C-IPC/client.c

#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <sys/msg.h>
#include <sys/stat.h>
#include <unistd.h>

#include "commands.h"

// Make a macro for this cause I'm not typing sizeof twice every time
#define send(queue_id, msgbuf_ptr)                                             \
  msgsnd(queue_id, msgbuf_ptr, sizeof(*(msgbuf_ptr)) - sizeof(long), 0)

static void heartbeat_loop(int server_queue_id, const char *client_id) {
  msgbuf_t msg = {.mtype = Hearbeat, .sender = ""};
  strncpy(msg.sender, client_id, COMMAND_LENGTH - 1);
  while (1) {
    if (send(server_queue_id, &msg) == -1) {
      perror("msgsnd(heartbeat) failed");
      break;
    }
    sleep(HEARTBEAT_INTERVAL);
  }
}

static void cleanup_queue(int qid) {
  if (qid != -1) {
    msgctl(qid, IPC_RMID, NULL);
  }
}

static void input_loop(int server_queue_id, const char *client_id) {
  while (1) {
    // Minimum length plus extra space fore command name and seperators
    // I'd prefer some more space than required to not have to worry about cut
    // offs
    char buffer[COMMAND_LENGTH + MESSAGE_LENGTH + 64];
    if (fgets(buffer, sizeof(buffer), stdin) == NULL) {
      break;
    }

    buffer[strcspn(buffer, "\n")] = '\0';

    if (strncmp(buffer, "/msg ", 5) == 0) {
      // In a /msg command we expect {u|g}:<nickname up to 14 chars> <message up
      // to 256 chars>
      char *space_ptr = strchr(buffer + 5, ' ');
      if (space_ptr == NULL) {
        printf("Invalid /msg format. Use /msg u:<nickname> <message>\n");
        continue;
      }
      char target[COMMAND_LENGTH];
      size_t target_len = space_ptr - (buffer + 5);
      if (target_len >= COMMAND_LENGTH) {
        printf("Target nickname too long\n");
        continue;
      }
      strncpy(target, buffer + 5, target_len);
      target[target_len] = '\0';
      char *message = space_ptr + 1;
      if (strlen(message) == 0) {
        printf("Message cannot be empty\n");
        continue;
      }

      // Check the format of the command string
      if (target[1] != ':') {
        printf("Invalid target format. Use u:<nickname> or g:<groupname>\n");
        continue;
      }

      if (target[0] != 'u' && target[0] != 'g') {
        printf("Invalid target type. Use 'u' for user or 'g' for group\n");
        continue;
      }

      msgbuf_t msg = {.mtype = Message, .sender = ""};
      strncpy(msg.sender, client_id, COMMAND_LENGTH - 1);
      snprintf(msg.command, COMMAND_LENGTH, "%s", target);
      strncpy(msg.message, message, MESSAGE_LENGTH - 1);
      if (send(server_queue_id, &msg) == -1) {
        perror("msgsnd(/msg) failed");
      }
    } else if (strncmp(buffer, "/list ", 6) == 0) {
      char *offset = buffer + 6;

      if (strcmp(offset, "active") != 0 && strcmp(offset, "all") != 0) {
        printf("Invalid list type. Use /list active or /list all\n");
        continue;
      }

      msgbuf_t msg = {.mtype = List_clients, .sender = ""};
      strncpy(msg.sender, client_id, COMMAND_LENGTH - 1);
      strncpy(msg.command, offset, COMMAND_LENGTH - 1);
      if (send(server_queue_id, &msg) == -1) {
        perror("msgsnd(/list) failed");
      }
    } else if (strncmp(buffer, "/mute ", 6) == 0) {
      // handle mute
    } else if (strcmp(buffer, "/quit") == 0) {
      // TODO: Would be nice to have a way to gracefully logout and not just
      // depend on heartbeats, maybe
    } else if (strncmp(buffer, "/inbox", 8) == 0) {
      msgbuf_t msg = {.mtype = Inbox, .sender = ""};
      strncpy(msg.sender, client_id, COMMAND_LENGTH - 1);
      if (send(server_queue_id, &msg) == -1) {
        perror("msgsnd(/mailbox) failed");
      }
    } else {
      printf("Unknown command\n");
    }
  }
}

