/*
 * Copyright (C) 2012 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.Constants;
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.ByteArrayDictBuffer;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.Map;
import java.util.Stack;

public final class BinaryDictIOUtils {
    private static final boolean DBG = false;

    private BinaryDictIOUtils() {
        // This utility class is not publicly instantiable.
    }

    private static final class Position {
        public static final int NOT_READ_PTNODE_COUNT = -1;

        public int mAddress;
        public int mNumOfPtNode;
        public int mPosition;
        public int mLength;

        public Position(int address, int length) {
            mAddress = address;
            mLength = length;
            mNumOfPtNode = NOT_READ_PTNODE_COUNT;
        }
    }

    /**
     * Retrieves all node arrays without recursive call.
     */
    private static void readUnigramsAndBigramsBinaryInner(final DictDecoder dictDecoder,
            final int headerSize, final Map<Integer, String> words,
            final Map<Integer, Integer> frequencies,
            final Map<Integer, ArrayList<PendingAttribute>> bigrams,
            final FormatOptions formatOptions) {
        int[] pushedChars = new int[FormatSpec.MAX_WORD_LENGTH + 1];

        Stack<Position> stack = new Stack<Position>();
        int index = 0;

        Position initPos = new Position(headerSize, 0);
        stack.push(initPos);

        while (!stack.empty()) {
            Position p = stack.peek();

            if (DBG) {
                MakedictLog.d("read: address=" + p.mAddress + ", numOfPtNode=" +
                        p.mNumOfPtNode + ", position=" + p.mPosition + ", length=" + p.mLength);
            }

            if (dictDecoder.getPosition() != p.mAddress) dictDecoder.setPosition(p.mAddress);
            if (index != p.mLength) index = p.mLength;

            if (p.mNumOfPtNode == Position.NOT_READ_PTNODE_COUNT) {
                p.mNumOfPtNode = dictDecoder.readPtNodeCount();
                p.mAddress += getPtNodeCountSize(p.mNumOfPtNode);
                p.mPosition = 0;
            }
            if (p.mNumOfPtNode == 0) {
                stack.pop();
                continue;
            }
            PtNodeInfo info = dictDecoder.readPtNode(p.mAddress, formatOptions);
            for (int i = 0; i < info.mCharacters.length; ++i) {
                pushedChars[index++] = info.mCharacters[i];
            }
            p.mPosition++;

            final boolean isMovedPtNode = isMovedPtNode(info.mFlags,
                    formatOptions);
            final boolean isDeletedPtNode = isDeletedPtNode(info.mFlags,
                    formatOptions);
            if (!isMovedPtNode && !isDeletedPtNode
                    && info.mFrequency != FusionDictionary.PtNode.NOT_A_TERMINAL) {// found word
                words.put(info.mOriginalAddress, new String(pushedChars, 0, index));
                frequencies.put(info.mOriginalAddress, info.mFrequency);
                if (info.mBigrams != null) bigrams.put(info.mOriginalAddress, info.mBigrams);
            }

            if (p.mPosition == p.mNumOfPtNode) {
                if (formatOptions.mSupportsDynamicUpdate) {
                    final boolean hasValidForwardLinkAddress =
                            dictDecoder.readAndFollowForwardLink();
                    if (hasValidForwardLinkAddress && dictDecoder.hasNextPtNodeArray()) {
                        // The node array has a forward link.
                        p.mNumOfPtNode = Position.NOT_READ_PTNODE_COUNT;
                        p.mAddress = dictDecoder.getPosition();
                    } else {
                        stack.pop();
                    }
                } else {
                    stack.pop();
                }
            } else {
                // The Ptnode array has more PtNodes.
                p.mAddress = dictDecoder.getPosition();
            }

            if (!isMovedPtNode && hasChildrenAddress(info.mChildrenAddress)) {
                final Position childrenPos = new Position(info.mChildrenAddress, index);
                stack.push(childrenPos);
            }
        }
    }

    /**
     * Reads unigrams and bigrams from the binary file.
     * Doesn't store a full memory representation of the dictionary.
     *
     * @param dictDecoder the dict decoder.
     * @param words the map to store the address as a key and the word as a value.
     * @param frequencies the map to store the address as a key and the frequency as a value.
     * @param bigrams the map to store the address as a key and the list of address as a value.
     * @throws IOException if the file can't be read.
     * @throws UnsupportedFormatException if the format of the file is not recognized.
     */
    /* package */ static void readUnigramsAndBigramsBinary(final DictDecoder dictDecoder,
            final Map<Integer, String> words, final Map<Integer, Integer> frequencies,
            final Map<Integer, ArrayList<PendingAttribute>> bigrams) throws IOException,
            UnsupportedFormatException {
        // Read header
        final FileHeader header = dictDecoder.readHeader();
        readUnigramsAndBigramsBinaryInner(dictDecoder, header.mHeaderSize, words,
                frequencies, bigrams, header.mFormatOptions);
    }

