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 *
 *  Copyright (c) 2014-2019 Appsicle
 *  Copyright (c) 2019-2023 QuestDB
 *
 *  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.
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package io.questdb.std;

import io.questdb.std.str.CharSinkBase;
import io.questdb.std.str.Sinkable;
import org.jetbrains.annotations.NotNull;

import java.util.Arrays;


public class LongHashSet extends AbstractLongHashSet implements Sinkable {

    private static final int MIN_INITIAL_CAPACITY = 16;
    private final LongList list;

    public LongHashSet() {
        this(MIN_INITIAL_CAPACITY);
    }

    public LongHashSet(int initialCapacity) {
        this(initialCapacity, 0.4, noEntryKey);
    }

    public LongHashSet(int initialCapacity, double loadFactor, long noKeyValue) {
        super(initialCapacity, loadFactor, noKeyValue);
        list = new LongList(free);
        clear();
    }

    /**
     * Adds key to hash set preserving key uniqueness.
     *
     * @param key key to be added.
     * @return false if key is already in the set and true otherwise.
     */
    public boolean add(long key) {
        int index = keyIndex(key);
        if (index < 0) {
            return false;
        }

        addAt(index, key);
        return true;
    }

    public void addAt(int index, long key) {
        keys[index] = key;
        list.add(key);
        if (--free < 1) {
            rehash();
        }
    }

    public final void clear() {
        free = capacity;
        Arrays.fill(keys, noEntryKeyValue);
        list.clear();
    }

    public boolean contains(long key) {
        return keyIndex(key) < 0;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        LongHashSet that = (LongHashSet) o;
        if (size() != that.size()) {
            return false;
        }
        for (int i = 0, n = list.size(); i < n; i++) {
            long key = list.getQuick(i);
            if (key != noEntryKeyValue && that.excludes(key)) {
                return false;
            }
        }
        return true;
    }

    public long get(int index) {
        return list.getQuick(index);
    }

    public long getLast() {
        return list.getLast();
    }

    @Override
    public int hashCode() {
        int hashCode = 0;
        for (int i = 0, n = keys.length; i < n; i++) {
            if (keys[i] != noEntryKeyValue) {
                hashCode += (int) keys[i];
            }
        }
        return hashCode;
    }

    public void removeAt(int index) {
        if (index < 0) {
            long key = keys[-index - 1];
            super.removeAt(index);
            list.remove(key);
        }
    }

    @Override
    public void toSink(@NotNull CharSinkBase sink) {
        list.toSink(sink);
    }

    @Override
    public String toString() {
        return list.toString();
    }

    private void rehash() {
        int newCapacity = capacity * 2;
        free = capacity = newCapacity;
        int len = Numbers.ceilPow2((int) (newCapacity / loadFactor));
        this.keys = new long[len];
        Arrays.fill(keys, noEntryKeyValue);
        mask = len - 1;
        int n = list.size();
        free -= n;
        for (int i = 0; i < n; i++) {
            long key = list.getQuick(i);
            int keyIndex = keyIndex(key);
            keys[keyIndex] = key;
        }
    }

    @Override
    protected void erase(int index) {
        keys[index] = noEntryKeyValue;
    }

    @Override
    protected void move(int from, int to) {
        keys[to] = keys[from];
        erase(from);
    }
}