/*
 * Copyright 2004-2008 H2 Group. Licensed under the H2 License, Version 1.0
 * (http://h2database.com/html/license.html).
 * Initial Developer: H2 Group
 */
package org.h2.value;

import java.io.BufferedInputStream;
import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;
import java.sql.PreparedStatement;
import java.sql.SQLException;

import org.h2.constant.SysProperties;
import org.h2.engine.Constants;
import org.h2.message.Message;
import org.h2.store.DataHandler;
import org.h2.store.FileStore;
import org.h2.store.FileStoreInputStream;
import org.h2.store.FileStoreOutputStream;
import org.h2.store.fs.FileSystem;
import org.h2.util.ByteUtils;
import org.h2.util.FileUtils;
import org.h2.util.IOUtils;
import org.h2.util.MathUtils;
import org.h2.util.SmallLRUCache;
import org.h2.util.StringUtils;

/**
 * Implementation of the BLOB and CLOB data types.
 */
public class ValueLob extends Value {
    // TODO lob: concatenate function for blob and clob 
    // (to create a large blob from pieces)
    // and a getpart function (to get it in pieces) and make sure a file is created!

    public static final int TABLE_ID_SESSION = -1;

    private final int type;
    private long precision;
    private DataHandler handler;
    private int tableId;
    private int objectId;
    private String fileName;
    private boolean linked;
    private byte[] small;
    private int hash;
    private boolean compression;
    private FileStore tempFile;

    /**
     * This counter is used to calculate the next directory to store lobs.
     * It is better than using a random number because less directories are created.
     */
    private static int dirCounter;

    private ValueLob(int type, DataHandler handler, String fileName, int tableId, int objectId, boolean linked,
            long precision, boolean compression) {
        this.type = type;
        this.handler = handler;
        this.fileName = fileName;
        this.tableId = tableId;
        this.objectId = objectId;
        this.linked = linked;
        this.precision = precision;
        this.compression = compression;
    }

    private static ValueLob copy(ValueLob lob) {
        ValueLob copy = new ValueLob(lob.type, lob.handler, lob.fileName, lob.tableId, lob.objectId, lob.linked, lob.precision, lob.compression);
        copy.small = lob.small;
        copy.hash = lob.hash;
        return copy;
    }

    private ValueLob(int type, byte[] small) throws SQLException {
        this.type = type;
        this.small = small;
        if (small != null) {
            if (type == Value.BLOB) {
                this.precision = small.length;
            } else {
                this.precision = getString().length();
            }
        }
    }

    public static ValueLob createSmallLob(int type, byte[] small) throws SQLException {
        return new ValueLob(type, small);
    }

    private static String getFileName(DataHandler handler, int tableId, int objectId) {
        if (SysProperties.CHECK && tableId == 0 && objectId == 0) {
            throw Message.getInternalError("0 LOB");
        }
        if (handler.getLobFilesInDirectories()) {
            String table = tableId < 0 ? ".temp" : ".t" + tableId;
            return getFileNamePrefix(handler.getDatabasePath(), objectId) + table + Constants.SUFFIX_LOB_FILE;
        } else {
            return handler.getDatabasePath() + "." + tableId + "." + objectId + Constants.SUFFIX_LOB_FILE;
        }
    }

    /**
     * Create a LOB value with the given parameters.
     * 
     * @param type the data type
     * @param handler the file handler
     * @param tableId the table object id
     * @param objectId the object id
     * @param precision the precision (length in elements)
     * @param compression if compression is used
     * @return the value object
     */
    public static ValueLob open(int type, DataHandler handler, int tableId, int objectId, long precision, boolean compression) {
        String fileName = getFileName(handler, tableId, objectId);
        return new ValueLob(type, handler, fileName, tableId, objectId, true, precision, compression);
    }

