/*
 * Copyright (C) 2013 The Android Open Source Project
 *
 * 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.
 */

package com.android.inputmethod.latin.makedict;

import com.android.inputmethod.annotations.UsedForTesting;
import com.android.inputmethod.latin.makedict.BinaryDictDecoderUtils.CharEncoding;
import com.android.inputmethod.latin.makedict.BinaryDictDecoderUtils.DictBuffer;
import com.android.inputmethod.latin.makedict.FormatSpec.FileHeader;
import com.android.inputmethod.latin.makedict.FormatSpec.FormatOptions;
import com.android.inputmethod.latin.makedict.FusionDictionary.PtNode;
import com.android.inputmethod.latin.makedict.FusionDictionary.WeightedString;
import com.android.inputmethod.latin.utils.CollectionUtils;

import android.util.Log;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;

/**
 * An implementation of binary dictionary decoder for version 4 binary dictionary.
 */
@UsedForTesting
public class Ver4DictDecoder extends AbstractDictDecoder {
    private static final String TAG = Ver4DictDecoder.class.getSimpleName();

    private static final int FILETYPE_TRIE = 1;
    private static final int FILETYPE_FREQUENCY = 2;
    private static final int FILETYPE_TERMINAL_ADDRESS_TABLE = 3;
    private static final int FILETYPE_BIGRAM_FREQ = 4;
    private static final int FILETYPE_SHORTCUT = 5;

    private final File mDictDirectory;
    private final DictionaryBufferFactory mBufferFactory;
    protected DictBuffer mDictBuffer;
    private DictBuffer mFrequencyBuffer;
    private DictBuffer mTerminalAddressTableBuffer;
    private DictBuffer mBigramBuffer;
    private DictBuffer mShortcutBuffer;
    private SparseTable mBigramAddressTable;
    private SparseTable mShortcutAddressTable;

    @UsedForTesting
    /* package */ Ver4DictDecoder(final File dictDirectory, final int factoryFlag) {
        mDictDirectory = dictDirectory;
        mDictBuffer = mFrequencyBuffer = null;

        if ((factoryFlag & MASK_DICTBUFFER) == USE_READONLY_BYTEBUFFER) {
            mBufferFactory = new DictionaryBufferFromReadOnlyByteBufferFactory();
        } else if ((factoryFlag  & MASK_DICTBUFFER) == USE_BYTEARRAY) {
            mBufferFactory = new DictionaryBufferFromByteArrayFactory();
        } else if ((factoryFlag & MASK_DICTBUFFER) == USE_WRITABLE_BYTEBUFFER) {
            mBufferFactory = new DictionaryBufferFromWritableByteBufferFactory();
        } else {
            mBufferFactory = new DictionaryBufferFromReadOnlyByteBufferFactory();
        }
    }

    @UsedForTesting
    /* package */ Ver4DictDecoder(final File dictDirectory, final DictionaryBufferFactory factory) {
        mDictDirectory = dictDirectory;
        mBufferFactory = factory;
        mDictBuffer = mFrequencyBuffer = null;
    }

    private File getFile(final int fileType) {
        if (fileType == FILETYPE_TRIE) {
            return new File(mDictDirectory,
                    mDictDirectory.getName() + FormatSpec.TRIE_FILE_EXTENSION);
        } else if (fileType == FILETYPE_FREQUENCY) {
            return new File(mDictDirectory,
                    mDictDirectory.getName() + FormatSpec.FREQ_FILE_EXTENSION);
        } else if (fileType == FILETYPE_TERMINAL_ADDRESS_TABLE) {
            return new File(mDictDirectory,
                    mDictDirectory.getName() + FormatSpec.TERMINAL_ADDRESS_TABLE_FILE_EXTENSION);
        } else if (fileType == FILETYPE_BIGRAM_FREQ) {
            return new File(mDictDirectory,
                    mDictDirectory.getName() + FormatSpec.BIGRAM_FILE_EXTENSION
                            + FormatSpec.BIGRAM_FREQ_CONTENT_ID);
        } else if (fileType == FILETYPE_SHORTCUT) {
            return new File(mDictDirectory,
                    mDictDirectory.getName() + FormatSpec.SHORTCUT_FILE_EXTENSION
                            + FormatSpec.SHORTCUT_CONTENT_ID);
        } else {
            throw new RuntimeException("Unsupported kind of file : " + fileType);
        }
    }

