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

struct in_addr* name_to_IP_addr(char* hostname)
{
    struct hostent* hostp;

    /* Gets host info for the given hostname */
    hostp = gethostbyname(hostname);
    /* Extract first IP address (in network byte order ) & return it */
    return (struct in_addr*)hostp->h_addr_list[0];
}

int connect_to(struct in_addr* ipAddress, int port)
{

    struct sockaddr_in socketAddr;
    int fd;
    
    /* Create socket - SOCK_STREAM means TCP */
    fd = socket(AF_INET, SOCK_STREAM, 0);
    if(fd < 0) {
	perror("Error creating socket");
	exit(1);
    }

    /* Create a structure that contains info on the address we want to
    ** connect to.
    */
    socketAddr.sin_family = AF_INET;	/* Family = Internet */
    socketAddr.sin_port = htons(port);	/* Port number in network byte order */
    socketAddr.sin_addr.s_addr = ipAddress->s_addr; /* IP address we're 
    						    ** connecting to. */

    /* Try to connect to the given address/port */
    if(connect(fd, (struct sockaddr*)&socketAddr, sizeof(socketAddr)) < 0) {
	perror("Error connecting");
	exit(1);
    }
    return fd;
    /* Now have a connected file descriptor */
}

void send_HTTP_request(int fd, char* file)
{
    char* requestString;

    /* Construct the HTTP request string */
    requestString = (char*)malloc(strlen(file) + 20);
    sprintf(requestString, "GET %s HTTP/1.0\r\n\r\n", file);

    /* Send the string to the file descriptor */
    /* Should really loop until all bytes sent OR error happens.
    ** Note that write() returns number of bytes written */
    if(write(fd, requestString, strlen(requestString)) < 1) {
	perror("Write error");
	exit(1);
    }
}

void get_and_output_HTTP_response(int fd)
{
    char buffer[1024];
    int numBytesRead;
    int eof = 0;

    while(!eof) {
	/* Read up to 1024 bytes from connection */
	numBytesRead = read(fd, buffer, 1024);
	if(numBytesRead < 0) {
	    perror("Read error\n");
	    exit(1);
	} else if(numBytesRead == 0) {
	    /* End of file - no more data to be received */
	    eof = 1;
	} else {
	    /* Got some data - write it out to standard output */
	    fwrite(buffer, 1, numBytesRead, stdout);
	}
    }
}

int main(int argc, char* argv[]) {
    int fd;
    struct in_addr* ipAddress;

    if(argc != 2) {
	fprintf(stderr, "Usage: %s hostname\n", argv[0]);
	exit(1);
    }

    ipAddress = name_to_IP_addr(argv[1]);
    if(!ipAddress) {
	fprintf(stderr, "%s is not a valid hostname\n", argv[1]);
	exit(1);
    }

    fd = connect_to(ipAddress, 80);
    send_HTTP_request(fd, "/");
    get_and_output_HTTP_response(fd);
    close(fd);
    return 0;
}