chat_application/main.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#include <assert.h>
#include <unistd.h>
#include <signal.h>

#include "message.h"
#include "user.h"
#include "easysock.h"
#include "file_helpers.h"
#include "message_helpers.h"
#include "stack.h"

#define BUFFER_SIZE 10000
#define MAX_CONNECTIONS 100
#define DATA_SIZE 50000
#define MESSAGE_SIZE 50000

User** create_user_list(char* filename);
void sigint_handler(int dummy);
User* fetch_user(char* username);
int user_to_index(User* user);
bool user_equals(User* this, User* other);

User** users;
int num_users;

bool stop_running;

int main() {
	stop_running = false;

	signal(SIGINT,sigint_handler);

	struct sockaddr temp_addr;
	socklen_t temp_addrlen;

	fd_set read_fd_set;
	int conn_sockets[MAX_CONNECTIONS] = {-1}; 
	User* to_user[MAX_CONNECTIONS] = {NULL}; 
	User* from_user[MAX_CONNECTIONS] = {NULL}; 
	FD_ZERO(&read_fd_set); char buffer[BUFFER_SIZE]; 
	char data[DATA_SIZE]; 

	num_users = num_of_lines("user_file.txt");
	users = create_user_list("user_file.txt");
	
	Stack* message_stack[num_users];

	for (int i=0;i < num_users; i++) {
		message_stack[i] = new_stack(10);
	}
	
	struct sockaddr addr_struct;
	int server_sock = create_local(4,'T',"127.0.0.1",30000,&addr_struct);
	conn_sockets[0] = server_sock;

	assert(listen(server_sock,MAX_CONNECTIONS) == 0);

	while (true) {
		FD_ZERO(&read_fd_set);
		for (int i=0; i < MAX_CONNECTIONS; i++) {
			if (conn_sockets[i] > 0) {
				FD_SET(conn_sockets[i],&read_fd_set);
			}
		}

		int num_conns = select(FD_SETSIZE, &read_fd_set, NULL, NULL, NULL);

		if (num_conns > 0) {
			if (FD_ISSET(conn_sockets[0],&read_fd_set)) {
				int client_sock = accept(conn_sockets[0],&temp_addr,&temp_addrlen);
				for (int i=0;i < MAX_CONNECTIONS; i++) {
					if (conn_sockets[i] <= 0) {
						conn_sockets[i] = client_sock;
						break;
					}
				}
			}

			for (int i=1; i < MAX_CONNECTIONS; i++) {

				memset(data,0x00,DATA_SIZE);

				if (FD_ISSET(conn_sockets[i],&read_fd_set)) {

					while ( strstr(buffer,"END_OF_DATA") == NULL ) {
						int num_bytes_read = recv(conn_sockets[i],buffer,sizeof(buffer),0);
                               	                if (num_bytes_read <= 0) {
							close(conn_sockets[i]);
							conn_sockets[i] = 0;
							to_user[i] = NULL;
							goto continue_for_loop;
                                                } 
						strcat(data, buffer);
					}
					strcat(data,"\0"); 

					buffer[0] = '\0'; /* Clear the buffer */

					char* send_or_receive = malloc(10);
					int k=0;
					while (*(data + k) != '\n') {
						k++;
					}
					memcpy(send_or_receive,data,k);

					if (strstr(send_or_receive, "SENDING") != NULL) {
						if (from_user[i] == NULL) {
							from_user[i] = fetch_user(fetch_from_string(data,"IAM"));
							if (from_user[i] == NULL) {
								printf("Please identify yourself.\n");
								close(conn_sockets[i]);
								continue;
							} else {
								printf("You are %s\n",from_user[i]->username);
							}
						}
	
						if (to_user[i] == NULL) {
							to_user[i] = fetch_user(fetch_from_string(data,"TO"));
							if (to_user[i] == NULL) {
								printf("Invalid user or message format.\n");
								close(conn_sockets[i]);
								continue;
							} else {
								printf("Message intended for %s\n",to_user[i]->username);
							}
						}

						char* message_string = malloc(sizeof(char) * MESSAGE_SIZE);	
						memset(message_string, 0x00, MESSAGE_SIZE);
						message_string = fetch_message_string(data);
						if (message_string == NULL) {
							printf("Invalid message.\n");
							return -10;
						}	
	
						printf("Your message is: \n------------------\n%s\n------------------\n",message_string);
	
						if (user_to_index(to_user[i]) < 0) {
							printf("Recipient user does not exist!\n");
							return -20;
						}
	