    /**
     * Gets the address of the last PtNode of the exact matching word in the dictionary.
     * If no match is found, returns NOT_VALID_WORD.
     *
     * @param dictDecoder the dict decoder.
     * @param word the word we search for.
     * @return the address of the terminal node.
     * @throws IOException if the file can't be read.
     * @throws UnsupportedFormatException if the format of the file is not recognized.
     */
    @UsedForTesting
    /* package */ static int getTerminalPosition(final DictDecoder dictDecoder,
            final String word) throws IOException, UnsupportedFormatException {
        if (word == null) return FormatSpec.NOT_VALID_WORD;
        dictDecoder.setPosition(0);

        final FileHeader header = dictDecoder.readHeader();
        int wordPos = 0;
        final int wordLen = word.codePointCount(0, word.length());
        for (int depth = 0; depth < Constants.DICTIONARY_MAX_WORD_LENGTH; ++depth) {
            if (wordPos >= wordLen) return FormatSpec.NOT_VALID_WORD;

            do {
                final int ptNodeCount = dictDecoder.readPtNodeCount();
                boolean foundNextPtNode = false;
                for (int i = 0; i < ptNodeCount; ++i) {
                    final int ptNodePos = dictDecoder.getPosition();
                    final PtNodeInfo currentInfo = dictDecoder.readPtNode(ptNodePos,
                            header.mFormatOptions);
                    final boolean isMovedNode = isMovedPtNode(currentInfo.mFlags,
                            header.mFormatOptions);
                    final boolean isDeletedNode = isDeletedPtNode(currentInfo.mFlags,
                            header.mFormatOptions);
                    if (isMovedNode) continue;
                    boolean same = true;
                    for (int p = 0, j = word.offsetByCodePoints(0, wordPos);
                            p < currentInfo.mCharacters.length;
                            ++p, j = word.offsetByCodePoints(j, 1)) {
                        if (wordPos + p >= wordLen
                                || word.codePointAt(j) != currentInfo.mCharacters[p]) {
                            same = false;
                            break;
                        }
                    }

                    if (same) {
                        // found the PtNode matches the word.
                        if (wordPos + currentInfo.mCharacters.length == wordLen) {
                            if (currentInfo.mFrequency == PtNode.NOT_A_TERMINAL
                                    || isDeletedNode) {
                                return FormatSpec.NOT_VALID_WORD;
                            } else {
                                return ptNodePos;
                            }
                        }
                        wordPos += currentInfo.mCharacters.length;
                        if (currentInfo.mChildrenAddress == FormatSpec.NO_CHILDREN_ADDRESS) {
                            return FormatSpec.NOT_VALID_WORD;
                        }
                        foundNextPtNode = true;
                        dictDecoder.setPosition(currentInfo.mChildrenAddress);
                        break;
                    }
                }

                // If we found the next PtNode, it is under the file pointer.
                // But if not, we are at the end of this node array so we expect to have
                // a forward link address that we need to consult and possibly resume
                // search on the next node array in the linked list.
                if (foundNextPtNode) break;
                if (!header.mFormatOptions.mSupportsDynamicUpdate) {
                    return FormatSpec.NOT_VALID_WORD;
                }

                final boolean hasValidForwardLinkAddress =
                        dictDecoder.readAndFollowForwardLink();
                if (!hasValidForwardLinkAddress || !dictDecoder.hasNextPtNodeArray()) {
                    return FormatSpec.NOT_VALID_WORD;
                }
            } while(true);
        }
        return FormatSpec.NOT_VALID_WORD;
    }

    /**
     * @return the size written, in bytes. Always 3 bytes.
     */
    static int writeSInt24ToBuffer(final DictBuffer dictBuffer,
            final int value) {
        final int absValue = Math.abs(value);
        dictBuffer.put((byte)(((value < 0 ? 0x80 : 0) | (absValue >> 16)) & 0xFF));
        dictBuffer.put((byte)((absValue >> 8) & 0xFF));
        dictBuffer.put((byte)(absValue & 0xFF));
        return 3;
    }

