/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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
 *
 *      https://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 org.apache.commons.codec.language.bm;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.EnumMap;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Objects;
import java.util.Set;
import java.util.TreeMap;
import java.util.function.Supplier;
import java.util.regex.Pattern;
import java.util.stream.Collectors;

import org.apache.commons.codec.language.bm.Languages.LanguageSet;
import org.apache.commons.codec.language.bm.Rule.Phoneme;

/**
 * Converts words into potential phonetic representations.
 * <p>
 * This is a two-stage process. Firstly, the word is converted into a phonetic representation that takes into account the likely source language. Next, this
 * phonetic representation is converted into a pan-European 'average' representation, allowing comparison between different versions of essentially the same
 * word from different languages.
 * </p>
 * <p>
 * This class is intentionally immutable and thread-safe. If you wish to alter the settings for a PhoneticEngine, you must make a new one with the updated
 * settings.
 * </p>
 * <p>
 * Ported from phoneticengine.php
 * </p>
 *
 * @since 1.6
 */
public class PhoneticEngine {

    /**
     * Builder for a PhoneticEngine.
     *
     * @since 1.23.0
     */
    public static class Builder implements Supplier<PhoneticEngine> {

        /** See https://en.wikipedia.org/wiki/Hubert_Blaine_Wolfeschlegelsteinhausenbergerdorff_Sr. */
        private static final int MAX_INPUT_LENGTH = 666;

        private static final int MAX_PHONEMES = 20;

        private boolean concat = true;

        private int maxInputLength = MAX_INPUT_LENGTH;

        private int maxPhonemes = MAX_PHONEMES;

        private NameType nameType = NameType.GENERIC;

        private RuleType ruleType = RuleType.APPROX;

        private Builder() {
            // empty
        }

        @Override
        public PhoneticEngine get() {
            return new PhoneticEngine(this);
        }

        /**
         * Sets all the properties of this builder to match those of the given engine.
         *
         * @param engine The engine to copy properties from.
         * @return This builder.
         */
        public Builder setAll(final PhoneticEngine engine) {
            this.nameType = engine.getNameType();
            this.ruleType = engine.getRuleType();
            this.concat = engine.isConcat();
            this.maxPhonemes = engine.getMaxPhonemes();
            return this;
        }

        /**
         * Sets whether the engine will concatenate multiple encodings.
         *
         * @param concat Whether the engine will concatenate multiple encodings.
         * @return This builder.
         */
        public Builder setConcat(final boolean concat) {
            this.concat = concat;
            return this;
        }

        /**
         * Sets the maximum input length allowed.
         * <p>
         * A value less than 0 will reset the maximum input length to the default value of {@value #MAX_INPUT_LENGTH}, see
         * <a href="https://en.wikipedia.org/wiki/Hubert_Blaine_Wolfeschlegelsteinhausenbergerdorff_Sr.">Hubert Blaine Wolfeschlegelsteinhausenbergerdorff
         * Sr.</a>.
         * </p>
         *
         * @param maxInputLength the maximum input length allowed.
         * @return This builder.
         */
        public Builder setMaxInputLength(final int maxInputLength) {
            this.maxInputLength = maxInputLength < 0 ? MAX_INPUT_LENGTH : maxInputLength;
            return this;
        }

        /**
         * Sets maximum number of phonemes the engine will handle.
         * <p>
         * A value less than 0 will reset the maximum number of phonemes to the default {@value #MAX_PHONEMES}.
         * </p>
         *
         * @param maxPhonemes The maximum number of phonemes the engine will handle.
         * @return This builder.
         */
        public Builder setMaxPhonemes(final int maxPhonemes) {
            this.maxPhonemes = maxPhonemes < 0 ? MAX_PHONEMES : maxPhonemes;
            return this;
        }

        /**
         * Sets the name type for the engine to be built.
         * <p>
         * A null value will reset the name type to the default of {@link NameType#GENERIC}.
         * </p>
         *
         * @param nameType The type of names the engine will use.
         * @return This builder.
         */
        public Builder setNameType(final NameType nameType) {
            this.nameType = nameType != null ? nameType : NameType.GENERIC;
            return this;
        }

        /**
         * Sets the rule type for the engine to be built.
         * <p>
         * A null value will reset the rule type to the default of {@link RuleType#APPROX}.
         * </p>
         *
         * @param ruleType The type of rules the engine will use.
         * @return This builder.
         */
        public Builder setRuleType(final RuleType ruleType) {
            this.ruleType = ruleType != null ? ruleType : RuleType.APPROX;
            return this;
        }
    }

