org.ambraproject.wombat.config.theme.ThemeGraph.java Source code

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Here is the source code for org.ambraproject.wombat.config.theme.ThemeGraph.java

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/*
 * Copyright (c) 2017 Public Library of Science
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 */

package org.ambraproject.wombat.config.theme;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableBiMap;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import org.ambraproject.wombat.config.site.SiteSet;

import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.TreeMap;
import java.util.function.Function;
import java.util.stream.Collectors;

/**
 * Internal representation of the set of all themes.
 * <p/>
 * The themes have the structure of a directed acyclic graph (DAG). If each theme declares no more than one parent, the
 * graph will be a tree.
 */
public class ThemeGraph {

    private final ImmutableBiMap<String, Theme> themes;

    @VisibleForTesting
    public ThemeGraph(Map<String, Theme> themes) {
        this.themes = ImmutableBiMap.copyOf(themes);
    }

    public Theme getTheme(String key) {
        return themes.get(key);
    }

    @VisibleForTesting
    public ImmutableSet<Theme> getThemes() {
        return themes.values();
    }

    public static class ThemeConfigurationException extends Exception {
        private ThemeConfigurationException(String message) {
            super(message);
        }

        public ThemeConfigurationException(String message, Throwable cause) {
            super(message, cause);
        }
    }

    /**
     * Factory method for the graph.
     */
    public static ThemeGraph create(Theme rootTheme, Collection<? extends Theme> internalThemes,
            Collection<? extends ThemeBuilder<?>> externalThemes) throws ThemeConfigurationException {
        Preconditions.checkArgument(internalThemes.contains(rootTheme));

        Map<String, ThemeBuilder<?>> themeBuilderMap = externalThemes.stream()
                .collect(Collectors.toMap(ThemeBuilder::getKey, Function.identity()));

        Map<String, Theme> created = new TreeMap<>(); // will eventually contain all themes
        created.putAll(Maps.uniqueIndex(internalThemes, Theme::getKey)); // initialize with internal themes

        // Make repeated passes looking for nodes whose parents have all been created
        int sizeLastPass = 0;
        while (!themeBuilderMap.isEmpty()) {
            for (Iterator<ThemeBuilder<?>> iterator = themeBuilderMap.values().iterator(); iterator.hasNext();) {
                ThemeBuilder<?> node = iterator.next();

                // Search for this node's parents in the map of already-created, immutable themes
                List<String> parentKeys = node.getParentKeys();
                List<Theme> parentThemes = Lists.newArrayListWithCapacity(parentKeys.size());
                for (String parentKey : parentKeys) {
                    Theme parentTheme = created.get(parentKey);
                    if (parentTheme != null) {
                        parentThemes.add(parentTheme);
                    } else if (!themeBuilderMap.containsKey(parentKey)) {
                        throw new ThemeConfigurationException("Unrecognized theme key: " + parentKey);
                    } else {
                        // At least one parent has not been created yet
                        parentThemes = null;
                        break;
                    }
                }

                if (parentThemes != null) {
                    // All parents were found
                    Theme immutableNode = node.build(rootTheme, parentThemes);
                    created.put(immutableNode.getKey(), immutableNode);
                    iterator.remove(); // Remove this node from the to-be-created pool
                } // Else, leave this node in the pool and look for more matches
            }

            // Check that the to-be-created pool shrank by at least 1, to prevent infinite looping
            if (created.size() <= sizeLastPass) {
                throw new ThemeConfigurationException(
                        "A parentage cycle exists within: " + themeBuilderMap.keySet());
            }
            sizeLastPass = created.size();
        }

        return new ThemeGraph(created);
    }

    /**
     * Dump a human-friendly description of all themes, starting at the root, for logging and debugging purposes only.
     */
    public Iterable<ThemeDebugInfo> describe(SiteSet siteSet) {
        return ThemeDebugInfo.describe(this, siteSet);
    }

}