#include "Router.h"

#include <algorithm>
#include <streambuf>
#include <iostream> // Only for warning when handling client error
#include <istream>
#include <ostream>
#include <fstream>
#include <vector>
#include <string>
#include <sstream>
#include <map>

#include "Socket.h"
#include "StringUtil.h"


static std::map<int, const char*> STATUS_STR =
{
	{ 100, "Continue" },
	{ 101, "Switching Protocols" },
	{ 102, "Processing" },
	{ 103, "Early Hints" },
	{ 104, "Upload Resumption Supported" },
	{ 200, "OK" },
	{ 201, "Created" },
	{ 202, "Accepted" },
	{ 203, "Non - Authoritative Information" },
	{ 204, "No Content" },
	{ 205, "Reset Content" },
	{ 206, "Partial Content" },
	{ 207, "Multi - Status" },
	{ 208, "Already Reported" },
	{ 226, "IM Used" },
	{ 300, "Multiple Choices" },
	{ 301, "Moved Permanently" },
	{ 302, "Found" },
	{ 303, "See Other" },
	{ 304, "Not Modified" },
	{ 305, "Use Proxy" },
	{ 306, "Switch Proxy" },
	{ 307, "Temporary Redirect" },
	{ 308, "Permanent Redirect" },
	{ 400, "Bad Request" },
	{ 401, "Unauthorized" },
	{ 402, "Payment Required" },
	{ 403, "Forbidden" },
	{ 404, "Not Found" },
	{ 405, "Method Not Allowed" },
	{ 406, "Not Acceptable" },
	{ 407, "Proxy Authentication Required" },
	{ 408, "Request Timeout" },
	{ 409, "Conflict" },
	{ 410, "Gone" },
	{ 411, "Length Required" },
	{ 412, "Precondition Failed" },
	{ 413, "Content Too Large" },
	{ 414, "URI Too Long" },
	{ 415, "Unsupported Media Type" },
	{ 416, "Range Not Satisfiable" },
	{ 417, "Expectation Failed" },
	{ 418, "I’m a Teapot" },
	{ 421, "Misdirected Request" },
	{ 422, "Unprocessable Content" },
	{ 423, "Locked" },
	{ 424, "Failed Dependency" },
	{ 425, "Too Early" },
	{ 426, "Upgrade Required" },
	{ 427, "Unassigned" },
	{ 428, "Precondition Required" },
	{ 429, "Too Many Requests" },
	{ 430, "Unassigned" },
	{ 431, "Request Header Fields Too Large" },
	{ 451, "Unavailable For Legal Reasons" },
	{ 500, "Internal Server Error" },
	{ 501, "Not Implemented" },
	{ 502, "Bad Gateway" },
	{ 503, "Service Unavailable" },
	{ 504, "Gateway Timeout" },
	{ 505, "HTTP Version Not Supported" },
	{ 506, "Variant Also Negotiates" },
	{ 507, "Insufficient Storage" },
	{ 508, "Loop Detected" },
	{ 509, "Unassigned" },
	{ 510, "Not Extended" },
	{ 511, "Network Authentication Required" },
};


namespace
{
	class ClientError : public std::exception
	{
	public:
		ClientError(const char* what) : std::exception(what)
		{
		}
	};


	class ReqBuf : public std::streambuf
	{
	public:
		ReqBuf(std::istream& stream) : _stream(stream)
		{
			constexpr int header_max = 64;
			constexpr int line_max = 512;

			for (int n = 0;; n++)
			{
				if (n == header_max)
				{
					throw ClientError("Too many headers");
				}

				std::string line;
				line += (char)_stream.get();
				line += (char)_stream.get();
				while (line.substr(line.size() - 2, 2) != "\r\n")
				{
					int byte = _stream.get();
					if (byte == EOF)
					{
						throw ClientError("Connection closed prmaturely");
					}
					if (line.size() > line_max)
					{
						throw ClientError("Header field too long");
					}
					line += (char)byte;
				}

				if (line == "\r\n")
					break;

				line = line.substr(0, line.size() - 2);