    /**
     * Manipulates a set of phonemes as they are being built up. Not intended for use outside this package, and probably not outside the {@link PhoneticEngine}
     * class.
     *
     * @since 1.6
     */
    static final class PhonemeBuilder {

        /**
         * An empty builder where all phonemes must come from some set of languages. This will contain a single phoneme of zero characters. This can then be
         * appended to. This should be the only way to create a new phoneme from scratch.
         *
         * @param languages The set of languages.
         * @return a new, empty phoneme builder.
         */
        public static PhonemeBuilder empty(final Languages.LanguageSet languages) {
            return new PhonemeBuilder(new Rule.Phoneme("", languages));
        }

        private final Set<Rule.Phoneme> phonemes;

        private PhonemeBuilder(final Rule.Phoneme phoneme) {
            this.phonemes = new LinkedHashSet<>();
            this.phonemes.add(phoneme);
        }

        private PhonemeBuilder(final Set<Rule.Phoneme> phonemes) {
            this.phonemes = phonemes;
        }

        /**
         * Creates a new phoneme builder containing all phonemes in this one extended by {@code str}.
         *
         * @param str The characters to append to the phonemes.
         */
        public void append(final CharSequence str) {
            phonemes.forEach(ph -> ph.append(str));
        }

        /**
         * Applies the given phoneme expression to all phonemes in this phoneme builder.
         * <p>
         * This will lengthen phonemes that have compatible language sets to the expression, and drop those that are incompatible.
         * </p>
         *
         * @param phonemeExpr The expression to apply.
         * @param maxPhonemes The maximum number of phonemes to build up.
         */
        public void apply(final Rule.PhonemeExpr phonemeExpr, final int maxPhonemes) {
            final Set<Rule.Phoneme> newPhonemes = new LinkedHashSet<>(Math.min(phonemes.size() * phonemeExpr.size(), maxPhonemes));
            EXPR: for (final Rule.Phoneme left : phonemes) {
                for (final Rule.Phoneme right : phonemeExpr.getPhonemes()) {
                    final LanguageSet languages = left.getLanguages().restrictTo(right.getLanguages());
                    if (!languages.isEmpty()) {
                        final Rule.Phoneme join = new Phoneme(left, right, languages);
                        if (newPhonemes.size() < maxPhonemes) {
                            newPhonemes.add(join);
                            if (newPhonemes.size() >= maxPhonemes) {
                                break EXPR;
                            }
                        }
                    }
                }
            }
            phonemes.clear();
            phonemes.addAll(newPhonemes);
        }

        /**
         * Gets underlying phoneme set. Please don't mutate.
         *
         * @return the phoneme set.
         */
        public Set<Rule.Phoneme> getPhonemes() {
            return phonemes;
        }

        /**
         * Stringifies the phoneme set. This produces a single string of the strings of each phoneme, joined with a pipe. This is explicitly provided in place
         * of toString as it is a potentially expensive operation, which should be avoided when debugging.
         *
         * @return the stringified phoneme set.
         */
        public String makeString() {
            return phonemes.stream().map(Rule.Phoneme::getPhonemeText).collect(Collectors.joining("|"));
        }
    }

    /**
     * A function closure capturing the application of a list of rules to an input sequence at a particular offset. After invocation, the values {@code i} and
     * {@code found} are updated. {@code i} points to the index of the next char in {@code input} that must be processed next (the input up to that index having
     * been processed already), and {@code found} indicates if a matching rule was found or not. In the case where a matching rule was found,
     * {@code phonemeBuilder} is replaced with a new builder containing the phonemes updated by the matching rule.
     * <p>
     * Although this class is not thread-safe (it has mutable unprotected fields), it is not shared between threads as it is constructed as needed by the
     * calling methods.
     * </p>
     */
    private static final class RulesApplication {

        private final Map<String, List<Rule>> finalRules;

        private boolean found;

        private int i;

        private final CharSequence input;

        private final int maxPhonemes;

        private final PhonemeBuilder phonemeBuilder;

        RulesApplication(final Map<String, List<Rule>> finalRules, final CharSequence input, final PhonemeBuilder phonemeBuilder, final int i,
                final int maxPhonemes) {
            this.finalRules = Objects.requireNonNull(finalRules, "finalRules");
            this.phonemeBuilder = phonemeBuilder;
            this.input = input;
            this.i = i;
            this.maxPhonemes = maxPhonemes;
        }

        public int getI() {
            return i;
        }

        public PhonemeBuilder getPhonemeBuilder() {
            return phonemeBuilder;
        }

