#include <iostream>
#include <ctime>
#include <sys/socket.h>
#include <netinet/in.h>
#include <unistd.h>
#include <cstring>
#include <pthread.h>
#include <arpa/inet.h>
#include <ncurses.h>
#include <regex>
#include <chrono>
#include <thread>
#include <fcntl.h>
#include <unistd.h>
#include <sys/stat.h>
#include <fstream>
#include <cstdio>
#include <termios.h>
#include <unistd.h>
#include <signal.h>
#include <sys/resource.h>


/* Configuration */

// Name of the pipe used to transfer logs to the log server
std::string LOG_FIFO_NAME = "./../tmp/log";

// Type of the server: server1 - last error & cursor position, server2 - mem % & vmem %
std::string SERVER_TYPE = "server1";

// Port to run server
int PORT = 9001;

// Maximum amount of socket connections
int MAX_CONNECTIONS = 128;

// Amount of log messages displayed on screen 
const int CMD_LOG_BUFFER = 10;

// Amount of milliseconds between screen rerenders
int CMD_REFRESH_TIME = 500;


/* Current status to display */

// Buffer with recent log messages
std::string last_log_messages[CMD_LOG_BUFFER];

// Amount of active client sessions served by different threads
int active_connections = 0;

// Mutex to change counter
pthread_mutex_t conn_mutex;

// Log pipe file descriptor
int is_log_ok = false;

// Initializes ncurses lib
void init_ncurses() {
    initscr();
    cbreak();
    noecho();
    clear();
}

// Returns info about last error
std::string get_last_error() {
    const int error_code = errno;
    const char* error_description = std::strerror(errno);
    return "Last error: " + std::to_string(error_code) + " - " + error_description + "\n";
}

// Returns info about current cursor position in console
std::string get_cursor_position() {
    int x, y;

    getyx(stdscr, y, x);

    return "Cursor position: y: " + std::to_string(y) + " x: " + std::to_string(x) + "\n";
}

// Returns info about used physical memory
std::string get_mem_percent() {
    std::ifstream meminfo("/proc/meminfo");
    if(!meminfo) {
        return "Error: failed to open /proc/meminfo\n";
    }

    std::string line;
    long free_mem = -1, total_mem = -1;

    while((std::getline(meminfo, line))) {
        if(line.find("MemAvailable:") == 0) {
            std::sscanf(line.c_str(), "MemAvailable: %ld kB", &free_mem);
        } else if(line.find("MemTotal:") == 0) {
            std::sscanf(line.c_str(), "MemTotal: %ld kB", &total_mem);
        }

        if(free_mem != -1 && total_mem != -1) {
            break;
        }
    }

    meminfo.close();

    if(total_mem == -1 || free_mem == -1) {
        return "Error: failed to read info from /proc/meminfo\n";
    }

    return "Physical memory: " + std::to_string(100 * (total_mem - free_mem)/total_mem) + "%\n";
}


std::string get_vmem() {
    std::ifstream meminfo("/proc/self/status");
    if(!meminfo) {
        return "Error: failed to open /proc/meminfo\n";
    }

    std::string line;
    long not_free_mem = -1, total_mem = -1;

    while((std::getline(meminfo, line))) {
        if(line.find("VmRSS:") == 0) {
            std::sscanf(line.c_str(), "VmRSS: %ld kB", &not_free_mem);
        } else if(line.find("VmSize:") == 0) {
            std::sscanf(line.c_str(), "VmSize: %ld kB", &total_mem);
        }

        if(not_free_mem != -1 && total_mem != -1) {
            break;
        }
    }

    meminfo.close();

    if(total_mem == -1 || not_free_mem == -1) {
        return "Error: failed to read info from /proc/meminfo\n";
    }

    return "Virtual memory of the proccess: " + std::to_string(100.0 * not_free_mem/total_mem) + "%\n";
}

// Writes log message on screen and passes it to the logging pipe
void log(std::string msg) {
    // Add log message to the screen buffer
    for (int i = CMD_LOG_BUFFER - 1; i > 0; i--) {
        last_log_messages[i] = last_log_messages[i-1];
    }
    time_t now = time(0);
    struct tm tstruct;
    tstruct = *localtime(&now);
    char timestamp[32];
    std::strftime(timestamp, 32, "%H:%M:%S ", &tstruct);
    last_log_messages[0] = timestamp + std::string(" ") + msg;

    // Write message to the logging pipe
    int log_fd = open(LOG_FIFO_NAME.c_str(), O_WRONLY);
    if(log_fd != -1) {
        is_log_ok = true;
        write(log_fd, msg.c_str(), msg.length());
        close(log_fd);
    } else {
        is_log_ok = false;
    }
}

// // Opens file descriptor for logging pipe TODO
// void init_log_pipe() {
//     log_fd = open(LOG_FIFO_NAME.c_str(), O_WRONLY);
// }

