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

void send_message(const char *msg, struct sockaddr_in *addr);

void add_friend(const char *name, struct sockaddr_in *addr) {
    friends = realloc(friends, (num_friends + 1) * sizeof(Friend));
    if (friends != NULL) {
        strcpy(friends[num_friends].name, name);
        friends[num_friends].addr = *addr;
        num_friends++;
    }
}

int is_friend(struct sockaddr_in *addr) {
    for (int i = 0; i < num_friends; i++) {
        if (friends[i].addr.sin_addr.s_addr == addr->sin_addr.s_addr &&
            friends[i].addr.sin_port == addr->sin_port) {
            return 1;
        }
    }
    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_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 send_to_all(const char *msg) {
    for (int i = 0; i < num_friends; i++) {
        send_message(msg, &friends[i].addr);
    }
}

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) {
        for (int i = 0; i < num_friends; i++) {
            printf("%s %s %d\n", friends[i].name, inet_ntoa(friends[i].addr.sin_addr), ntohs(friends[i].addr.sin_port));
        }
    } else if (strcmp(command, "@exit") == 0) {
        close(sock);
        exit(0);
    }
}

void terminate_handler(int signum) {
    free(friends);
    close(sock);
    exit(0);
}

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

    signal(SIGTERM, terminate_handler);
    signal(SIGINT, terminate_handler);

    friends = (Friend *)malloc(sizeof(Friend) * 10);
    if (friends == NULL) {
        perror("Error allocating memory for friends list");
        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);
    }

    pid_t pid = fork();
    if (pid == -1) {
        perror("Error forking process");
        exit(1);
    } else if (pid == 0) {
        receive_messages();
    } else {
        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);
            }
        }
    }

    return 0;
}