        /**
         * Invokes the rules. Loops over the rules list, stopping at the first one that has a matching context and pattern. Then applies this rule to the
         * phoneme builder to produce updated phonemes. If there was no match, {@code i} is advanced one and the character is silently dropped from the phonetic
         * spelling.
         *
         * @return {@code this}.
         */
        public RulesApplication invoke() {
            found = false;
            int patternLength = 1;
            final List<Rule> rules = finalRules.get(input.subSequence(i, i + patternLength));
            if (rules != null) {
                for (final Rule rule : rules) {
                    final String pattern = rule.getPattern();
                    patternLength = pattern.length();
                    if (rule.patternAndContextMatches(input, i)) {
                        phonemeBuilder.apply(rule.getPhoneme(), maxPhonemes);
                        found = true;
                        break;
                    }
                }
            }
            if (!found) {
                patternLength = 1;
            }
            i += patternLength;
            return this;
        }

        public boolean isFound() {
            return found;
        }
    }

    private static final Map<NameType, Set<String>> NAME_PREFIXES = new EnumMap<>(NameType.class);

    private static final Pattern QUOTE = Pattern.compile("'");
    static {
        NAME_PREFIXES.put(NameType.ASHKENAZI, Collections.unmodifiableSet(new HashSet<>(Arrays.asList("bar", "ben", "da", "de", "van", "von"))));
        NAME_PREFIXES.put(NameType.SEPHARDIC, Collections.unmodifiableSet(
                new HashSet<>(Arrays.asList("al", "el", "da", "dal", "de", "del", "dela", "de la", "della", "des", "di", "do", "dos", "du", "van", "von"))));
        NAME_PREFIXES.put(NameType.GENERIC, Collections.unmodifiableSet(
                new HashSet<>(Arrays.asList("da", "dal", "de", "del", "dela", "de la", "della", "des", "di", "do", "dos", "du", "van", "von"))));
    }

    /**
     * Creates a new builder for a PhoneticEngine.
     *
     * @return a new builder for a PhoneticEngine.
     * @since 1.23.0
     */
    public static Builder builder() {
        return new Builder();
    }

    /**
     * Joins some strings with an internal separator.
     *
     * @param strings Strings to join.
     * @param sep     String to separate them with.
     * @return A single String consisting of each element of {@code strings} interleaved by {@code sep}.
     */
    private static String join(final List<String> strings, final String sep) {
        return strings.stream().collect(Collectors.joining(sep));
    }

    private final boolean concat;

    private final Lang lang;

    private final int maxInputLength;

    private final int maxPhonemes;

    private final NameType nameType;

    private final RuleType ruleType;

    /**
     * Creates a new, fully-configured phonetic engine.
     *
     * @param builder The builder to use for configuration.
     * @throws IllegalArgumentException Thrown if ruleType is RULES.
     */
    private PhoneticEngine(final Builder builder) {
        if (builder.ruleType == RuleType.RULES) {
            throw new IllegalArgumentException("ruleType must not be " + RuleType.RULES);
        }
        this.nameType = builder.nameType;
        this.ruleType = builder.ruleType;
        this.concat = builder.concat;
        this.lang = Lang.instance(builder.nameType);
        this.maxPhonemes = builder.maxPhonemes;
        this.maxInputLength = builder.maxInputLength;
    }

    /**
     * Generates a new, fully-configured phonetic engine.
     *
     * @param nameType    the type of names it will use, null is treated as {@link NameType#GENERIC}.
     * @param ruleType    the type of rules it will apply, null is treated as {@link RuleType#APPROX}.
     * @param concatenate if it will concatenate multiple encodings.
     * @deprecated Use {@link #builder()} instead.
     */
    @Deprecated
    public PhoneticEngine(final NameType nameType, final RuleType ruleType, final boolean concatenate) {
        this(nameType, ruleType, concatenate, Builder.MAX_PHONEMES);
    }

    /**
     * Generates a new, fully-configured phonetic engine.
     *
     * @param nameType    the type of names it will use, null is treated as {@link NameType#GENERIC}.
     * @param ruleType    the type of rules it will apply, null is treated as {@link RuleType#APPROX}.
     * @param concatenate if it will concatenate multiple encodings.
     * @param maxPhonemes the maximum number of phonemes that will be handled, less than 0 will reset to the default of {@value Builder#MAX_PHONEMES}.
     * @throws IllegalArgumentException Thrown if ruleType is RULES.
     * @since 1.7
     * @deprecated Use {@link #builder()} instead.
     */
    @Deprecated
    public PhoneticEngine(final NameType nameType, final RuleType ruleType, final boolean concatenate, final int maxPhonemes) {
        this(builder().setNameType(nameType).setRuleType(ruleType).setConcat(concatenate).setMaxPhonemes(maxPhonemes)
                .setMaxInputLength(Builder.MAX_INPUT_LENGTH));
    }

