/*
 * Copyright (c) 2011-2012 TMate Software Ltd
 *  
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2 of the License.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * For information on how to redistribute this software under
 * the terms of a license other than GNU General Public License
 * contact TMate Software at support@hg4j.com
 */
package org.tmatesoft.hg.internal;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintStream;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.FileLock;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

import org.tmatesoft.hg.core.SessionContext;
import org.tmatesoft.hg.repo.HgInvalidFileException;
import org.tmatesoft.hg.util.LogFacility;

/**
 * .ini / .rc file reader
 * @author Artem Tikhomirov
 * @author TMate Software Ltd.
 */
public class ConfigFile {

	private final SessionContext sessionContext;
	private List<String> sections;
	private List<Map<String,String>> content;

	public ConfigFile(SessionContext ctx) {
		sessionContext = ctx;
	}

	public void addLocation(File path) throws HgInvalidFileException {
		read(path);
	}
	
	public boolean hasSection(String sectionName) {
		return sections == null ? false : sections.indexOf(sectionName) != -1;
	}
	
	public List<String> getSectionNames() {
		return sections == null ? Collections.<String>emptyList() : Collections.unmodifiableList(sections);
	}

	/**
	 * Access map of section keys and values.
	 * @param sectionName name of the section to retrieve
	 * @return never <code>null</code>, empty map in case no section with specified name found 
	 */
	public Map<String,String> getSection(String sectionName) {
		if (sections == null) {
			return Collections.emptyMap();
		}
		int x = sections.indexOf(sectionName);
		if (x == -1) {
			return Collections.emptyMap();
		}
		return Collections.unmodifiableMap(content.get(x));
	}

	public boolean getBoolean(String sectionName, String key, boolean defaultValue) {
		String value = getSection(sectionName).get(key);
		if (value == null) {
			return defaultValue;
		}
		for (String s : new String[] { "true", "yes", "on", "1" }) {
			if (s.equalsIgnoreCase(value)) {
				return true;
			}
		}
		return false;
	}
	
	public String getString(String sectionName, String key, String defaultValue) {
		String value = getSection(sectionName).get(key);
		return value == null ? defaultValue : value;
	}
	
	public int getInteger(String sectionName, String key, int defaultValue) {
		String value = getSection(sectionName).get(key);
		return value == null ? defaultValue : Integer.parseInt(value);
	}
	
	public void putString(String sectionName, String key, String newValue) {
		Map<String, String> section = null;
		if (sections == null) {
			// init, in case we didn't read any file with prev config
			sections = new ArrayList<String>();
			content = new ArrayList<Map<String,String>>();
		}
		int x = sections.indexOf(sectionName);
		if (x == -1) {
			if (newValue == null) {
				return;
			}
			sections.add(sectionName);
			content.add(section = new LinkedHashMap<String, String>());
		} else {
			section = content.get(x);
		}
		if (newValue == null) {
			section.remove(key);
		} else {
			section.put(key, newValue);
		}
	}
	
	private void read(File f) throws HgInvalidFileException {
		if (f == null || !f.canRead()) {
			return;
		}
		if (sections == null) {
			sections = new ArrayList<String>();
			content = new ArrayList<Map<String,String>>();
		}
		new Parser().go(f, this);
		((ArrayList<?>) sections).trimToSize();
		((ArrayList<?>) content).trimToSize();
		assert sections.size() == content.size();
	}

	public void writeTo(File f) throws IOException {
		byte[] data = compose();
		if (!f.exists()) {
			f.createNewFile();
		}
		FileChannel fc = new FileOutputStream(f).getChannel();
		FileLock fl = fc.lock();
		try {
			fc.write(ByteBuffer.wrap(data));
		} finally {
			fl.release();
			fc.close();
		}
	}
	
	private byte[] compose() {
		ByteArrayOutputStream bos = new ByteArrayOutputStream(1024);
		PrintStream ps = new PrintStream(bos);
		Iterator<String> sectionNames = sections.iterator();
		for (Map<String,String> s : content) {
			final String name = sectionNames.next(); // iterate through names despite section may be empty
			if (s.isEmpty()) {
				continue; // do not write an empty section
			}
			ps.print('[');
			ps.print(name);
			ps.println(']');
			for (Map.Entry<String, String> e : s.entrySet()) {
				ps.print(e.getKey());
				ps.print('=');
				ps.println(e.getValue());
			}
			ps.println();
		}
		ps.flush();
		return bos.toByteArray();
	}

	private static class Parser implements LineReader.LineConsumer<ConfigFile> {
		
		private String sectionName = "";
		private Map<String,String> section = new LinkedHashMap<String, String>();
		private File contextFile;

		// TODO "" and lists
		// XXX perhaps, single string to keep whole section with substrings for keys/values to minimize number of arrays (String.value)
		public boolean consume(String line, ConfigFile cfg) throws IOException {
			int x;
			if ((x = line.indexOf('#')) != -1) {
				// do not keep comments in memory, get new, shorter string
				line = new String(line.substring(0, x).trim());
			}
			if (line.length() <= 2) { // a=b or [a] are at least of length 3
				return true;
			}
			if (line.charAt(0) == '[' && line.charAt(line.length() - 1) == ']') {
				sectionName = line.substring(1, line.length() - 1);
				if (cfg.sections.indexOf(sectionName) == -1) {
					cfg.sections.add(sectionName);
					cfg.content.add(section = new LinkedHashMap<String, String>());
				} else {
					section = null; // drop cached value
				}
			} else if (line.startsWith("%unset")) {
				if (section != null) {
					section.remove(line.substring(7).trim());
				}
			} else if (line.startsWith("%include")) {
				processInclude(line.substring(9).trim(), cfg);
			} else if ((x = line.indexOf('=')) != -1) {
				// share char[] of the original string
				String key = line.substring(0, x).trim();
				String value = line.substring(x+1).trim();
				if (section == null) {
					int i = cfg.sections.indexOf(sectionName);
					assert i >= 0;
					section = cfg.content.get(i);
				}
				if (sectionName.length() == 0) {
					// add fake section only if there are any values 
					cfg.sections.add(sectionName);
					cfg.content.add(section);
				}
				section.put(key, value);
			}
			return true;
		}
		
		public void go(File f, ConfigFile cfg) throws HgInvalidFileException {
			contextFile = f;
			LineReader lr = new LineReader(f, cfg.sessionContext.getLog());
			lr.ignoreLineComments("#");
			lr.read(this, cfg);
		}
		
		// include failure doesn't propagate
		private void processInclude(String includeValue, ConfigFile cfg) {
			File f; 
			// TODO handle environment variable expansion
			if (includeValue.startsWith("~/")) {
				f = new File(System.getProperty("user.home"), includeValue.substring(2));
			} else {
				f = new File(contextFile.getParentFile(), includeValue);
			}
			try {
				if (f.canRead()) {
					new Parser().go(f, cfg);
				} else {
					LogFacility lf = cfg.sessionContext.getLog();
					lf.dump(ConfigFile.class, LogFacility.Severity.Debug, "Can't read file to  include: %s", f);
				}
			} catch (HgInvalidFileException ex) {
				LogFacility lf = cfg.sessionContext.getLog();
				lf.dump(ConfigFile.class, LogFacility.Severity.Warn, "Can't include %s (%s)", f, includeValue);
			}
		}
	}
}