/*
 * Raffael Himmelreich <raffi@raffi.at>
 *
 * Compile with:
 * gcc cover_art.c -o cover_art -lcurl `xml2-config --cflags` `xml2-config --libs`
 * 
 * Usage:
 * raffi@sofie:~/src/gtkpod/src$ ./cover_art "raffi banana phone"
 * http://images.amazon.com/images/P/B0000003HW.01.THUMBZZZ.jpg
 * raffi@sofie:~/src/gtkpod/src$
 *
*/ 

#include <curl/curl.h>
#include <curl/multi.h>
#include <curl/types.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <libxml/tree.h>
#include <libxml/parser.h>
#include <libxml/xpath.h>
#include <libxml/xpathInternals.h>

struct MemoryStruct {
	char *memory;
	size_t size;
};

void *myrealloc(void *ptr, size_t size)
{
	/* There might be a realloc() out there that doesn't like reallocing
	*      NULL pointers, so we take care of it here */
	if (ptr)
		return (void *)realloc(ptr, size);
	else
		return (void *)malloc(size);
}

size_t WriteMemoryCallback(void *ptr, size_t size, size_t nmemb, void *data)
{
	size_t realsize = size * nmemb;
	struct MemoryStruct *mem = (struct MemoryStruct *)data;

	mem->memory = (char *)myrealloc(mem->memory, mem->size + realsize + 1);
	if (mem->memory) {
		memcpy(&(mem->memory[mem->size]), ptr, realsize);
		mem->size += realsize;
		mem->memory[mem->size] = 0;
	}

	return realsize;
}

int get_cover_url(char *content, int length)
{
	xmlDocPtr doc;
	xmlXPathContextPtr xpathCtx; 
	xmlXPathObjectPtr xpathObj;
	const xmlChar *xpathExpr = BAD_CAST "//Details/ImageUrlSmall";
	int node_nr, ret = 0;
	
	xmlInitParser();

	doc = xmlReadMemory(content, length, "amazon.xml", NULL, 0);
	if ( doc == NULL ) {
		fprintf(stderr, "Failed to parse XML\n");
		return -1;
	}

	/* Create xpath evaluation context */
	xpathCtx = xmlXPathNewContext(doc);
	if( xpathCtx == NULL ) {
		fprintf(stderr,"Error: unable to create new XPath context\n");
		xmlFreeDoc(doc); 
		return -1;
	}

	/* Evaluate xpath expression */
	xpathObj = xmlXPathEvalExpression(xpathExpr, xpathCtx);
	if( xpathObj == NULL ) {
		fprintf(stderr,"Error: unable to evaluate xpath expression \"%s\"\n", xpathExpr);
		xmlXPathFreeContext(xpathCtx); 
		xmlFreeDoc(doc); 
		return -1;
	}

	node_nr = (xpathObj->nodesetval) ? xpathObj->nodesetval->nodeNr : 0;

	if ( node_nr )
		printf("%s\n", xmlNodeGetContent(xpathObj->nodesetval->nodeTab[0]));
	else ret = -1;

	/* Cleanup of XPath data */
	xmlXPathFreeObject(xpathObj);
	xmlXPathFreeContext(xpathCtx); 

	xmlFreeDoc(doc);
	xmlCleanupParser();

	return ret;
}


int main(int argc, char **argv)
{
#if defined(LIBXML_XPATH_ENABLED) && defined(LIBXML_SAX1_ENABLED)
	const char *LICENSE = "D1URM11J3F2CEH",
	           *tld = "com",
	           *music_mode = "music",
	           *locale = "us";
	char url[512];
	int ret, running_handles;
	CURL *curl;
	CURLM *curlm;
	char *search = curl_escape(argv[1], 0);
	struct MemoryStruct chunk;

	chunk.memory=NULL; /* we expect realloc(NULL, size) to work */
	chunk.size = 0;    /* no data at this point */

	ret = snprintf(url, sizeof(url), "http://xml.amazon.%s"
	        "/onca/xml3?t=webservices-20&dev-t=%s"
	        "&KeywordSearch=%s&mode=%s&type=lite&locale=%s&page=1&f=xml",
		tld, LICENSE, search, music_mode, locale);
	if ( ret == -1 ) fprintf(stderr, "Amazon search string too long!\n");

	curl_free(search);

	curl = curl_easy_init();
	curlm = curl_multi_init();

	curl_easy_setopt(curl, CURLOPT_URL, url);
	curl_easy_setopt(curl, CURLOPT_CONNECTTIMEOUT, 15);

	/* send all data to this function  */
	curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteMemoryCallback);

	/* we pass our 'chunk' struct to the callback function */
	curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)&chunk);

	/* some servers don't like requests that are made without a user-agent
	*      field, so we provide one */
	curl_easy_setopt(curl, CURLOPT_USERAGENT, "libcurl-agent/1.0");


	curl_multi_add_handle(curlm, curl);

	running_handles = 1;
	while ( running_handles > 0 )
		curl_multi_perform(curlm, &running_handles);

	curl_easy_cleanup(curl);
	curl_global_cleanup();

	get_cover_url(chunk.memory, chunk.size);

	if(chunk.memory)
		free(chunk.memory);

#else
 #error Please compile libxml2 with Xpath support to enjoy gtkpod's album art retrieval feature!
	fprintf(stderr, "You don't have Xpath support!");
#endif

	return 0;
}