/*
 * Copyright 1999-2004 The Apache Software Foundation.
 * 
 * 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.
 */

/* $Id$ */
 
package com.lowagie.text.pdf.hyphenation;

import java.io.InputStream;
import java.util.ArrayList;
import java.util.HashMap;

/**
 * This tree structure stores the hyphenation patterns in an efficient
 * way for fast lookup. It provides the provides the method to
 * hyphenate a word.
 *
 * @author Carlos Villegas <cav@uniscope.co.jp>
 */
public class HyphenationTree extends TernaryTree 
            implements PatternConsumer {

    private static final long serialVersionUID = -7763254239309429432L;

	/**
     * value space: stores the interletter values
     */
    protected ByteVector vspace;

    /**
     * This map stores hyphenation exceptions
     */
    protected HashMap stoplist;

    /**
     * This map stores the character classes
     */
    protected TernaryTree classmap;

    /**
     * Temporary map to store interletter values on pattern loading.
     */
    private transient TernaryTree ivalues;

    public HyphenationTree() {
        stoplist = new HashMap(23);    // usually a small table
        classmap = new TernaryTree();
        vspace = new ByteVector();
        vspace.alloc(1);    // this reserves index 0, which we don't use
    }

    /**
     * Packs the values by storing them in 4 bits, two values into a byte
     * Values range is from 0 to 9. We use zero as terminator,
     * so we'll add 1 to the value.
     * @param values a string of digits from '0' to '9' representing the
     * interletter values.
     * @return the index into the vspace array where the packed values
     * are stored.
     */
    protected int packValues(String values) {
        int i, n = values.length();
        int m = (n & 1) == 1 ? (n >> 1) + 2 : (n >> 1) + 1;
        int offset = vspace.alloc(m);
        byte[] va = vspace.getArray();
        for (i = 0; i < n; i++) {
            int j = i >> 1;
            byte v = (byte)((values.charAt(i) - '0' + 1) & 0x0f);
            if ((i & 1) == 1) {
                va[j + offset] = (byte)(va[j + offset] | v);
            } else {
                va[j + offset] = (byte)(v << 4);    // big endian
            }
        }
        va[m - 1 + offset] = 0;    // terminator
        return offset;
    }

    protected String unpackValues(int k) {
        StringBuffer buf = new StringBuffer();
        byte v = vspace.get(k++);
        while (v != 0) {
            char c = (char)((v >>> 4) - 1 + '0');
            buf.append(c);
            c = (char)(v & 0x0f);
            if (c == 0) {
                break;
            }
            c = (char)(c - 1 + '0');
            buf.append(c);
            v = vspace.get(k++);
        }
        return buf.toString();
    }

    public void loadSimplePatterns(InputStream stream) {
        SimplePatternParser pp = new SimplePatternParser();
        ivalues = new TernaryTree();

        pp.parse(stream, this);

        // patterns/values should be now in the tree
        // let's optimize a bit
        trimToSize();
        vspace.trimToSize();
        classmap.trimToSize();

        // get rid of the auxiliary map
        ivalues = null;
    }


    public String findPattern(String pat) {
        int k = super.find(pat);
        if (k >= 0) {
            return unpackValues(k);
        }
        return "";
    }

    /**
     * String compare, returns 0 if equal or
     * t is a substring of s
     */
    protected int hstrcmp(char[] s, int si, char[] t, int ti) {
        for (; s[si] == t[ti]; si++, ti++) {
            if (s[si] == 0) {
                return 0;
            }
        }
        if (t[ti] == 0) {
            return 0;
        }
        return s[si] - t[ti];
    }

    protected byte[] getValues(int k) {
        StringBuffer buf = new StringBuffer();
        byte v = vspace.get(k++);
        while (v != 0) {
            char c = (char)((v >>> 4) - 1);
            buf.append(c);
            c = (char)(v & 0x0f);
            if (c == 0) {
                break;
            }
            c = (char)(c - 1);
            buf.append(c);
            v = vspace.get(k++);
        }
        byte[] res = new byte[buf.length()];
        for (int i = 0; i < res.length; i++) {
            res[i] = (byte)buf.charAt(i);
        }
        return res;
    }

