/*************************************************************************
** AttributeExtractor.cpp                                               **
**                                                                      **
** This file is part of dvisvgm -- a fast DVI to SVG converter          **
** Copyright (C) 2005-2022 Martin Gieseking <martin.gieseking@uos.de>   **
**                                                                      **
** This program is free software; you can redistribute it and/or        **
** modify it under the terms of the GNU General Public License as       **
** published by the Free Software Foundation; either version 3 of       **
** the License, or (at your option) any later version.                  **
**                                                                      **
** This program is distributed in the hope that it will be useful, but  **
** WITHOUT ANY WARRANTY; without even the implied warranty of           **
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the         **
** GNU General Public License for more details.                         **
**                                                                      **
** You should have received a copy of the GNU General Public License    **
** along with this program; if not, see <http://www.gnu.org/licenses/>. **
*************************************************************************/

#include <algorithm>
#include <array>
#include "AttributeExtractor.hpp"

using namespace std;

/** Constructs a new run object for an attribute and a sequence of sibling nodes.
 *  @param[in] attr attribute to look for
 *  @param[in] first first element of node sequence to scan */
AttributeExtractor::AttributeRun::AttributeRun (const Attribute &attr, XMLElement *first) {
	_length = 1;
	_first = first;
	for (_last=_first->next(); _last; _last=_last->next()) {
		if (_last->toText() || _last->toCData())  // don't include text/CDATA nodes
			break;
		if (XMLElement *childElem = _last->toElement()) {
			if (!groupable(*childElem))
				break;
			const char *val = childElem->getAttributeValue(attr.name);
			if (val && val == attr.value)
				++_length;
			else
				break;
		}
	}
	if (_first != _last && _last)
		_last = _last->prev();
}


const char* AttributeExtractor::info () const {
	return "move common attributes from a sequence of elements to enclosing groups";
}


/** Performs the attribute extraction on a given context node. Each extracted
 *  attribute gets its own group, i.e. the extraction of multiple attributes
 *  of the same elements leads to nested groups.
 *  @param[in] context attributes of all children in this element are extracted
 *  @param[in] recurse if true, the algorithm is recursively performed on all descendant elements */
void AttributeExtractor::execute (XMLElement *context, bool recurse) {
	if (!context || context->empty())
		return;
	if (recurse) {
		for (auto node : *context) {
			if (XMLElement *elem = node->toElement())
				execute(elem, true);
		}
	}
	for (XMLNode *child=context->firstChild(); child; child=child->next()) {
		if (XMLElement *elem = child->toElement())
			child = extractAttribute(elem);
	}
}


/** Looks for the first attribute not yet processed and tries to group it. If
 *  there is a sequence of adjacent sibling nodes N1,...,Nn with an identical inheritable
 *  attribute, the function creates a group element with this attribute and moves the
 *  nodes N1,...,Nn into that group. The group is inserted at the former position of N1.
 *  @param[in] elem first element of a node sequence with potentially identical attributes
 *  @return the new group element if attributes could be grouped, 'elem' otherwise  */
XMLNode* AttributeExtractor::extractAttribute (XMLElement *elem) {
	for (const auto &currentAttribute : elem->attributes()) {
		if (!inheritable(currentAttribute) || extracted(currentAttribute))
			continue;
		AttributeRun run(currentAttribute, elem);
		if (run.length() >= MIN_RUN_LENGTH) {
			XMLElement::Attribute attrib = currentAttribute;
			XMLElement *group = XMLElement::wrap(run.first(), run.last(), "g");
			group->addAttribute(attrib.name, attrib.value);
			// remove attribute from the grouped elements but keep it on elements with 'id' attribute
			// since they can be referenced, and keep 'fill' attribute on animation elements
			for (XMLNode *node : *group) {
				XMLElement *elem = node->toElement();
				if (elem && extractable(attrib, *elem))
					elem->removeAttribute(attrib.name);
			}
			// continue with children of the new group but ignore the just extracted attribute
			_extractedAttributes.insert(attrib.name);
			execute(group, false);
			_extractedAttributes.erase(attrib.name);
			return group;
		}
	}
	return elem;
}


/** Checks whether an element type is allowed to be put in a group element (<g>...</g>).
 *  For now we only consider a subset of the actually allowed set of elements.
 *  @param[in] elem name of element to check
 *  @return true if the element is groupable */
bool AttributeExtractor::groupable (const XMLElement &elem) {
	// https://www.w3.org/TR/SVG/struct.html#GElement
	static const char *names[] = {
		"a", "altGlyphDef", "animate", "animateColor", "animateMotion", "animateTransform",
		"circle", "clipPath", "color-profile", "cursor", "defs", "desc", "ellipse", "filter",
		"font", "font-face", "foreignObject", "g", "image", "line", "linearGradient", "marker",
		"mask", "path", "pattern", "polygon", "polyline", "radialGradient", "rect", "set",
		"style", "switch", "symbol", "text", "title", "use", "view"
	};
	return binary_search(begin(names), end(names), elem.name(), [](const string &name1, const string &name2) {
		return name1 < name2;
	});
}


/** Checks whether an SVG attribute A of an element E implicitly propagates its properties
 *  to all child elements of E that don't specify A. For now we only consider a subset of
 *  the inheritable properties.
 *  @param[in] attrib name of attribute to check
 *  @return true if the attribute is inheritable */
bool AttributeExtractor::inheritable (const Attribute &attrib) {
	// subset of inheritable properties listed on https://www.w3.org/TR/SVG11/propidx.html
	// clip-path is not inheritable but can be moved to the parent element as long as
	// no child gets an different clip-path attribute
	// https://www.w3.org/TR/SVG11/styling.html#Inheritance
	static const char *names[] = {
		"clip-path", "clip-rule", "color", "color-interpolation", "color-interpolation-filters", "color-profile",
		"color-rendering", "direction", "fill", "fill-opacity", "fill-rule", "font", "font-family", "font-size",
		"font-size-adjust", "font-stretch", "font-style", "font-variant", "font-weight", "glyph-orientation-horizontal",
		"glyph-orientation-vertical", "letter-spacing", "paint-order", "stroke", "stroke-dasharray", "stroke-dashoffset",
		"stroke-linecap", "stroke-linejoin", "stroke-miterlimit", "stroke-opacity", "stroke-width", "transform",
		"visibility", "word-spacing", "writing-mode"
	};
	return binary_search(begin(names), end(names), attrib.name, [](const string &name1, const string &name2) {
		return name1 < name2;
	});
}


/** Checks whether an attribute is allowed to be removed from a given element. */
bool AttributeExtractor::extractable (const Attribute &attrib, XMLElement &element) {
	if (element.hasAttribute("id"))
		return false;
	if (attrib.name != "fill")
		return true;
	// the 'fill' attribute of animation elements has different semantics than
	// that of graphics elements => don't extract it from animation nodes
	// https://www.w3.org/TR/SVG11/animate.html#TimingAttributes
	static const char *names[] = {
		"animate", "animateColor", "animateMotion", "animateTransform", "set"
	};
	auto it = find_if(begin(names), end(names), [&](const string &name) {
		return element.name() == name;
	});
	return it == end(names);
}


/** Returns true if a given attribute was already extracted from the
 *  current run of elements. */
bool AttributeExtractor::extracted (const Attribute &attr) const {
	return _extractedAttributes.find(attr.name) != _extractedAttributes.end();
}
