From c89cafa820ec02f041c3b0e52877bc321f6a1ba9 Mon Sep 17 00:00:00 2001
From: ipknHama <ipknhama@gmail.com>
Date: Sun, 7 Sep 2014 01:24:45 +0900
Subject: add Middlewares template to Crow main class, context implementation

---
 examples/example.cpp         |  2 +-
 examples/example_chat.cpp    |  2 +-
 include/crow.h               | 19 +++++++++++-
 include/http_request.h       |  2 ++
 include/middleware.h         | 50 ++++++++++++++++++++++++++++++
 include/middleware_context.h | 32 +++++++++++++++++++
 include/utility.h            | 73 ++++++++++++++++++++++++++++++++++++++++++++
 tests/unittest.cpp           | 14 ++++-----
 8 files changed, 184 insertions(+), 10 deletions(-)
 create mode 100644 include/middleware.h
 create mode 100644 include/middleware_context.h

diff --git a/examples/example.cpp b/examples/example.cpp
index b8e58f8..b360adb 100644
--- a/examples/example.cpp
+++ b/examples/example.cpp
@@ -12,7 +12,7 @@ class ExampleLogHandler : public crow::ILogHandler {
 
 int main()
 {
-    crow::Crow app;
+    crow::SimpleApp app;
 
     CROW_ROUTE(app, "/")
         .name("hello")
diff --git a/examples/example_chat.cpp b/examples/example_chat.cpp
index b12926a..31f16c5 100644
--- a/examples/example_chat.cpp
+++ b/examples/example_chat.cpp
@@ -28,7 +28,7 @@ void broadcast(const string& msg)
 
 int main()
 {
-    crow::App app;
+    crow::SimpleApp app;
     crow::mustache::set_base(".");
 
     CROW_ROUTE(app, "/")
diff --git a/include/crow.h b/include/crow.h
index 55572bf..a018f31 100644
--- a/include/crow.h
+++ b/include/crow.h
@@ -13,6 +13,8 @@
 #include "http_server.h"
 #include "utility.h"
 #include "routing.h"
+#include "middleware_impl.h"
+#include "http_request.h"
 
 // TEST
 #include <iostream>
@@ -21,6 +23,7 @@
 
 namespace crow
 {
+    template <typename ... Middlewares>
     class Crow
     {
     public:
@@ -78,12 +81,26 @@ namespace crow
             router_.debug_print();
         }
 
+        // middleware
+        using context_t = detail::context<Middlewares...>;
+        template <typename T>
+        T& get_middleware_context(request& req)
+        {
+            static_assert(black_magic::contains<T, Middlewares...>::value, "App doesn't have the specified middleware type.");
+            auto& ctx = *reinterpret_cast<context_t*>(req.middleware_context);
+            return ctx.get<T>();
+        }
+
     private:
         uint16_t port_ = 80;
         uint16_t concurrency_ = 1;
 
+        std::tuple<Middlewares...> middlewares_;
+
         Router router_;
     };
-    using App = Crow;
+    template <typename ... Middlewares>
+    using App = Crow<Middlewares...>;
+    using SimpleApp = Crow<>;
 };
 
diff --git a/include/http_request.h b/include/http_request.h
index 83b6059..77b3ecb 100644
--- a/include/http_request.h
+++ b/include/http_request.h
@@ -10,5 +10,7 @@ namespace crow
         std::string url;
         std::unordered_map<std::string, std::string> headers;
         std::string body;
+
+        void* middleware_context;
     };
 }
diff --git a/include/middleware.h b/include/middleware.h
new file mode 100644
index 0000000..270e026
--- /dev/null
+++ b/include/middleware.h
@@ -0,0 +1,50 @@
+#pragma once
+#include "http_request.h"
+#include "http_response.h"
+
+namespace crow
+{
+    class CookieParser
+    {
+        struct context
+        {
+            std::unordered_map<std::string, std::string> jar;
+        };
+
+        template <typename AllContext>
+        void before_handle(request& req, response& res, context& ctx, AllContext& all_ctx)
+        {
+            // ctx == all_ctx.bind<CookieParser>()
+            // ctx.jar[] = ;
+        }
+
+        template <typename AllContext>
+        void after_handle(request& req, response& res, context& ctx, AllContext& all_ctx)
+        {
+        }
+    }
+
+    /*
+    App<CookieParser, AnotherJarMW> app;
+    A B C
+    A::context
+        int aa;
+
+    ctx1 : public A::context
+    ctx2 : public ctx1, public B::context
+    ctx3 : public ctx2, public C::context
+
+    C depends on A
+
+    C::handle
+        context.aaa
+
+    App::context : private CookieParser::contetx, ... 
+    {
+        jar
+
+    }
+
+    SimpleApp
+    */
+}
diff --git a/include/middleware_context.h b/include/middleware_context.h
new file mode 100644
index 0000000..6dbf923
--- /dev/null
+++ b/include/middleware_context.h
@@ -0,0 +1,32 @@
+#pragma once
+
+#include "utility.h"
+
+namespace crow
+{
+    namespace detail
+    {
+        template <typename ... Middlewares>
+        struct partial_context
+            : public black_magic::pop_back<Middlewares...>::template rebind<partial_context>
+            , public black_magic::last_element_type<Middlewares...>::type::context
+        {
+        };
+
+        template <>
+        struct partial_context<>
+        {
+        };
+
+        template <typename ... Middlewares>
+        struct context : private partial_context<Middlewares...>
+        //struct context : private Middlewares::context... // simple but less type-safe
+        {
+            template <typename T> 
+            typename T::context& get()
+            {
+                return static_cast<typename T::context&>(*this);
+            }
+        };
+    }
+}
diff --git a/include/utility.h b/include/utility.h
index a46d577..35ea848 100644
--- a/include/utility.h
+++ b/include/utility.h
@@ -2,6 +2,8 @@
 
