// from: http://beej.us/guide/bgnet/html/#blocking

/*
** pollserver.c -- a cheezy multiperson chat server
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <poll.h>

#define PORT "47380"   // Port we're listening on

// Get sockaddr, IPv4 or IPv6:
void *get_in_addr(struct sockaddr *sa)
{
    if (sa->sa_family == AF_INET) {
        return &(((struct sockaddr_in*)sa)->sin_addr);
    }

    return &(((struct sockaddr_in6*)sa)->sin6_addr);
}

// Return a listening socket
int get_listener_socket(void)
{
    int listener;     // Listening socket descriptor
    int yes=1;        // For setsockopt() SO_REUSEADDR, below
    int rv;

    struct addrinfo hints, *ai, *p;

    // Get us a socket and bind it
    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_flags = AI_PASSIVE;
    if ((rv = getaddrinfo(NULL, PORT, &hints, &ai)) != 0) {
        fprintf(stderr, "selectserver: %s\n", gai_strerror(rv));
        exit(1);
    }
    
    for(p = ai; p != NULL; p = p->ai_next) {
        listener = socket(p->ai_family, p->ai_socktype, p->ai_protocol);
        if (listener < 0) { 
            continue;
        }
        
        // Lose the pesky "address already in use" error message
        setsockopt(listener, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int));

        if (bind(listener, p->ai_addr, p->ai_addrlen) < 0) {
            close(listener);
            continue;
        }

        break;
    }

    freeaddrinfo(ai); // All done with this

    // If we got here, it means we didn't get bound
    if (p == NULL) {
        return -1;
    }

    // Listen
    if (listen(listener, 10) == -1) {
        return -1;
    }

    return listener;
}

// Add a new file descriptor to the set
void add_to_pfds(struct pollfd *pfds[], int newfd, int *fd_count, int *fd_size)
{
    // If we don't have room, add more space in the pfds array
    if (*fd_count == *fd_size) {
        *fd_size *= 2; // Double it

        *pfds = realloc(*pfds, sizeof(**pfds) *       (*fd_size));
	//                     sizeof(struct pollfd)
    }

    (*pfds)[*fd_count].fd = newfd;
    (*pfds)[*fd_count].events = POLLIN; // Check ready-to-read

    (*fd_count)++;
}

// Remove an index from the set
void del_from_pfds(struct pollfd pfds[], int i, int *fd_count)
{
    // Copy the one from the end over this one
    pfds[i] = pfds[*fd_count-1];

    (*fd_count)--;
}

// Main
int main(void)
{
    int listener;     // Listening socket descriptor

    int newfd;        // Newly accept()ed socket descriptor
    struct sockaddr_storage remoteaddr; // Client address
    socklen_t addrlen;

    char buf[256];    // Buffer for client data

    char remoteIP[INET6_ADDRSTRLEN];

    // Start off with room for 5 connections
    // (We'll realloc as necessary)
    int fd_count = 0;
    int fd_size = 5;
    struct pollfd *pfds = malloc(sizeof *pfds * fd_size);

    // Set up and get a listening socket
    listener = get_listener_socket(); // getaddrinfo, socket, bind, listen

    if (listener == -1) {
        fprintf(stderr, "error getting listening socket\n");
        exit(1);
    }

    // Add the listener to set
    pfds[0].fd = listener;
    pfds[0].events = POLLIN; // Report ready to read on incoming connection

    fd_count = 1; // For the listener

    // Main loop.  probably there is accept.  probably also recv (then send).  probably poll.
    for(;;) {
        int poll_count = poll(pfds, fd_count, -1);

        if (poll_count == -1) {
            perror("poll");
            exit(1);
        }

        // Run through the existing connections looking for data to read
        for(int i = 0; i < fd_count; i++) {

            // Check if someone's ready to read
            if (pfds[i].revents & POLLIN) { // We got one!!

	      if (pfds[i].fd == listener) { // could have used, if (i == 0) 
                    // If listener is ready to read, handle new connection

                    addrlen = sizeof remoteaddr;
                    newfd = accept(listener,
                        (struct sockaddr *)&remoteaddr,
                        &addrlen);

                    if (newfd == -1) {
                        perror("accept");
                    } else {
                        add_to_pfds(&pfds, newfd, &fd_count, &fd_size);

                        printf("pollserver: new connection from %s on "
                            "socket %d\n",
                            inet_ntop(remoteaddr.ss_family,
                                get_in_addr((struct sockaddr*)&remoteaddr),
                                remoteIP, INET6_ADDRSTRLEN),
                            newfd);

			// send message to this client - "welcome"?
			// send message to all the clients that there is a new one?
                    }
                } else {
                    // If not the listener, we're just a regular client
                    int nbytes = recv(pfds[i].fd, buf, sizeof buf, 0);

                    int sender_fd = pfds[i].fd;

                    if (nbytes <= 0) {
                        // Got error or connection closed by client
                        if (nbytes == 0) {
                            // Connection closed
                            printf("pollserver: socket %d hung up\n", sender_fd);
                        } else {
                            perror("recv");
                        }

                        close(pfds[i].fd); // Bye!

                        del_from_pfds(pfds, i, &fd_count);

                    } else {
		      // look at buf?
		      
		      // We got some good data from a client
		      char *response_ok = "HTTP/1.1 200 OK\r\n"
			"Date: Fri, 31 Dec 1999 23:59:59 GMT\r\n"
			"Content-Length: 5\r\n"
			"Content-Type: text/plain\r\n"
			"\r\n"
			"Hello";
		      if (send(sender_fd, response_ok, strlen(response_ok), 0) == -1) {
			perror("send");
		      }
                    }
                } // END handle data from client
            } // END got ready-to-read from poll()
        } // END looping through file descriptors
    } // END for(;;)--and you thought it would never end!
    
    return 0;
}