// Returns file descriptor for server socket
int start_socket() {
    int option = 1;
    int server_socket = socket(AF_INET, SOCK_STREAM, 0);
    setsockopt(server_socket, SOL_SOCKET, SO_REUSEADDR, &option, sizeof(option));

    sockaddr_in server_address;
    server_address.sin_family = AF_INET;
    server_address.sin_port = htons(PORT);
    server_address.sin_addr.s_addr = INADDR_ANY;
    bind(server_socket, (struct sockaddr*)&server_address, sizeof(server_address));

    if (errno == 98) {
        log("Error: " + std::string(std::strerror(errno)));
        return -1;
    }

    int status = listen(server_socket, MAX_CONNECTIONS);

    if (status != 0) {
        log("Error: can't listen with socket");
        return -1;
    }

    return server_socket;
}

// Handles one connection in sepparate thread
void* handle_connection(void* arg) {
    // Cast client socket descriptor
    int client_socket = *(int*)arg;
    delete (int*)arg;

    std::string info1 = "";
    std::string info2 = "";

    log("New thread created for socket " + std::to_string(client_socket) + '\0');

    while (true) {
        // Recieve message from client
        char buffer[128];
        ssize_t bytes_recieved = recv(client_socket, buffer, sizeof(buffer) - 1, 0);
        buffer[bytes_recieved] = '\0';

        // If connection closed
        if (bytes_recieved == 0) {
            log("Connection with client " + std::to_string(client_socket) + " closed");
            pthread_mutex_lock(&conn_mutex);
            active_connections--;
            pthread_mutex_unlock(&conn_mutex);
            break;
        }

        if (bytes_recieved == -1) {
            log("Error while recieving message: " + std::to_string(errno) + " - " + std::strerror(errno) + '\0');
            break;
        }

        log("Got new message from client " + std::to_string(client_socket) + '\0');

        std::string new_info, req = std::string(buffer);
        log(req + '\0');

        if (SERVER_TYPE == "server1") {
            if (req == "last_error") {
                new_info = get_last_error();
                if (new_info == info1) {
                    log("Actual info already on client\0");
                    continue;
                }
                info1 = new_info;
            } else if (req == "cursor_position") {
                new_info = get_cursor_position();
                if (new_info == info2) {
                    log("Actual info already on client\0");
                    continue;
                }
                info2 = new_info;
            } else {
                new_info = "Invalid request. Available options: last_error, cursor_position";
            }
        }

        if (SERVER_TYPE == "server2") {
            if (req == "mem") {
                new_info = get_mem_percent();
                if (new_info == info1) {
                    log("Actual info already on client\0");
                    continue;
                }
                info1 = new_info;
            } else if (req == "vmem") {
                new_info = get_vmem();
                if (new_info == info2) {
                    log("Actual info already on client\0");
                    continue;
                }
                info2 = new_info;
            } else {
                new_info = "Invalid request. Available options: mem, vmem";
            }
        }

        time_t now = time(0);
        struct tm tstruct;
        tstruct = *localtime(&now);
        char timestamp[32];
        std::strftime(timestamp, 32, "%Y/%m/%d %H:%M:%S ", &tstruct);
        std::string msg = timestamp + new_info;
        send(client_socket, msg.c_str(), strlen(msg.c_str()) + 1, 0);
        log("Sent new info to client\0");
    }

    close(client_socket);

    return nullptr;
}

// Refreshes console output
void* draw(void* arg) {
    while (true) {
        // Update info
        clear();

        printw("Use q + Enter to quit\n\n");

        // Print configuration
        printw(
            "LOG_FIFO_NAME=%s\nSERVER_TYPE=%s\nPORT=%i\nCMD_LOG_BUFFER=%i\nCMD_REFRESH_TIME=%i\n\n",
            LOG_FIFO_NAME.c_str(), SERVER_TYPE.c_str(), PORT, CMD_LOG_BUFFER, CMD_REFRESH_TIME
        );

        if (is_log_ok) {
            printw("Log server connected\n\n");
        } else {
            printw("Log server is not connected\n\n");
        }

        // Print statistics
        printw("Active connections: %i\n", active_connections);
        
        // Print logs
        for (int i = CMD_LOG_BUFFER-1; i >= 0; i--) {
            printw("\n%s", last_log_messages[i].c_str());
        }

        refresh();

        // Wait to update again
        std::this_thread::sleep_for(std::chrono::milliseconds(CMD_REFRESH_TIME));
    }
}

// Read commands from screen
void* commands(void* arg) {
    // Cast server socket descriptor
    int server_socket = *(int*)arg;
    delete (int*)arg;

    while (true) {
        std::string command;
        std::cin >> command;
        
        if (command == "quit" || command == "exit" || command == "q") {
            endwin();
            close(server_socket);
            kill(0, 15);
        }
    }
}

int main() {
    init_ncurses();

    // Create thread to redraw console output
    pthread_t tid;
    if (pthread_create(&tid, nullptr, &draw, nullptr) != 0) {
        std::cout << ("Failed to create drawing thread") << std::endl;
        endwin();
        return 2;
    }
    pthread_detach(tid);

    int server_socket = start_socket();

    if (server_socket == -1) {
        getch();
        endwin();
        return 3;
    }

    log("Socket created\0");

    // Create thread to read commands
    pthread_t tcid;
    int* server_socket_copy = new int(server_socket);
    if (pthread_create(&tcid, nullptr, &commands, server_socket_copy) != 0) {
        std::cout << ("Failed to create commands thread") << std::endl;
        endwin();
        return 2;
    }
    pthread_detach(tcid);

    while (true) {
        int client_socket = accept(server_socket, nullptr, nullptr);

        if (client_socket == -1) {
            continue;
        }

        pthread_mutex_lock(&conn_mutex);
        active_connections++;
        pthread_mutex_unlock(&conn_mutex);

        // Create thread for each connection
        int* client_socket_copy = new int(client_socket);
        pthread_t tid;
        if (pthread_create(&tid, nullptr, &handle_connection, client_socket_copy) != 0) {
            delete client_socket_copy;
        }
        pthread_detach(tid);
    }
    
    return 0;
}