				if (n == 0)
				{
					std::vector<std::string> req = StringUtil::splitClean(line, ' ');
					method = req[0];
					url = req[1];
					http_version = req[2];

					std::transform(method.begin(), method.end(), method.begin(), ::toupper);
				}
				else
				{
					size_t sep = line.find(':');
					std::string name = StringUtil::strip(line.substr(0, sep));
					std::string value = StringUtil::strip(line.substr(sep + 1));
					headers[name] = value;
				}
			}
		}

		virtual int underflow()
		{
			return _stream.get();
		}

		std::string method, url, http_version;
		std::map<std::string, std::string> headers;

	private:
		std::istream& _stream;
	};
}


#define buf ((ReqBuf*)rdbuf())
Request::Request(std::istream& stream) : std::istream(new ReqBuf(stream))
{
}

Request::~Request()
{
	delete rdbuf();
}

std::string Request::url() const
{
	return buf->url;
}

std::string Request::method() const
{
	return buf->method;
}

const std::string* Request::header(std::string name) const
{
	auto field = buf->headers.find(name);
	if (field == buf->headers.end())
		return nullptr;
	return &field->second;
}
#undef buf


namespace
{
	class ResBuf : public std::streambuf
	{
	public:
		ResBuf(std::ostream& stream) : _stream(stream)
		{
		}

		void send_head()
		{
			if (head_sent)
				throw std::exception("Head has already been sent");
			head_sent = true;

			_stream
				<< "HTTP/1.1 " << status << ' ' << STATUS_STR[status] << "\r\n";

			for (auto& pair : headers)
				_stream << pair.first << ": " << pair.second << "\r\n";

			_stream << "\r\n";
		}

		int status = 200;
		bool head_sent = false;
		std::map<std::string, std::string> headers = {
			{"Connection", "Close"},
		};

	protected:
		virtual int overflow(int c) override
		{
			if (!head_sent)
				send_head();
			_stream.put(c);
			return c;
		}

		virtual int sync() override
		{
			_stream.flush();
			return 0;
		}

	private:
		std::ostream& _stream;
	};
}


#define buf ((ResBuf*)rdbuf())
Response::Response(std::ostream& stream) : std::ostream(new ResBuf(stream))
{
}

Response::~Response()
{
	delete rdbuf();
}

void Response::status(int status)
{
	buf->status = status;
}

void Response::header(std::string name, std::string value)
{
	if (buf->head_sent)
		throw std::exception("Headers already sent.");
	buf->headers[name] = value;
}

void Response::send(std::string text)
{
	if (buf->headers.find("Content-Type") == buf->headers.end())
		header("Content-Type", "text/plain");
	header("Content-Length", text.size());

	*this << text;

	flush();
}

void Response::send(const void* data, size_t size)
{
	if (buf->headers.find("Content-Type") == buf->headers.end())
		header("Content-Type", "application/octet-stream");
	header("Content-Length", size);

	write((const char*)data, size);

	flush();
}

void Response::sendFile(std::string filename)
{
	std::ifstream fs(filename, std::ifstream::binary | std::ifstream::ate);

	if (!fs.is_open())
		throw std::exception(("Could not open \""+filename+"\"").c_str());

	header("Content-Length", (size_t)fs.tellg());
	fs.seekg(0, std::ifstream::beg);

	*this << fs.rdbuf();

	flush();
}
#undef buf


static void default_404(Request& req, Response& res)
{
	std::stringstream ss;

	ss << "<html>"
		<< "<head>"
		<< "<title>Not Found</title>"
		<< "</head>"
		<< "<body>"
		<< "<h1>Not Found</h1>"
		<< "<p>"
		<< '"' << req.url() << '"'
		<< " could not be found."
		<< "</p>"
		<< "</body>"
		<< "</html>";

	res.status(404);
	res.header("Content-Type", "text/html");
	res.send(ss.str());
}


static void default_500(Request& req, Response& res, std::string msg)
{
	std::stringstream ss;

	ss << "<html>"
		<< "<head>"
		<< "<title>Error</title>"
		<< "</head>"
		<< "<body>"
		<< "<h1>Error</h1>"
		<< "<p>"
		<< msg
		<< "</p>"
		<< "</body>"
		<< "</html>";

	res.status(500);
	res.header("Content-Type", "text/html");
	res.send(ss.str());
}