    @Override
    public void openDictBuffer() throws FileNotFoundException, IOException {
        mDictBuffer = mBufferFactory.getDictionaryBuffer(getFile(FILETYPE_TRIE));
        mFrequencyBuffer = mBufferFactory.getDictionaryBuffer(getFile(FILETYPE_FREQUENCY));
        mTerminalAddressTableBuffer = mBufferFactory.getDictionaryBuffer(
                getFile(FILETYPE_TERMINAL_ADDRESS_TABLE));
        mBigramBuffer = mBufferFactory.getDictionaryBuffer(getFile(FILETYPE_BIGRAM_FREQ));
        loadBigramAddressSparseTable();
        mShortcutBuffer = mBufferFactory.getDictionaryBuffer(getFile(FILETYPE_SHORTCUT));
        loadShortcutAddressSparseTable();
    }

    @Override
    public boolean isDictBufferOpen() {
        return mDictBuffer != null;
    }

    /* package */ DictBuffer getDictBuffer() {
        return mDictBuffer;
    }

    @Override
    public FileHeader readHeader() throws IOException, UnsupportedFormatException {
        if (mDictBuffer == null) {
            openDictBuffer();
        }
        final FileHeader header = super.readHeader(mDictBuffer);
        final int version = header.mFormatOptions.mVersion;
        if (version != 4) {
            throw new UnsupportedFormatException("File header has a wrong version : " + version);
        }
        return header;
    }

    private void loadBigramAddressSparseTable() throws IOException {
        final File lookupIndexFile = new File(mDictDirectory, mDictDirectory.getName()
                + FormatSpec.BIGRAM_FILE_EXTENSION + FormatSpec.LOOKUP_TABLE_FILE_SUFFIX);
        final File freqsFile = new File(mDictDirectory, mDictDirectory.getName()
                + FormatSpec.BIGRAM_FILE_EXTENSION + FormatSpec.CONTENT_TABLE_FILE_SUFFIX
                + FormatSpec.BIGRAM_FREQ_CONTENT_ID);
        mBigramAddressTable = SparseTable.readFromFiles(lookupIndexFile, new File[] { freqsFile },
                FormatSpec.BIGRAM_ADDRESS_TABLE_BLOCK_SIZE);
    }

    // TODO: Let's have something like SparseTableContentsReader in this class.
    private void loadShortcutAddressSparseTable() throws IOException {
        final File lookupIndexFile = new File(mDictDirectory, mDictDirectory.getName()
                + FormatSpec.SHORTCUT_FILE_EXTENSION + FormatSpec.LOOKUP_TABLE_FILE_SUFFIX);
        final File contentFile = new File(mDictDirectory, mDictDirectory.getName()
                + FormatSpec.SHORTCUT_FILE_EXTENSION + FormatSpec.CONTENT_TABLE_FILE_SUFFIX
                + FormatSpec.SHORTCUT_CONTENT_ID);
        final File timestampsFile = new File(mDictDirectory, mDictDirectory.getName()
                + FormatSpec.SHORTCUT_FILE_EXTENSION + FormatSpec.CONTENT_TABLE_FILE_SUFFIX
                + FormatSpec.SHORTCUT_CONTENT_ID);
        mShortcutAddressTable = SparseTable.readFromFiles(lookupIndexFile,
                new File[] { contentFile, timestampsFile },
                FormatSpec.SHORTCUT_ADDRESS_TABLE_BLOCK_SIZE);
    }

    protected static class PtNodeReader extends AbstractDictDecoder.PtNodeReader {
        protected static int readFrequency(final DictBuffer frequencyBuffer, final int terminalId) {
            frequencyBuffer.position(terminalId * FormatSpec.FREQUENCY_AND_FLAGS_SIZE + 1);
            return frequencyBuffer.readUnsignedByte();
        }