    /**
     * @return the size written, in bytes. Always 3 bytes.
     */
    static int writeSInt24ToStream(final OutputStream destination, final int value)
            throws IOException {
        final int absValue = Math.abs(value);
        destination.write((byte)(((value < 0 ? 0x80 : 0) | (absValue >> 16)) & 0xFF));
        destination.write((byte)((absValue >> 8) & 0xFF));
        destination.write((byte)(absValue & 0xFF));
        return 3;
    }

    /**
     * @return the size written, in bytes. 1, 2, or 3 bytes.
     */
    private static int writeVariableAddress(final OutputStream destination, final int value)
            throws IOException {
        switch (BinaryDictEncoderUtils.getByteSize(value)) {
        case 1:
            destination.write((byte)value);
            break;
        case 2:
            destination.write((byte)(0xFF & (value >> 8)));
            destination.write((byte)(0xFF & value));
            break;
        case 3:
            destination.write((byte)(0xFF & (value >> 16)));
            destination.write((byte)(0xFF & (value >> 8)));
            destination.write((byte)(0xFF & value));
            break;
        }
        return BinaryDictEncoderUtils.getByteSize(value);
    }

    static void skipString(final DictBuffer dictBuffer,
            final boolean hasMultipleChars) {
        if (hasMultipleChars) {
            int character = CharEncoding.readChar(dictBuffer);
            while (character != FormatSpec.INVALID_CHARACTER) {
                character = CharEncoding.readChar(dictBuffer);
            }
        } else {
            CharEncoding.readChar(dictBuffer);
        }
    }

    /**
     * Write a string to a stream.
     *
     * @param destination the stream to write.
     * @param word the string to be written.
     * @return the size written, in bytes.
     * @throws IOException
     */
    private static int writeString(final OutputStream destination, final String word)
            throws IOException {
        int size = 0;
        final int length = word.length();
        for (int i = 0; i < length; i = word.offsetByCodePoints(i, 1)) {
            final int codePoint = word.codePointAt(i);
            if (CharEncoding.getCharSize(codePoint) == 1) {
                destination.write((byte)codePoint);
                size++;
            } else {
                destination.write((byte)(0xFF & (codePoint >> 16)));
                destination.write((byte)(0xFF & (codePoint >> 8)));
                destination.write((byte)(0xFF & codePoint));
                size += 3;
            }
        }
        destination.write((byte)FormatSpec.PTNODE_CHARACTERS_TERMINATOR);
        size += FormatSpec.PTNODE_TERMINATOR_SIZE;
        return size;
    }

    /**
     * Write a PtNode to an output stream from a PtNodeInfo.
     * A PtNode is an in-memory representation of a node in the patricia trie.
     * A PtNode info is a container for low-level information about how the
     * PtNode is stored in the binary format.
     *
     * @param destination the stream to write.
     * @param info the PtNode info to be written.
     * @return the size written, in bytes.
     */
    private static int writePtNode(final OutputStream destination, final PtNodeInfo info)
            throws IOException {
        int size = FormatSpec.PTNODE_FLAGS_SIZE;
        destination.write((byte)info.mFlags);
        final int parentOffset = info.mParentAddress == FormatSpec.NO_PARENT_ADDRESS ?
                FormatSpec.NO_PARENT_ADDRESS : info.mParentAddress - info.mOriginalAddress;
        size += writeSInt24ToStream(destination, parentOffset);

        for (int i = 0; i < info.mCharacters.length; ++i) {
            if (CharEncoding.getCharSize(info.mCharacters[i]) == 1) {
                destination.write((byte)info.mCharacters[i]);
                size++;
            } else {
                size += writeSInt24ToStream(destination, info.mCharacters[i]);
            }
        }
        if (info.mCharacters.length > 1) {
            destination.write((byte)FormatSpec.PTNODE_CHARACTERS_TERMINATOR);
            size++;
        }

        if ((info.mFlags & FormatSpec.FLAG_IS_TERMINAL) != 0) {
            destination.write((byte)info.mFrequency);
            size++;
        }

        if (DBG) {
            MakedictLog.d("writePtNode origin=" + info.mOriginalAddress + ", size=" + size
                    + ", child=" + info.mChildrenAddress + ", characters ="
                    + new String(info.mCharacters, 0, info.mCharacters.length));
        }
        final int childrenOffset = info.mChildrenAddress == FormatSpec.NO_CHILDREN_ADDRESS ?
                0 : info.mChildrenAddress - (info.mOriginalAddress + size);
        writeSInt24ToStream(destination, childrenOffset);
        size += FormatSpec.SIGNED_CHILDREN_ADDRESS_SIZE;