						Message* message = new_message(message_string,from_user[i],to_user[i]);
						stack_push( message_stack[user_to_index(to_user[i])],message );
	
						printf("Message has been pushed onto stack for %s\n",to_user[i]->username);
	
					} else if (strstr(send_or_receive, "RECEIVING") != NULL) {

                                                if (from_user[i] == NULL) {
                                                        from_user[i] = fetch_user(fetch_from_string(data,"IAM"));
                                                        if (from_user[i] == NULL) {
                                                                printf("Please identify yourself.\n");
                                                                close(conn_sockets[i]);
                                                                continue;
                                                        } else {
                                                                printf("You are %s\n",from_user[i]->username);
                                                        }
                                                }

						int num_of_messages;
						char* num_of_messages_string = fetch_from_string(data,"GETLAST");

						if (num_of_messages_string == NULL) {
							printf("Invalid GET request.\n");
							return -30;
						} else {
							if (strstr(num_of_messages_string,"ALL") != NULL) {
								num_of_messages = stack_size(message_stack[user_to_index(from_user[i])]);
							} else {
								num_of_messages = atoi(num_of_messages_string);
							}
						}

						if (num_of_messages > stack_size(message_stack[user_to_index(from_user[i])])) {
							num_of_messages = stack_size(message_stack[user_to_index(from_user[i])]);
						}
							
						for (int k=0;k<num_of_messages;k++) {
							Message* message = stack_pop(message_stack[user_to_index(from_user[i])]);
							printf("You have a message from %s"
								", sent at %s"
								": \"%s\"\n",
								message->sender->username,
								asctime(message->timeinfo),
								message->text);
						}
						
					} else {
						printf("You are not sending or receiving.\n");
					}
					close(conn_sockets[i]);
					conn_sockets[i] = -1;

					continue_for_loop:
					memset(data,0,DATA_SIZE);
					memset(buffer,0,BUFFER_SIZE);
					to_user[i] = NULL;
					from_user[i] = NULL;
				}
			}
		

			if (stop_running == true) {
				printf("Stopping...\n");
				for (int i=MAX_CONNECTIONS-1; i>= 0;  i--) {
					close(i);
					close(conn_sockets[i]);
				}
				return 130;
			}

		}


	}
	
}


User** create_user_list(char* filename) {

	/* Structure of user file - <username> <password> on every line */

	int num_users = num_of_lines(filename);
        char* file_str = file_to_string(filename);

        char* token = malloc(sizeof(char) * 30);
        User** users = malloc (num_users * sizeof(User*));

	for (int i=0;i<num_users;i++) {
		(*(users+i)) = malloc(sizeof(User));
	}

        token = strtok(file_str," \r\n");
        for (int i=0;i<num_users;i++) {
		(*(users + i))->username = strdup(token);
                token = strtok(NULL," \r\n");
                (*(users + i))->password = strdup(token);
                token = strtok(NULL," \r\n");
        }

	return users;

}

void sigint_handler(int dummy) {
	stop_running = true;
	printf("sigint_handler is stopping...\n");
	exit(130);
}

User* fetch_user(char* username) {
	if (username == NULL) {
		return NULL;
	}

	for (int i=0;i<num_users;i++) {
		if (strcmp(users[i]->username, username) == 0) {
			return users[i];
		}
	}

	return NULL;
}

int user_to_index(User* user) {
	int index = -1;
	for (int i=0;i < num_users; i++) {
		if (user_equals(users[i],user) == true) {
			index = i;
			break;
		}
	}

	return index;

}

bool user_equals(User* this, User* other) {
	if (( strcmp(this->username,other->username) == 0 ) && ( strcmp(this->password,other->password) == 0 )) {
		return true;
	} else {
		return false;
	}
}