#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)
{
    int error;
    struct addrinfo* addressInfo;

    /* Convert hostname into IP address */
    error = getaddrinfo(hostname, NULL, NULL, &addressInfo);
    if(error) {
	return NULL;
    }
    /* Return first address in list */
    return &(((struct sockaddr_in*)(addressInfo->ai_addr))->sin_addr);
}

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);
    }

    socketAddr.sin_family = AF_INET;	/* Internet v4 family of protocols */
    socketAddr.sin_port = htons(port);	/* Port num - converted to network 
                                        ** byte order */
    socketAddr.sin_addr.s_addr = ipAddress->s_addr; /* IP address of server */

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

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

    /* Wrong original code: requestString = (char*)malloc(strlen(file) + 20);*/
    requestString = (char*)malloc(strlen(file) + strlen(host) + 26);
    /* Create request string to send:
     GET / HTTP/1.0
     Host: hostname

    */
    sprintf(requestString, "GET %s HTTP/1.0\r\nHost: %s\r\n\r\n", file, host);

    /* Send our request via fd (i.e. to server */
    /* Could have used fdopen then fprintf */
    /* Should really loop to ensure all bytes are sent -  note that write()
     * returns number of bytes sent, or -1 on error
     */
    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;

    /* Repeatedly loop until data received */
    while(!eof) {
	/* Read up to 1024 bytes */
	numBytesRead = read(fd, buffer, 1024);
	if(numBytesRead < 0) {
	    perror("Read error\n");
	    exit(1);
	} else if(numBytesRead == 0) {
	    /* End of file - connection closed */
	    eof = 1;
	} else {
	    /* Write out bytes to standard output */
	    /* Using fwrite allows for null characters in data */
	    fwrite(buffer, 1, numBytesRead, stdout);
	    /* Original code incorrectly used STDOUT_FILENO as second arg */
	}
    }
}

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

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

    /* Convert hostname to IP address */
    ipAddress = name_to_IP_addr(hostname);
    if(!ipAddress) {
	fprintf(stderr, "%s is not a valid hostname\n", hostname);
	exit(1);
    }

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