/*
 * Java Genetic Algorithm Library (jenetics-7.1.0).
 * Copyright (c) 2007-2022 Franz Wilhelmstötter
 *
 * 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.
 *
 * Author:
 *    Franz Wilhelmstötter (franz.wilhelmstoetter@gmail.com)
 */
package io.jenetics.util;

import static java.util.Objects.requireNonNull;

import java.io.Serial;
import java.io.Serializable;
import java.util.Arrays;
import java.util.regex.PatternSyntaxException;
import java.util.stream.Collector;

import io.jenetics.internal.collection.Array;
import io.jenetics.internal.collection.ArrayISeq;
import io.jenetics.internal.collection.CharStore;

/**
 * This class is used for holding the valid characters of an
 * {@link io.jenetics.CharacterGene}. It is not a character sequence in the
 * classical sense. The characters of this sequence are sorted and doesn't
 * contain duplicate values, like a set.
 *
 * <pre>{@code
 * final CharSeq cs1 = new CharSeq("abcdeaafg");
 * final CharSeq cs2 = new CharSeq("gfedcbabb");
 * assert(cs1.equals(cs2));
 * }</pre>
 *
 * @author <a href="mailto:franz.wilhelmstoetter@gmail.com">Franz Wilhelmstötter</a>
 * @since 1.0
 * @version 2.0
 */
public final class CharSeq
        extends CharSeqBase
        implements
                CharSequence,
                ISeq<Character>,
                Comparable<CharSeq>,
                Serializable
{
        @Serial
        private static final long serialVersionUID = 2L;

        /**
         * Create a new (distinct) CharSeq from the given {@code characters}. The
         * given {@link CharSequence} is sorted and duplicate values are removed
         *
         * @see #CharSeq(CharSequence)
         *
         * @param characters the characters.
         * @throws NullPointerException if the {@code characters} are {@code null}.
         */
        public CharSeq(final char[] characters) {
                super(distinct(characters.clone()));
        }

        /**
         * Create a new (distinct) CharSeq from the given {@code characters}. The
         * given {@link CharSequence} is sorted and duplicate values are removed.
         *
         * @param characters the characters.
         * @throws NullPointerException if the {@code characters} are {@code null}.
         */
        public CharSeq(final CharSequence characters) {
                super(distinct(toCharArray(characters)));
        }

        private static char[] toCharArray(final CharSequence characters) {
                requireNonNull(characters, "Characters");

                final char[] chars = new char[characters.length()];
                for (int i = chars.length; --i >= 0;) {
                        chars[i] = characters.charAt(i);
                }

                return chars;
        }

        private static char[] distinct(final char[] chars) {
                Arrays.sort(chars);

                int j = 0;
                for (int i = 1; i < chars.length; ++i) {
                        if (chars[j] != chars[i]) {
                                chars[++j] = chars[i];
                        }
                }

                final int size = Math.min(chars.length, j + 1);
                final char[] array = new char[size];
                System.arraycopy(chars, 0, array, 0, size);
                return array;
        }

        @Override
        public boolean contains(final Object object) {
                return object instanceof Character && contains((Character)object);
        }

        /**
         * Test whether this character set contains the given character {@code c}.
         *
         * @param c the character to test.
         * @return {@code true} if this character set contains the given character,
         *          {@code false} otherwise.
         * @throws NullPointerException if the given character {@code c} is
         *          {@code null}.
         */
        public boolean contains(final Character c) {
                return contains(c.charValue());
        }

        /**
         * Test whether this character set contains the given character {@code c}.
         *
         * @param c the character to test.
         * @return {@code true} if this character set contains the given character,
         *          {@code false} otherwise.
         */
        public boolean contains(final char c) {
                return Arrays.binarySearch(array, c) >= 0;
        }

        @Override
        public char charAt(final int index) {
                return array[index];
        }

        @Override
        public int length() {
                return array.length;
        }

        @Override
        public CharSeq subSequence(final int start, final int end) {
                return new CharSeq(new String(array, start, end - start));
        }

        /**
         * Test whether this character set is empty.
         *
         * @return {@code true} if this character set is empty, {@code false}
         *          otherwise.
         */
        public boolean isEmpty() {
                return array.length == 0;
        }

        @Override
        public int hashCode() {
                return 17 + 31*Arrays.hashCode(array);
        }

        @Override
        public boolean equals(final Object obj) {
                return obj == this ||
                        obj instanceof CharSeq other &&
                        Arrays.equals(other.array, array);
        }

