#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);
static css_error named_sibling_node(void *pw, void *node,
		const css_qname *qname, void **sibling);
static css_error named_generic_sibling_node(void *pw, void *node,
		const css_qname *qname, void **sibling);
static css_error parent_node(void *pw, void *node, void **parent);
static css_error sibling_node(void *pw, void *node, void **sibling);
static css_error node_has_name(void *pw, void *node,
		const css_qname *qname, bool *match);
static css_error node_has_class(void *pw, void *node,
		lwc_string *name, bool *match);
static css_error node_has_id(void *pw, void *node,
		lwc_string *name, bool *match);
static css_error node_has_attribute(void *pw, void *node,
		const css_qname *qname, bool *match);
static css_error node_has_attribute_equal(void *pw, void *node,
		const css_qname *qname, lwc_string *value,
		bool *match);


/**
 * 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;
}


/**
 * Find the "next-sibling" of the given element having the given name
 *
 * This search corresponds to the "+ foo" combinator in CSS and will
 * find only "foo" element nodes that immediately precede the given
 * node under the same parent in the DOM. In CSS the tree is viewed
 * top-down and in libdom it is viewed from the bottom-up; as a result
 * "next" and "previous" are sometimes backwards. This is case-sensitive.
 *
 * \param pw       Pointer to the current SVG parser state
 * \param node     Libdom SVG node
 * \param qname    Name of the sibling node to search for
 * \param sibling  Address at which to store the sibling 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 sibling; otherwise,
 *       NULL will be stored at the address pointed to by \a sibling
 */
css_error named_sibling_node(void *pw, void *node,
		const css_qname *qname, void **sibling)
{
	UNUSED(pw);
	dom_node *n = node; /* the current node */
	dom_node *prev; /* the previous node */
	dom_exception err;
	dom_node_type type;
	dom_string *name;

	*sibling = NULL; /* default to nothing found */

	/* Begin the search; the first iteration we do outside of the
	 * loop. Implementation detil: dom_node_get_previous_sibling()
	 * increments the reference counter on the returned node. A
	 * comment within named_parent_node() explains why we
	 * decrement it ASAP. */
	err = dom_node_get_previous_sibling(n, &n);
	if (err != DOM_NO_ERR) {
		return CSS_OK;
	}

	while (n != NULL) {
		/* We're looking for the first ELEMENT sibling */
		err = dom_node_get_node_type(n, &type);
		if (err != DOM_NO_ERR) {
			dom_node_unref(n);
			return CSS_OK;
		}

		if (type == DOM_ELEMENT_NODE) {
			/* We found an element node, does it have the
			 * right name? */
			err = dom_node_get_node_name(n, &name);
			if (err != DOM_NO_ERR) {
				dom_node_unref(n);
				return CSS_OK;
			}

			if (dom_string_lwc_isequal(name,
					qname->name)) {
				/* The name is right, return it */
				*sibling = n;
			}

			/* There's only one next-sibling element node
			 * and we've already found it, so if its name
			 * wasn't right, we return the default value
			 * of NULL below */
			dom_string_unref(name);
			dom_node_unref(n);
			return CSS_OK;
		}

		/* Not an element node, so we move on the the previous
		 * previous sibling */
		err = dom_node_get_previous_sibling(n, &prev);
		if (err != DOM_NO_ERR) {
			dom_node_unref(n);
			return CSS_OK;
		}

		dom_node_unref(n);
		n = prev;
	}

	return CSS_OK;
}


/**
 * Find the first "subsequent-sibling" of the given element having the
 * given name
 *
 * This search corresponds to the "~ foo" combinator in CSS and will
 * find only "foo" element nodes that precede the given node (under
 * the same parent) in the DOM. In CSS the tree is viewed top-down and
 * in libdom it is viewed from the bottom-up; as a result "next" and
 * "previous" are sometimes backwards. This is case-sensitive.
 *
 * \param pw       Pointer to the current SVG parser state
 * \param node     Libdom SVG node
 * \param qname    Name of the sibling node to search for
 * \param sibling  Address at which to store the sibling 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 sibling; otherwise,
 *       NULL will be stored at the address pointed to by \a sibling
 */
css_error named_generic_sibling_node(void *pw, void *node,
		const css_qname *qname, void **sibling)
{
	UNUSED(pw);
	dom_node *n = node; /* the current node */
	dom_node *prev;     /* the previous node */
	dom_exception err;
	dom_node_type type;
	dom_string *name;