    /**
     * Applies the final rules to convert from a language-specific phonetic representation to a language-independent representation.
     *
     * @param phonemeBuilder The current phonemes.
     * @param finalRules     The final rules to apply.
     * @return The resulting phonemes.
     */
    private PhonemeBuilder applyFinalRules(final PhonemeBuilder phonemeBuilder, final Map<String, List<Rule>> finalRules) {
        Objects.requireNonNull(finalRules, "finalRules");
        if (finalRules.isEmpty()) {
            return phonemeBuilder;
        }
        final Map<Rule.Phoneme, Rule.Phoneme> phonemes = new TreeMap<>(Rule.Phoneme.COMPARATOR);
        phonemeBuilder.getPhonemes().forEach(phoneme -> {
            PhonemeBuilder subBuilder = PhonemeBuilder.empty(phoneme.getLanguages());
            final CharSequence phonemeText = phoneme.getPhonemeText();
            final int length = phonemeText.length();
            for (int i = 0; i < length;) {
                final RulesApplication rulesApplication = new RulesApplication(finalRules, phonemeText, subBuilder, i, maxPhonemes).invoke();
                final boolean found = rulesApplication.isFound();
                subBuilder = rulesApplication.getPhonemeBuilder();
                if (!found) {
                    // not found, appending as-is
                    subBuilder.append(phonemeText.subSequence(i, i + 1));
                }
                i = rulesApplication.getI();
            }
            // the phonemes map orders the phonemes only based on their text, but ignores the language set
            // when adding new phonemes, check for equal phonemes and merge their language set, otherwise
            // phonemes with the same text but different language set get lost
            subBuilder.getPhonemes().forEach(newPhoneme -> {
                if (phonemes.containsKey(newPhoneme)) {
                    final Rule.Phoneme oldPhoneme = phonemes.remove(newPhoneme);
                    final Rule.Phoneme mergedPhoneme = oldPhoneme.mergeWithLanguage(newPhoneme.getLanguages());
                    phonemes.put(mergedPhoneme, mergedPhoneme);
                } else {
                    phonemes.put(newPhoneme, newPhoneme);
                }
            });
        });
        return new PhonemeBuilder(phonemes.keySet());
    }

    /**
     * Encodes a string to its phonetic representation.
     *
     * @param input the String to encode, not null.
     * @return The encoding of the input.
     * @throws IllegalArgumentException Thrown if the input is longer than the maximum allowed length.
     */
    public String encode(final String input) {
        // enforce the input length limit before language guessing runs over the input,
        // so over-limit input cannot buy a full multi-pass scan before the guard fires
        if (input.length() > maxInputLength) {
            throw new IllegalArgumentException("Input is greater than maxInputLength (" + maxInputLength + ").");
        }
        return encode(input, lang.guessLanguages(input));
    }

