#include "fcgi.h"

#include "fastcgi.h"
#include "socket.h"

#include <boost/algorithm/string/predicate.hpp>
#include <boost/array.hpp>
#include <boost/endian/conversion.hpp>
#include <boost/coroutine2/coroutine.hpp>
#include <boost/process.hpp>

#include <algorithm>
#include <filesystem>
#include <fstream>
#include <iostream>
#include <string>
#include <unordered_map>

using namespace std::string_literals;
namespace bp = boost::process;
namespace fs = std::filesystem;

using boost::asio::ip::tcp;

struct FCGIContext
{
  std::function<std::string(const std::string& key)>& GetServerParam;
  std::function<std::string(const std::string& key)>& GetRequestParam; // request including body (POST...)
  std::function<void(const std::string& key, const std::string& value)>& SetResponseHeader; // to be added to result string

  FCGIContext(std::function<std::string(const std::string& key)>& p_GetServerParam,
             std::function<std::string(const std::string& key)>& p_GetRequestParam,
             std::function<void(const std::string& key, const std::string& value)>& p_SetResponseHeader
             )
   : GetServerParam(p_GetServerParam)
   , GetRequestParam(p_GetRequestParam)
   , SetResponseHeader(p_SetResponseHeader)
 {
 }
};

namespace {

 const std::string gateway_interface{"CGI/1.1"};

 typedef boost::coroutines2::coroutine<std::string> coro_t;

 // returns true iff std::string is empty or contains newline
 bool isEmpty(const std::string& s)
 {
  return s.empty() || s == "\r" || s == "\n"s || s == "\r\n"s;
 }

 void trimLinebreak(std::string& s)
 {
  size_t pos = s.find_last_not_of("\r\n");
  if (pos != s.npos)
   s = s.substr(0, pos + 1);
 }

 std::unordered_map<std::string, std::function<void(std::string&, FCGIContext&)>> headerMap {
  { "CACHE-CONTROL", [](std::string& v, FCGIContext& c){ c.SetResponseHeader("cache_control", v); } },

  { "CONTENT-TYPE", [](std::string& v, FCGIContext& c){ c.SetResponseHeader("content_type", v); } },

  { "SET-COOKIE", [](std::string& v, FCGIContext& c){ c.SetResponseHeader("set_cookie", v); } },
  
  { "STATUS", [](std::string& v, FCGIContext& c) {
      std::string status{"500"};
      if (v.size() >= 3) {
       status = v.substr(0, 3);
      }
      c.SetResponseHeader("status", status);
  } }
 };

 void handleHeader(const std::string& s, FCGIContext& context)
 {
  size_t pos = s.find(": ");
  if (pos == s.npos)
   return;

  std::string key {s.substr(0, pos)};
  std::string value {s.substr(pos + 2)};

  std::transform(key.begin(), key.end(), key.begin(), ::toupper);
  auto it {headerMap.find(key)};
  if (it == headerMap.end())
   std::cout << "Warning: Unhandled CGI header: " << s << std::endl;
  else
   it->second(value, context);
 }

 void setFCGIEnvironment(std::unordered_map<std::string, std::string>& env, FCGIContext& c)
 {
  std::string authorization {c.GetRequestParam("authorization")};
  if (!authorization.empty())
   env["AUTH_TYPE"] = c.GetRequestParam("authorization");

  env["CONTENT_LENGTH"] = c.GetRequestParam("content_length");
  env["CONTENT_TYPE"] = c.GetRequestParam("content_type");
  env["GATEWAY_INTERFACE"] = gateway_interface;

  std::string target {c.GetRequestParam("target")};
  size_t query_pos {target.find("?")};
  std::string query;
  if (query_pos != target.npos) {
   query = target.substr(query_pos + 1);
   target = target.substr(0, query_pos);
  }

