/*

 * Copyright (c) 2015, 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.

 *

 * 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

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

/*

 * @test

 * @bug 8072909

 * @summary Test TimSort stack size on big arrays

 */

import java.util.ArrayList;

import java.util.Arrays;

import java.util.List;

import java.util.function.Consumer;

public class TimSortStackSize2 {

    public static void main(String[] args) {

        boolean passed = doTest("TimSort", lengthOfTest,

            (Integer [] a) -> Arrays.sort(a));

        passed = doTest("ComparableTimSort", lengthOfTest, (Integer [] a) ->

            Arrays.sort(a, (Object first, Object second) -> {

                return ((Comparable<Object>)first).compareTo(second);

            }))

            && passed;

        if ( !passed ){

            throw new RuntimeException();

        }

    }

    private static boolean doTest(final String msg, final int lengthOfTest,

                                  final  Consumer<Integer[]> c){

        Integer [] a = null;

        try {

            a = new TimSortStackSize2(lengthOfTest).createArray();

            long begin = System.nanoTime();

            c.accept(a);

            long end = System.nanoTime();

            System.out.println(msg + " OK. Time: " + (end - begin) + "ns");

        } catch (ArrayIndexOutOfBoundsException e){

            System.out.println(msg + " broken:");

            e.printStackTrace();

            return false;

        } finally {

            a = null;

        }

        return true;

    }

    private static final int MIN_MERGE = 32;

    private final int minRun;

    private final int length;

    private final List<Long> runs = new ArrayList<Long>();

    public TimSortStackSize2(final int len) {

        this.length = len;

        minRun = minRunLength(len);

        fillRunsJDKWorstCase();

    }

    private static int minRunLength(int n) {

        assert n >= 0;

        int r = 0;      // Becomes 1 if any 1 bits are shifted off

        while (n >= MIN_MERGE) {

            r |= (n & 1);

            n >>= 1;

        }

        return n + r;

    }

    /**

     * Adds a sequence x_1, ..., x_n of run lengths to <code>runs</code> such that:<br>

     * 1. X = x_1 + ... + x_n <br>

     * 2. x_j >= minRun for all j <br>

     * 3. x_1 + ... + x_{j-2}  <  x_j  <  x_1 + ... + x_{j-1} for all j <br>

     * These conditions guarantee that TimSort merges all x_j's one by one

     * (resulting in X) using only merges on the second-to-last element.

     * @param X  The sum of the sequence that should be added to runs.

     */

    private void generateJDKWrongElem(long X) {

        for(long newTotal; X >= 2 * minRun + 1; X = newTotal) {

            //Default strategy

            newTotal = X / 2 + 1;

            //Specialized strategies

            if(3 * minRun + 3 <= X && X <= 4*minRun+1) {

                // add x_1=MIN+1, x_2=MIN, x_3=X-newTotal  to runs

                newTotal = 2 * minRun + 1;

            } else if (5 * minRun + 5 <= X && X <= 6 * minRun + 5) {

                // add x_1=MIN+1, x_2=MIN, x_3=MIN+2, x_4=X-newTotal  to runs

                newTotal = 3 * minRun + 3;

            } else if (8 * minRun + 9 <= X && X <= 10 * minRun + 9) {

                // add x_1=MIN+1, x_2=MIN, x_3=MIN+2, x_4=2MIN+2, x_5=X-newTotal  to runs

                newTotal = 5 * minRun + 5;

            } else if (13 * minRun + 15 <= X && X <= 16 * minRun + 17) {

                // add x_1=MIN+1, x_2=MIN, x_3=MIN+2, x_4=2MIN+2, x_5=3MIN+4, x_6=X-newTotal  to runs

                newTotal = 8 * minRun + 9;

            }

            runs.add(0, X - newTotal);

        }

        runs.add(0, X);

    }

    /**

     * Fills <code>runs</code> with a sequence of run lengths of the form<br>

     * Y_n     x_{n,1}   x_{n,2}   ... x_{n,l_n} <br>

     * Y_{n-1} x_{n-1,1} x_{n-1,2} ... x_{n-1,l_{n-1}} <br>

     * ... <br>

     * Y_1     x_{1,1}   x_{1,2}   ... x_{1,l_1}<br>

     * The Y_i's are chosen to satisfy the invariant throughout execution,

     * but the x_{i,j}'s are merged (by <code>TimSort.mergeCollapse</code>)

     * into an X_i that violates the invariant.

     * X is the sum of all run lengths that will be added to <code>runs</code>.

     */

    private void fillRunsJDKWorstCase() {

        long runningTotal = 0;

        long Y = minRun + 4;

        long X = minRun;

        while (runningTotal + Y + X <= length) {

            runningTotal += X + Y;

            generateJDKWrongElem(X);

            runs.add(0, Y);

            // X_{i+1} = Y_i + x_{i,1} + 1, since runs.get(1) = x_{i,1}

            X = Y + runs.get(1) + 1;

            // Y_{i+1} = X_{i+1} + Y_i + 1

            Y += X + 1;

        }

        if (runningTotal + X <= length) {

            runningTotal += X;

            generateJDKWrongElem(X);

        }

        runs.add(length - runningTotal);

    }

    private Integer [] createArray() {

        Integer [] a = new Integer[length];

        Arrays.fill(a, 0);

        int endRun = -1;

        for (long len : runs) {

            a[endRun += len] = 1;

        }

        a[length - 1] = 0;

        return a;

    }

}