    /**
     * Encodes an input string into an output phonetic representation, given a set of possible origin languages.
     *
     * @param input       String to phoneticise; a String with dashes or spaces separating each word, not null.
     * @param languageSet set of possible origin languages.
     * @return A phonetic representation of the input; a String containing '-'-separated phonetic representations of the input.
     * @throws IllegalArgumentException Thrown if the input is longer than the maximum allowed length.
     */
    public String encode(String input, final Languages.LanguageSet languageSet) {
        if (input.length() > maxInputLength) {
            throw new IllegalArgumentException("Input is greater than maxInputLength (" + maxInputLength + ").");
        }
        final Map<String, List<Rule>> rules = Rule.getInstanceMap(this.nameType, RuleType.RULES, languageSet);
        // rules common across many (all) languages
        final Map<String, List<Rule>> finalRules1 = Rule.getInstanceMap(this.nameType, this.ruleType, "common");
        // rules that apply to a specific language that may be ambiguous or wrong if applied to other languages
        final Map<String, List<Rule>> finalRules2 = Rule.getInstanceMap(this.nameType, this.ruleType, languageSet);
        // tidy the input
        // lower case is a locale-dependent operation
        input = input.toLowerCase(Locale.ENGLISH).replace('-', ' ').trim();
        if (this.nameType == NameType.GENERIC) {
            final String dQuotePrefix = "d'";
            final int dqpLen = dQuotePrefix.length();
            if (input.startsWith(dQuotePrefix)) { // check for d'
                String remainder = input.substring(dqpLen);
                // Find remainder without allocating new string.
                final int start = lastRepeat(remainder, dQuotePrefix, dqpLen);
                remainder = remainder.substring(start);
                final String combined = "d" + remainder;
                return "(" + encode(remainder) + ")-(" + encode(combined) + ")";
            }
            for (final String l : NAME_PREFIXES.get(this.nameType)) {
                // handle generic prefixes
                if (input.startsWith(l + " ")) {
                    // check for any prefix in the words list
                    final String remainder = input.substring(l.length() + 1); // input without the prefix
                    final String combined = l + remainder; // input with prefix without space
                    return "(" + encode(remainder) + ")-(" + encode(combined) + ")";
                }
            }
        }
        final List<String> words = Arrays.asList(ResourceConstants.SPACES.split(input));
        final List<String> words2 = new ArrayList<>();
        // special-case handling of word prefixes based upon the name type
        switch (this.nameType) {
        case SEPHARDIC:
            words.forEach(aWord -> {
                final String[] parts = QUOTE.split(aWord, -1);
                words2.add(parts[parts.length - 1]);
            });
            words2.removeAll(NAME_PREFIXES.get(this.nameType));
            break;
        case ASHKENAZI:
            words2.addAll(words);
            words2.removeAll(NAME_PREFIXES.get(this.nameType));
            break;
        case GENERIC:
            words2.addAll(words);
            break;
        default:
            throw new IllegalStateException("Unreachable case: " + this.nameType);
        }
        if (this.concat) {
            // concat mode enabled
            input = join(words2, " ");
        } else if (words2.size() == 1) {
            // not a multi-word name
            input = words.iterator().next();
        } else if (!words2.isEmpty()) {
            // encode each word in a multi-word name separately (normally used for approx matches)
            final StringBuilder result = new StringBuilder();
            words2.forEach(word -> result.append("-").append(encode(word)));
            // return the result without the leading "-"
            return result.substring(1);
        }
        PhonemeBuilder phonemeBuilder = PhonemeBuilder.empty(languageSet);
        // loop over each char in the input - we will handle the increment manually
        for (int i = 0; i < input.length();) {
            final RulesApplication rulesApplication = new RulesApplication(rules, input, phonemeBuilder, i, maxPhonemes).invoke();
            i = rulesApplication.getI();
            phonemeBuilder = rulesApplication.getPhonemeBuilder();
        }
        // Apply the general rules
        phonemeBuilder = applyFinalRules(phonemeBuilder, finalRules1);
        // Apply the language-specific rules
        phonemeBuilder = applyFinalRules(phonemeBuilder, finalRules2);
        return phonemeBuilder.makeString();
    }

    /**
     * Gets the Lang language guessing rules being used.
     *
     * @return The Lang in use.
     */
    public Lang getLang() {
        return this.lang;
    }

    /**
     * Gets the maximum number of phonemes the engine will calculate for a given input.
     *
     * @return The maximum number of phonemes.
     * @since 1.7
     */
    public int getMaxPhonemes() {
        return this.maxPhonemes;
    }

    /**
     * Gets the NameType being used.
     *
     * @return The NameType in use.
     */
    public NameType getNameType() {
        return this.nameType;
    }

    /**
     * Gets the RuleType being used.
     *
     * @return The RuleType in use.
     */
    public RuleType getRuleType() {
        return this.ruleType;
    }

    /**
     * Tests whether multiple phonetic encodings are concatenated or just the first one is kept.
     *
     * @return true if multiple phonetic encodings are returned, false if just the first is.
     */
    public boolean isConcat() {
        return this.concat;
    }

    /**
     * Finds the index past the last occurrence of a repeating prefix in a string, starting from the beginning of the string and moving forward.
     *
     * @param source    The source string to search within.
     * @param prefix    The prefix to look for.
     * @param prefixLen The length of the prefix.
     * @return The index in the source string where the last occurrence of the repeating prefix ends.
     */
    private int lastRepeat(final String source, final String prefix, final int prefixLen) {
        // Find without allocating new string.
        int start = 0;
        while (start + prefixLen <= source.length()) {
            int i = 0;
            while (i < prefixLen && source.charAt(start + i) == prefix.charAt(i)) {
                i++;
            }
            if (i != prefixLen) {
                break;
            }
            start += prefixLen;
        }
        return start;
    }
}