  env["PATH_INFO"] = c.GetRequestParam("rel_target");
  env["PATH_TRANSLATED"] = fs::path{c.GetRequestParam("doc_root")} / c.GetRequestParam("rel_target");
  env["QUERY_STRING"] = query;
  env["REMOTE_ADDR"] = "";
  env["REMOTE_HOST"] = "";
  env["REMOTE_IDENT"] = "";
  env["REMOTE_USER"] = "";
  env["REQUEST_METHOD"] = c.GetRequestParam("method");
  env["DOCUMENT_ROOT"] = c.GetRequestParam("doc_root");
  env["DOCUMENT_URI"] = target;
  env["REQUEST_URI"] = target;
  env["SCRIPT_NAME"] = c.GetRequestParam("target");
  env["SCRIPT_FILENAME"] = fs::path{c.GetRequestParam("doc_root")} / c.GetRequestParam("target");
  env["SERVER_NAME"] = c.GetRequestParam("host");
  env["SERVER_PORT"] = c.GetServerParam("port");
  env["SERVER_PROTOCOL"] = c.GetRequestParam("http_version");
  env["SERVER_SOFTWARE"] = c.GetServerParam("version");

  env["HTTP_ACCEPT"] = c.GetRequestParam("http_accept");
  env["HTTP_ACCEPT_CHARSET"] = c.GetRequestParam("http_accept_charset");
  env["HTTP_ACCEPT_ENCODING"] = c.GetRequestParam("http_accept_encoding");
  env["HTTP_ACCEPT_LANGUAGE"] = c.GetRequestParam("http_accept_language");
  env["HTTP_CONNECTION"] = c.GetRequestParam("http_connection");
  env["HTTP_HOST"] = c.GetRequestParam("http_host");
  env["HTTP_USER_AGENT"] = c.GetRequestParam("http_user_agent");
  env["HTTP_REFERER"] = c.GetRequestParam("referer");
  env["HTTP_COOKIE"] = c.GetRequestParam("cookie");
  env["HTTPS"] = c.GetRequestParam("https");
 }

 class FCGI_Record
 {
  std::vector<char> m_data;
 public:
  // create record to send
  FCGI_Record(unsigned char type, uint16_t id, unsigned char arg1, unsigned char arg2)
  {
   if (type == FCGI_BEGIN_REQUEST) {
    size_t size {sizeof(FCGI_BeginRequestRecord)};
    m_data.resize(size, 0);
    FCGI_BeginRequestRecord& r{*reinterpret_cast<FCGI_BeginRequestRecord*>(m_data.data())};
    r.header.version = FCGI_VERSION_1;
    r.header.type = type;
    r.header.requestIdB1 = id >> 8;
    r.header.requestIdB0 = id & 0xFF;
    r.header.contentLengthB1 = sizeof(r.body) >> 8;
    r.header.contentLengthB0 = sizeof(r.body) & 0xFF;
    r.body.roleB1 = 0;
    r.body.roleB0 = arg1;
    r.body.flags = arg2;
   } else
    throw std::runtime_error("Bad FCGI type: "s + std::to_string(type));
  }
  
  // create record to send
  FCGI_Record(unsigned char type, uint16_t id, const std::string& data)
  {
   if (type == FCGI_PARAMS || type == FCGI_STDIN || type == FCGI_GET_VALUES || type == FCGI_DATA) {
    size_t size {sizeof(FCGI_Header) + data.size()};
    m_data.resize(size);
    FCGI_Header& h{*reinterpret_cast<FCGI_Header*>(m_data.data())};
    h.version = FCGI_VERSION_1;
    h.type = type;
    h.requestIdB1 = id >> 8;
    h.requestIdB0 = id & 0xFF;
    h.contentLengthB1 = data.size() >> 8;
    h.contentLengthB0 = data.size() & 0xFF;
    memcpy((void*)&m_data[sizeof(FCGI_Header)], (void*)data.data(), data.size());
   } else
    throw std::runtime_error("Bad FCGI type: "s + std::to_string(type));
  }

  // parse record
  FCGI_Record(std::vector<char>& v, size_t& start_at)
  {
   if (v.size() - start_at < sizeof(FCGI_Header))
    throw std::length_error("No full FCGI header available");

