
}
template<typename Signature>
uint64_t register_callback( const std::function<Signature>& cb )
{
_local_callbacks.push_back( detail::to_generic( cb ) );
return _local_callbacks.size() - 1;
}
std::vector<std::string> get_method_names( api_id_type local_api_id = 0 )const { return _local_apis[local_api_id]->get_method_names(); }
fc::signal<void()> closed;
private:
std::vector< std::unique_ptr<generic_api> > _local_apis;
std::map< uint64_t, api_id_type > _handle_to_id;
std::vector< std::function<variant(const variants&)> > _local_callbacks;
struct api_visitor
{
uint32_t _api_id;
std::shared_ptr<fc::api_connection> _connection;
api_visitor( uint32_t api_id, std::shared_ptr<fc::api_connection> con )
:_api_id(api_id),_connection(std::move(con))
{
}
api_visitor() = delete;
template<typename Result>
static Result from_variant( const variant& v, Result*, const std::shared_ptr<fc::api_connection>& )
{
return v.as<Result>();
}
template<typename ResultInterface>
static fc::api<ResultInterface> from_variant( const variant& v,
fc::api<ResultInterface>* /*used for template deduction*/,
const std::shared_ptr<fc::api_connection>& con
)
{
return con->get_remote_api<ResultInterface>( v.as_uint64() );
}
static fc::api_ptr from_variant(
const variant& v,
fc::api_ptr* /* used for template deduction */,
const std::shared_ptr<fc::api_connection>& con
)
{
return fc::api_ptr( new detail::any_api( v.as_uint64(), con ) );
}
template<typename T>
static fc::variant convert_callbacks( const std::shared_ptr<fc::api_connection>&, const T& v )
{
return fc::variant(v);
}
template<typename Signature>
static fc::variant convert_callbacks( const std::shared_ptr<fc::api_connection>& con, const std::function<Signature>& v )
{
return con->register_callback( v );
}
template<typename Result, typename... Args>
void operator()( const char* name, std::function<Result(Args...)>& memb )const
{
auto con = _connection;
auto api_id = _api_id;
memb = [con,api_id,name]( Args... args ) {
auto var_result = con->send_call( api_id, name, { convert_callbacks(con,args)...} );
return from_variant( var_result, (Result*)nullptr, con );
};
}
template<typename... Args>
void operator()( const char* name, std::function<void(Args...)>& memb )const
{
auto con = _connection;
auto api_id = _api_id;
memb = [con,api_id,name]( Args... args ) {
con->send_call( api_id, name, { convert_callbacks(con,args)...} );
};
}
};
};
class local_api_connection : public api_connection
{
public:
/** makes calls to the remote server */
virtual variant send_call( api_id_type api_id, string method_name, variants args = variants() ) override
{
FC_ASSERT( _remote_connection );
return _remote_connection->receive_call( api_id, method_name, std::move(args) );
}
virtual variant send_callback( uint64_t callback_id, variants args = variants() ) override
{
FC_ASSERT( _remote_connection );
return _remote_connection->receive_callback( callback_id, args );
}
virtual void send_notice( uint64_t callback_id, variants args = variants() ) override
{
FC_ASSERT( _remote_connection );
_remote_connection->receive_notice( callback_id, args );
}
void set_remote_connection( const std::shared_ptr<fc::api_connection>& rc )
{
FC_ASSERT( !_remote_connection );
FC_ASSERT( rc != this->shared_from_this() );
_remote_connection = rc;
}
const std::shared_ptr<fc::api_connection>& remote_connection()const { return _remote_connection; }
std::shared_ptr<fc::api_connection> _remote_connection;
};
template<typename Api>
generic_api::generic_api( const Api& a, const std::shared_ptr<fc::api_connection>& c )
:_api_connection(c),_api(a)
{
boost::any_cast<const Api&>(a)->visit( api_visitor( *this, c ) );
}
template<typename Interface, typename Adaptor, typename ... Args>
std::function<variant(const fc::variants&)> generic_api::api_visitor::to_generic(
const std::function<fc::api<Interface,Adaptor>(Args...)>& f )const
{
auto api_con = _api_con;
auto gapi = &api;
return [=]( const variants& args ) {
auto con = api_con.lock();
FC_ASSERT( con, "not connected" );
auto api_result = gapi->call_generic( f, args.begin(), args.end() );
return con->register_api( api_result );
};
}
