#include <libcss/libcss.h>

#include "svgtiny.h"
#include "svgtiny_internal.h"

static css_error node_name(void *pw, void *node, css_qname *qname);
static css_error node_classes(void *pw, void *node,
		lwc_string ***classes, uint32_t *n_classes);
static css_error node_id(void *pw, void *node, lwc_string **id);
static css_error named_parent_node(void *pw, void *node,
		const css_qname *qname, void **parent);


/**
 * Resolve a relative URL to an absolute one by doing nothing. This is
 * the simplest possible implementation of a URL resolver, needed for
 * parsing CSS.
 */
css_error svgtiny_resolve_url(void *pw,
		const char *base, lwc_string *rel, lwc_string **abs)
{
	UNUSED(pw);
	UNUSED(base);

	/* Copy the relative URL to the absolute one (the return
	   value) */
	*abs = lwc_string_ref(rel);
	return CSS_OK;
}

/**
 * Create a stylesheet with the default set of params.
 *
 * \param sheet A stylesheet pointer, passed in by reference, that
 * we use to store the newly-created stylesheet.
 * \param inline_style True if this stylesheet represents an inline
 * style, and false otherwise.
 *
 * \return The return value from css_stylesheet_create() is returned.
 */
css_error svgtiny_create_stylesheet(css_stylesheet **sheet,
		bool inline_style)
{
	css_stylesheet_params params;

	params.params_version = CSS_STYLESHEET_PARAMS_VERSION_1;
	params.level = CSS_LEVEL_DEFAULT;
	params.charset = NULL;
	params.url = "";
	params.title = NULL;
	params.allow_quirks = false;
	params.inline_style = inline_style;
	params.resolve = svgtiny_resolve_url;
	params.resolve_pw = NULL;
	params.import = NULL;
	params.import_pw = NULL;
	params.color = NULL;
	params.color_pw = NULL;
	params.font = NULL;
	params.font_pw = NULL;

	return css_stylesheet_create(&params, sheet);
}


/**************************/
/* libcss select handlers */
/**************************/
/*
 * From here on we implement the "select handler "API defined in
 * libcss's include/libcss/select.h and discussed briefly in its
 * docs/API document.
 */


/**
 * Retrieve the given node's name
 *
 * \param pw     Pointer to the current SVG parser state
 * \param node   Libdom SVG node
 * \param qname  Address at which to store the node name
 *
 * \return CSS_OK on success, or CSS_NOMEM if anything goes wrong
 */
css_error node_name(void *pw, void *node, css_qname *qname)
{
	dom_string *name;
	dom_exception err;
	struct svgtiny_parse_state *state;

	err = dom_node_get_node_name((dom_node *)node, &name);
	if (err != DOM_NO_ERR) {
		return CSS_NOMEM;
	}

	state = (struct svgtiny_parse_state *)pw;
	qname->ns = lwc_string_ref(state->interned_svg_xmlns);

	err = dom_string_intern(name, &qname->name);
	if (err != DOM_NO_ERR) {
		dom_string_unref(name);
		return CSS_NOMEM;
	}

	dom_string_unref(name);

	return CSS_OK;
}


/**
 * Retrieve the given node's classes
 *
 * \param pw         Pointer to the current SVG parser state
 * \param node       Libdom SVG node
 * \param classes    Address at which to store the class name array
 * \param n_classes  Address at which to store the length of the class
 *                   name array
 *
 * \return CSS_OK on success, or CSS_NOMEM if anything goes wrong
 *
 * \note CSS_NOMEM is not possible in practice as of libdom-0.4.1,
 *       because the underlying libdom function never fails
 */
css_error node_classes(void *pw, void *node,
		lwc_string ***classes, uint32_t *n_classes)
{
	UNUSED(pw);
	dom_exception err;

	err = dom_element_get_classes((dom_node *)node, classes, n_classes);

	/* The implementation does not do it, but the documentation
	   for dom_element_get_classes() says that a DOM_NO_MEM_ERR is
	   possible here, so we handle it to be on the safe side. */
	if (err != DOM_NO_ERR) {
		return CSS_NOMEM;
	}

	return CSS_OK;
}


/**
 * Retrieve the given node's id
 *
 * \param pw    Pointer to the current SVG parser state
 * \param node  Libdom SVG node
 * \param id    Address at which to store the id
 *
 * \return      CSS_OK on success, or CSS_NOMEM if anything goes wrong
 */
css_error node_id(void *pw, void *node, lwc_string **id)
{
	dom_string *attr;
	dom_exception err;
	struct svgtiny_parse_state *state;

	/* Begin with the assumption that this node has no id */
	*id = NULL;

	state = (struct svgtiny_parse_state *)pw;
	err = dom_element_get_attribute((dom_node *)node,
					state->interned_id, &attr);
	if (err != DOM_NO_ERR) {
		return CSS_NOMEM;
	}
	else if (attr == NULL) {
		/* The node has no id attribute and our return value
		   is already set to NULL so we're done */
		return CSS_OK;
	}

	/* If we found an id attribute (a dom_string), intern it into
	   an lwc_string that we can return, and then cleanup the
	   dom_string. */
	err = dom_string_intern(attr, id);
	if (err != DOM_NO_ERR) {
		dom_string_unref(attr);
		return CSS_NOMEM;
	}
	dom_string_unref(attr);
	return CSS_OK;
}



/**
 * Find the first parent of the given element having the given name
 *
 * \param pw      Pointer to the current SVG parser state
 * \param node    Libdom SVG node
 * \param qname   Name of the parent node to search for
 * \param parent  Address at which to store the parent node pointer
 *
 * \return Always returns CSS_OK
 *
 * \post If a suitable element is found, a pointer to it will be
 *       stored at the address pointed to by \a parent; otherwise,
 *       NULL will be stored at the address pointed to by \a parent
 */
css_error named_parent_node(void *pw, void *node,
		const css_qname *qname, void **parent)
{
	UNUSED(pw);
	/* dom_element_named_parent_node() was invented to implement
	 * this select handler so there isn't much for us to do except
	 * call it. It's OK if node isn't an element, libdom checks
	 * for it. */
	dom_element_named_parent_node((dom_element *)node,
				qname->name,
				(struct dom_element **)parent);

	/* Implementation detail: dom_element_named_parent_node()
	 * increments the reference count of the parent element before
	 * returning it to us. According to docs/RefCnt in the libdom
	 * repository, this will prevent the parent element from being
	 * destroyed if it is pruned from the DOM. That sounds good,
	 * since we don't want to be using a pointer to an object that
	 * has been destroyed... but we also have no way of later
	 * decrementing the reference count ourselves, and don't want
	 * to make the returned node eternal. Decrementing the
	 * reference counter now allows it to be destroyed when the
	 * DOM no longer needs it, and so long as no other parts of
	 * libsvgtiny are messing with the DOM during parsing, that
	 * shouldn't (ha ha) cause any problems. */
	dom_node_unref(*parent);

	return CSS_OK;
}