   FCGI_Header& r{*reinterpret_cast<FCGI_Header*>(v.data() + start_at)};
   
   size_t content_length {((size_t)r.contentLengthB1) << 8 | r.contentLengthB0};
   size_t record_size {sizeof(FCGI_Header) + content_length + r.paddingLength};
   if (v.size() - start_at < record_size)
    throw std::length_error("No full FCGI record available");

   m_data = std::vector(v.begin() + start_at, v.begin() + start_at + record_size - r.paddingLength);

   start_at += record_size;
  }

  std::vector<char>& getBuffer()
  {
   return m_data;
  }

  unsigned char getType() { return reinterpret_cast<FCGI_Header*>(m_data.data())->type; }

  std::string getContent()
  {
   if (m_data.size() < sizeof(FCGI_Header))
    throw std::runtime_error("No data available in FCGI_Record: "s + std::to_string(m_data.size()) + " of "s + std::to_string(sizeof(FCGI_Header)) + " bytes"s);
   return std::string(m_data.data() + sizeof(FCGI_Header), m_data.size() - sizeof(FCGI_Header));
  }
 };

 std::string encode_u8(size_t v)
 {
  unsigned char c {static_cast<unsigned char>(v)};
  return std::string(reinterpret_cast<char*>(&c), 1);
 }

 std::string encode_u32(size_t v)
 {
  uint32_t x {static_cast<uint32_t>(v)};
  x |= 0x80000000;
  boost::endian::native_to_big_inplace(x);
  return std::string(reinterpret_cast<char*>(&x), sizeof(x));
 }

 void FCGI_EncodeEnv(const std::unordered_map<std::string, std::string>& map, std::string& s)
 {
  s.clear();

  for (auto&[key, value]: map) {
   if (key.size() > 127)
    s += encode_u32(key.size());
   else
    s += encode_u8(key.size());
   
   if (value.size() > 127)
    s += encode_u32(value.size());
   else
    s += encode_u8(value.size());

   s += key;
   s += value;
  }
 }

 bool decode_size(const std::string& s, size_t& pos, size_t& size)
 {
  uint8_t byte {static_cast<uint8_t>(s[pos])};
  if (byte <= 127) {
   size = byte;
   pos += 1;

  } else {
   if (s.size() < pos + 4) {
    std::cerr << "FCGI Error: Broken FCGI_GET_VALUES data (size)" << std::endl;
    return false;
   }

   uint32_t v {*reinterpret_cast<const uint32_t*>(&s[pos])};
   boost::endian::big_to_native_inplace(v);
   v &= ~0x80000000;
   size = static_cast<size_t>(v);

   pos += 4;
  }

  return true;
 }

 void FCGI_DecodeEnv(const std::string& s, std::unordered_map<std::string, std::string>& map)
 {
  map.clear();

  size_t pos{0};

  while (pos < s.size()) {
   size_t keysize{};
   size_t valuesize{};

   if (!decode_size(s, pos, keysize))
    return;
   if (!decode_size(s, pos, valuesize))
    return;

   if (s.size() < pos + keysize) {
     std::cerr << "FCGI Error: Broken FCGI_GET_VALUES data (key)" << std::endl;
     return;
   }
   std::string key{s.substr(pos, keysize)};
   pos += keysize;
   
   if (s.size() < pos + valuesize) {
     std::cerr << "FCGI Error: Broken FCGI_GET_VALUES data (value) for key " << key << std::endl;
     return;
   }
   std::string value{s.substr(pos, valuesize)};
   pos += valuesize;

   if (map.find(key) != map.end()) {
    std::cerr << "FCGI Warning: Double key in FCGI_GET_VALUES: " << key << std::endl;
   } else {
    map[key] = value;
   }
  }
 }

 // Used to return errors by generating response page and HTTP status code
 std::string HttpStatus(std::string status, std::string message, std::function<plugin_interface_setter_type>& SetResponseHeader)
 {
  SetResponseHeader("status", status);
  SetResponseHeader("content_type", "text/plain");
  return status + " " + message;
 }