        protected static int readTerminalId(final DictBuffer dictBuffer) {
            return dictBuffer.readInt();
        }
    }

    private ArrayList<WeightedString> readShortcuts(final int terminalId) {
        if (mShortcutAddressTable.get(0, terminalId) == SparseTable.NOT_EXIST) return null;

        final ArrayList<WeightedString> ret = CollectionUtils.newArrayList();
        final int posOfShortcuts = mShortcutAddressTable.get(FormatSpec.SHORTCUT_CONTENT_INDEX,
                terminalId);
        mShortcutBuffer.position(posOfShortcuts);
        while (true) {
            final int flags = mShortcutBuffer.readUnsignedByte();
            final String word = CharEncoding.readString(mShortcutBuffer);
            ret.add(new WeightedString(word,
                    flags & FormatSpec.FLAG_BIGRAM_SHORTCUT_ATTR_FREQUENCY));
            if (0 == (flags & FormatSpec.FLAG_BIGRAM_SHORTCUT_ATTR_HAS_NEXT)) break;
        }
        return ret;
    }

    // TODO: Make this buffer thread safe.
    // TODO: Support words longer than FormatSpec.MAX_WORD_LENGTH.
    private final int[] mCharacterBuffer = new int[FormatSpec.MAX_WORD_LENGTH];
    @Override
    public PtNodeInfo readPtNode(int ptNodePos, FormatOptions options) {
        int addressPointer = ptNodePos;
        final int flags = PtNodeReader.readPtNodeOptionFlags(mDictBuffer);
        addressPointer += FormatSpec.PTNODE_FLAGS_SIZE;

        final int parentAddress = PtNodeReader.readParentAddress(mDictBuffer, options);
        if (BinaryDictIOUtils.supportsDynamicUpdate(options)) {
            addressPointer += FormatSpec.PARENT_ADDRESS_SIZE;
        }

        final int characters[];
        if (0 != (flags & FormatSpec.FLAG_HAS_MULTIPLE_CHARS)) {
            int index = 0;
            int character = CharEncoding.readChar(mDictBuffer);
            addressPointer += CharEncoding.getCharSize(character);
            while (FormatSpec.INVALID_CHARACTER != character
                    && index < FormatSpec.MAX_WORD_LENGTH) {
                mCharacterBuffer[index++] = character;
                character = CharEncoding.readChar(mDictBuffer);
                addressPointer += CharEncoding.getCharSize(character);
            }
            characters = Arrays.copyOfRange(mCharacterBuffer, 0, index);
        } else {
            final int character = CharEncoding.readChar(mDictBuffer);
            addressPointer += CharEncoding.getCharSize(character);
            characters = new int[] { character };
        }
        final int terminalId;
        if (0 != (FormatSpec.FLAG_IS_TERMINAL & flags)) {
            terminalId = PtNodeReader.readTerminalId(mDictBuffer);
            addressPointer += FormatSpec.PTNODE_TERMINAL_ID_SIZE;
        } else {
            terminalId = PtNode.NOT_A_TERMINAL;
        }

        final int frequency;
        if (0 != (FormatSpec.FLAG_IS_TERMINAL & flags)) {
            frequency = PtNodeReader.readFrequency(mFrequencyBuffer, terminalId);
        } else {
            frequency = PtNode.NOT_A_TERMINAL;
        }
        int childrenAddress = PtNodeReader.readChildrenAddress(mDictBuffer, flags, options);
        if (childrenAddress != FormatSpec.NO_CHILDREN_ADDRESS) {
            childrenAddress += addressPointer;
        }
        addressPointer += BinaryDictIOUtils.getChildrenAddressSize(flags, options);
        final ArrayList<WeightedString> shortcutTargets = readShortcuts(terminalId);