	*sibling = NULL; /* default to nothing found */

	/* Begin the search; the first iteration we do outside of the
	 * loop. Implementation detil: dom_node_get_previous_sibling()
	 * increments the reference counter on the returned node. A
	 * comment within named_parent_node() explains why we
	 * decrement it ASAP. */
	err = dom_node_get_previous_sibling(n, &n);
	if (err != DOM_NO_ERR) {
		return CSS_OK;
	}

	while (n != NULL) {
		err = dom_node_get_node_type(n, &type);
		if (err != DOM_NO_ERR) {
			dom_node_unref(n);
			return CSS_OK;
		}

		if (type == DOM_ELEMENT_NODE) {
			/* We only want ELEMENT nodes */
			err = dom_node_get_node_name(n, &name);
			if (err != DOM_NO_ERR) {
				dom_node_unref(n);
				return CSS_OK;
			}

			if (dom_string_lwc_isequal(name,
					qname->name)) {
				/* Found one. Save it and stop the search */
				dom_string_unref(name);
				dom_node_unref(n);
				*sibling = n;
				return CSS_OK;
			}

			dom_string_unref(name);
		}

		/* This sibling wasn't an element with the desired
		   name, so move on to the previous sibling */
		err = dom_node_get_previous_sibling(n, &prev);
		if (err != DOM_NO_ERR) {
			dom_node_unref(n);
			return CSS_OK;
		}

		dom_node_unref(n);
		n = prev;
	}

	return CSS_OK;
}


/**
 * Return a pointer to the given node's parent
 *
 * \param pw      Pointer to the current SVG parser state
 * \param node    Libdom SVG node
 * \param parent  Address at which to store the node's parent pointer
 *
 * \return Always returns CSS_OK
 */
css_error parent_node(void *pw, void *node, void **parent)
{
	UNUSED(pw);
	/* Libdom basically implements this for us */
	dom_element_parent_node(node, (struct dom_element **)parent);

	/* See the comment in named_parent_node() for why we decrement
	 * this reference counter here. */
	dom_node_unref(*parent);

	return CSS_OK;
}


/**
 * Find the "next-sibling" of the given element
 *
 * This search corresponds "+ *" in CSS and will find the first
 * element node that immediately precedes the given node under the
 * same parent in the DOM. In CSS the tree is viewed top-down and in
 * libdom it is viewed from the bottom-up; as a result "next" and
 * "previous" are sometimes backwards.
 *
 * \param pw       Pointer to the current SVG parser state
 * \param node     Libdom SVG node
 * \param sibling  Address at which to store the sibling 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 sibling; otherwise,
 *       NULL will be stored at the address pointed to by \a sibling
 */
css_error sibling_node(void *pw, void *node, void **sibling)
{
	UNUSED(pw);
	dom_node *n = node; /* the current node */
	dom_node *prev;     /* the previous node */
	dom_exception err;
	dom_node_type type;

	*sibling = NULL; /* default to nothing found */

	/* Begin the search; the first iteration we do outside of the
	 * loop. Implementation detil: dom_node_get_previous_sibling()
	 * increments the reference counter on the returned node. A
	 * comment within named_parent_node() explains why we
	 * decrement it ASAP. */
	err = dom_node_get_previous_sibling(n, &n);
	if (err != DOM_NO_ERR) {
		return CSS_OK;
	}

	while (n != NULL) {
		err = dom_node_get_node_type(n, &type);
		if (err != DOM_NO_ERR) {
			dom_node_unref(n);
			return CSS_OK;
		}

		if (type == DOM_ELEMENT_NODE) {
			/* We found a sibling node that is also an
			   element and that's all we wanted. */
			*sibling = n;
			dom_node_unref(n);
			return CSS_OK;
		}

		/* This sibling node was not an element; move on to
		   the previous sibling */
		err = dom_node_get_previous_sibling(n, &prev);
		if (err != DOM_NO_ERR) {
			dom_node_unref(n);
			return CSS_OK;
		}

		dom_node_unref(n);
		n = prev;
	}

	return CSS_OK;
}


/**
 * Test the given node for the given name
 *
 * This will return true (via the "match" pointer) if the libdom node
 * has the given name or if that name is the universal selector;
 * otherwise it returns false. The comparison is case-sensitive. It
 * corresponds to a rule like "body { ... }" in CSS.
 *
 * \param pw       Pointer to the current SVG parser state
 * \param node     Libdom SVG node to test
 * \param qname    Name to check for
 * \param match    Pointer to the test result
 *
 * \return Always returns CSS_OK
 */
css_error node_has_name(void *pw, void *node,
		const css_qname *qname, bool *match)
{
	struct svgtiny_parse_state *state;
	dom_string *name;
	dom_exception err;

	/* Start by checking to see if qname is the universal selector */
	state = (struct svgtiny_parse_state *)pw;
	if (lwc_string_isequal(qname->name,
			state->interned_universal, match) == lwc_error_ok) {
	  if (*match) {
		/* It's the universal selector. In NetSurf, all node
		 * names match the universal selector, and nothing in
		 * the libcss documentation suggests another approach,
		 * so we follow NetSurf here. */
		return CSS_OK;
	  }
	}

