#ifndef SERVER_HTTP_HPP
#define	SERVER_HTTP_HPP

#include <boost/asio.hpp>
#include <boost/algorithm/string/predicate.hpp>
#include <boost/functional/hash.hpp>

#include <map>
#include <unordered_map>
#include <thread>
#include <functional>
#include <iostream>
#include <sstream>

#ifndef CASE_INSENSITIVE_EQUALS_AND_HASH
#define CASE_INSENSITIVE_EQUALS_AND_HASH
//Based on http://www.boost.org/doc/libs/1_60_0/doc/html/unordered/hash_equality.html
class case_insensitive_equals {
public:
  bool operator()(const std::string &key1, const std::string &key2) const {
    return boost::algorithm::iequals(key1, key2);
  }
};
class case_insensitive_hash {
public:
  size_t operator()(const std::string &key) const {
    std::size_t seed=0;
    for(auto &c: key)
      boost::hash_combine(seed, std::tolower(c));
    return seed;
  }
};
#endif

// Late 2017 TODO: remove the following checks and always use std::regex
#ifdef USE_BOOST_REGEX
#include <boost/regex.hpp>
#define REGEX_NS boost
#else
#include <regex>
#define REGEX_NS std
#endif

// TODO when switching to c++14, use [[deprecated]] instead
#ifndef DEPRECATED
#ifdef __GNUC__
#define DEPRECATED __attribute__((deprecated))
#elif defined(_MSC_VER)
#define DEPRECATED __declspec(deprecated)
#else
#define DEPRECATED
#endif
#endif

namespace SimpleWeb {
    template <class socket_type>
    class Server;
    
    template <class socket_type>
    class ServerBase {
    public:
        virtual ~ServerBase() {}

        class Response : public std::ostream {
            friend class ServerBase<socket_type>;

            boost::asio::streambuf streambuf;

            std::shared_ptr<socket_type> socket;

            Response(const std::shared_ptr<socket_type> &socket): std::ostream(&streambuf), socket(socket) {}

        public:
            size_t size() {
                return streambuf.size();
            }

            /// If true, force server to close the connection after the response have been sent.
            ///
            /// This is useful when implementing a HTTP/1.0-server sending content
            /// without specifying the content length.
            bool close_connection_after_response = false;
        };
        
        class Content : public std::istream {
            friend class ServerBase<socket_type>;
        public:
            size_t size() {
                return streambuf.size();
            }
            std::string string() {
                std::stringstream ss;
                ss << rdbuf();
                return ss.str();
            }
        private:
            boost::asio::streambuf &streambuf;
            Content(boost::asio::streambuf &streambuf): std::istream(&streambuf), streambuf(streambuf) {}
        };
        
        class Request {
            friend class ServerBase<socket_type>;
            friend class Server<socket_type>;
        public:
            std::string method, path, http_version;

            Content content;

            std::unordered_multimap<std::string, std::string, case_insensitive_hash, case_insensitive_equals> header;

            REGEX_NS::smatch path_match;
            
            std::string remote_endpoint_address;
            unsigned short remote_endpoint_port;
            
        private:
            Request(const socket_type &socket): content(streambuf) {
                try {
                    remote_endpoint_address=socket.lowest_layer().remote_endpoint().address().to_string();
                    remote_endpoint_port=socket.lowest_layer().remote_endpoint().port();
                }
                catch(...) {}
            }
            
            boost::asio::streambuf streambuf;
        };
        
        class Config {
            friend class ServerBase<socket_type>;