int main(int argc, char *argv[]) {
  if (argc < 2) {
    fprintf(stderr, "Usage: %s <client_id>\n", argv[0]);
    return 1;
  }

  char *client_id = argv[1];

  int client_queue_id = msgget(IPC_PRIVATE, IPC_CREAT | 0666);
  if (client_queue_id == -1) {
    perror("msgget(client) failed");
    return 1;
  }

  int server_queue_id = -1;
  const char *id_path = "/home/piotr/server_queue_id";
  int fd = open(id_path, O_RDONLY);
  if (fd == -1) {
    perror("Failed to open server queue id file");
    cleanup_queue(client_queue_id);
    return 1;
  }

  if (read(fd, &server_queue_id, sizeof(int)) == -1) {
    fprintf(stderr, "Failed to read server queue id from %s\n", id_path);
    server_queue_id = -1;
  }
  close(fd);

  msgbuf_t msg = {.mtype = Login, .sender = ""};
  strncpy(msg.sender, client_id, COMMAND_LENGTH - 1);
  snprintf(msg.command, COMMAND_LENGTH, "%d", client_queue_id);

  if (msgsnd(server_queue_id, &msg, sizeof(msg) - sizeof(long), 0) == -1) {
    perror("msgsnd(login) failed");
    cleanup_queue(client_queue_id);
    return 1;
  }

  /* Wait for login response (server replies with mtype = Login) */
  msgbuf_t resp;
  ssize_t r =
      msgrcv(client_queue_id, &resp, sizeof(resp) - sizeof(long), Login, 0);
  if (r == -1) {
    perror("msgrcv(login response) failed");
    cleanup_queue(client_queue_id);
    return 1;
  }

  if (resp.stype != ACK_ACCEPTED) {
    fprintf(stderr, "Login rejected: code=%d\n", resp.stype);
    cleanup_queue(client_queue_id);
    return 1;
  }

  printf("Login accepted. Welcome, %s!\n", resp.command);

  if (fork() == 0) {
    heartbeat_loop(server_queue_id, client_id);
    return 0;
  }

  if (fork() == 0) {
    input_loop(server_queue_id, client_id);
    return 0;
  }

  while (1) {
    msgbuf_t incoming;
    ssize_t got = msgrcv(client_queue_id, &incoming,
                         sizeof(incoming) - sizeof(long), 0, 0);
    if (got == -1) {
      perror("msgrcv(incoming) failed");

      if (errno == EINTR) {
        continue;
      }
      perror("msgrcv(incoming) failed");
      break;
    }

    switch (incoming.mtype) {
    case Message:
      printf("%s: %s\n", incoming.sender, incoming.message);
      break;
    case List_clients: {
      // Check the command field for the list type
      if (strncmp(incoming.command, "active", COMMAND_LENGTH) == 0) {
        printf("Active clients:\n%s\n", incoming.message);
      } else {
        printf("All clients:\n%s\n", incoming.message);
      }
      break;
    }
    case Inbox: {
      // Upon recieving an inbox message, check the command field for the index
      // Index of 0 means that there are messages in the mailbox
      if (strcmp(incoming.command, "0") == 0) {
        printf("You have messages in your mailbox!\n");
        continue;
      }

      // Index of 1 is just the first message so print a header
      if (strcmp(incoming.command, "1") == 0) {
        printf("Your inbox messages:\n");
      }
      printf("[%s] %s: %s\n", incoming.command, incoming.sender,
             incoming.message);
      break;
    }
    case Signal:
      // Tell the user if the previous message was accepted and/or delivered
      if (incoming.stype == ACK_ACCEPTED) {
        printf("Message sent successfully.\n");
      } else if (incoming.stype == ACK_DELIVERED) {
        printf("Message delivered to the %s.\n", incoming.command);
      } else if (incoming.stype == ERR_USER_NOT_FOUND) {
        printf("Your message could not be delivered: User not found.\n");
      } else {
        // Display whatever if I forgot to handle something
        printf("Your message could not be delivered: Error code %d.\n",
               incoming.stype);
      }

      break;
    default:
      printf("Received unknown command of mtype=%ld stype=%d\n",
             (long)incoming.mtype, incoming.stype);
      break;
    }
  }

  cleanup_queue(client_queue_id);
  return 0;
}