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 * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package jdk.jfr.internal;

import java.util.BitSet;

import java.util.function.Consumer;

import java.util.function.LongConsumer;

@SuppressWarnings("unchecked")

public final class LongMap<T> {

    private static final int MAXIMUM_CAPACITY = 1 << 30;

    private static final long[] EMPTY_KEYS = new long[0];

    private static final Object[] EMPTY_OBJECTS = new Object[0];

    private static final int DEFAULT_SIZE = 32;

    private static final Object NULL_OBJECT = new Object();

    private final int bitCount;

    private BitSet bitSet;

    private long[] keys = EMPTY_KEYS;

    private T[] objects = (T[]) EMPTY_OBJECTS;

    private int count;

    private int shift;

    public LongMap() {

        this.bitCount = 0;

    }

    public LongMap(int markBits) {

        this.bitCount = markBits;

        this.bitSet = new BitSet();

    }

    // Should be 2^n

    private void initialize(int capacity) {

        keys = new long[capacity];

        objects = (T[]) new Object[capacity];

        shift = 64 - (31 - Integer.numberOfLeadingZeros(capacity));

    }

    public void claimBits() {

        // flip last bit back and forth to make bitset expand to max size

        int lastBit = bitSetIndex(objects.length - 1, bitCount -1);

        bitSet.flip(lastBit);

        bitSet.flip(lastBit);

    }

    public void setId(long id, int bitIndex) {

        int bitSetIndex = bitSetIndex(tableIndexOf(id), bitIndex);

        bitSet.set(bitSetIndex, true);

    }

    public void clearId(long id, int bitIndex) {

        int bitSetIndex = bitSetIndex(tableIndexOf(id), bitIndex);

        bitSet.set(bitSetIndex, false);

    }

    public boolean isSetId(long id, int bitIndex) {

        int bitSetIndex = bitSetIndex(tableIndexOf(id), bitIndex);

        return bitSet.get(bitSetIndex);

    }

    private int bitSetIndex(int tableIndex, int bitIndex) {

        return bitCount * tableIndex + bitIndex;

    }

    private int tableIndexOf(long id) {

        int index = index(id);

        while (true) {

            if (objects[index] == null) {

                throw new InternalError("Unknown id");

            }

            if (keys[index] == id) {

                return index;

            }

            index++;

            if (index == keys.length) {

                index = 0;

            }

        }

    }

    public boolean hasKey(long id) {

        int index = index(id);

        while (true) {

            if (objects[index] == null) {

               return false;

            }

            if (keys[index] == id) {

                return true;

            }

            index++;

            if (index == keys.length) {

                index = 0;

            }

        }

    }

    public void expand(int size) {

        int l = 4 * size / 3;

        if (l <= keys.length) {

            return;

        }

        int n = tableSizeFor(l);

        LongMap<T> temp = new LongMap<>(bitCount);

        temp.initialize(n);

        // Optimization, avoid growing while copying bits

        if (bitCount > 0 && !bitSet.isEmpty()) {

           temp.claimBits();

           claimBits();

        }

        for (int tIndex = 0; tIndex < keys.length; tIndex++) {

            T o = objects[tIndex];

            if (o != null) {

                long key = keys[tIndex];

                temp.put(key, o);

                if (bitCount != 0) {

                    for (int bIndex = 0; bIndex < bitCount; bIndex++) {

                        boolean bitValue = isSetId(key, bIndex);

                        if (bitValue) {

                            temp.setId(key, bIndex);

                        }

                    }

                }

            }

        }

        keys = temp.keys;

        objects = temp.objects;

        shift = temp.shift;

        bitSet = temp.bitSet;

    }

    public void put(long id, T object) {

        if (keys == EMPTY_KEYS) {

            // Lazy initialization

            initialize(DEFAULT_SIZE);

        }

        if (count > 3 * keys.length / 4) {

            expand(2 * keys.length);

        }

        if (object == null) {

            object = (T) NULL_OBJECT;

        }

        int index = index(id);

        // probe for empty slot

        while (true) {

            if (objects[index] == null) {

                keys[index] = id;

                objects[index] = object;

                count++;

                return;

            }

            // if it already exists, replace

            if (keys[index] == id) {

                objects[index] = object;

                return;

            }

            index++;

            if (index == keys.length) {

                index = 0;

            }

        }

    }

    public T getAt(int tableIndex) {

        T o =  objects[tableIndex];

        return o == NULL_OBJECT ? null : o;

    }

    public T get(long id) {

        if (keys == EMPTY_KEYS) {

            return null;

        }

        int index = index(id);

        while (true) {

            if (objects[index] == null) {

                return null;

            }

            if (keys[index] == id) {

                return getAt(index);

            }

            index++;

            if (index == keys.length) {

                index = 0;

            }

        }

    }

    private int index(long id) {

        return (int) ((id * -7046029254386353131L) >>> shift);

    }

    // Copied from HashMap::tableSizeFor

    private static final int tableSizeFor(int cap) {

        int n = -1 >>> Integer.numberOfLeadingZeros(cap - 1);

        return (n < 0) ? 1 : (n >= MAXIMUM_CAPACITY) ? MAXIMUM_CAPACITY : n + 1;

    }

    public void forEachKey(LongConsumer keyTraverser) {

        for (int i = 0; i < keys.length; i++) {

            if (objects[i] != null) {

                keyTraverser.accept(keys[i]);

            }

        }

    }

    public void forEach(Consumer<T> consumer) {

        for (int i = 0; i < keys.length; i++) {

            T o = objects[i];

            if (o != null) {

                consumer.accept(o);

            }

        }

    }

    public int size() {

        return count;

    }

    public String toString() {

        StringBuilder sb = new StringBuilder();

        for (int i = 0; i < objects.length; i++) {

            sb.append(i);

            sb.append(": id=");

            sb.append(keys[i]);

            sb.append(" ");

            sb.append(objects[i]);

            sb.append("\n");

        }

        return sb.toString();

    }

}