    /**
     * <p>Search for all possible partial matches of word starting
     * at index an update interletter values. In other words, it
     * does something like:</p>
     * <code>
     * for(i=0; i<patterns.length; i++) {
     * if ( word.substring(index).startsWidth(patterns[i]) )
     * update_interletter_values(patterns[i]);
     * }
     * </code>
     * <p>But it is done in an efficient way since the patterns are
     * stored in a ternary tree. In fact, this is the whole purpose
     * of having the tree: doing this search without having to test
     * every single pattern. The number of patterns for languages
     * such as English range from 4000 to 10000. Thus, doing thousands
     * of string comparisons for each word to hyphenate would be
     * really slow without the tree. The tradeoff is memory, but
     * using a ternary tree instead of a trie, almost halves the
     * the memory used by Lout or TeX. It's also faster than using
     * a hash table</p>
     * @param word null terminated word to match
     * @param index start index from word
     * @param il interletter values array to update
     */
    protected void searchPatterns(char[] word, int index, byte[] il) {
        byte[] values;
        int i = index;
        char p, q;
        char sp = word[i];
        p = root;

        while (p > 0 && p < sc.length) {
            if (sc[p] == 0xFFFF) {
                if (hstrcmp(word, i, kv.getArray(), lo[p]) == 0) {
                    values = getValues(eq[p]);    // data pointer is in eq[]
                    int j = index;
                    for (int k = 0; k < values.length; k++) {
                        if (j < il.length && values[k] > il[j]) {
                            il[j] = values[k];
                        }
                        j++;
                    }
                }
                return;
            }
            int d = sp - sc[p];
            if (d == 0) {
                if (sp == 0) {
                    break;
                }
                sp = word[++i];
                p = eq[p];
                q = p;

                // look for a pattern ending at this position by searching for
                // the null char ( splitchar == 0 )
                while (q > 0 && q < sc.length) {
                    if (sc[q] == 0xFFFF) {        // stop at compressed branch
                        break;
                    }
                    if (sc[q] == 0) {
                        values = getValues(eq[q]);
                        int j = index;
                        for (int k = 0; k < values.length; k++) {
                            if (j < il.length && values[k] > il[j]) {
                                il[j] = values[k];
                            }
                            j++;
                        }
                        break;
                    } else {
                        q = lo[q];

                        /**
                         * actually the code should be:
                         * q = sc[q] < 0 ? hi[q] : lo[q];
                         * but java chars are unsigned
                         */
                    }
                }
            } else {
                p = d < 0 ? lo[p] : hi[p];
            }
        }
    }

    /**
     * Hyphenate word and return a Hyphenation object.
     * @param word the word to be hyphenated
     * @param remainCharCount Minimum number of characters allowed
     * before the hyphenation point.
     * @param pushCharCount Minimum number of characters allowed after
     * the hyphenation point.
     * @return a {@link Hyphenation Hyphenation} object representing
     * the hyphenated word or null if word is not hyphenated.
     */
    public Hyphenation hyphenate(String word, int remainCharCount,
                                 int pushCharCount) {
        char[] w = word.toCharArray();
        return hyphenate(w, 0, w.length, remainCharCount, pushCharCount);
    }

    /**
     * w = "****nnllllllnnn*****",
     * where n is a non-letter, l is a letter,
     * all n may be absent, the first n is at offset,
     * the first l is at offset + iIgnoreAtBeginning;
     * word = ".llllll.'\0'***",
     * where all l in w are copied into word.
     * In the first part of the routine len = w.length,
     * in the second part of the routine len = word.length.
     * Three indices are used:
     * index(w), the index in w,
     * index(word), the index in word,
     * letterindex(word), the index in the letter part of word.
     * The following relations exist:
     * index(w) = offset + i - 1
     * index(word) = i - iIgnoreAtBeginning
     * letterindex(word) = index(word) - 1
     * (see first loop).
     * It follows that:
     * index(w) - index(word) = offset - 1 + iIgnoreAtBeginning
     * index(w) = letterindex(word) + offset + iIgnoreAtBeginning
     */

    /**
     * Hyphenate word and return an array of hyphenation points.
     * @param w char array that contains the word
     * @param offset Offset to first character in word
     * @param len Length of word
     * @param remainCharCount Minimum number of characters allowed
     * before the hyphenation point.
     * @param pushCharCount Minimum number of characters allowed after
     * the hyphenation point.
     * @return a {@link Hyphenation Hyphenation} object representing
     * the hyphenated word or null if word is not hyphenated.
     */
    public Hyphenation hyphenate(char[] w, int offset, int len,
                                 int remainCharCount, int pushCharCount) {
        int i;
        char[] word = new char[len + 3];

