/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the Elastic License
 * 2.0 and the Server Side Public License, v 1; you may not use this file except
 * in compliance with, at your election, the Elastic License 2.0 or the Server
 * Side Public License, v 1.
 */

package org.elasticsearch.analysis.common;

import org.apache.lucene.analysis.CharArraySet;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.miscellaneous.WordDelimiterFilter;
import org.apache.lucene.analysis.miscellaneous.WordDelimiterIterator;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.env.Environment;
import org.elasticsearch.index.IndexSettings;
import org.elasticsearch.index.analysis.AbstractTokenFilterFactory;
import org.elasticsearch.index.analysis.Analysis;
import org.elasticsearch.index.analysis.TokenFilterFactory;

import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.SortedMap;
import java.util.TreeMap;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import static org.apache.lucene.analysis.miscellaneous.WordDelimiterFilter.CATENATE_ALL;
import static org.apache.lucene.analysis.miscellaneous.WordDelimiterFilter.CATENATE_NUMBERS;
import static org.apache.lucene.analysis.miscellaneous.WordDelimiterFilter.CATENATE_WORDS;
import static org.apache.lucene.analysis.miscellaneous.WordDelimiterFilter.GENERATE_NUMBER_PARTS;
import static org.apache.lucene.analysis.miscellaneous.WordDelimiterFilter.GENERATE_WORD_PARTS;
import static org.apache.lucene.analysis.miscellaneous.WordDelimiterFilter.PRESERVE_ORIGINAL;
import static org.apache.lucene.analysis.miscellaneous.WordDelimiterFilter.SPLIT_ON_CASE_CHANGE;
import static org.apache.lucene.analysis.miscellaneous.WordDelimiterFilter.SPLIT_ON_NUMERICS;
import static org.apache.lucene.analysis.miscellaneous.WordDelimiterFilter.STEM_ENGLISH_POSSESSIVE;

public class WordDelimiterTokenFilterFactory extends AbstractTokenFilterFactory {

    private final byte[] charTypeTable;
    private final int flags;
    private final CharArraySet protoWords;

    @SuppressWarnings("HiddenField")
    public WordDelimiterTokenFilterFactory(IndexSettings indexSettings, Environment env, String name, Settings settings) {
        super(name, settings);

        // Sample Format for the type table:
        // $ => DIGIT
        // % => DIGIT
        // . => DIGIT
        // \u002C => DIGIT
        // \u200D => ALPHANUM
        List<String> charTypeTableValues = Analysis.getWordList(env, settings, "type_table");
        if (charTypeTableValues == null) {
            this.charTypeTable = WordDelimiterIterator.DEFAULT_WORD_DELIM_TABLE;
        } else {
            this.charTypeTable = parseTypes(charTypeTableValues);
        }
        int flags = 0;
        // If set, causes parts of words to be generated: "PowerShot" => "Power" "Shot"
        flags |= getFlag(GENERATE_WORD_PARTS, settings, "generate_word_parts", true);
        // If set, causes number subwords to be generated: "500-42" => "500" "42"
        flags |= getFlag(GENERATE_NUMBER_PARTS, settings, "generate_number_parts", true);
        // 1, causes maximum runs of word parts to be catenated: "wi-fi" => "wifi"
        flags |= getFlag(CATENATE_WORDS, settings, "catenate_words", false);
        // If set, causes maximum runs of number parts to be catenated: "500-42" => "50042"
        flags |= getFlag(CATENATE_NUMBERS, settings, "catenate_numbers", false);
        // If set, causes all subword parts to be catenated: "wi-fi-4000" => "wifi4000"
        flags |= getFlag(CATENATE_ALL, settings, "catenate_all", false);
        // 1, causes "PowerShot" to be two tokens; ("Power-Shot" remains two parts regards)
        flags |= getFlag(SPLIT_ON_CASE_CHANGE, settings, "split_on_case_change", true);
        // If set, includes original words in subwords: "500-42" => "500" "42" "500-42"
        flags |= getFlag(PRESERVE_ORIGINAL, settings, "preserve_original", false);
        // 1, causes "j2se" to be three tokens; "j" "2" "se"
        flags |= getFlag(SPLIT_ON_NUMERICS, settings, "split_on_numerics", true);
        // If set, causes trailing "'s" to be removed for each subword: "O'Neil's" => "O", "Neil"
        flags |= getFlag(STEM_ENGLISH_POSSESSIVE, settings, "stem_english_possessive", true);
        // If not null is the set of tokens to protect from being delimited
        Set<?> protectedWords = Analysis.getWordSet(env, settings, "protected_words");
        this.protoWords = protectedWords == null ? null : CharArraySet.copy(protectedWords);
        this.flags = flags;
    }