    public static ValueLob createClob(Reader in, long length, DataHandler handler) throws SQLException {
        try {
            boolean compress = handler.getLobCompressionAlgorithm(Value.CLOB) != null;
            long remaining = Long.MAX_VALUE;
            if (length >= 0 && length < remaining) {
                remaining = length;
            }
            int len = getBufferSize(handler, compress, remaining);
            char[] buff = new char[len];
            len = IOUtils.readFully(in, buff, len);
            len = len < 0 ? 0 : len;
            if (len <= handler.getMaxLengthInplaceLob()) {
                byte[] small = StringUtils.utf8Encode(new String(buff, 0, len));
                return ValueLob.createSmallLob(Value.CLOB, small);
            }
            ValueLob lob = new ValueLob(Value.CLOB, null);
            lob.createFromReader(buff, len, in, remaining, handler);
            return lob;
        } catch (IOException e) {
            throw Message.convertIOException(e, null);
        }
    }

    private static int getBufferSize(DataHandler handler, boolean compress, long remaining) {
        if (remaining < 0 || remaining > Integer.MAX_VALUE) {
            remaining = Integer.MAX_VALUE;
        }
        long inplace = handler.getMaxLengthInplaceLob();
        if (inplace >= Integer.MAX_VALUE) {
           inplace = remaining;
        }
        long m = compress ? Constants.IO_BUFFER_SIZE_COMPRESS : Constants.IO_BUFFER_SIZE;
        if (m < remaining && m <= inplace) {
            m = Math.min(remaining, inplace + 1);
            // the buffer size must be bigger than the inplace lob, otherwise we can't
            // know if it must be stored in-place or not
            m = MathUtils.roundUpLong(m, Constants.IO_BUFFER_SIZE);
        }
        m = Math.min(remaining, m);
        m = MathUtils.convertLongToInt(m);
        if (m < 0) {
            m = Integer.MAX_VALUE;
        }
        return (int) m;
    }

    private void createFromReader(char[] buff, int len, Reader in, long remaining, DataHandler handler) throws SQLException {
        try {
            FileStoreOutputStream out = initLarge(handler);
            boolean compress = handler.getLobCompressionAlgorithm(Value.CLOB) != null;
            try {
                while (true) {
                    precision += len;
                    byte[] b = StringUtils.utf8Encode(new String(buff, 0, len));
                    out.write(b, 0, b.length);
                    remaining -= len;
                    if (remaining <= 0) {
                        break;
                    }
                    len = getBufferSize(handler, compress, remaining);
                    len = IOUtils.readFully(in, buff, len);
                    if (len <= 0) {
                        break;
                    }
                }
            } finally {
                out.close();
            }
        } catch (IOException e) {
            throw Message.convertIOException(e, null);
        }
    }

    private static String getFileNamePrefix(String path, int objectId) {
        String name;
        int f = objectId % SysProperties.LOB_FILES_PER_DIRECTORY;
        if (f > 0) {
            name = File.separator + objectId;
        } else {
            name = "";
        }
        objectId /= SysProperties.LOB_FILES_PER_DIRECTORY;
        while (objectId > 0) {
            f = objectId % SysProperties.LOB_FILES_PER_DIRECTORY;
            name = File.separator + f + Constants.SUFFIX_LOBS_DIRECTORY + name;
            objectId /= SysProperties.LOB_FILES_PER_DIRECTORY;
        }
        name = path + Constants.SUFFIX_LOBS_DIRECTORY + name;
        return name;
    }