template<typename Interface, typename Adaptor, typename ... Args>
std::function<variant(const fc::variants&)> generic_api::api_visitor::to_generic(
const std::function<fc::optional<fc::api<Interface,Adaptor>>(Args...)>& f )const
{
auto api_con = _api_con;
auto gapi = &api;
return [=]( const variants& args )-> fc::variant {
auto con = api_con.lock();
FC_ASSERT( con, "not connected" );
auto api_result = gapi->call_generic( f, args.begin(), args.end() );
if( api_result )
return con->register_api( *api_result );
return variant();
};
}
template<typename ... Args>
std::function<variant(const fc::variants&)> generic_api::api_visitor::to_generic(
const std::function<fc::api_ptr(Args...)>& f )const
{
auto api_con = _api_con;
auto gapi = &api;
return [=]( const variants& args ) -> fc::variant {
auto con = api_con.lock();
FC_ASSERT( con, "not connected" );
auto api_result = gapi->call_generic( f, args.begin(), args.end() );
if( !api_result )
return variant();
return api_result->register_api( *con );
};
}
template<typename R, typename ... Args>
std::function<variant(const fc::variants&)> generic_api::api_visitor::to_generic( const std::function<R(Args...)>& f )const
{
generic_api* gapi = &api;
return [f,gapi]( const variants& args ) {
return variant( gapi->call_generic( f, args.begin(), args.end() ) );
};
}
template<typename ... Args>
std::function<variant(const fc::variants&)> generic_api::api_visitor::to_generic( const std::function<void(Args...)>& f )const
{
generic_api* gapi = &api;
return [f,gapi]( const variants& args ) {
gapi->call_generic( f, args.begin(), args.end() );
return variant();
};
}
/**
* It is slightly unclean tight coupling to have this method in the api class.
* It breaks encapsulation by requiring an api class method to have a pointer
* to an api_connection. The reason this is necessary is we have a goal of being
* able to call register_api() on an api<T> through its base class api_base. But
* register_api() must know the template parameters!
*
* The only reasonable way to achieve the goal is to implement register_api()
* as a method in api<T> (which obviously knows the template parameter T),
* then make the implementation accessible through the base class (by making
* it a pure virtual method in the base class which is overridden by the subclass's
* implementation).
*/
template< typename Interface, typename Transform >
api_id_type api< Interface, Transform >::register_api( api_connection& conn )const
{
return conn.register_api( *this );
}
template< typename T >
api<T> api_base::as()
{
// TODO: this method should probably be const (if it is not too hard)
api<T>* maybe_requested_type = dynamic_cast< api<T>* >(this);
if( maybe_requested_type != nullptr )
return *maybe_requested_type;
detail::any_api* maybe_any = dynamic_cast< detail::any_api* >(this);
FC_ASSERT( maybe_any != nullptr );
std::shared_ptr< api_connection > api_conn = maybe_any->_api_connection.lock();
FC_ASSERT( api_conn );
return api_conn->get_remote_api<T>( maybe_any->_api_id );
}
namespace detail {
template<typename Signature>
template<typename... Args>
typename callback_functor<Signature>::result_type callback_functor<Signature>::operator()( Args... args )const
{
std::shared_ptr< fc::api_connection > locked = _api_connection.lock();
// TODO: make new exception type for this instead of recycling eof_exception
if( !locked )
throw fc::eof_exception();
locked->send_callback( _callback_id, fc::variants{ args... } ).template as< result_type >();
}
template<typename... Args>
class callback_functor<void(Args...)>
{
public:
typedef void result_type;
callback_functor( std::weak_ptr< fc::api_connection > con, uint64_t id )
:_callback_id(id),_api_connection(con){}
void operator()( Args... args )const
{
std::shared_ptr< fc::api_connection > locked = _api_connection.lock();
// TODO: make new exception type for this instead of recycling eof_exception
if( !locked )
throw fc::eof_exception();
locked->send_notice( _callback_id, fc::variants{ args... } );
}
private:
uint64_t _callback_id;
std::weak_ptr< fc::api_connection > _api_connection;
};
} // namespace detail
} // fc
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