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

int connect_to_server(const char* hostname, unsigned short port)
{
    int fd;
    struct sockaddr_in in;
    struct hostent *hp;

    if((hp = gethostbyname(hostname)) == NULL)
    {
	perror("gethostbyname");
	exit(1);
    }

    memset(&in, 0, sizeof(in));
    in.sin_family = AF_INET;
    in.sin_port   = htons(port);
    memcpy(&in.sin_addr, hp->h_addr, hp->h_length);

    if((fd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
    {
	perror("socket");
	exit(1);
    }

    if(connect(fd, (struct sockaddr *)&in, sizeof(in)) < 0)
    {
	perror("connect");
	exit(1);
    }

    return fd;
}

int parse_url(const char* url,
	      char* host, unsigned short* port,
	      char* filename)
{
    *port = 0;
    if(strncmp(url, "http://", 7) != 0)
	return 0;
    url += 7;
    if(!*url)
	return 0;
    while(*url && *url != '/' &&  *url != ':')
	*host++ = *url++;
    *host = '\0';
    if(*url == ':')
    {
	url++;
	*port = atoi(url);
	while(*url && *url != '/')
	    url++;
    }

    while(*url)
	*filename++ = *url++;
    *filename = '\0';
    return 1;
}

char* truncate_newline(char* s)
{
    int len = strlen(s);

    if(len < 2)
    {
	if(len == 0)
	    return s;
	if(s[0] == '\n' || s[0] == '\r')
	    s[0] = '\0';
	return s;
    }
    if(s[len - 1] == '\n')
	s[--len] = '\0';
    if(s[len - 1] == '\r')
	s[--len] = '\0';
    return s;
}

int main(int argc, char** argv)
{
    int fd;
    FILE* fp;
    char hostname[BUFSIZ];
    char filename[BUFSIZ];
    char buff[BUFSIZ];
    int n;
    struct servent* sp;
    unsigned short port;
    char* url;
    int doc = 0;

    if(argc == 3 && !strcmp(argv[1], "-d"))
    {
	doc = 1;
	url = argv[2];
    }
    else if(argc == 2)
    {
	url = argv[1];
    }
    else
    {
	fprintf(stderr, "Usage: httpget [-d] URL\n");
	return 1;
    }

    if(strlen(url) >= BUFSIZ)
    {
	fprintf(stderr, "URL is too long.\n");
	return 1;
    }

    if(parse_url(url, hostname, &port, filename) == 0)
    {
	fprintf(stderr, "Invalid URL:%s\n", url);
	return 1;
    }

    if(port == 0)
    {
	sp = getservbyname("http", "tcp");
	if(sp == NULL)
	{
	    /* fprintf(stderr, "WARNING http/tcp: unknown service\n"); */
	    port = 80;
	}
	else
	    port = sp->s_port;
    }

    fd = connect_to_server(hostname, port);
    if((fp = fdopen(fd, "r")) == NULL)
    {
	perror("fdopen");
	return 1;
    }

    write(fd, "GET ", 4);
    write(fd, filename, strlen(filename));
    write(fd, " HTTP/1.0\r\n\r\n", 13);

    if(doc)
    {
	do
	{
	    if(fgets(buff, BUFSIZ, fp) == NULL)
	    {
		fprintf(stderr, "No documentation.\n");
		fclose(fp);
		close(fd);
		return 1;
	    }
	    truncate_newline(buff);
	} while(buff[0] != '\0');
    }

    while((n = fread(buff, 1, BUFSIZ, fp)) > 0)
	fwrite(buff, 1, n, stdout);
    fclose(fp);
    close(fd);
    return 0;
}