Router::Router()
{
}


void Router::handle(std::istream& req_s, std::ostream& res_s)
{
	Request req(req_s);
	Response res(res_s);

	auto f = _handlers.find(req.url());

	if (f == _handlers.end())
	{
		default_404(req, res);
		return;
	}
	else
	{
		std::vector<Handler>& handlers = f->second;
		auto h = handlers.begin();

		jmp_buf next;
		setjmp(next);

		if (h == handlers.end())
		{
			default_404(req, res);
			return;
		}
		else
		{
			try
			{
				(*h)(req, res, [&]() { h += 1; longjmp(next, 0); });
			}
			catch (std::exception& ex)
			{
				default_500(req, res, std::string(ex.what()));
			}
			catch (std::string& str)
			{
				default_500(req, res, str);
			}
			catch (const char* str)
			{
				default_500(req, res, std::string(str));
			}
			catch (...)
			{
				default_500(req, res, "Unhandeled exception has accrued");
			}
		}
	}
}


void Router::on(std::string url, Handler handler)
{
	// if vector already existed it is returned.
	// If not, a new one is created and returned.
	auto pair = _handlers.emplace(std::piecewise_construct, std::make_tuple(url), std::make_tuple());

	// First is the key-value pair iterator,
	// second is true if new vector was created.
	auto& iter = pair.first;

	iter
		// First is the key, second is the vector.
		->second
		.push_back(handler);
}

void Router::on_get(std::string url, Handler handler)
{
	on(url, [=](Request& req, Response& res, Next next) { if (req.method() == "GET") handler(req, res, next); else next(); });
}

void Router::on_head(std::string url, Handler handler)
{
	on(url, [=](Request& req, Response& res, Next next) { if (req.method() == "HEAD") handler(req, res, next); else next(); });
}

void Router::on_options(std::string url, Handler handler)
{
	on(url, [=](Request& req, Response& res, Next next) { if (req.method() == "OPTIONS") handler(req, res, next); else next(); });
}

void Router::on_trace(std::string url, Handler handler)
{
	on(url, [=](Request& req, Response& res, Next next) { if (req.method() == "TRACE") handler(req, res, next); else next(); });
}

void Router::on_put(std::string url, Handler handler)
{
	on(url, [=](Request& req, Response& res, Next next) { if (req.method() == "PUT") handler(req, res, next); else next(); });
}

void Router::on_delete(std::string url, Handler handler)
{
	on(url, [=](Request& req, Response& res, Next next) { if (req.method() == "DELETE") handler(req, res, next); else next(); });
}

void Router::on_post(std::string url, Handler handler)
{
	on(url, [=](Request& req, Response& res, Next next) { if (req.method() == "POST") handler(req, res, next); else next(); });
}

void Router::on_patch(std::string url, Handler handler)
{
	on(url, [=](Request& req, Response& res, Next next) { if (req.method() == "PATCH") handler(req, res, next); else next(); });
}

void Router::on_connect(std::string url, Handler handler)
{
	on(url, [=](Request& req, Response& res, Next next) { if (req.method() == "CONNECT") handler(req, res, next); else next(); });
}

void Router::listen(std::string address, short port)
{
	Socket server;
	server.bind(address.c_str(), port);
	server.listen();

	while (true)
	{
		Socket client = server.accept();
		SocketStream stream(client);
		handle(stream, stream);
	}
}

void Router::listen(short port)
{
	Socket server;
	server.bind(port);
	server.listen();

	while (true) try
	{
		Socket client = server.accept();
		SocketStream stream(client);
		handle(stream, stream);
	}
	catch (ClientError& err)
	{
		// Nothing major, ignore
		std::cout << "Client Error: " << err.what() << std::endl;
	}
}