    private int getNewObjectId(DataHandler handler) throws SQLException {
        String path = handler.getDatabasePath();
        int objectId = 0;
        while (true) {
            String dir = getFileNamePrefix(path, objectId);
            String[] list = getFileList(handler, dir);
            int fileCount = 0;
            boolean[] used = new boolean[SysProperties.LOB_FILES_PER_DIRECTORY];
            for (int i = 0; i < list.length; i++) {
                String name = list[i];
                if (name.endsWith(Constants.SUFFIX_DB_FILE)) {
                    name = name.substring(name.lastIndexOf(File.separatorChar) + 1);
                    String n = name.substring(0, name.indexOf('.'));
                    int id;
                    try {
                        id = Integer.parseInt(n);
                    } catch (NumberFormatException e) {
                        id = -1;
                    }
                    if (id > 0) {
                        fileCount++;
                        used[id % SysProperties.LOB_FILES_PER_DIRECTORY] = true;
                    }
                }
            }
            int fileId = -1;
            if (fileCount < SysProperties.LOB_FILES_PER_DIRECTORY) {
                for (int i = 1; i < SysProperties.LOB_FILES_PER_DIRECTORY; i++) {
                    if (!used[i]) {
                        fileId = i;
                        break;
                    }
                }
            }
            if (fileId > 0) {
                objectId += fileId;
                invalidateFileList(handler, dir);
                break;
            } else {
                if (objectId > Integer.MAX_VALUE / SysProperties.LOB_FILES_PER_DIRECTORY) {
                    // this directory path is full: start from zero
                    // (this can happen only theoretically, 
                    // for example if the random number generator is broken)
                    objectId = 0;
                } else {
                    // calculate the directory
                    // start with 1 (otherwise we don't know the number of directories)
                    // it doesn't really matter what directory is used, it might as well be random
                    // (but that would generate more directories):
                    // int dirId = RandomUtils.nextInt(
                    //         SysProperties.LOB_FILES_PER_DIRECTORY - 1) + 1;
                    int dirId = (dirCounter++ / (SysProperties.LOB_FILES_PER_DIRECTORY - 1)) + 1;
                    objectId = objectId * SysProperties.LOB_FILES_PER_DIRECTORY;
                    objectId += dirId * SysProperties.LOB_FILES_PER_DIRECTORY;
                }
            }
        }
        return objectId;
    }

    private void invalidateFileList(DataHandler handler, String dir) {
        SmallLRUCache cache = handler.getLobFileListCache();
        if (cache != null) {
            synchronized (cache) {
                cache.remove(dir);
            }
        }
    }

    private String[] getFileList(DataHandler handler, String dir) throws SQLException {
        SmallLRUCache cache = handler.getLobFileListCache();
        String[] list;
        if (cache == null) {
            list = FileUtils.listFiles(dir);
        } else {
            synchronized (cache) {
                list = (String[]) cache.get(dir);
                if (list == null) {
                    list = FileUtils.listFiles(dir);
                    cache.put(dir, list);
                }
            }
        }
        return list;
    }

    public static ValueLob createBlob(InputStream in, long length, DataHandler handler) throws SQLException {
        try {
            long remaining = Long.MAX_VALUE;
            boolean compress = handler.getLobCompressionAlgorithm(Value.BLOB) != null;
            if (length >= 0 && length < remaining) {
                remaining = length;
            }
            int len = getBufferSize(handler, compress, remaining);
            byte[] buff = new byte[len];
            len = IOUtils.readFully(in, buff, 0, len);
            if (len <= handler.getMaxLengthInplaceLob()) {
                byte[] small = new byte[len];
                System.arraycopy(buff, 0, small, 0, len);
                return ValueLob.createSmallLob(Value.BLOB, small);
            }
            ValueLob lob = new ValueLob(Value.BLOB, null);
            lob.createFromStream(buff, len, in, remaining, handler);
            return lob;
        } catch (IOException e) {
            throw Message.convertIOException(e, null);
        }
    }

    private FileStoreOutputStream initLarge(DataHandler handler) throws IOException, SQLException {
        this.handler = handler;
        this.tableId = 0;
        this.linked = false;
        this.precision = 0;
        this.small = null;
        this.hash = 0;
        String compressionAlgorithm = handler.getLobCompressionAlgorithm(type);
        this.compression = compressionAlgorithm != null;
        synchronized (handler) {
            if (handler.getLobFilesInDirectories()) {
                objectId = getNewObjectId(handler);
                fileName = getFileNamePrefix(handler.getDatabasePath(), objectId) + ".temp.db";
            } else {
                objectId = handler.allocateObjectId(false, true);
                fileName = handler.createTempFile();
            }
            tempFile = handler.openFile(fileName, "rw", false);
            tempFile.autoDelete();
        }
        FileStoreOutputStream out = new FileStoreOutputStream(tempFile, handler, compressionAlgorithm);
        return out;
    }

    private void createFromStream(byte[] buff, int len, InputStream in, long remaining, DataHandler handler)
            throws SQLException {
        try {
            FileStoreOutputStream out = initLarge(handler);
            boolean compress = handler.getLobCompressionAlgorithm(Value.BLOB) != null;
            try {
                while (true) {
                    precision += len;
                    out.write(buff, 0, len);