/* 
 * myturl.com URL Shortener (C Client)
 * by Mike Crute (mcrute@gmail.com)
 * on December 1, 2009
 *
 * compile with: gcc -lcurl -o myturl myturl_client.c
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <curl/curl.h>

#define TRUE 1
#define FALSE 0


static const char *URL_BASE = "http://myturl.com/add-url?url=";
static int it_worked = FALSE;


inline
void
blow_up(const char *message)
{
    perror(message);
    exit(EXIT_FAILURE);
}


inline
void *
safe_malloc(size_t size)
{
    char *location = calloc(1, size);

    if (location == NULL) {
        blow_up("You ran out of memory!");
    }

    return location;
}


inline
void
safe_free(void *stuff)
{
    free(stuff);
    stuff = NULL;
}


char *
chomp_end(const char *instr)
{
    size_t len = strlen(instr);

    char *output = safe_malloc(len);
    strlcpy(output, instr, len - 1);

    return output;
}


inline 
int
starts_with(const char *instr, const char* value)
{
    return !(strncmp(instr, value, strlen(value)));
}


inline 
int
char_in(const char *instr, char testval)
{
    return !(strchr(instr, (int)testval) == NULL);
}


char
to_hex(char code)
{
    static char hex[] = "0123456789abcdef";
    return hex[code & 15];
}


char *
url_quote(char *string)
{
    static char *acceptable = "-_.~";

    char *buffer = safe_malloc(strlen(string) * 3 + 1);
    char *strpos = string;
    char *bufpos = buffer;

    while (*strpos) {
        if (isalnum(*strpos) || char_in(acceptable, *strpos)) {
            *bufpos++ = *strpos;
        } else if (*strpos == ' ') {
            *bufpos++ = '+';
        } else {
            *bufpos++ = '%';
            *bufpos++ = to_hex(*strpos >> 4);
            *bufpos++ = to_hex(*strpos & 15);
        }

        *strpos++;
    }

    return buffer;
}


char *
get_value_part(const char *instr)
{
    size_t len = strlen(instr);

    char *offset = strpbrk(instr, ":") + 2;
    size_t slice_size = len - (instr - offset);

    char *output = safe_malloc(len);
    strlcpy(output, offset, slice_size);

    return output;
}


size_t 
handle_headers(char *instr, size_t size, size_t slen, void *outstream)
{ 
    char *header = chomp_end(instr);

    if (starts_with(header, "X-MyTurl:")) {
        char *value = get_value_part(header);
        printf("%s\n", value);
        safe_free(value);
        it_worked = TRUE;
    }

    safe_free(header);
    return size * slen;
}


void
silence_curl(CURL *curl)
{
    FILE *devnull = fopen("/dev/null", "w");
    if (devnull == NULL) {
        blow_up("Could not open /dev/null.");
    }

    curl_easy_setopt(curl, CURLOPT_WRITEDATA, devnull);
}


inline
char *
string_join(const char *lhs, const char *rhs)
{
    char *output = safe_malloc(strlen(lhs) + strlen(rhs));
    sprintf(output, "%s%s", lhs, rhs);
    return output;
}


int
main(int argc, char **argv)
{
    if (argc < 2) {
        blow_up("This program takes only one argument, the URL.");
    }

    CURL *curl = curl_easy_init();
    if (!curl) {
        blow_up("Failed to initialize curl!");
    }

    silence_curl(curl);
    curl_easy_setopt(curl, CURLOPT_HEADERFUNCTION, handle_headers);

    char *encoded = url_quote(argv[1]);
    char *url = string_join(URL_BASE, encoded);
    curl_easy_setopt(curl, CURLOPT_URL, url);

    CURLcode result = curl_easy_perform(curl);
    if (result != 0) {
        blow_up("Couldn't contact the service!");
    }

    if (it_worked == FALSE) {
        perror("No turl was generated. Check your URL.");
    }

    curl_easy_cleanup(curl);
    safe_free(url);
    safe_free(encoded);

    return EXIT_SUCCESS;
}