#include <asm-generic/socket.h>
#include <vector>
#include <string>
#include <iostream>
#include <fstream>
#include "json.hpp"
#include <netinet/in.h>
#include <unistd.h>
#include <sys/socket.h>
#include <format>
#include <signal.h>
#include <unistd.h>
#include <cstdlib>

using Db = std::vector<std::vector<std::string>>;
Db database;

void save_database(std::string file_name) {
  nlohmann::json json_data = database;
  std::string serialised_json_data = json_data.dump();
  std::ofstream db_file(file_name);
  db_file << serialised_json_data;
  db_file.close();
}

void load_database(std::string file_name) {
  std::ifstream db_file(file_name);
  std::stringstream raw_file_text;
  raw_file_text << db_file.rdbuf();
  db_file.close();
  database = nlohmann::json::parse(raw_file_text.str());
}


std::vector<std::string> parse_resp_request(char* request) {
  std::string request_str(request);
  std::string delimiter = "\r\n";
  std::vector<std::string> split_request;
  size_t pos = 0;
  
  while ((pos = request_str.find(delimiter)) != std::string::npos) {
    split_request.push_back(request_str.substr(0, pos));
    request_str.erase(0, pos + delimiter.length());
  }
  
  if (request_str.length() > 0) {
    split_request.push_back(request_str);
  }


  for (std::string entry: split_request) {
    if (entry.contains("*")) {
      split_request.erase(find(split_request.begin(), split_request.end(), entry));
    }
  }
  for (std::string entry: split_request) {
    if (entry.contains("$")) {
      split_request.erase(find(split_request.begin(), split_request.end(), entry));
    }
  }

  return split_request;
}

void safe_exit(int signum) {
  std::cout << "[W] Exiting..." << std::endl;
  save_database("db.json");
  exit(signum);
}

int main() {
  std::cout << "[i] Starting blueis server..." << std::endl;

  signal(SIGINT, safe_exit);

  load_database("db.json");
  int listening_socket = socket(AF_INET, SOCK_STREAM, 0 );
  if (listening_socket < 0) {
    std::cerr << "[E] Failed to create socket." << std::endl;
    return 1;
  }

  int optval = 1;
  if (setsockopt(listening_socket, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof(optval)) < 0) {
    std::cerr << "[W] Failed to use SO_REUSEADDR. Continuing." << std::endl;
  }
  
  sockaddr_in server_address;
  server_address.sin_family = AF_INET;
  server_address.sin_port = htons(6379);
  server_address.sin_addr.s_addr = INADDR_ANY;

  if (bind(listening_socket, (sockaddr*)&server_address, sizeof(server_address)) < 0) {
    std::cerr << "[E] Failed to bind to port 6379. Check for any other running redis or blueis instances." << std::endl;
    close(listening_socket);
    return 1;
  }

  if (listen(listening_socket, 5) < 0) {
    std::cerr << "[E] Failed to listen on socket." << std::endl;
    close(listening_socket);
    return 1;
  }

  std::cout << "[i] Server listening on port 6379..." << std::endl;

  sockaddr_in client_address;
  socklen_t client_size = sizeof(client_address);

  while (true) {
    int client_socket = accept(listening_socket, (sockaddr*)&client_address, &client_size);
    if (client_socket < 0) {
      std::cerr << "[E] Failed to accept connection." << std::endl;
      close(listening_socket);
      return 1;
    }
    std::cout << "[i] Client connected." << std::endl;
    while (true) {
      char buffer[4096];
      int bytes_received = recv(client_socket, buffer, 4096, 0);
  
      if (bytes_received > 0) {
        buffer[bytes_received] = '\0';
        std::vector<std::string> parsed = parse_resp_request(buffer);

        if (parsed[0] == "GET") {
          bool found = false;

          for (const auto& inner_vec: database) { // Iterate through DB and find the required item
            if (!inner_vec.empty() && inner_vec[0] == parsed[1]) {
              int length = inner_vec[1].length();
              std::string return_string = std::format("${}\r\n{}\r\n", length, inner_vec[1]); // Serialise to RESP
              std::cout << "[d] Sending: " << return_string << std::endl;
              send(client_socket, return_string.data(), return_string.length(), 0);
              found = true;
            }
          }

          if (!found) {
            send(client_socket, "$-1\r\n", strlen("$-1\r\n"), 0); // Not found
          }
        } else if (parsed[0] == "SET") {
          bool found = false; // Avoids SEGFAULT
                              
          for (auto& inner_vec: database) {
            if (!inner_vec.empty() && inner_vec[0] == parsed[1]) {
              inner_vec[1] = parsed[2];
              send(client_socket, "+OK\r\n", strlen("+OK\r\n"), 0);
              found = true;
            }

            if (!found) {
              std::vector<std::string> new_kv = { parsed[1], parsed[2] };
              database.push_back(new_kv);
              send(client_socket, "+OK\r\n", strlen("+OK\r\n"), 0);
              found = true;
            }
          }
        } else {
          send(client_socket, "+OK\r\n", strlen("+OK\r\n"), 0); // Temporary catch-all (for more advanced handshake)
        }
      } else {
        close(client_socket);
        std::cout << "[i] Client disconnected." << std::endl;
        break;
      }
    }
  }


  return 0;
}