ede/ede-panel/applets/start-menu/MenuRules.cpp

#include <edelib/Debug.h>

#include "MenuRules.h"
#include "DesktopEntry.h"

typedef list<bool> Stack;
typedef list<bool>::iterator StackIt;

#if 0
static char *rules_str[] = {
	"None",
	"Filename",
	"Category",
	"And",
	"Or",
	"Not",
	"All"
};
#endif

MenuRules *menu_rules_new(void) {
	MenuRules *r = new MenuRules;
	r->rule_operator = MENU_RULES_OPERATOR_NONE;
	return r;
}

MenuRules *menu_rules_append_rule(MenuRulesList &rules, short rule, const char *data) {
	MenuRules *r = menu_rules_new();
	r->rule_operator = rule;

	if(data)
		r->data = data;

	/* NOTE: things are evaluated recursively, so we push deepest rule at the top */
	rules.push_front(r);
	return r;
}

void menu_rules_delete(MenuRules *r) {
	if(!r->subrules.empty()) {
		MenuRulesListIt it = r->subrules.begin(), it_end = r->subrules.end();

		while(it != it_end) {
			menu_rules_delete(*it);
			it = r->subrules.erase(it);
		}
	}

	delete r;
}

/* 
 * Rules are evaluated starting from the deepest one, and are much more like
 * lisp expressions. Each rule behaves like function, returning false or true and top function
 * gets applied on those results.
 *
 * TODO: this case will not work (KDE 3.5.x applications.menu):
 * <And>
 *   <Or>
 *     <Category>c1</Category>
 *     <Category>c2</Category>
 *     <Category>c3</Category>
 *   </Or>
 *   <Not><Category>c4</Category></Not>
 * </And>
 *
 * because due recrusion '<Not>...</Not>' result will be calculated inside '<Or>...</Or>' expression and
 * '<And>' will receive the only one value.
 */
static void eval_with_stack(MenuRules *m, DesktopEntry *en, Stack &result_stack) {
	if(!m->subrules.empty()) {
		MenuRulesListIt it = m->subrules.begin(), it_end = m->subrules.end();

		/* go to the deepest node */
		for(; it != it_end; ++it)
			eval_with_stack(*it, en, result_stack);
	}

	/* this will always evaluate to true so all items can be included */
	if(m->rule_operator == MENU_RULES_OPERATOR_ALL) {
		result_stack.push_front(true);
		return;
	}

	if(m->rule_operator == MENU_RULES_OPERATOR_FILENAME) {
		bool st = (m->data == en->get_id());
		result_stack.push_front(st);
		return;
	}

	if(m->rule_operator == MENU_RULES_OPERATOR_CATEGORY) {
		bool st = en->in_category(m->data.c_str());
		result_stack.push_front(st);
		return;
	}

	if(m->rule_operator == MENU_RULES_OPERATOR_AND) {
		StackIt it = result_stack.begin(), it_end = result_stack.end();

		/* 'and' always evalutes to true */
		bool st = true;

		while(it != it_end) {
			st &= *it;
			it = result_stack.erase(it);
		}

		result_stack.push_front(st);
		return;
	}

	/* operators 'not' and 'or' behaves much the same, except 'not' reverse the result additionally */
	if(m->rule_operator == MENU_RULES_OPERATOR_OR || m->rule_operator == MENU_RULES_OPERATOR_NOT) {
		StackIt it = result_stack.begin(), it_end = result_stack.end();

		/* 'or' and 'not' always evalutes to false */
		bool st = false;

		while(it != it_end) {
			st |= *it;
			it = result_stack.erase(it);
		}

		if(m->rule_operator == MENU_RULES_OPERATOR_NOT)
			st = !st;

		result_stack.push_front(st);
		return;
	}
}

bool menu_rules_eval(MenuRules *m, DesktopEntry *en) {
	Stack result_stack;
	eval_with_stack(m, en, result_stack);

	if(result_stack.size() == 1)
		goto get_first;
	else {
		/* 
		 * From the spec: "Each rule in a list of rules has a logical OR relationship, that is, desktop entries 
		 * which  match any rule are included in the menu."
		 */
		bool result = false;

		StackIt it = result_stack.begin(), it_end = result_stack.end();
		while(it != it_end) {
			result |= *it;
			result_stack.erase(it);
		}

		return result;
	}

get_first:
	return result_stack.front();
}