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/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */

package com.aliyun.fs.oss.common;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.io.IOUtils;

import java.io.*;

/**
 * Holds file metadata including type (regular file, or directory),
 * and the list of blocks that are pointers to the data.
 */
@InterfaceAudience.Private
@InterfaceStability.Unstable
public class INode {

    public enum FileType {
        FILE, DIRECTORY
    }

    public static final FileType[] FILE_TYPES = {
            FileType.FILE,
            FileType.DIRECTORY
    };

    public static final INode DIRECTORY_INODE = new INode(FileType.DIRECTORY, null);

    private FileType fileType;
    private Block[] blocks;

    public INode(FileType fileType, Block[] blocks) {
        this.fileType = fileType;
        if (isDirectory() && blocks != null) {
            throw new IllegalArgumentException("A directory cannot contain blocks.");
        }
        this.blocks = blocks;
    }

    public Block[] getBlocks() {
        return blocks;
    }

    public FileType getFileType() {
        return fileType;
    }

    public boolean isDirectory() {
        return fileType == FileType.DIRECTORY;
    }

    public boolean isFile() {
        return fileType == FileType.FILE;
    }

    public long getSerializedLength() {
        return 1L + (blocks == null ? 0 : 4 + blocks.length * 16);
    }


    public InputStream serialize() throws IOException {
        ByteArrayOutputStream bytes = new ByteArrayOutputStream();
        DataOutputStream out = new DataOutputStream(bytes);
        try {
            out.writeByte(fileType.ordinal());
            if (isFile()) {
                out.writeInt(blocks.length);
                for (int i = 0; i < blocks.length; i++) {
                    out.writeLong(blocks[i].getId());
                    out.writeLong(blocks[i].getLength());
                }
            }
            out.close();
            out = null;
        } finally {
            IOUtils.closeStream(out);
        }
        return new ByteArrayInputStream(bytes.toByteArray());
    }

    public static INode deserialize(InputStream in) throws IOException {
        if (in == null) {
            return null;
        }
        DataInputStream dataIn = new DataInputStream(in);
        FileType fileType = INode.FILE_TYPES[dataIn.readByte()];
        switch (fileType) {
            case DIRECTORY:
                in.close();
                return INode.DIRECTORY_INODE;
            case FILE:
                int numBlocks = dataIn.readInt();
                Block[] blocks = new Block[numBlocks];
                for (int i = 0; i < numBlocks; i++) {
                    long id = dataIn.readLong();
                    long length = dataIn.readLong();
                    blocks[i] = new Block(id, length);
                }
                in.close();
                return new INode(fileType, blocks);
            default:
                throw new IllegalArgumentException("Cannot deserialize inode.");
        }
    }

}