/*
 * ============LICENSE_START=======================================================
 * ONAP : ccsdk features
 * ================================================================================
 * Copyright (C) 2019 highstreet technologies GmbH Intellectual Property.
 * All rights reserved.
 * ================================================================================
 * 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.
 * ============LICENSE_END=========================================================
 *
 */
package org.onap.ccsdk.features.sdnr.wt.dataprovider.data;

import java.io.File;
import java.io.FileInputStream;
import java.io.FilenameFilter;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.file.Path;
import java.text.ParseException;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.Date;
import java.util.List;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class YangFileProvider {

	private static final Logger LOG = LoggerFactory.getLogger(YangFileProvider.class);

	private static final FilenameFilter yangFilenameFilter = new FilenameFilter() {

		@Override
		public boolean accept(File dir, String name) {
			return name.toLowerCase().endsWith(".yang");
		}
	};

	private static final int BUFFER_SIZE = 1024;

	private final Path mainSourcePath;
	private final List<Path> additionalSources;

	public YangFileProvider(String path) {
		this.mainSourcePath = new File(path).toPath();
		this.additionalSources = new ArrayList<>();
	}

	public boolean hasFileForModule(String module, String version) {
		return this.mainSourcePath.resolve(YangFilename.createFilename(module, version)).toFile().exists();
	}

	public boolean hasFileForModule(String module) {
		return this.findYangFiles(module).size() > 0;
	}

	private List<YangFilename> findYangFiles(String module) {
		List<YangFilename> list = new ArrayList<>();
		String[] files = this.mainSourcePath.toFile().list(yangFilenameFilter);
		YangFilename yangfile;
		for (String file : files) {
			files = this.mainSourcePath.toFile().list(yangFilenameFilter);
			for (String fn : files) {
				try {
					yangfile = new YangFilename(this.mainSourcePath.resolve(fn).toString());
					if (yangfile.getModule().equals(module)) {
						list.add(yangfile);
					}
				} catch (ParseException e) {
					LOG.warn("unable to handle yangfile {}: {}", file, e);
				}
			}
		}
		for (Path addPath : this.additionalSources) {
			files = addPath.toFile().list(yangFilenameFilter);
			for (String file : files) {
				try {
					yangfile = new YangFilename(addPath.resolve(file).toString());
					if (yangfile.getModule().equals(module)) {
						list.add(yangfile);
					}
				} catch (ParseException e) {
					LOG.warn("unable to handle yangfile {}: {}", file, e);
				}
			}
		}
		return list;
	}

	/**
	 * get yang file from source with specified version or least newer one if
	 * version is null then the latest one
	 * 
	 * @param module
	 * @param version
	 * @return
	 * @throws ParseException
	 */
	private @Nullable YangFilename getYangFile(@Nonnull String module, @Nullable String version) throws ParseException {
		YangFilename f = null;
		List<YangFilename> list = this.findYangFiles(module);

		list.sort(SortByDateAscComparator.getInstance());

		// find specific version or nearest oldest
		if (version != null) {
			Date rev = YangFilename.parseRevision(version);
			for (YangFilename item : list) {
				if (rev.equals(item.getRevision())) {
					f = item;
					break;
				}
				if (item.getRevision().after(rev)) {
					f = item;
					break;
				}
			}
		}
		// get latest
		else {
			f = list.get(list.size() - 1);
		}
		return f;
	}

	/**
	 * write filestream directly to output stream easier for http handling
	 * 
	 * @param module
	 * @param version
	 * @param outputStream
	 * @return
	 * @throws IOException
	 * @throws ParseException
	 */
	public int writeOutput(@Nonnull String module, @Nullable String version, @Nonnull OutputStream outputStream)
			throws IOException, ParseException {
		YangFilename fn = this.getYangFile(module, version);
		if(fn==null) {
			return 0;
		}
		byte[] buffer = new byte[BUFFER_SIZE];
		int bytesRead = -1;
		int sumlen = 0;
		InputStream inputStream = null ;
		try {
			inputStream= new FileInputStream(fn.getFilename());

		while ((bytesRead = inputStream.read(buffer)) != -1) {
			outputStream.write(buffer, 0, bytesRead);
			sumlen += bytesRead;
		}}
		catch(IOException e) {
			LOG.warn("problem sending {}: {}",fn.getFilename(),e);
		}
		finally {
			if(inputStream!=null) {
				inputStream.close();		
			}
		}
		return sumlen;
	}

	private static class SortByDateAscComparator implements Comparator<YangFilename> {

		private static SortByDateAscComparator instance;

		@Override
		public int compare(YangFilename o1, YangFilename o2) {
			return o1.getRevision().compareTo(o2.getRevision());
		}

		public static Comparator<YangFilename> getInstance() {
			if (instance == null) {
				instance = new SortByDateAscComparator();
			}
			return instance;
		}

	}

	public YangFilename getFileForModule(String module, String rev) throws ParseException {
		return this.getYangFile(module, rev);
	}

	public YangFilename getFileForModule(String module) throws ParseException {
		return this.getFileForModule(module, null);
	}

	public boolean hasFileOrNewerForModule(String module, String version) throws ParseException {
		return this.getYangFile(module, version) != null;
	}

}