        final ArrayList<PendingAttribute> bigrams;
        if (0 != (flags & FormatSpec.FLAG_HAS_BIGRAMS)) {
            bigrams = new ArrayList<PendingAttribute>();
            final int posOfBigrams = mBigramAddressTable.get(0 /* contentTableIndex */, terminalId);
            mBigramBuffer.position(posOfBigrams);
            while (bigrams.size() < FormatSpec.MAX_BIGRAMS_IN_A_PTNODE) {
                // If bigrams.size() reaches FormatSpec.MAX_BIGRAMS_IN_A_PTNODE,
                // remaining bigram entries are ignored.
                final int bigramFlags = mBigramBuffer.readUnsignedByte();
                final int targetTerminalId = mBigramBuffer.readUnsignedInt24();
                mTerminalAddressTableBuffer.position(
                        targetTerminalId * FormatSpec.TERMINAL_ADDRESS_TABLE_ADDRESS_SIZE);
                final int targetAddress = mTerminalAddressTableBuffer.readUnsignedInt24();
                bigrams.add(new PendingAttribute(
                        bigramFlags & FormatSpec.FLAG_BIGRAM_SHORTCUT_ATTR_FREQUENCY,
                        targetAddress));
                if (0 == (bigramFlags & FormatSpec.FLAG_BIGRAM_SHORTCUT_ATTR_HAS_NEXT)) break;
            }
            if (bigrams.size() >= FormatSpec.MAX_BIGRAMS_IN_A_PTNODE) {
                throw new RuntimeException("Too many bigrams in a PtNode (" + bigrams.size()
                        + " but max is " + FormatSpec.MAX_BIGRAMS_IN_A_PTNODE + ")");
            }
        } else {
            bigrams = null;
        }
        return new PtNodeInfo(ptNodePos, addressPointer, flags, characters, frequency,
                parentAddress, childrenAddress, shortcutTargets, bigrams);
    }

    private void deleteDictFiles() {
        final File[] files = mDictDirectory.listFiles();
        for (int i = 0; i < files.length; ++i) {
            files[i].delete();
        }
    }

    @Override
    public FusionDictionary readDictionaryBinary(final FusionDictionary dict,
            final boolean deleteDictIfBroken)
            throws FileNotFoundException, IOException, UnsupportedFormatException {
        if (mDictBuffer == null) {
            openDictBuffer();
        }
        try {
            return BinaryDictDecoderUtils.readDictionaryBinary(this, dict);
        } catch (IOException e) {
            Log.e(TAG, "The dictionary " + mDictDirectory.getName() + " is broken.", e);
            if (deleteDictIfBroken) {
                deleteDictFiles();
            }
            throw e;
        } catch (UnsupportedFormatException e) {
            Log.e(TAG, "The dictionary " + mDictDirectory.getName() + " is broken.", e);
            if (deleteDictIfBroken) {
                deleteDictFiles();
            }
            throw e;
        }
    }

    @Override
    public void setPosition(int newPos) {
        mDictBuffer.position(newPos);
    }

    @Override
    public int getPosition() {
        return mDictBuffer.position();
    }

    @Override
    public int readPtNodeCount() {
        return BinaryDictDecoderUtils.readPtNodeCount(mDictBuffer);
    }

    @Override
    public boolean readAndFollowForwardLink() {
        final int nextAddress = mDictBuffer.readUnsignedInt24();
        if (nextAddress >= 0 && nextAddress < mDictBuffer.limit()) {
            mDictBuffer.position(nextAddress);
            return true;
        }
        return false;
    }

    @Override
    public boolean hasNextPtNodeArray() {
        return mDictBuffer.position() != FormatSpec.NO_FORWARD_LINK_ADDRESS;
    }

    @Override
    public void skipPtNode(final FormatOptions formatOptions) {
        final int flags = PtNodeReader.readPtNodeOptionFlags(mDictBuffer);
        PtNodeReader.readParentAddress(mDictBuffer, formatOptions);
        BinaryDictIOUtils.skipString(mDictBuffer,
                (flags & FormatSpec.FLAG_HAS_MULTIPLE_CHARS) != 0);
        if ((flags & FormatSpec.FLAG_IS_TERMINAL) != 0) PtNodeReader.readTerminalId(mDictBuffer);
        PtNodeReader.readChildrenAddress(mDictBuffer, flags, formatOptions);
    }
}