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

	/* Unlike with HTML, SVG element names are case-sensitive */
	*match = dom_string_lwc_isequal(name, qname->name);
	dom_string_unref(name);

	return CSS_OK;
}


/**
 * Test the given node for the given class
 *
 * This will return true (via the "match" pointer) if the libdom node
 * has the given class. The comparison is case-sensitive. It
 * corresponds to node.class in CSS.
 *
 * \param pw       Pointer to the current SVG parser state
 * \param node     Libdom SVG node to test
 * \param name     Class name to check for
 * \param match    Pointer to the test result
 *
 * \return Always returns CSS_OK
 */
css_error node_has_class(void *pw, void *node,
		lwc_string *name, bool *match)
{
	UNUSED(pw);
	/* libdom implements this for us and apparently it cannot fail */
	dom_element_has_class((dom_node *)node, name, match);
	return CSS_OK;
}


/**
 * Test the given node for the given id
 *
 * This will return true (via the "match" pointer) if the libdom node
 * has the given id. The comparison is case-sensitive. It corresponds
 * to node#id in CSS.
 *
 * \param pw       Pointer to the current SVG parser state
 * \param node     Libdom SVG node to test
 * \param name     Id to check for
 * \param match    Pointer to the test result
 *
 * \return Always returns CSS_OK
 */
css_error node_has_id(void *pw, void *node,
		lwc_string *name, bool *match)
{
	dom_string *attr;
	dom_exception err;
	struct svgtiny_parse_state *state;

	attr = NULL;    /* a priori the "id" attribute may not exist */
	*match = false; /* default to no match */

	state = (struct svgtiny_parse_state *)pw;
	err = dom_element_get_attribute((dom_node *)node,
				state->interned_id, &attr);
	if (err != DOM_NO_ERR || attr == NULL) {
		return CSS_OK;
	}

	*match = dom_string_lwc_isequal(attr, name);
	dom_string_unref(attr);

	return CSS_OK;
}


/**
 * Test the given node for the given attribute
 *
 * This will return true (via the "match" pointer) if the libdom node
 * has an attribute with the given name. The comparison is
 * case-sensitive. It corresponds to node[attr] in CSS.
 *
 * \param pw       Pointer to the current SVG parser state
 * \param node     Libdom SVG node to test
 * \param qname    Attribute name to check for
 * \param match    Pointer to the test result
 *
 * \return Returns CSS_OK if successful and CSS_NOMEM if anything
 *         goes wrong
 */
css_error node_has_attribute(void *pw, void *node,
		const css_qname *qname, bool *match)
{
	UNUSED(pw);
	dom_string *name;
	dom_exception err;

	/* intern the attribute name as a dom_string so we can
	 * delegate to dom_element_has_attribute() */
	err = dom_string_create_interned(
		(const uint8_t *) lwc_string_data(qname->name),
		lwc_string_length(qname->name),
		&name);
	if (err != DOM_NO_ERR) {
		return CSS_NOMEM;
	}

	err = dom_element_has_attribute((dom_node *)node, name, match);
	if (err != DOM_NO_ERR) {
		dom_string_unref(name);
		return CSS_OK;
	}

	dom_string_unref(name);
	return CSS_OK;
}


/**
 * Test the given node for an attribute with a specific value
 *
 * This will return true (via the "match" pointer) if the libdom node
 * has an attribute with the given name and value. The comparison is
 * case-sensitive. It corresponds to node[attr=value] in CSS.
 *
 * \param pw       Pointer to the current SVG parser state
 * \param node     Libdom SVG node to test
 * \param qname    Attribute name to check for
 * \param value    Attribute value to check for
 * \param match    Pointer to the test result
 *
 * \return Returns CSS_OK if successful and CSS_NOMEM if we cannot
 *         intern the attribute name (which usually indicates memory
 *         exhaustion)
 */
css_error node_has_attribute_equal(void *pw, void *node,
		const css_qname *qname, lwc_string *value,
		bool *match)
{
	/* Implementation note: NetSurf always returns "no match" when
	 * the value is empty (length zero). We allow it, because why
	 * not? */

	UNUSED(pw);
	dom_string *name;
	dom_string *attr_val;
	dom_exception err;

	/* Intern the attribute name as a dom_string so we can
	 * use dom_element_get_attribute() */
	err = dom_string_create_interned(
		(const uint8_t *) lwc_string_data(qname->name),
		lwc_string_length(qname->name),
		&name);
	if (err != DOM_NO_ERR) {
		return CSS_NOMEM;
	}

	err = dom_element_get_attribute((dom_node *)node, name, &attr_val);
	if ((err != DOM_NO_ERR) || (attr_val == NULL)) {
		/* There was an error getting the attribute's value or
		 * the attribute doesn't exist. So, no match? */
		dom_string_unref(name);
		*match = false;
		return CSS_OK;
	}

	/* Otherwise, we have the attribute value from the given node
	 * and all we need to do is compare. */
	dom_string_unref(name);
	*match = dom_string_lwc_isequal(attr_val, value);
	dom_string_unref(attr_val);

	return CSS_OK;
}