            Config(unsigned short port): port(port) {}
        public:
            /// Port number to use. Defaults to 80 for HTTP and 443 for HTTPS.
            unsigned short port;
            /// Number of threads that the server will use when start() is called. Defaults to 1 thread.
            size_t thread_pool_size=1;
            /// Timeout on request handling. Defaults to 5 seconds.
            size_t timeout_request=5;
            /// Timeout on content handling. Defaults to 300 seconds.
            size_t timeout_content=300;
            /// IPv4 address in dotted decimal form or IPv6 address in hexadecimal notation.
            /// If empty, the address will be any address.
            std::string address;
            /// Set to false to avoid binding the socket to an address that is already in use. Defaults to true.
            bool reuse_address=true;
        };
        ///Set before calling start().
        Config config;
        
    private:
        class regex_orderable : public REGEX_NS::regex {
            std::string str;
        public:
            regex_orderable(const char *regex_cstr) : REGEX_NS::regex(regex_cstr), str(regex_cstr) {}
            regex_orderable(const std::string &regex_str) : REGEX_NS::regex(regex_str), str(regex_str) {}
            bool operator<(const regex_orderable &rhs) const {
                return str<rhs.str;
            }
        };
    public:
        /// Warning: do not add or remove resources after start() is called
        std::map<regex_orderable, std::map<std::string,
            std::function<void(std::shared_ptr<typename ServerBase<socket_type>::Response>, std::shared_ptr<typename ServerBase<socket_type>::Request>)> > > resource;
        
        std::map<std::string,
            std::function<void(std::shared_ptr<typename ServerBase<socket_type>::Response>, std::shared_ptr<typename ServerBase<socket_type>::Request>)> > default_resource;
        
        std::function<void(std::shared_ptr<typename ServerBase<socket_type>::Request>, const boost::system::error_code&)> on_error;
        
        std::function<void(std::shared_ptr<socket_type> socket, std::shared_ptr<typename ServerBase<socket_type>::Request>)> on_upgrade;
        
        virtual void start() {
            if(!io_service)
                io_service=std::make_shared<boost::asio::io_service>();

            if(io_service->stopped())
                io_service->reset();

            boost::asio::ip::tcp::endpoint endpoint;
            if(config.address.size()>0)
                endpoint=boost::asio::ip::tcp::endpoint(boost::asio::ip::address::from_string(config.address), config.port);
            else
                endpoint=boost::asio::ip::tcp::endpoint(boost::asio::ip::tcp::v4(), config.port);
            
            if(!acceptor)
                acceptor=std::unique_ptr<boost::asio::ip::tcp::acceptor>(new boost::asio::ip::tcp::acceptor(*io_service));
            acceptor->open(endpoint.protocol());
            acceptor->set_option(boost::asio::socket_base::reuse_address(config.reuse_address));
            acceptor->bind(endpoint);
            acceptor->listen();
     
            accept(); 
            
            //If thread_pool_size>1, start m_io_service.run() in (thread_pool_size-1) threads for thread-pooling
            threads.clear();
            for(size_t c=1;c<config.thread_pool_size;c++) {
                threads.emplace_back([this]() {
                    io_service->run();
                });
            }

            //Main thread
            if(config.thread_pool_size>0)
                io_service->run();

            //Wait for the rest of the threads, if any, to finish as well
            for(auto& t: threads) {
                t.join();
            }
        }
        
        void stop() {
            acceptor->close();
            if(config.thread_pool_size>0)
                io_service->stop();
        }
        
        ///Use this function if you need to recursively send parts of a longer message
        void send(const std::shared_ptr<Response> &response, const std::function<void(const boost::system::error_code&)>& callback=nullptr) const {
            boost::asio::async_write(*response->socket, response->streambuf, [this, response, callback](const boost::system::error_code& ec, size_t /*bytes_transferred*/) {
                if(callback)
                    callback(ec);
            });
        }

        /// If you have your own boost::asio::io_service, store its pointer here before running start().
        /// You might also want to set config.thread_pool_size to 0.
        std::shared_ptr<boost::asio::io_service> io_service;
    protected:
        std::unique_ptr<boost::asio::ip::tcp::acceptor> acceptor;
        std::vector<std::thread> threads;
        
