/*
 * 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
 *
 *      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.
 */

/*
 * Portions Copyright (c) Microsoft Corporation
 */

package com.azure.cosmos.implementation.apachecommons.lang;

import java.util.Random;

public class RandomStringUtils {
    /**
     * <p>Random object used by random method. This has to be not local
     * to the random method so as to not return the same value in the
     * same millisecond.</p>
     */
    private static final Random RANDOM = new Random();

    private RandomStringUtils() {
        super();
    }

    /**
     * <p>Creates a random string whose length is the number of characters
     * specified.</p>
     *
     * <p>Characters will be chosen from the set of Latin alphabetic
     * characters (a-z, A-Z).</p>
     *
     * @param count  the length of random string to create
     * @return the random string
     */
    public static String randomAlphabetic(final int count) {
        return random(count, true, false);
    }

    /**
     * <p>Creates a random string whose length is the number of characters
     * specified.</p>
     *
     * <p>Characters will be chosen from the set of alpha-numeric
     * characters as indicated by the arguments.</p>
     *
     * @param count  the length of random string to create
     * @param letters  if {@code true}, generated string may include
     *  alphabetic characters
     * @param numbers  if {@code true}, generated string may include
     *  numeric characters
     * @return the random string
     */
    private static String random(final int count, final boolean letters, final boolean numbers) {
        return random(count, 0, 0, letters, numbers);
    }

    /**
     * <p>Creates a random string whose length is the number of characters
     * specified.</p>
     *
     * <p>Characters will be chosen from the set of alpha-numeric
     * characters as indicated by the arguments.</p>
     *
     * @param count  the length of random string to create
     * @param start  the position in set of chars to start at
     * @param end  the position in set of chars to end before
     * @param letters  if {@code true}, generated string may include
     *  alphabetic characters
     * @param numbers  if {@code true}, generated string may include
     *  numeric characters
     * @return the random string
     */
    private static String random(final int count, final int start, final int end, final boolean letters, final boolean numbers) {
        return random(count, start, end, letters, numbers, null, RANDOM);
    }

    /**
     * <p>Creates a random string based on a variety of options, using
     * supplied source of randomness.</p>
     *
     * <p>If start and end are both {@code 0}, start and end are set
     * to {@code ' '} and {@code 'z'}, the ASCII printable
     * characters, will be used, unless letters and numbers are both
     * {@code false}, in which case, start and end are set to
     * {@code 0} and {@link Character#MAX_CODE_POINT}.
     *
     * <p>If set is not {@code null}, characters between start and
     * end are chosen.</p>
     *
     * <p>This method accepts a user-supplied {@link Random}
     * instance to use as a source of randomness. By seeding a single
     * {@link Random} instance with a fixed seed and using it for each call,
     * the same random sequence of strings can be generated repeatedly
     * and predictably.</p>
     *
     * @param count  the length of random string to create
     * @param start  the position in set of chars to start at (inclusive)
     * @param end  the position in set of chars to end before (exclusive)
     * @param letters  only allow letters?
     * @param numbers  only allow numbers?
     * @param chars  the set of chars to choose randoms from, must not be empty.
     *  If {@code null}, then it will use the set of all chars.
     * @param random  a source of randomness.
     * @return the random string
     * @throws ArrayIndexOutOfBoundsException if there are not
     *  {@code (end - start) + 1} characters in the set array.
     * @throws IllegalArgumentException if {@code count} &lt; 0 or the provided chars array is empty.
     */
    private static String random(int count, int start, int end, final boolean letters, final boolean numbers,
                                final char[] chars, final Random random) {
        if (count == 0) {
            return StringUtils.EMPTY;
        } else if (count < 0) {
            throw new IllegalArgumentException("Requested random string length " + count + " is less than 0.");
        }
        if (chars != null && chars.length == 0) {
            throw new IllegalArgumentException("The chars array must not be empty");
        }

        if (start == 0 && end == 0) {
            if (chars != null) {
                end = chars.length;
            } else {
                if (!letters && !numbers) {
                    end = Character.MAX_CODE_POINT;
                } else {
                    end = 'z' + 1;
                    start = ' ';
                }
            }
        } else {
            if (end <= start) {
                throw new IllegalArgumentException("Parameter end (" + end + ") must be greater than start (" + start + ")");
            }
        }

        final int zero_digit_ascii = 48;
        final int first_letter_ascii = 65;

        if (chars == null && (numbers && end <= zero_digit_ascii
            || letters && end <= first_letter_ascii)) {
            throw new IllegalArgumentException("Parameter end (" + end + ") must be greater then (" + zero_digit_ascii + ") for generating digits " +
                "or greater then (" + first_letter_ascii + ") for generating letters.");
        }

        final StringBuilder builder = new StringBuilder(count);
        final int gap = end - start;

        while (count-- != 0) {
            int codePoint;
            if (chars == null) {
                codePoint = random.nextInt(gap) + start;

                switch (Character.getType(codePoint)) {
                    case Character.UNASSIGNED:
                    case Character.PRIVATE_USE:
                    case Character.SURROGATE:
                        count++;
                        continue;
                }

            } else {
                codePoint = chars[random.nextInt(gap) + start];
            }

            final int numberOfChars = Character.charCount(codePoint);
            if (count == 0 && numberOfChars > 1) {
                count++;
                continue;
            }

            if (letters && Character.isLetter(codePoint)
                || numbers && Character.isDigit(codePoint)
                || !letters && !numbers) {
                builder.appendCodePoint(codePoint);

                if (numberOfChars == 2) {
                    count--;
                }

            } else {
                count++;
            }
        }
        return builder.toString();
    }
}
