ResourcesTemplatingFunctions

/**
 * This file Copyright (c) 2016-2017 Magnolia International
 * Ltd.  (http://www.magnolia-cms.com). All rights reserved.
 *
 *
 * This file is dual-licensed under both the Magnolia
 * Network Agreement and the GNU General Public License.
 * You may elect to use one or the other of these licenses.
 *
 * This file is distributed in the hope that it will be
 * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the
 * implied warranty of MERCHANTABILITY or FITNESS FOR A
 * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT.
 * Redistribution, except as permitted by whichever of the GPL
 * or MNA you select, is prohibited.
 *
 * 1. For the GPL license (GPL), you can redistribute and/or
 * modify this file under the terms of the GNU General
 * Public License, Version 3, as published by the Free Software
 * Foundation.  You should have received a copy of the GNU
 * General Public License, Version 3 along with this program;
 * if not, write to the Free Software Foundation, Inc., 51
 * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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package info.magnolia.modules.resources.templating;

import info.magnolia.module.resources.ResourceLinker;
import info.magnolia.resourceloader.Resource;
import info.magnolia.resourceloader.ResourceOrigin;
import info.magnolia.resourceloader.ResourceVisitor;

import java.util.Arrays;
import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.regex.PatternSyntaxException;

import javax.inject.Inject;

/**
 * Templating functions for creating links to web resources such as css and js files by given patterns.
 *
 * <p>Provide a single pattern or a list of patterns to match files from all resources. Use methods {@link #css(String)},
 * {@link #css(List)}, {@link #cachedCss(String)}, {@link #cachedCss(List)}, {@link #js(String)}, {@link #js(List)},
 * {@link #cachedJs(String)} or {@link #cachedJs(List)} demanding on your needs.</p>
 *
 * <p>The methods create printable html tags such as the followings:<br/>
 * <code>
 * &lt;script src="/.resources/travel-demo-theme/js/html5shiv.js"&gt;&lt;/script&gt;<br/>
 * &lt;link rel="stylesheet" type="text/css" href="/.resources/foobar/webresources/css/a.css"/&gt;<br/>
 * &lt;link rel="stylesheet" type="text/css" media="all" href="/.resources/foobar/webresources/css/a~2016-12-08-02-56-06-000~cache.css"/&gt;
 * </code></p>
 *
 * <p>Example calls:
 * <pre>
 * ${resfn.css("/travel-demo-theme.*css")} (single pattern)
 * ${resfn.js("/travel-demo-theme.*js")} (single pattern)
 * ${resfn.css(["/foobar.*css", ".*magnolia.*css"])} (pattern list)
 * ${resfn.css(["/foobar.*css", ".*magnolia.*css"], "media='all'")} (pattern list and other properties argument with single quotes)
 * ${resfn.css(["/foobar.*css", ".*magnolia.*css"], "media=\"all\"")} (pattern list and other properties argument with escaped double quotes)
 * ${resfn.cachedJs(["/foobar/.*.js", "/travel-demo/.*.js"])} (call to cached files)
 * </pre></p>
 *
 * <p>This templating functions class originates from the project <i>neat-resources</i> by rah003@github.com.</p>
 *
 * @see <a href="https://documentation.magnolia-cms.com/display/DOCS/resfn">https://documentation.magnolia-cms.com/display/DOCS/resfn</a>
 */
public class ResourcesTemplatingFunctions {

    public static final String NAME = "resfn";

    protected static final String CSS_SUFFIX = "\"/>";
    protected static final String JS_PREFIX = "<script src=\"";
    protected static final String JS_SUFFIX = "\"></script>";

    private final ResourceOrigin origin;
    private final ResourceLinker linker;

    @Inject
    public ResourcesTemplatingFunctions(ResourceOrigin resourceOrigin, ResourceLinker linker) {
        this.origin = resourceOrigin;
        this.linker = linker;
    }


    /**
     * Generates css links for all css files matching the provided pattern.
     */
    public String css(String pattern) {
        return css(Arrays.asList(new String[] { pattern }));
    }