        ServerBase(unsigned short port) : config(port) {}
        
        virtual void accept()=0;
        
        std::shared_ptr<boost::asio::deadline_timer> get_timeout_timer(const std::shared_ptr<socket_type> &socket, long seconds) {
            if(seconds==0)
                return nullptr;
            
            auto timer=std::make_shared<boost::asio::deadline_timer>(*io_service);
            timer->expires_from_now(boost::posix_time::seconds(seconds));
            timer->async_wait([socket](const boost::system::error_code& ec){
                if(!ec) {
                    boost::system::error_code ec;
                    socket->lowest_layer().shutdown(boost::asio::ip::tcp::socket::shutdown_both, ec);
                    socket->lowest_layer().close();
                }
            });
            return timer;
        }
        
        void read_request_and_content(const std::shared_ptr<socket_type> &socket) {
            //Create new streambuf (Request::streambuf) for async_read_until()
            //shared_ptr is used to pass temporary objects to the asynchronous functions
            std::shared_ptr<Request> request(new Request(*socket));

            //Set timeout on the following boost::asio::async-read or write function
            auto timer=this->get_timeout_timer(socket, config.timeout_request);
                        
            boost::asio::async_read_until(*socket, request->streambuf, "\r\n\r\n",
                    [this, socket, request, timer](const boost::system::error_code& ec, size_t bytes_transferred) {
                if(timer)
                    timer->cancel();
                if(!ec) {
                    //request->streambuf.size() is not necessarily the same as bytes_transferred, from Boost-docs:
                    //"After a successful async_read_until operation, the streambuf may contain additional data beyond the delimiter"
                    //The chosen solution is to extract lines from the stream directly when parsing the header. What is left of the
                    //streambuf (maybe some bytes of the content) is appended to in the async_read-function below (for retrieving content).
                    size_t num_additional_bytes=request->streambuf.size()-bytes_transferred;
                    
                    if(!this->parse_request(request))
                        return;
                    
                    //If content, read that as well
                    auto it=request->header.find("Content-Length");
                    if(it!=request->header.end()) {
                        unsigned long long content_length;
                        try {
                            content_length=stoull(it->second);
                        }
                        catch(const std::exception &e) {
                            if(on_error)
                                on_error(request, boost::system::error_code(boost::system::errc::protocol_error, boost::system::generic_category()));
                            return;
                        }
                        if(content_length>num_additional_bytes) {
                            //Set timeout on the following boost::asio::async-read or write function
                            auto timer=this->get_timeout_timer(socket, config.timeout_content);
                            boost::asio::async_read(*socket, request->streambuf,
                                    boost::asio::transfer_exactly(content_length-num_additional_bytes),
                                    [this, socket, request, timer]
                                    (const boost::system::error_code& ec, size_t /*bytes_transferred*/) {
                                if(timer)
                                    timer->cancel();
                                if(!ec)
                                    this->find_resource(socket, request);
                                else if(on_error)
                                    on_error(request, ec);
                            });
                        }
                        else
                            this->find_resource(socket, request);
                    }
                    else
                        this->find_resource(socket, request);
                }
                else if(on_error)
                    on_error(request, ec);
            });
        }

        bool parse_request(const std::shared_ptr<Request> &request) const {
            std::string line;
            getline(request->content, line);
            size_t method_end;
            if((method_end=line.find(' '))!=std::string::npos) {
                size_t path_end;
                if((path_end=line.find(' ', method_end+1))!=std::string::npos) {
                    request->method=line.substr(0, method_end);
                    request->path=line.substr(method_end+1, path_end-method_end-1);

                    size_t protocol_end;
                    if((protocol_end=line.find('/', path_end+1))!=std::string::npos) {
                        if(line.compare(path_end+1, protocol_end-path_end-1, "HTTP")!=0)
                            return false;
                        request->http_version=line.substr(protocol_end+1, line.size()-protocol_end-2);
                    }
                    else
                        return false;

                    getline(request->content, line);
                    size_t param_end;
                    while((param_end=line.find(':'))!=std::string::npos) {
                        size_t value_start=param_end+1;
                        if((value_start)<line.size()) {
                            if(line[value_start]==' ')
                                value_start++;
                            if(value_start<line.size())
                                request->header.emplace(line.substr(0, param_end), line.substr(value_start, line.size()-value_start-1));
                        }
    
