#include "cgi.h"

#include "libcommon/mime.h"

#include <boost/algorithm/string/predicate.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;

namespace {

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

 struct CGIContext
 {
   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
   fs::path& path;
   fs::path& file_path;
   fs::path& path_info;

   CGIContext(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,
              fs::path& p_path,
              fs::path& p_file_path,
              fs::path& p_path_info
              )
    : GetServerParam(p_GetServerParam)
    , GetRequestParam(p_GetRequestParam)
    , SetResponseHeader(p_SetResponseHeader)
    , path(p_path)
    , file_path(p_file_path)
    , path_info(p_path_info)
  {
  }
 };

 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&, CGIContext&)>> headerMap {
  { "CACHE-CONTROL", [](std::string& v, CGIContext& c){ c.SetResponseHeader("cache_control", v); } },

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

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

 void handleHeader(const std::string& s, CGIContext& 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 setCGIEnvironment(bp::environment& env, CGIContext& 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.path_info.string();
  env["PATH_TRANSLATED"] = c.path.string();
  env["QUERY_STRING"] = query;
  env["REMOTE_ADDR"] = "";
  env["REMOTE_HOST"] = "";
  env["REMOTE_IDENT"] = "";
  env["REMOTE_USER"] = "";
  env["REQUEST_METHOD"] = c.GetRequestParam("method");
  env["REQUEST_URI"] = target;
  env["SCRIPT_NAME"] = c.file_path;
  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");
 }

 std::string executeFile(CGIContext& context)
 {
  bp::pipe is_in;
  bp::ipstream is_out;

  bp::environment env {boost::this_process::environment()};
  setCGIEnvironment(env, context);

  bp::child child(context.path.string(), env, bp::std_out > is_out, bp::std_err > stderr, bp::std_in < is_in);

  std::string body{ context.GetRequestParam("body") };
  is_in.write(body.data(), body.size());
  is_in.close();

  std::string output;
  std::string line;

  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();

                                // read remainder
                                while (in) {
                                 line = in.get();
                                 output += line + '\n';
                                 in();
                                }

                                throw std::runtime_error("Input missing on processing CGI body");
  });

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

  child.wait();

  return output;
 }

 // 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/html");
  return status + " " + message;
 }

} // anonymous namespace

std::string cgi_plugin::name()
{
 return "cgi";
}

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

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

std::string cgi_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);
  }

  // Build the path to the requested file
  std::string doc_root{GetRequestParam("doc_root")};
  fs::path path {fs::path{doc_root} / rel_target};
  if (target.size() && target.back() != '/' && fs::is_directory(path)) {
   std::string location{GetRequestParam("location") + "/"s};
   SetResponseHeader("location", location);
   return HttpStatus("301", "Correcting directory path", SetResponseHeader);
  }

  fs::path path_info{};
  fs::path file_path{target};
  try {
   // file file name part and separate path_info
   while (!fs::is_regular_file(path) && path != "/" && path != "") {
    if (path_info.string() == "")
     path_info = fs::path{"/"} / path.filename();
    else
     path_info = fs::path{"/"} / path.filename() / path_info.relative_path();

    path = path.parent_path();
    file_path = file_path.parent_path();
   }

   if (!fs::is_regular_file(path)) {
    return HttpStatus("500", "Bad Script: "s + rel_target, SetResponseHeader);
   }
  } catch (const std::exception& ex) {
   return HttpStatus("500", "Bad file access: "s + rel_target, SetResponseHeader);
  }

  try {
   if ((fs::status(path).permissions() & fs::perms::others_exec) == fs::perms::none) {
     return HttpStatus("500", "Script not executable: "s + rel_target, SetResponseHeader);
   }
  } catch (const std::exception& ex) {
    return HttpStatus("500", "Bad file status access: "s + rel_target, SetResponseHeader);
  }

  SetResponseHeader("content_type", mime_type(path.string()));

  CGIContext context(GetServerParam, GetRequestParam, SetResponseHeader, path, file_path, path_info);

  try {
   return executeFile(context);
  } catch (const std::runtime_error& ex) {
   return HttpStatus("404", "Not found: "s + GetRequestParam("target"), SetResponseHeader);
  } 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 cgi_plugin::has_own_authentication()
{
 return false;
}