} // anonymous namespace

std::string fcgi_plugin::fcgiQuery(FCGIContext& context)
{
 // host:port or unix domain socket
 std::string app_addr{context.GetRequestParam("doc_root")};

 std::string output_data;

 std::unordered_map<std::string, std::string> system_config{{"FCGI_MAX_CONNS", ""}, {"FCGI_MAX_REQS", ""}, {"FCGI_MPXS_CONNS", ""}};
 std::string system_config_bytes;
 FCGI_EncodeEnv(system_config, system_config_bytes);

 std::unordered_map<std::string, std::string> env;
 setFCGIEnvironment(env, context);
 std::string env_bytes;
 FCGI_EncodeEnv(env, env_bytes);

 std::unordered_map<std::string, std::string> app_values; // will be read by FCGI_GET_VALUES

 auto it {m_sockets.find(app_addr)};

 std::shared_ptr<Socket> socket;

 if (it == m_sockets.end()) { // add new element
  socket = m_socket_factory.create(app_addr);

  if (!socket) {
   std::cerr << "FCGI Error: Invalid app_addr." << std::endl;
   return HttpStatus("500", "FCGI configuration", context.SetResponseHeader);
  }

  m_sockets[app_addr] = socket;

 } else { // use already existing element
  socket = it->second;
 }

 bool opening{false};
  
 std::lock_guard<std::mutex> socket_lock{socket->getMutex()};

 if (!socket->is_open()) {
  std::cout << "FCGI: Opening new socket to " << app_addr << std::endl;

  socket->open();
  opening = true;
 }

 if (!socket->is_open()) {
  return HttpStatus("500", "FCGI connection", context.SetResponseHeader);
 }

 FCGI_ID_Guard id_guard(socket->fcgi_id());
 uint16_t id {id_guard.getID()};

 try {
  std::vector<char> buffer;

  if (opening) {
   FCGI_Record get_values{FCGI_GET_VALUES, 0, system_config_bytes};
   buffer.insert(buffer.end(), get_values.getBuffer().begin(), get_values.getBuffer().end());
  }

  FCGI_Record begin_request{FCGI_BEGIN_REQUEST, id, FCGI_RESPONDER, FCGI_KEEP_CONN};
  buffer.insert(buffer.end(), begin_request.getBuffer().begin(), begin_request.getBuffer().end());

  FCGI_Record params{FCGI_PARAMS, id, env_bytes};
  buffer.insert(buffer.end(), params.getBuffer().begin(), params.getBuffer().end());

  if (env_bytes.size()) { 
   FCGI_Record params_end{FCGI_PARAMS, id, std::string{}};
   buffer.insert(buffer.end(), params_end.getBuffer().begin(), params_end.getBuffer().end());
  }

  std::string body {context.GetRequestParam("body")};
  FCGI_Record stdin_{FCGI_STDIN, id, body};
  buffer.insert(buffer.end(), stdin_.getBuffer().begin(), stdin_.getBuffer().end());

  if (body.size()) {
   FCGI_Record stdin_end{FCGI_STDIN, id, std::string{}};
   buffer.insert(buffer.end(), stdin_end.getBuffer().begin(), stdin_end.getBuffer().end());
  }
  
  if (socket->write(buffer) != buffer.size())
   std::cerr << "Warning: Not all bytes written" << std::endl;
 } catch (const fcgi_eof_error&) {
   std::cerr << "FCGI Error: EOF on write" << std::endl; // seems to be ok here
   m_sockets.erase(app_addr); // force new socket next time
   return HttpStatus("500", "FCGI connection: EOF on write", context.SetResponseHeader);
 } catch (const fcgi_broken_pipe_error&) {
   std::cerr << "FCGI Error: Broken pipe on write" << std::endl; // seems to be ok here
   m_sockets.erase(app_addr); // force new socket next time
   return HttpStatus("500", "FCGI connection: Broken pipe on write", context.SetResponseHeader);
 }