                        getline(request->content, line);
                    }
                }
                else
                    return false;
            }
            else
                return false;
            return true;
        }

        void find_resource(const std::shared_ptr<socket_type> &socket, const std::shared_ptr<Request> &request) {
            //Upgrade connection
            if(on_upgrade) {
                auto it=request->header.find("Upgrade");
                if(it!=request->header.end()) {
                    on_upgrade(socket, request);
                    return;
                }
            }
            //Find path- and method-match, and call write_response
            for(auto &regex_method: resource) {
                auto it=regex_method.second.find(request->method);
                if(it!=regex_method.second.end()) {
                    REGEX_NS::smatch sm_res;
                    if(REGEX_NS::regex_match(request->path, sm_res, regex_method.first)) {
                        request->path_match=std::move(sm_res);
                        write_response(socket, request, it->second);
                        return;
                    }
                }
            }
            auto it=default_resource.find(request->method);
            if(it!=default_resource.end()) {
                write_response(socket, request, it->second);
            }
        }
        
        void write_response(const std::shared_ptr<socket_type> &socket, const std::shared_ptr<Request> &request, 
                std::function<void(std::shared_ptr<typename ServerBase<socket_type>::Response>,
                                   std::shared_ptr<typename ServerBase<socket_type>::Request>)>& resource_function) {
            //Set timeout on the following boost::asio::async-read or write function
            auto timer=this->get_timeout_timer(socket, config.timeout_content);

            auto response=std::shared_ptr<Response>(new Response(socket), [this, request, timer](Response *response_ptr) {
                auto response=std::shared_ptr<Response>(response_ptr);
                this->send(response, [this, response, request, timer](const boost::system::error_code& ec) {
                    if(timer)
                        timer->cancel();
                    if(!ec) {
                        if (response->close_connection_after_response)
                            return;

                        auto range=request->header.equal_range("Connection");
                        for(auto it=range.first;it!=range.second;it++) {
                            if(boost::iequals(it->second, "close")) {
                                return;
                            } else if (boost::iequals(it->second, "keep-alive")) {
                                this->read_request_and_content(response->socket);
                                return;
                            }
                        }
                        if(request->http_version >= "1.1")
                            this->read_request_and_content(response->socket);
                    }
                    else if(on_error)
                        on_error(request, ec);
                });
            });

            try {
                resource_function(response, request);
            }
            catch(const std::exception &e) {
                if(on_error)
                    on_error(request, boost::system::error_code(boost::system::errc::operation_canceled, boost::system::generic_category()));
                return;
            }
        }
    };
    
    template<class socket_type>
    class Server : public ServerBase<socket_type> {};
    
    typedef boost::asio::ip::tcp::socket HTTP;
    
    template<>
    class Server<HTTP> : public ServerBase<HTTP> {
    public:
        DEPRECATED Server(unsigned short port, size_t thread_pool_size=1, long timeout_request=5, long timeout_content=300) :
                Server() {
            config.port=port;
            config.thread_pool_size=thread_pool_size;
            config.timeout_request=timeout_request;
            config.timeout_content=timeout_content;
        }
        
        Server() : ServerBase<HTTP>::ServerBase(80) {}
        
    protected:
        void accept() {
            //Create new socket for this connection
            //Shared_ptr is used to pass temporary objects to the asynchronous functions
            auto socket=std::make_shared<HTTP>(*io_service);
                        
            acceptor->async_accept(*socket, [this, socket](const boost::system::error_code& ec){
                //Immediately start accepting a new connection (if io_service hasn't been stopped)
                if (ec != boost::asio::error::operation_aborted)
                    accept();
                                
                if(!ec) {
                    boost::asio::ip::tcp::no_delay option(true);
                    socket->set_option(option);
                    
                    this->read_request_and_content(socket);
                }
                else if(on_error)
                    on_error(std::shared_ptr<Request>(new Request(*socket)), ec);
            });
        }
    };
}
#endif	/* SERVER_HTTP_HPP */
