//
// !!! THIS IS A BUGGY CONCEPT/PROTOTYPE. USE AT YOUR OWN RISK !!!
//
// The following simple Webkit2GTK+ extension was hacked together
// in the sleepless night between 09th and 10th March 2018 by:
//
// Michal Idziorek <m.i@gmx.at>.
//
// It regjsters a document_loaded_callback, where the DOM is manipulated,
// i.e: a <span> with a number added to every link encountered.
//
// The urls are extracted from the DOM and shared with the browsers 
// process over a system V memory segment. 
//
// As an example, this can be used to enable keyboardless navigation 
// in surf by simply typing in the number of the link. 
//
// TODO: Support multiple clients! See source for more TODOS!
//       THE biggest limitation by now is the lazily hardcoded:
//       key_t my_ftok = ftok("~/surf-webext-dom-shared-mem",'a');
//
// Last Update: 10th March 2018
// 
// Last Tested: with surf commit 81f0452bc6c2a110239fa303ad1e72f11c33dc94
//              from htps://git.suckless.org/surf
// 

#include <webkit2/webkit-web-extension.h>

#include <sys/ipc.h>
#include <sys/shm.h>
#include <errno.h>
#include <string.h>

bool str_prefix(const char *str, const char *pre);

void
document_loaded_callback (WebKitWebPage *web_page,
                          GPtrArray     *elements,
                          GVariant      *user_data)
{

    // TODO: g_free where appropriate !!
    // TODO: allow focus on input boxes/forms 
    // TODO: Put this somehwere else? (but I dislike #defines)
    // share this info with surf itself! maybe surf can supply this along
    // the ftok path via the user_data GVariant.
    int MAX_LINKS=1024;
    int MAX_LINK_LENGTH=1024;
    int DEBUG=3;

    // get html doc
    WebKitDOMHTMLDocument *doc	   = webkit_web_page_get_dom_document(web_page);
    if(!WEBKIT_DOM_IS_HTML_DOCUMENT(doc))return;

    // get url
    char *url = webkit_dom_document_get_url (doc); 
    if(DEBUG>1) g_print("document_loaded (callback): %s\n", url);

    // tokenize url
    char *url_proto=strtok(url,"/");
    char *url_host=strtok(NULL,"/");
    if(DEBUG>2) g_print("proto: %s\n", url_proto);
    if(DEBUG>2) g_print("host: %s\n", url_host);

    // get html body
    WebKitDOMHTMLElement *body  = webkit_dom_document_get_body(doc);

    // get links (alt)
    /* altenative way, what is the difference (TODO)?
    WebKitDOMNodeList *links = webkit_dom_document_query_selector_all(doc,"a",NULL);
    gulong links_count		   = webkit_dom_node_list_get_length (links);
    g_print("extracted %i links\n",links_count);
    */

    // get links 
    WebKitDOMHTMLCollection *links = webkit_dom_document_get_links(doc);
    gulong links_count		   = webkit_dom_html_collection_get_length (links);
    if(DEBUG>1) g_print("extracted %i links\n",links_count);

    // attach to shared memory;
    key_t my_ftok = ftok("~/surf-webext-dom-shared-mem",'a');
    
    // TODO: should we need the size again here?
    int mem_seg=shmget(my_ftok,MAX_LINKS*MAX_LINK_LENGTH,IPC_CREAT|0660);
    if(mem_seg==-1)
    {
	g_print("shmget failed: %s\n",strerror(errno));
    }

    char *shared_buf=shmat(mem_seg,NULL,0);
    if(shared_buf==(void*)-1)
    {
	g_print("shmat failed: %s\n",strerror(errno));
    }
    
    // iterate over links
    for(gulong i=0;i<links_count;i++)
    {
	char buf[MAX_LINK_LENGTH]; // TODO: dynamic!

	WebKitDOMHTMLLinkElement * node = webkit_dom_html_collection_item (links,i);

	// add hint for keyboard navigation
	char *txt = webkit_dom_html_element_get_inner_html (node); 

	// TODO: style via stylesheet
	snprintf(buf,MAX_LINK_LENGTH, 
		"<span style='padding-right:5px;border-bottom:1px solid black;'>\
		<span style='font-size:13px;font-weight:bold;font-face:Arial;\
		      border:1px solid black;display:inline;color:white;\
		      background-color:#c0474c;padding:0 5px;margin:0;\
		      margin-right:5px;'>%i</span>%s</span>", i,txt);

	webkit_dom_html_element_set_inner_html (node,buf,NULL);

	// alternatively add hints at the end of the body
	// webkit_dom_element_insert_adjacent_html (body,"beforeend",buf,NULL);

	// TODO: this does not work for some sad reason. 
	// sadly, likely due to my misunderstanding.
	// node seems not to be a LinkElement at all :(
	// txt = webkit_dom_html_link_element_get_href (node); 
	// so we have to use this:
	txt = webkit_dom_element_get_attribute (node,"href");
	if(str_prefix(txt,"//"))     snprintf(buf,MAX_LINK_LENGTH,"%s%s",url_proto,txt);
	else if(str_prefix(txt,"/")) snprintf(buf,MAX_LINK_LENGTH,"%s//%s%s",url_proto,url_host,txt);
	else                         snprintf(buf,MAX_LINK_LENGTH,"%s",txt);
	
	if(i<MAX_LINKS) snprintf(&(shared_buf[MAX_LINK_LENGTH*i]),MAX_LINK_LENGTH,"%s\0",buf);
        if(DEBUG>10) g_print("extracted link : %s\n",buf);
    }
}

static void
page_created_callback (WebKitWebExtension *extension,
                       WebKitWebPage      *web_page,
                       GVariant           *user_data)
{
    g_signal_connect (web_page, "document-loaded", 
                      G_CALLBACK (document_loaded_callback), 
                      user_data);
}

G_MODULE_EXPORT void
webkit_web_extension_initialize_with_user_data (WebKitWebExtension *extension,
					        GVariant           *user_data)
{
    g_signal_connect (extension, "page-created", 
                      G_CALLBACK (page_created_callback),
                      user_data );
}

//https://stackoverflow.com/questions/4770985/how-to-check-if-a-string-starts-with-another-string-in-c
bool str_prefix(const char *str, const char *pre)
{
    size_t lenpre = strlen(pre),
           lenstr = strlen(str);
    return lenstr < lenpre ? false : strncmp(pre, str, lenpre) == 0;
}