#if 0
 FCGI_Record data{FCGI_DATA, id, std::string{}};
 if (socket->write(data.getBuffer()) != data.getBuffer().size())
  std::cerr << "Warning: Not all bytes written 8" << std::endl;
#endif

 std::vector<char> inbuf;
 size_t processed{0};
 
 bool ended{false};
 while (!ended) {
  try {
   socket->read(inbuf);
  } catch (const fcgi_eof_error&) {
   std::cerr << "FCGI Warning: Early EOF from application server. Break." << std::endl; // seems to be ok here
   m_sockets.erase(app_addr); // force new socket next time
   ended = true;
   //return HttpStatus("500", "FCGI connection: EOF on read", context.SetResponseHeader);
  }

  while (inbuf.size() - processed > 0) {
 
   try {
    FCGI_Record r{inbuf, processed};
    if (r.getType() == FCGI_END_REQUEST) {
     ended = true;
    } else if (r.getType() == FCGI_STDOUT) {
     output_data += r.getContent();
    } else if (r.getType() == FCGI_STDERR) {
     std::string msg {r.getContent()};
     if (!msg.empty()) // final FCGI_STDERR sends empty message: ignore
      std::cerr << "FCGI STDERR: " << msg << std::endl;
    } else if (r.getType() == FCGI_GET_VALUES_RESULT) {
     FCGI_DecodeEnv(r.getContent(), app_values);
    } else
     throw std::runtime_error("Unhandled FCGI type: "s + std::to_string(r.getType()));
   } catch (const std::length_error& ex) {
    // ignore FCGI_Record construction if not enough data available for full record yet
    break;
   }
  }
 }

 std::istringstream is_out{output_data};
 std::string line;

 // TODO: C++20 coroutine 
 coro_t::push_type processLine( [&](coro_t::pull_type& in){
                               std::string line;
                               // read header lines
                               while (in && !isEmpty(line = in.get())) {
                                trimLinebreak(line);
                                handleHeader(line, context);
                                in();
                               }
                               
                               // read empty line
                               if (!isEmpty(line))
                                throw std::runtime_error("Missing empty line between CGI header and body");

                               if (in)
                                in();
 });

 do {
  std::getline(is_out, line);
  processLine(line);
 } while (!is_out.eof() && !isEmpty(line));

 std::string r = output_data.substr(is_out.tellg());

 return r;
}

std::string fcgi_plugin::name()
{
 return "fcgi";
}

fcgi_plugin::fcgi_plugin()
{
 //std::cout << "Plugin constructor" << std::endl;
}

fcgi_plugin::~fcgi_plugin()
{
 //std::cout << "Plugin destructor" << std::endl;
}

std::string fcgi_plugin::generate_page(
  std::function<std::string(const std::string& key)>& GetServerParam,
  std::function<std::string(const std::string& key)>& GetRequestParam, // request including body (POST...)
  std::function<void(const std::string& key, const std::string& value)>& SetResponseHeader // to be added to result string
)
{
 try {
  // Request path must not contain "..".
  std::string rel_target{GetRequestParam("rel_target")};
  size_t query_pos{rel_target.find("?")};
  if (query_pos != rel_target.npos)
   rel_target = rel_target.substr(0, query_pos);

  std::string target{GetRequestParam("target")};
  if (rel_target.find("..") != std::string::npos) {
   return HttpStatus("400", "Illegal request: "s + target, SetResponseHeader);
  }

  SetResponseHeader("content_type", "text/html");

  FCGIContext context(GetServerParam, GetRequestParam, SetResponseHeader);

  try {
   return fcgiQuery(context);
  } catch (const std::exception& ex) {
   return HttpStatus("500", "Internal Server Error: "s + ex.what(), SetResponseHeader);
  }

 } catch (const std::exception& ex) {
  return HttpStatus("500", "Unknown Error: "s + ex.what(), SetResponseHeader);
 }
}

bool fcgi_plugin::has_own_authentication()
{
 return false;
}