    /**
     * Generates css links for all css files matching the provided pattern; css links will contain the provided other attributes.
     */
    public String css(String pattern, String otherAttributes) {
        return css(Arrays.asList(new String[] { pattern }), otherAttributes);
    }

    /**
     * Generates css links for all css files matching the provided pattern(s).
     */
    public String css(final List<String> patterns) {
        return css(patterns, null);
    }

    /**
     * Generates css links for all css files matching the provided pattern(s); css links will contain the provided other attributes.
     */
    public String css(List<String> patterns, String otherAttributes) {
        return generate(patterns, getCssPrefix(otherAttributes), CSS_SUFFIX, false);
    }

    /**
     * Generates cached css links for all css files matching the provided pattern.
     */
    public String cachedCss(String pattern) {
        return cachedCss(Arrays.asList(new String[] { pattern }));
    }

    /**
     * Generates cached css links for all css files matching the provided pattern; css links will contain the provided other attributes.
     */
    public String cachedCss(String pattern, String otherAttributes) {
        return cachedCss(Arrays.asList(new String[] { pattern }), otherAttributes);
    }

    /**
     * Generates cached css links for all css files matching the provided pattern(s).
     */
    public String cachedCss(final List<String> patterns) {
        return cachedCss(patterns, null);
    }

    /**
     * Generates cached css links for all css files matching the provided pattern(s); css links will contain the provided other attributes.
     */
    public String cachedCss(List<String> patterns, String otherAttributes) {
        return generate(patterns, getCssPrefix(otherAttributes), CSS_SUFFIX, true);
    }

    /**
     * Generates js links for all js files matching the provided pattern.
     */
    public String js(String pattern) {
        return js(Arrays.asList(new String[] { pattern }));
    }

    /**
     * Generates js links for all js files matching provided pattern(s).
     */
    public String js(final List<String> patterns) {
        return generate(patterns, JS_PREFIX, JS_SUFFIX, false);
    }

    /**
     * Generates cached js links for all js files matching the provided pattern.
     */
    public String cachedJs(String pattern) {
        return cachedJs(Arrays.asList(new String[] { pattern }));
    }

    /**
     * Generates cached js links for all js files matching the provided pattern(s).
     */
    public String cachedJs(final List<String> patterns) {
        return generate(patterns, JS_PREFIX, JS_SUFFIX, true);
    }

    /**
     * Generates the links to .css or .js files. Returns all "links" as printable html code.
     */
    private String generate(List<String> patterns, String prefix, String suffix, final boolean isCached) {
        // yes, order matters!
        Map<String, List<String>> intermediates = new LinkedHashMap<>();
        patterns.stream()
                .forEach(pattern -> intermediates.put(pattern, new LinkedList<>()));
        origin.traverseWith(new ResourceVisitor() {

            @Override
            public void visitFile(final Resource resource) {
                patterns.stream()
                        .filter(pattern -> matchSafely(resource.getPath(), pattern))
                        .map(pattern -> intermediates.get(pattern))
                        .forEach(results -> results.add(prefix + linker.linkTo(resource.getPath(), isCached) + suffix));
            }

            private boolean matchSafely(String resource, String pattern) {
                try {
                    return resource.matches(pattern);
                } catch (PatternSyntaxException e) {
                    // ignore
                }
                return false;
            }

            @Override
            public boolean visitDirectory(Resource resource) {
                return true;
            }
        });

        StringBuilder results = new StringBuilder();
        List<String> hits = new LinkedList<>();
        // de dup (first match wins)
        intermediates.values().stream()
                .forEach(patternResults -> patternResults.stream()
                        .filter(potentialHit -> !hits.contains(potentialHit))
                        .forEach(hit -> {
                            results.append(hit).append("\n");
                            hits.add(hit);
                        }));

        return results.toString();
    }

    private static String getCssPrefix(String otherAttributes) {
        return "<link rel=\"stylesheet\" type=\"text/css\" " + (otherAttributes == null ? "" : otherAttributes + " ") + "href=\"";
    }

}