#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <signal.h>
#include <sys/wait.h>
#include <fcntl.h>

#define MAX_MSG_SIZE 500
#define MAX_NAME_SIZE 50

typedef struct {
    char name[MAX_NAME_SIZE];
    struct sockaddr_in addr;
} Friend;

Friend *friends = NULL;
int num_friends = 0;
int sock;
char user_name[MAX_NAME_SIZE];
int friends_fd;

void handle_sigint(int sig) {
    close(friends_fd);
    close(sock);
    exit(0);
}

void send_message(const char *msg, struct sockaddr_in *addr) {
    char buffer[MAX_MSG_SIZE];
    snprintf(buffer, MAX_MSG_SIZE, "%s%c%s%c", user_name, '\0', msg, '\0');
    sendto(sock, buffer, strlen(user_name) + 1 + strlen(msg) + 1, 0, (struct sockaddr *)addr, sizeof(*addr));
}

void add_friend(const char *name, struct sockaddr_in *addr) {
    FILE *fp = fopen("polz.txt", "a");
    if (fp != NULL) {
        fprintf(fp, "%s %s %d\n", name, inet_ntoa(addr->sin_addr), ntohs(addr->sin_port));
        fclose(fp);
    }
}

int is_friend(struct sockaddr_in *addr) {
    FILE *fp = fopen("polz.txt", "r");
    if (fp == NULL) {
        return 0;
    }
    char line[256];
    char name[MAX_NAME_SIZE];
    char ip[INET_ADDRSTRLEN];
    int port;
    while (fgets(line, sizeof(line), fp)) {
        sscanf(line, "%s %s %d", name, ip, &port);
        if (strcmp(ip, inet_ntoa(addr->sin_addr)) == 0 && port == ntohs(addr->sin_port)) {
            fclose(fp);
            return 1;
        }
    }
    fclose(fp);
    return 0;
}

void receive_messages() {
    struct sockaddr_in src_addr;
    socklen_t addr_len = sizeof(src_addr);
    char buffer[MAX_MSG_SIZE];
    while (1) {
        int msg_len = recvfrom(sock, buffer, MAX_MSG_SIZE, 0, (struct sockaddr *)&src_addr, &addr_len);
        if (msg_len > 0) {
            buffer[msg_len] = '\0';
            char *name = buffer;
            char *msg = buffer + strlen(name) + 1;

            if (strcmp(msg, "#hi!") == 0) {
                send_message("#hello!", &src_addr);
                if (!is_friend(&src_addr)) {
                    add_friend(name, &src_addr);
                }
            } else if (strcmp(msg, "#hello!") == 0) {
                if (!is_friend(&src_addr)) {
                    add_friend(name, &src_addr);
                }
            } else {
                printf("%s: %s\n", name, msg);
            }
        }
    }
}

void send_to_all(const char *msg) {
    FILE *fp = fopen("polz.txt", "r");
    if (fp == NULL) {
        return;
    }
    char line[256];
    char name[MAX_NAME_SIZE];
    char ip[INET_ADDRSTRLEN];
    int port;
    struct sockaddr_in addr;
    addr.sin_family = AF_INET;
    while (fgets(line, sizeof(line), fp)) {
        sscanf(line, "%s %s %d", name, ip, &port);
        inet_pton(AF_INET, ip, &addr.sin_addr);
        addr.sin_port = htons(port);
        send_message(msg, &addr);
    }
    fclose(fp);
}

void handle_command(const char *command) {
    if (strncmp(command, "@hi", 3) == 0) {
        char ip[INET_ADDRSTRLEN];
        int port;
        sscanf(command + 4, "%s %d", ip, &port);
        struct sockaddr_in new_friend;
        new_friend.sin_family = AF_INET;
        new_friend.sin_port = htons(port);
        inet_pton(AF_INET, ip, &new_friend.sin_addr);
        send_message("#hi!", &new_friend);
    } else if (strcmp(command, "@friends") == 0) {
        FILE *fp = fopen("polz.txt", "r");
        if (fp == NULL) {
            return;
        }
        char line[256];
        char name[MAX_NAME_SIZE];
        char ip[INET_ADDRSTRLEN];
        int port;
        while (fgets(line, sizeof(line), fp)) {
            sscanf(line, "%s %s %d", name, ip, &port);
            printf("%s %s %d\n", name, ip, port);
        }
        fclose(fp);
    } else if (strcmp(command, "@exit") == 0) {
        kill(0, SIGINT);
    }
}

int main(int argc, char *argv[]) {
    if (argc != 3) {
        fprintf(stderr, "Usage: %s <name> <port>\n", argv[0]);
        exit(1);
    }

    strcpy(user_name, argv[1]);
    int port = atoi(argv[2]);

    sock = socket(AF_INET, SOCK_DGRAM, 0);
    if (sock == -1) {
        perror("Error creating socket");
        exit(1);
    }

    struct sockaddr_in server_addr;
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = INADDR_ANY;
    server_addr.sin_port = htons(port);

    if (bind(sock, (struct sockaddr *)&server_addr, sizeof(server_addr)) == -1) {
        perror("Error binding socket");
        exit(1);
    }

    signal(SIGINT, handle_sigint);

    if (fork() == 0) {
        // Child process for receiving messages
        receive_messages();
    } else {
        // Parent process for sending messages
        char input[MAX_MSG_SIZE];
        while (1) {
            fgets(input, sizeof(input), stdin);
            input[strcspn(input, "\n")] = '\0';
            if (input[0] == '@') {
                handle_command(input);
            } else {
                send_to_all(input);
            }
        }
    }

    close(sock);
    return 0;
}