        // normalize word
        char[] c = new char[2];
        int iIgnoreAtBeginning = 0;
        int iLength = len;
        boolean bEndOfLetters = false;
        for (i = 1; i <= len; i++) {
            c[0] = w[offset + i - 1];
            int nc = classmap.find(c, 0);
            if (nc < 0) {    // found a non-letter character ...
                if (i == (1 + iIgnoreAtBeginning)) {
                    // ... before any letter character
                    iIgnoreAtBeginning ++;
                } else {
                    // ... after a letter character
                    bEndOfLetters = true;
                }
                iLength --;
            } else {
                if (!bEndOfLetters) {
                    word[i - iIgnoreAtBeginning] = (char)nc;
                } else {
                    return null;
                }
            }
        }
        len = iLength;
        if (len < (remainCharCount + pushCharCount)) {
            // word is too short to be hyphenated
            return null;
        }
        int[] result = new int[len + 1];
        int k = 0;

        // check exception list first
        String sw = new String(word, 1, len);
        if (stoplist.containsKey(sw)) {
            // assume only simple hyphens (Hyphen.pre="-", Hyphen.post = Hyphen.no = null)
            ArrayList hw = (ArrayList)stoplist.get(sw);
            int j = 0;
            for (i = 0; i < hw.size(); i++) {
                Object o = hw.get(i);
                // j = index(sw) = letterindex(word)?
                // result[k] = corresponding index(w)
                if (o instanceof String) {
                    j += ((String)o).length();
                    if (j >= remainCharCount && j < (len - pushCharCount)) {
                        result[k++] = j + iIgnoreAtBeginning;
                    }
                }
            }
        } else {
            // use algorithm to get hyphenation points
            word[0] = '.';                    // word start marker
            word[len + 1] = '.';              // word end marker
            word[len + 2] = 0;                // null terminated
            byte[] il = new byte[len + 3];    // initialized to zero
            for (i = 0; i < len + 1; i++) {
                searchPatterns(word, i, il);
            }

            // hyphenation points are located where interletter value is odd
            // i is letterindex(word),
            // i + 1 is index(word),
            // result[k] = corresponding index(w)
            for (i = 0; i < len; i++) {
                if (((il[i + 1] & 1) == 1) && i >= remainCharCount
                        && i <= (len - pushCharCount)) {
                    result[k++] = i + iIgnoreAtBeginning;
                }
            }
        }


        if (k > 0) {
            // trim result array
            int[] res = new int[k];
            System.arraycopy(result, 0, res, 0, k);
            return new Hyphenation(new String(w, offset, len), res);
        } else {
            return null;
        }
    }

    /**
     * Add a character class to the tree. It is used by
     * {@link SimplePatternParser SimplePatternParser} as callback to
     * add character classes. Character classes define the
     * valid word characters for hyphenation. If a word contains
     * a character not defined in any of the classes, it is not hyphenated.
     * It also defines a way to normalize the characters in order
     * to compare them with the stored patterns. Usually pattern
     * files use only lower case characters, in this case a class
     * for letter 'a', for example, should be defined as "aA", the first
     * character being the normalization char.
     */
    public void addClass(String chargroup) {
        if (chargroup.length() > 0) {
            char equivChar = chargroup.charAt(0);
            char[] key = new char[2];
            key[1] = 0;
            for (int i = 0; i < chargroup.length(); i++) {
                key[0] = chargroup.charAt(i);
                classmap.insert(key, 0, equivChar);
            }
        }
    }

    /**
     * Add an exception to the tree. It is used by
     * {@link SimplePatternParser SimplePatternParser} class as callback to
     * store the hyphenation exceptions.
     * @param word normalized word
     * @param hyphenatedword a vector of alternating strings and
     * {@link Hyphen hyphen} objects.
     */
    public void addException(String word, ArrayList hyphenatedword) {
        stoplist.put(word, hyphenatedword);
    }

    /**
     * Add a pattern to the tree. Mainly, to be used by
     * {@link SimplePatternParser SimplePatternParser} class as callback to
     * add a pattern to the tree.
     * @param pattern the hyphenation pattern
     * @param ivalue interletter weight values indicating the
     * desirability and priority of hyphenating at a given point
     * within the pattern. It should contain only digit characters.
     * (i.e. '0' to '9').
     */
    public void addPattern(String pattern, String ivalue) {
        int k = ivalues.find(ivalue);
        if (k <= 0) {
            k = packValues(ivalue);
            ivalues.insert(ivalue, (char)k);
        }
        insert(pattern, (char)k);
    }

    public void printStats() {
        System.out.println("Value space size = "
                           + Integer.toString(vspace.length()));
        super.printStats();
    }
}