        @Override
        public int compareTo(final CharSeq set) {
                int result = 0;

                final int n = Math.min(array.length, set.array.length);
                for (int i = 0; i < n && result == 0; ++i) {
                        result = array[i] - set.array[i];
                }
                if (result == 0) {
                        result = array.length - set.array.length;
                }

                return result;
        }

        @Override
        public String toString() {
                return new String(array);
        }

        /**
         * Expands the character range for the given {@code pattern}. E.g
         * {@code a-zA-Z0-1} will return a string containing all upper and lower
         * case characters (from a to z) and all digits form 0 to 9.
         *
         * @param pattern the {@code pattern} to expand.
         * @return the expanded pattern.
         * @throws PatternSyntaxException if the pattern could not be expanded.
         * @throws NullPointerException if the pattern is {@code null}.
         */
        public static String expand(final CharSequence pattern) {
                requireNonNull(pattern, "Pattern");
                final StringBuilder out = new StringBuilder();

                for (int i = 0, n = pattern.length(); i < n; ++i) {
                        if (pattern.charAt(i) == '\\') {
                                ++i;
                                if (i < pattern.length()) {
                                        out.append(pattern.charAt(i));
                                }
                        } else if (pattern.charAt(i) == '-') {
                                if (i <= 0 || i >= (pattern.length() - 1)) {
                                        throw new PatternSyntaxException(
                                                "Dangling range operator '-'", pattern.toString(),
                                                pattern.length() - 1
                                        );
                                }

                                final String range = expand(
                                        pattern.charAt(i - 1),
                                        pattern.charAt(i + 1)
                                );
                                out.append(range);

                                ++i;
                        } else if (i + 1 == n || pattern.charAt(i + 1) != '-') {
                                out.append(pattern.charAt(i));
                        }
                }

                return out.toString();
        }

        /**
         * Expands the characters between {@code a} and {@code b}.
         *
         * @param a the start character.
         * @param b the stop character.
         * @return the expanded characters.
         */
        public static String expand(final char a, final char b) {
                final StringBuilder out = new StringBuilder();

                if (a < b) {
                        char c = a;
                        while (c <= b) {
                                out.append(c);
                                c = (char) (c + 1);
                        }
                } else if (a > b) {
                        char c = a;
                        while (c >= b) {
                                out.append(c);
                                c = (char)(c - 1);
                        }
                }

                return out.toString();
        }

        /**
         * Expands the character range for the given {@code pattern}. E.g.
         * {@code a-zA-Z0-1} will return a string containing all upper and lower
         * case characters (from a to z) and all digits form 0 to 9.
         *
         * @see #expand(CharSequence)
         *
         * @param pattern the {@code pattern} to expand.
         * @return the expanded pattern.
         * @throws PatternSyntaxException if the pattern could not be expanded.
         * @throws NullPointerException if the pattern is {@code null}.
         */
        public static CharSeq of(final CharSequence pattern) {
                return new CharSeq(expand(pattern));
        }

        /**
         * Expands the characters between {@code a} and {@code b}.
         *
         * @see #expand(char, char)
         *
         * @param a the start character.
         * @param b the stop character.
         * @return the expanded characters.
         */
        public static CharSeq of(final char a, final char b) {
                return new CharSeq(expand(a, b));
        }

        /**
         * Helper method for creating a sequence of characters from the given
         * {@code CharSequence}. The returned sequence will contain all characters
         * in the original order.
         *
         * @param chars the char sequence to convert.
         * @return a sequence which will contain all given chars in the original
         *         order.
         */
        public static ISeq<Character> toISeq(final CharSequence chars) {
                final MSeq<Character> seq = MSeq.ofLength(chars.length());
                for (int i = 0; i < chars.length(); ++i) {
                        seq.set(i, chars.charAt(i));
                }

                return seq.toISeq();
        }

        public static Collector<Character, ?, CharSeq> toCharSeq() {
                return Collector.of(
                        StringBuilder::new,
                        StringBuilder::append,
                        (a, b) -> {a.append(b); return a;},
                        CharSeq::new
                );
        }

}

abstract class CharSeqBase extends ArrayISeq<Character> {

        @Serial
        private static final long serialVersionUID = 1L;

        final char[] array;

        protected CharSeqBase(final char[] characters) {
                super(Array.of(CharStore.of(characters)).seal());
                array = characters;
        }

}