 #include <cstdint>
 #include <stdexcept>
+#include <tuple>
+#include <type_traits>
 
 namespace crow
 {
@@ -211,5 +213,76 @@ template <typename F, typename Set>
             using type = S<>;
         };
 
+        template <typename ... T>
+        struct last_element_type
+        {
+            using type = typename std::tuple_element<sizeof...(T)-1, std::tuple<T...>>::type;
+        };
+
+
+        template <>
+        struct last_element_type<>
+        {
+        };
+
+
+        // from http://stackoverflow.com/questions/13072359/c11-compile-time-array-with-logarithmic-evaluation-depth
+        template<class T> using Invoke = typename T::type;
+
+        template<unsigned...> struct seq{ using type = seq; };
+
+        template<class S1, class S2> struct concat;
+
+        template<unsigned... I1, unsigned... I2>
+        struct concat<seq<I1...>, seq<I2...>>
+          : seq<I1..., (sizeof...(I1)+I2)...>{};
+
+        template<class S1, class S2>
+        using Concat = Invoke<concat<S1, S2>>;
+
+        template<unsigned N> struct gen_seq;
+        template<unsigned N> using GenSeq = Invoke<gen_seq<N>>;
+
+        template<unsigned N>
+        struct gen_seq : Concat<GenSeq<N/2>, GenSeq<N - N/2>>{};
+
+        template<> struct gen_seq<0> : seq<>{};
+        template<> struct gen_seq<1> : seq<0>{};
+
+        template <typename Seq, typename Tuple> 
+        struct pop_back_helper;
+
+        template <unsigned ... N, typename Tuple>
+        struct pop_back_helper<seq<N...>, Tuple>
+        {
+            template <template <typename ... Args> class U>
+            using rebind = U<std::tuple_element<N, Tuple>...>;
+        };
+
+        template <typename ... T>
+        struct pop_back : public pop_back_helper<typename gen_seq<sizeof...(T)-1>::type, std::tuple<T...>>
+        {
+        };
+
+        template <>
+        struct pop_back<>
+        {
+            template <template <typename ... Args> class U>
+            using rebind = U<>;
+        };
+
+        // from http://stackoverflow.com/questions/2118541/check-if-c0x-parameter-pack-contains-a-type
+        template < typename Tp, typename... List >
+        struct contains : std::true_type {};
+
+        template < typename Tp, typename Head, typename... Rest >
+        struct contains<Tp, Head, Rest...>
+        : std::conditional< std::is_same<Tp, Head>::value,
+            std::true_type,
+            contains<Tp, Rest...>
+        >::type {};
+
+        template < typename Tp >
+        struct contains<Tp> : std::false_type {};
 	}
 }
diff --git a/tests/unittest.cpp b/tests/unittest.cpp
index 918d027..17bc53c 100644
--- a/tests/unittest.cpp
+++ b/tests/unittest.cpp
@@ -112,7 +112,7 @@ TEST(ParameterTagging)
 
 TEST(RoutingTest)
 {
-    Crow app;
+    SimpleApp app;
     int A{};
     uint32_t B{};
     double C{};
@@ -238,7 +238,7 @@ TEST(simple_response_routing_params)
 
 TEST(handler_with_response)
 {
-    Crow app;
+    SimpleApp app;
     CROW_ROUTE(app, "/")([](const crow::request&, crow::response&)
     {
     });
@@ -247,9 +247,9 @@ TEST(handler_with_response)
 TEST(server_handling_error_request)
 {
     static char buf[2048];
-    Crow app;
+    SimpleApp app;
     CROW_ROUTE(app, "/")([]{return "A";});
-    Server<Crow> server(&app, 45451);
+    Server<SimpleApp> server(&app, 45451);
     auto _ = async(launch::async, [&]{server.run();});
     std::string sendmsg = "POX";
     asio::io_service is;
@@ -276,12 +276,12 @@ TEST(server_handling_error_request)
 TEST(multi_server)
 {
     static char buf[2048];
-    Crow app1, app2;
+    SimpleApp app1, app2;
     CROW_ROUTE(app1, "/")([]{return "A";});
     CROW_ROUTE(app2, "/")([]{return "B";});
 
-    Server<Crow> server1(&app1, 45451);
-    Server<Crow> server2(&app2, 45452);
+    Server<SimpleApp> server1(&app1, 45451);
+    Server<SimpleApp> server2(&app2, 45452);
 
     auto _ = async(launch::async, [&]{server1.run();});
     auto _2 = async(launch::async, [&]{server2.run();});
-- 
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