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/*******************************************************************************
 * Copyright (c) 2003, 2017 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.osgi.internal.framework;

import java.io.*;
import java.nio.charset.StandardCharsets;
import java.util.*;
import java.util.Map.Entry;
import org.eclipse.osgi.internal.debug.Debug;
import org.eclipse.osgi.internal.util.Tokenizer;

/**
 * This class maps aliases.
 */
public class AliasMapper {
	private static final Map> processorAliasTable = new HashMap<>();
	private static final Map processorCanonicalTable = new HashMap<>();
	private static final Map> osnameAliasTable = new HashMap<>();
	private static final Map osnameCanonicalTable = new HashMap<>();
	static {
		getTables("osname.aliases", osnameAliasTable, osnameCanonicalTable); //$NON-NLS-1$
		getTables("processor.aliases", processorAliasTable, processorCanonicalTable); //$NON-NLS-1$
	}

	private static void getTables(String resourceName, Map> aliasTable, Map canonicalTable) {
		InputStream in = AliasMapper.class.getResourceAsStream(resourceName);
		if (in != null) {
			try {
				initAliases(in, aliasTable, canonicalTable);
			} finally {
				try {
					in.close();
				} catch (IOException ee) {
					// nothing
				}
			}
		}
	}

	/**
	 * Return the master alias for the processor.
	 *
	 * @param processor Input name
	 * @return aliased name (if any)
	 */
	public Collection getProcessorAliases(String processor) {
		return getAlias(processor.toLowerCase(), processorAliasTable);
	}

	/**
	 * Return the master alias for the osname.
	 *
	 * @param osname Input name
	 * @return aliased name (if any)
	 */
	public Collection getOSNameAliases(String osname) {
		return getAlias(osname.toLowerCase(), osnameAliasTable);
	}

	public String getCanonicalOSName(String osname) {
		String lowerName = osname.toLowerCase();
		String result = osnameCanonicalTable.get(lowerName);
		if (result == null) {
			if (lowerName.startsWith("windows")) { //$NON-NLS-1$
				return "win32"; //$NON-NLS-1$
			}
		}
		return result == null ? osname : result;
	}

	public String getCanonicalProcessor(String processor) {
		String result = processorCanonicalTable.get(processor.toLowerCase());
		return result == null ? processor : result;
	}

	private Collection getAlias(String name, Map> aliasMap) {
		if (name == null) {
			return Collections.emptyList();
		}
		Collection aliases = aliasMap == null ? null : aliasMap.get(name);
		if (aliases != null) {
			return Collections.unmodifiableCollection(aliases);
		}
		return Collections.singletonList(name.toLowerCase());
	}

	/**
	 * Read alias data and populate a Map.
	 *
	 * @param in InputStream from which to read alias data.
	 * @return Map of aliases.
	 */
	private static Map> initAliases(InputStream in, Map> aliasTable, Map canonicalTable) {
		try {
			BufferedReader br = new BufferedReader(new InputStreamReader(in, StandardCharsets.UTF_8));
			Map> multiMaster = new HashMap<>();
			while (true) {
				String line = br.readLine();
				if (line == null) /* EOF */ {
					break; /* done */
				}
				Tokenizer tokenizer = new Tokenizer(line);
				String master = tokenizer.getString("# \t"); //$NON-NLS-1$
				if (master != null) {
					String masterLower = master.toLowerCase();
					canonicalTable.put(masterLower, master);
					Collection aliasLine = new ArrayList<>(1);
					aliasLine.add(master);
					parseloop: while (true) {
						String alias = tokenizer.getString("# \t"); //$NON-NLS-1$
						if (alias == null) {
							break parseloop;
						}
						aliasLine.add(alias);
						String aliasLower = alias.toLowerCase();
						if (!canonicalTable.containsKey(aliasLower)) {
							canonicalTable.put(aliasLower, master);
						} else {
							// the alias has multiple masters just make its canonical name be the alias
							String existingMaster = canonicalTable.put(aliasLower, alias);
							Set masters = multiMaster.get(aliasLower);
							if (masters == null) {
								masters = new HashSet<>();
								multiMaster.put(aliasLower, masters);
								masters.add(existingMaster.toLowerCase());
							}
							masters.add(masterLower);
						}
					}
					aliasTable.put(masterLower, aliasLine);
				}
			}
			Map> multiMasterAliases = new HashMap<>(multiMaster.size());
			for (Entry> entry : multiMaster.entrySet()) {
				Set aliases = new HashSet<>();
				for (String master : entry.getValue()) {
					aliases.addAll(aliasTable.get(master));
				}
				multiMasterAliases.put(entry.getKey(), aliases);
			}
			aliasTable.putAll(multiMasterAliases);
		} catch (IOException e) {
			Debug.printStackTrace(e);
		}
		return aliasTable;
	}
}