/* tcpclient.c
 *
 * TCP Client
 * note: 'echo "hello" | nc -l -p 8080 localhost'
 *
 *
 */

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

#define TARGET_MAX_SZ 1*1024*1024

static int sockfd;
static struct addrinfo *res;
static char *recv_buff;

void cleanup(void)
{
    shutdown(sockfd, SHUT_RDWR);
    close(sockfd);

    if (recv_buff)
        free(recv_buff);

    /* free the linked list */
    if (res)
        freeaddrinfo(res);
}

int main(int argc, char **argv)
{
    if (argc != 2)
    {
        fprintf(stderr, "usage: %s <host>\n", argv[0]);
        exit(-1);
    }
    if (!strstr(argv[1], "http://"))
    {
        fprintf(stderr, "host needs to prefixed with \"http://\" protocol\n");
        exit(-1);
    }

    /* grab the host and path from the URL */
    char hoststr[100] = { 0 }, pathstr[100] = { 0 }, filestr[100] = { 0 };
    sscanf(argv[1], "http://%[^/]/%s", hoststr, pathstr);
    printf("host is: \"%s\"\n"
           "path is: \"%s\"\n", hoststr, pathstr);

    /* parse out a filestrname */
    char *filepart = strrchr(pathstr, '/');
    if (filepart && strlen(filepart + 1))
        strcpy(filestr, filepart + 1);
    else
        strcpy(filestr, "index.html");
    printf("file is: \"%s\"\n", filestr);

    int ret;

    /* prepare for getaddrinfo call */
    struct addrinfo hints;
    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;

    if ((ret = getaddrinfo(hoststr, "http", &hints, &res)) != 0)
    {
        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(ret));
        exit(-1);
    }

    /* try all available IP addresses */
    struct addrinfo *p;
    char ipstr[INET6_ADDRSTRLEN];
    void *addr;
    char *ipver;
    struct sockaddr_in *ipv4;
#if 0
    struct sockaddr_in6 *ipv6;
#endif

    printf("trying all available IP addresses for %s:\n", hoststr);
    for (p = res; p != NULL; p = p->ai_next)
    {
        /* get the pointer to the address itself,
         * different fields in IPv4 and IPv6 */
        if (p->ai_family == AF_INET)
        {   /* IPv4 */
            ipv4 = (struct sockaddr_in *) p->ai_addr;
            addr = &(ipv4->sin_addr);
            ipver = "IPv4";
        }
        else
            continue; /* ignore IPv6 for now */
#if 0
        else
        {   /* IPv6 */
            ipv6 = (struct sockaddr_in6 *) p->ai_addr;
            addr = &(ipv6->sin6_addr);
            ipver = "IPv6";
        }
#endif

        /* convert the IP to a string and print it */
        inet_ntop(p->ai_family, addr, ipstr, sizeof(ipstr));
        printf("attempting to connect to %s: %s\n", ipstr, ipver);

        /* create a socket */
        if ((sockfd = socket(p->ai_family, p->ai_socktype, res->ai_protocol)) == -1)
        {
            perror("socket");
            close(sockfd);
        }

        /* attempt to connect */
        if (connect(sockfd, (struct sockaddr *) ipv4, sizeof(*ipv4)) == -1)
            perror("connect");
        else
        {
            printf("successfully connected\n");
            break; /* break out of a loop, we got a connection */
        }
    }

    if (!p)
    {
        fprintf(stderr, "failed to connect to a host\n");
        exit(-1);
    }

    atexit(cleanup);

    /* send http commands and receive data */
    char request[128] = { 0 };
    sprintf(request, "GET /%s HTTP/1.0\r\nHost: %s\r\n\r\n", pathstr, hoststr);
    size_t request_len = strlen(request) * sizeof(char);

    ret = send(sockfd, (void *) request, request_len, 0);
    if (ret == -1)
    {
        perror("send");
        exit(-1);
    }
    else if (ret != request_len)
    {
        fprintf(stderr, "sent less bytes than requested\n");
        exit(-1);
    }

    /* receive until connection gets closed */
    recv_buff = (char *) malloc(sizeof(char) * TARGET_MAX_SZ);
    if (!recv_buff)
    {
        perror("malloc");
        exit(-1);
    }
    size_t recv_len = 0;

    do
    {
        ret = recv(sockfd, recv_buff + recv_len, TARGET_MAX_SZ - recv_len, 0);
        if (ret == -1)
        {
            perror("recv");
            exit(-1);
        }
        else if (ret == 0)
            printf("remote host has closed the connection, received %lu bytes\n", recv_len);

        recv_len += ret;

    } while (ret > 0);

    if (recv_len < 1)
    {
        fprintf(stderr, "did not receive any data from the host!\n");
        exit(-1);
    }

    /* poke at http header and check for errors */
    int code;
    sscanf(recv_buff, "HTTP/1.%*[01] %d ", &code);
    if (code == 200)
        printf("received file\n");
    else
    {
        printf("got an error code %d\n", code);
        char errorline[100];
        sscanf(recv_buff, "%[^\r\n]", errorline);
        fprintf(stderr, "%s\n", errorline);
        exit(-1);
    }

    /* save to disk */
    char *buff_p = strstr(recv_buff, "\r\n\r\n"); /* seek past http header */
    if (buff_p)
    {
        buff_p += 4;

        FILE *fp = fopen(filestr, "w");
        if (!fp)
        {
            perror("fopen");
            exit(-1);
        }

        ret = fwrite(buff_p, recv_len - (buff_p - recv_buff), sizeof(char), fp);
        fclose(fp);
    }
    else
        fprintf(stderr, "could not seek past http header\n");
}