    @Override
    public TokenStream create(TokenStream tokenStream) {
        return new WordDelimiterFilter(tokenStream, charTypeTable, flags, protoWords);
    }

    @Override
    public TokenFilterFactory getSynonymFilter() {
        throw new IllegalArgumentException("Token filter [" + name() + "] cannot be used to parse synonyms");
    }

    public static int getFlag(int flag, Settings settings, String key, boolean defaultValue) {
        if (settings.getAsBoolean(key, defaultValue)) {
            return flag;
        }
        return 0;
    }

    // source => type
    private static final Pattern typePattern = Pattern.compile("(.*)\\s*=>\\s*(.*)\\s*$");

    /**
     * parses a list of MappingCharFilter style rules into a custom byte[] type table
     */
    static byte[] parseTypes(Collection<String> rules) {
        SortedMap<Character, Byte> typeMap = new TreeMap<>();
        for (String rule : rules) {
            Matcher m = typePattern.matcher(rule);
            if (m.find() == false) {
                throw new RuntimeException("Invalid Mapping Rule : [" + rule + "]");
            }
            String lhs = parseString(m.group(1).trim());
            Byte rhs = parseType(m.group(2).trim());
            if (lhs.length() != 1) throw new RuntimeException("Invalid Mapping Rule : [" + rule + "]. Only a single character is allowed.");
            if (rhs == null) throw new RuntimeException("Invalid Mapping Rule : [" + rule + "]. Illegal type.");
            typeMap.put(lhs.charAt(0), rhs);
        }

        // ensure the table is always at least as big as DEFAULT_WORD_DELIM_TABLE for performance
        byte types[] = new byte[Math.max(typeMap.lastKey() + 1, WordDelimiterIterator.DEFAULT_WORD_DELIM_TABLE.length)];
        for (int i = 0; i < types.length; i++)
            types[i] = WordDelimiterIterator.getType(i);
        for (Map.Entry<Character, Byte> mapping : typeMap.entrySet())
            types[mapping.getKey()] = mapping.getValue();
        return types;
    }

    private static Byte parseType(String s) {
        if (s.equals("LOWER")) return WordDelimiterFilter.LOWER;
        else if (s.equals("UPPER")) return WordDelimiterFilter.UPPER;
        else if (s.equals("ALPHA")) return WordDelimiterFilter.ALPHA;
        else if (s.equals("DIGIT")) return WordDelimiterFilter.DIGIT;
        else if (s.equals("ALPHANUM")) return WordDelimiterFilter.ALPHANUM;
        else if (s.equals("SUBWORD_DELIM")) return WordDelimiterFilter.SUBWORD_DELIM;
        else return null;
    }

    private static String parseString(String s) {
        char[] out = new char[256];
        int readPos = 0;
        int len = s.length();
        int writePos = 0;
        while (readPos < len) {
            char c = s.charAt(readPos++);
            if (c == '\\') {
                if (readPos >= len) throw new RuntimeException("Invalid escaped char in [" + s + "]");
                c = s.charAt(readPos++);
                switch (c) {
                    case '\\' -> c = '\\';
                    case 'n' -> c = '\n';
                    case 't' -> c = '\t';
                    case 'r' -> c = '\r';
                    case 'b' -> c = '\b';
                    case 'f' -> c = '\f';
                    case 'u' -> {
                        if (readPos + 3 >= len) throw new RuntimeException("Invalid escaped char in [" + s + "]");
                        c = (char) Integer.parseInt(s.substring(readPos, readPos + 4), 16);
                        readPos += 4;
                    }
                }
            }
            out[writePos++] = c;
        }
        return new String(out, 0, writePos);
    }

    @Override
    public boolean breaksFastVectorHighlighter() {
        return true;
    }
}
