/*
 *******************************************************************************
 * Copyright (C) 2012, International Business Machines Corporation and         *
 * others. All Rights Reserved.                                                *
 *******************************************************************************
 */
package com.ibm.icu.text;

import java.io.DataInputStream;
import java.io.IOException;
import java.io.InputStream;

import com.ibm.icu.impl.Assert;
import com.ibm.icu.impl.ICUBinary;
import com.ibm.icu.impl.ICUData;
import com.ibm.icu.impl.ICUResourceBundle;
import com.ibm.icu.util.UResourceBundle;

final class DictionaryData {
    // disallow instantiation
    private DictionaryData() { }

    public static final int TRIE_TYPE_BYTES = 0;
    public static final int TRIE_TYPE_UCHARS = 1;
    public static final int TRIE_TYPE_MASK = 7;
    public static final int TRIE_HAS_VALUES = 8;
    public static final int TRANSFORM_NONE = 0;
    public static final int TRANSFORM_TYPE_OFFSET = 0x1000000;
    public static final int TRANSFORM_TYPE_MASK = 0x7f000000;
    public static final int TRANSFORM_OFFSET_MASK = 0x1fffff;

    public static final int IX_STRING_TRIE_OFFSET = 0;
    public static final int IX_RESERVED1_OFFSET = 1;
    public static final int IX_RESERVED2_OFFSET = 2;
    public static final int IX_TOTAL_SIZE = 3;
    public static final int IX_TRIE_TYPE = 4;
    public static final int IX_TRANSFORM = 5;
    public static final int IX_RESERVED6 = 6;
    public static final int IX_RESERVED7 = 7;
    public static final int IX_COUNT = 8;

    private static final byte DATA_FORMAT_ID[] = { (byte) 0x44, (byte) 0x69,
        (byte) 0x63, (byte) 0x74 };
    
    public static DictionaryMatcher loadDictionaryFor(String dictType) throws IOException {
        ICUResourceBundle rb = (ICUResourceBundle)UResourceBundle.getBundleInstance(ICUResourceBundle.ICU_BRKITR_BASE_NAME);
        String dictFileName = rb.getStringWithFallback("dictionaries/" + dictType);
        dictFileName = ICUResourceBundle.ICU_BUNDLE +ICUResourceBundle.ICU_BRKITR_NAME+ "/" + dictFileName;
        InputStream is = ICUData.getStream(dictFileName);
        ICUBinary.readHeader(is, DATA_FORMAT_ID, null);
        DataInputStream s = new DataInputStream(is);
        int[] indexes = new int[IX_COUNT];
        // TODO: read indexes[IX_STRING_TRIE_OFFSET] first, then read a variable-length indexes[]
        for (int i = 0; i < IX_COUNT; i++) {
            indexes[i] = s.readInt();
        }
        int offset = indexes[IX_STRING_TRIE_OFFSET];
        Assert.assrt(offset >= (4 * IX_COUNT));
        if (offset > (4 * IX_COUNT)) {
            int diff = offset - (4 * IX_COUNT);
            s.skipBytes(diff);
        }
        int trieType = indexes[IX_TRIE_TYPE] & TRIE_TYPE_MASK;
        int totalSize = indexes[IX_TOTAL_SIZE] - offset;
        DictionaryMatcher m = null;
        if (trieType == TRIE_TYPE_BYTES) {
            int transform = indexes[IX_TRANSFORM];
            byte[] data = new byte[totalSize];
            int i;
            for (i = 0; i < data.length; i++) {
                data[i] = s.readByte();
            }
            Assert.assrt(i == totalSize);
            m = new BytesDictionaryMatcher(data, transform);
        } else if (trieType == TRIE_TYPE_UCHARS) {
            Assert.assrt(totalSize % 2 == 0);
            int num = totalSize / 2;
            char[] data = new char[totalSize / 2];
            for (int i = 0; i < num; i++) {
                data[i] = s.readChar();
            }
            m = new CharsDictionaryMatcher(new String(data));
        } else {
            m = null;
        }
        s.close();
        is.close();
        return m;
    }
}