/*
 * Copyright 2000-2018 Vaadin Ltd.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package com.vaadin.client;

import com.google.gwt.core.client.JavaScriptObject;

/**
 * Utility class for fetching CSS properties from DOM StyleSheets JS object.
 */
public class CSSRule {

    private final String selector;
    private JavaScriptObject rules = null;

    /**
     *
     * @param selector
     *            the CSS selector to search for in the stylesheets
     * @param deep
     *            should the search follow any @import statements?
     */
    public CSSRule(final String selector, final boolean deep) {
        this.selector = selector;
        fetchRule(selector, deep);
    }

    // TODO how to find the right LINK-element? We should probably give the
    // stylesheet a name.
    private native void fetchRule(final String selector, final boolean deep)
    /*-{
    var sheets = $doc.styleSheets;
    for (var i = 0; i < sheets.length; i++) {
        var sheet = sheets[i];
        if (sheet.href && sheet.href.indexOf("VAADIN/themes")>-1) {
            // $entry not needed as function is not exported
            this.@com.vaadin.client.CSSRule::rules = @com.vaadin.client.CSSRule::searchForRule(Lcom/google/gwt/core/client/JavaScriptObject;Ljava/lang/String;Z)(sheet, selector, deep);
            return;
        }
    }
    this.@com.vaadin.client.CSSRule::rules = [];
    }-*/;

    /*
     * Loops through all current style rules and collects all matching to
     * 'rules' array. The array is reverse ordered (last one found is first).
     */
    private static native JavaScriptObject searchForRule(
            final JavaScriptObject sheet, final String selector,
            final boolean deep)
    /*-{
    if (!$doc.styleSheets)
    return null;

    selector = selector.toLowerCase('en');

    var allMatches = [];

    // IE handles imported sheet differently
    if (deep && sheet.imports && sheet.imports.length > 0) {
        for (var i=0; i < sheet.imports.length; i++) {
            // $entry not needed as function is not exported
            var imports = @com.vaadin.client.CSSRule::searchForRule(Lcom/google/gwt/core/client/JavaScriptObject;Ljava/lang/String;Z)(sheet.imports[i], selector, deep);
            allMatches.concat(imports);
        }
    }

    var theRules = new Array();
    if (sheet.cssRules)
        theRules = sheet.cssRules
    else if (sheet.rules)
        theRules = sheet.rules

    var j = theRules.length;
    for (var i=0; i<j; i++) {
        var r = theRules[i];
        if (r.type == 1 || sheet.imports) {
            var selectors = r.selectorText.toLowerCase('en').split(",");
            var n = selectors.length;
            for (var m=0; m<n; m++) {
                if (selectors[m].replace(/^\s+|\s+$/g, "") == selector) {
                    allMatches.unshift(r);
                    break; // No need to loop other selectors for this rule
                }
            }
        } else if (deep && r.type == 3) {
            // Search @import stylesheet
            // $entry not needed as function is not exported
            var imports = @com.vaadin.client.CSSRule::searchForRule(Lcom/google/gwt/core/client/JavaScriptObject;Ljava/lang/String;Z)(r.styleSheet, selector, deep);
            allMatches = allMatches.concat(imports);
        }
    }

    return allMatches;
    }-*/;

    /**
     * Returns a specific property value from this CSS rule.
     *
     * @param propertyName
     *            camelCase CSS property name
     * @return the value of the property as a String
     */
    public native String getPropertyValue(final String propertyName)
    /*-{
    var j = this.@com.vaadin.client.CSSRule::rules.length;
    for (var i=0; i<j; i++) {
        // $entry not needed as function is not exported
        var value = this.@com.vaadin.client.CSSRule::rules[i].style[propertyName];
        if (value)
            return value;
    }
    return null;
    }-*/;

    public String getSelector() {
        return selector;
    }

}