#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <dirent.h>
#include <sys/types.h>
#include <fcgiapp.h>

#include <iostream>
#include <functional>
#include <filesystem>
#include <random>
#include <regex>
#include <string>
#include <unordered_map>

#include <boost/algorithm/string/predicate.hpp>
#include <boost/algorithm/string/trim.hpp>
#include <boost/property_tree/xml_parser.hpp>

#include <ImageMagick-6/Magick++.h>

#include "config.h"
#include "file.h"
#include "qrcode.h"

namespace pt = boost::property_tree;
using namespace std::string_literals;
namespace fs = std::filesystem;

namespace {

 uint32_t checksum32(const std::string& s)
 {
  uint32_t result{0};
  for (int i = 0; i < s.size(); i++) {
   result = ((result >> 1) | ((result & 1) << 31)) ^ (s[i] & 0xFF);
  }
  return result & 0x7FFFFFFF;
 }

 fs::path data_path;

 std::string generate_id()
 {
  static std::random_device r;
  static std::default_random_engine e1(r());
  static std::uniform_int_distribution<int> uniform_dist(0, 15);

  // limit tries
  for (int j = 0; j < 100000; j++) {
   std::string result;
   for (int i = 0; i < 6; i++) {
    char c{static_cast<char>('0' + uniform_dist(e1))};
    if (c > '9')
     c = c - '9' + 'a';
    result.push_back(c);
   }
   fs::path path{data_path / result};

   if (!fs::exists(path))
   return result;
  }

  return "endofcodes";
 }

 void setFileById(const std::string& data, const std::string& id)
 {
  fs::path path{data_path / id};
 
  // skip if it doesn't exists 
  if (data.empty() && !fs::exists(path))
   return;

  // clean up immediately, if appropriate
  if (data.empty()) {
   fs::remove(path);
   return;
  }

  File::setFile(path, data);
 }

 std::string getFileById(const std::string& id)
 {
  fs::path path{data_path / id};

  if (!fs::exists(path))
   return {};

  return File::getFile(path);
 }
}

int main(void)
{
 Config config;
 data_path = config.getDataPath();

 Magick::InitializeMagick(NULL); // for qrcode.cpp

 int result = FCGX_Init();
 if (result != 0) { // error on init
  fprintf(stderr, "Error: FCGX_Init()\n");
  return 1;
 }

 result = FCGX_IsCGI();
 if (result) {
  fprintf(stderr, "Error: No FCGI environment available.\n");
  return 1;
 }

 FCGX_Request request;
 result = FCGX_InitRequest(&request, 0, 0);
 if (result != 0) {
  fprintf(stderr, "Error: FCGX_InitRequest()\n");
  return 1;
 }

 while (FCGX_Accept_r(&request) >= 0) {
  try {
   char* method = FCGX_GetParam("REQUEST_METHOD", request.envp);

   // POST for server actions, changes
   if (!strcmp(method, "POST")) {
    size_t contentLength { std::stoul(FCGX_GetParam("CONTENT_LENGTH", request.envp)) };
    std::string postData(contentLength, '\0'); // contentLength number of bytes, initialize with 0
    if (FCGX_GetStr(postData.data(), contentLength, request.in) != static_cast<int>(contentLength)) {
     throw std::runtime_error("Bad data read: Content length mismatch.\r\n");
    }
    // postData contains POST data
    std::string contentType(FCGX_GetParam("CONTENT_TYPE", request.envp));

    std::string xmlData = postData; // default: interpret whole POST data as xml request

    pt::ptree xml;
    std::istringstream ss{xmlData};
    pt::xml_parser::read_xml(ss, xml);

    std::string command {xml.get<std::string>("request.command")};

    if (command == "modify") {
     std::string id {xml.get<std::string>("request.id")};
     std::string data {xml.get<std::string>("request.data")};
     setFileById(data, id);
     FCGX_PutS("Content-Type: text/plain\r\n\r\n", request.out);
    } else if (command == "getfile") {
     std::string id {xml.get<std::string>("request.id")};

     std::string filedata {getFileById(id)};

     if (filedata.size() > 30000000)
      throw std::runtime_error("File too big");
  
     FCGX_PutS("Content-Type: application/octet-stream\r\n", request.out);
     FCGX_FPrintF(request.out, "Content-Length: %d\r\n\r\n", filedata.size());
     FCGX_PutStr(filedata.c_str(), filedata.size(), request.out);
    } else if (command == "checkupdate") {
     std::string id {xml.get<std::string>("request.id")};
     std::string checksum_s {xml.get<std::string>("request.checksum")};
     uint32_t checksum{static_cast<uint32_t>(stoul(checksum_s))};

     //std::cout << "Checksum JS: " << checksum_s << std::endl;
     //std::cout << "Checksum C++: " << checksum32(filedata) << std::endl;

     std::string filedata {getFileById(id)};
     if (checksum != checksum32(filedata)) {
      //std::cout << "Sending change..." << std::endl;
      FCGX_PutS("Content-Type: application/octet-stream\r\n", request.out);
      FCGX_FPrintF(request.out, "Content-Length: %d\r\n\r\n", filedata.size());
      FCGX_PutStr(filedata.c_str(), filedata.size(), request.out);
     } else {
      //std::cout << "No change..." << std::endl;
      FCGX_PutS("Content-Type: text/plain\r\n\r\n", request.out);
      FCGX_PutS("No change.\r\n", request.out);
     }
    } else if (command == "newid") {
     FCGX_PutS("Content-Type: text/plain\r\n\r\n", request.out);
     FCGX_PutS(generate_id().c_str(), request.out);
    } else if (command == "qrcode") {
     std::string url{xml.get<std::string>("request.url")};
     
     if (url.size() > 1000)
      throw std::runtime_error("URL too big");
  
     std::string pngdata {getQRCode(url)};
  
     FCGX_PutS("Content-Type: image/png\r\n", request.out);
     FCGX_FPrintF(request.out, "Content-Length: %d\r\n\r\n", pngdata.size());
     FCGX_PutStr(pngdata.c_str(), pngdata.size(), request.out);
    } else {
     throw std::runtime_error("Bad command: "s + command);
    }

   } else {
    throw std::runtime_error("Unsupported method.\r\n");
   }
  } catch (const std::runtime_error& ex) {
   FCGX_PutS("Status: 500 Internal Server Error\r\n", request.out);
   FCGX_PutS("Content-Type: text/html\r\n\r\n", request.out);
   FCGX_FPrintF(request.out, "Error: %s\r\n", ex.what());
  } catch (const std::exception& ex) {
   FCGX_PutS("Status: 500 Internal Server Error\r\n", request.out);
   FCGX_PutS("Content-Type: text/html\r\n\r\n", request.out);
   FCGX_FPrintF(request.out, "Unknown exception: %s\r\n", ex.what());
  }
 }

 return 0;
}