        if (info.mShortcutTargets != null && info.mShortcutTargets.size() > 0) {
            final int shortcutListSize =
                    BinaryDictEncoderUtils.getShortcutListSize(info.mShortcutTargets);
            destination.write((byte)(shortcutListSize >> 8));
            destination.write((byte)(shortcutListSize & 0xFF));
            size += 2;
            final Iterator<WeightedString> shortcutIterator = info.mShortcutTargets.iterator();
            while (shortcutIterator.hasNext()) {
                final WeightedString target = shortcutIterator.next();
                destination.write((byte)BinaryDictEncoderUtils.makeShortcutFlags(
                        shortcutIterator.hasNext(), target.mFrequency));
                size++;
                size += writeString(destination, target.mWord);
            }
        }

        if (info.mBigrams != null) {
            // TODO: Consolidate this code with the code that computes the size of the bigram list
            //        in BinaryDictEncoderUtils#computeActualNodeArraySize
            for (int i = 0; i < info.mBigrams.size(); ++i) {

                final int bigramFrequency = info.mBigrams.get(i).mFrequency;
                int bigramFlags = (i < info.mBigrams.size() - 1)
                        ? FormatSpec.FLAG_BIGRAM_SHORTCUT_ATTR_HAS_NEXT : 0;
                size++;
                final int bigramOffset = info.mBigrams.get(i).mAddress - (info.mOriginalAddress
                        + size);
                bigramFlags |= (bigramOffset < 0) ? FormatSpec.FLAG_BIGRAM_ATTR_OFFSET_NEGATIVE : 0;
                switch (BinaryDictEncoderUtils.getByteSize(bigramOffset)) {
                case 1:
                    bigramFlags |= FormatSpec.FLAG_BIGRAM_ATTR_ADDRESS_TYPE_ONEBYTE;
                    break;
                case 2:
                    bigramFlags |= FormatSpec.FLAG_BIGRAM_ATTR_ADDRESS_TYPE_TWOBYTES;
                    break;
                case 3:
                    bigramFlags |= FormatSpec.FLAG_BIGRAM_ATTR_ADDRESS_TYPE_THREEBYTES;
                    break;
                }
                bigramFlags |= bigramFrequency & FormatSpec.FLAG_BIGRAM_SHORTCUT_ATTR_FREQUENCY;
                destination.write((byte)bigramFlags);
                size += writeVariableAddress(destination, Math.abs(bigramOffset));
            }
        }
        return size;
    }

    /**
     * Compute the size of the PtNode.
     */
    static int computePtNodeSize(final PtNodeInfo info, final FormatOptions formatOptions) {
        int size = FormatSpec.PTNODE_FLAGS_SIZE + FormatSpec.PARENT_ADDRESS_SIZE
                + BinaryDictEncoderUtils.getPtNodeCharactersSize(info.mCharacters)
                + getChildrenAddressSize(info.mFlags, formatOptions);
        if ((info.mFlags & FormatSpec.FLAG_IS_TERMINAL) != 0) {
            size += FormatSpec.PTNODE_FREQUENCY_SIZE;
        }
        if (info.mShortcutTargets != null && !info.mShortcutTargets.isEmpty()) {
            size += BinaryDictEncoderUtils.getShortcutListSize(info.mShortcutTargets);
        }
        if (info.mBigrams != null) {
            for (final PendingAttribute attr : info.mBigrams) {
                size += FormatSpec.PTNODE_FLAGS_SIZE;
                size += BinaryDictEncoderUtils.getByteSize(attr.mAddress);
            }
        }
        return size;
    }

    /**
     * Write a node array to the stream.
     *
     * @param destination the stream to write.
     * @param infos an array of PtNodeInfo to be written.
     * @return the size written, in bytes.
     * @throws IOException
     */
    static int writeNodes(final OutputStream destination, final PtNodeInfo[] infos)
            throws IOException {
        int size = getPtNodeCountSize(infos.length);
        switch (getPtNodeCountSize(infos.length)) {
            case 1:
                destination.write((byte)infos.length);
                break;
            case 2:
                destination.write((byte)(infos.length >> 8));
                destination.write((byte)(infos.length & 0xFF));
                break;
            default:
                throw new RuntimeException("Invalid node count size.");
        }
        for (final PtNodeInfo info : infos) size += writePtNode(destination, info);
        writeSInt24ToStream(destination, FormatSpec.NO_FORWARD_LINK_ADDRESS);
        return size + FormatSpec.FORWARD_LINK_ADDRESS_SIZE;
    }

    private static final int HEADER_READING_BUFFER_SIZE = 16384;
    /**
     * Convenience method to read the header of a binary file.
     *
     * This is quite resource intensive - don't call when performance is critical.
     *
     * @param file The file to read.
     * @param offset The offset in the file where to start reading the data.
     * @param length The length of the data file.
     */
    private static FileHeader getDictionaryFileHeader(
            final File file, final long offset, final long length)
            throws FileNotFoundException, IOException, UnsupportedFormatException {
        final byte[] buffer = new byte[HEADER_READING_BUFFER_SIZE];
        final DictDecoder dictDecoder = FormatSpec.getDictDecoder(file,
                new DictDecoder.DictionaryBufferFactory() {
                    @Override
                    public DictBuffer getDictionaryBuffer(File file)
                            throws FileNotFoundException, IOException {
                        final FileInputStream inStream = new FileInputStream(file);
                        try {
                            inStream.skip(offset);
                            inStream.read(buffer);
                            return new ByteArrayDictBuffer(buffer);
                        } finally {
                            inStream.close();
                        }
                    }
                }
        );
        return dictDecoder.readHeader();
    }

    public static FileHeader getDictionaryFileHeaderOrNull(final File file, final long offset,
            final long length) {
        try {
            final FileHeader header = getDictionaryFileHeader(file, offset, length);
            return header;
        } catch (UnsupportedFormatException e) {
            return null;
        } catch (IOException e) {
            return null;
        }
    }

    /**
     * Helper method to hide the actual value of the no children address.
     */
    public static boolean hasChildrenAddress(final int address) {
        return FormatSpec.NO_CHILDREN_ADDRESS != address;
    }

    /**
     * Helper method to check whether the node is moved.
     */
    public static boolean isMovedPtNode(final int flags, final FormatOptions options) {
        return options.mSupportsDynamicUpdate
                && ((flags & FormatSpec.MASK_CHILDREN_ADDRESS_TYPE) == FormatSpec.FLAG_IS_MOVED);
    }

    /**
     * Helper method to check whether the dictionary can be updated dynamically.
     */
    public static boolean supportsDynamicUpdate(final FormatOptions options) {
        return options.mVersion >= FormatSpec.FIRST_VERSION_WITH_DYNAMIC_UPDATE
                && options.mSupportsDynamicUpdate;
    }

    /**
     * Helper method to check whether the node is deleted.
     */
    public static boolean isDeletedPtNode(final int flags, final FormatOptions formatOptions) {
        return formatOptions.mSupportsDynamicUpdate
                && ((flags & FormatSpec.MASK_CHILDREN_ADDRESS_TYPE) == FormatSpec.FLAG_IS_DELETED);
    }

    /**
     * Compute the binary size of the node count
     * @param count the node count
     * @return the size of the node count, either 1 or 2 bytes.
     */
    public static int getPtNodeCountSize(final int count) {
        if (FormatSpec.MAX_PTNODES_FOR_ONE_BYTE_PTNODE_COUNT >= count) {
            return 1;
        } else if (FormatSpec.MAX_PTNODES_IN_A_PT_NODE_ARRAY >= count) {
            return 2;
        } else {
            throw new RuntimeException("Can't have more than "
                    + FormatSpec.MAX_PTNODES_IN_A_PT_NODE_ARRAY + " PtNode in a PtNodeArray (found "
                    + count + ")");
        }
    }

    static int getChildrenAddressSize(final int optionFlags,
            final FormatOptions formatOptions) {
        if (formatOptions.mSupportsDynamicUpdate) return FormatSpec.SIGNED_CHILDREN_ADDRESS_SIZE;
        switch (optionFlags & FormatSpec.MASK_CHILDREN_ADDRESS_TYPE) {
            case FormatSpec.FLAG_CHILDREN_ADDRESS_TYPE_ONEBYTE:
                return 1;
            case FormatSpec.FLAG_CHILDREN_ADDRESS_TYPE_TWOBYTES:
                return 2;
            case FormatSpec.FLAG_CHILDREN_ADDRESS_TYPE_THREEBYTES:
                return 3;
            case FormatSpec.FLAG_CHILDREN_ADDRESS_TYPE_NOADDRESS:
            default:
                return 0;
        }
    }

    /**
     * Calculate bigram frequency from compressed value
     *
     * @param unigramFrequency
     * @param bigramFrequency compressed frequency
     * @return approximate bigram frequency
     */
    public static int reconstructBigramFrequency(final int unigramFrequency,
            final int bigramFrequency) {
        final float stepSize = (FormatSpec.MAX_TERMINAL_FREQUENCY - unigramFrequency)
                / (1.5f + FormatSpec.MAX_BIGRAM_FREQUENCY);
        final float resultFreqFloat = unigramFrequency + stepSize * (bigramFrequency + 1.0f);
        return (int)resultFreqFloat;
    }
}