/*

 * Copyright (c) 1996, 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,

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 *

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

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/*

 * (C) Copyright Taligent, Inc. 1996, 1997 - All Rights Reserved

 * (C) Copyright IBM Corp. 1996 - 1998 - All Rights Reserved

 *

 *   The original version of this source code and documentation is copyrighted

 * and owned by Taligent, Inc., a wholly-owned subsidiary of IBM. These

 * materials are provided under terms of a License Agreement between Taligent

 * and Sun. This technology is protected by multiple US and International

 * patents. This notice and attribution to Taligent may not be removed.

 *   Taligent is a registered trademark of Taligent, Inc.

 *

 */

package java.text;

import java.math.BigDecimal;

import java.math.BigInteger;

import java.math.RoundingMode;

import jdk.internal.math.FloatingDecimal;

/**

 * Digit List. Private to DecimalFormat.

 * Handles the transcoding

 * between numeric values and strings of characters.  Only handles

 * non-negative numbers.  The division of labor between DigitList and

 * DecimalFormat is that DigitList handles the radix 10 representation

 * issues; DecimalFormat handles the locale-specific issues such as

 * positive/negative, grouping, decimal point, currency, and so on.

 *

 * A DigitList is really a representation of a floating point value.

 * It may be an integer value; we assume that a double has sufficient

 * precision to represent all digits of a long.

 *

 * The DigitList representation consists of a string of characters,

 * which are the digits radix 10, from '0' to '9'.  It also has a radix

 * 10 exponent associated with it.  The value represented by a DigitList

 * object can be computed by mulitplying the fraction f, where 0 <= f < 1,

 * derived by placing all the digits of the list to the right of the

 * decimal point, by 10^exponent.

 *

 * @see  Locale

 * @see  Format

 * @see  NumberFormat

 * @see  DecimalFormat

 * @see  ChoiceFormat

 * @see  MessageFormat

 * @author       Mark Davis, Alan Liu

 */

final class DigitList implements Cloneable {

    /**

     * The maximum number of significant digits in an IEEE 754 double, that

     * is, in a Java double.  This must not be increased, or garbage digits

     * will be generated, and should not be decreased, or accuracy will be lost.

     */

    public static final int MAX_COUNT = 19; // == Long.toString(Long.MAX_VALUE).length()

    /**

     * These data members are intentionally public and can be set directly.

     *

     * The value represented is given by placing the decimal point before

     * digits[decimalAt].  If decimalAt is < 0, then leading zeros between

     * the decimal point and the first nonzero digit are implied.  If decimalAt

     * is > count, then trailing zeros between the digits[count-1] and the

     * decimal point are implied.

     *

     * Equivalently, the represented value is given by f * 10^decimalAt.  Here

     * f is a value 0.1 <= f < 1 arrived at by placing the digits in Digits to

     * the right of the decimal.

     *

     * DigitList is normalized, so if it is non-zero, figits[0] is non-zero.  We

     * don't allow denormalized numbers because our exponent is effectively of

     * unlimited magnitude.  The count value contains the number of significant

     * digits present in digits[].

     *

     * Zero is represented by any DigitList with count == 0 or with each digits[i]

     * for all i <= count == '0'.

     */

    public int decimalAt = 0;

    public int count = 0;

    public char[] digits = new char[MAX_COUNT];

    private char[] data;

    private RoundingMode roundingMode = RoundingMode.HALF_EVEN;

    private boolean isNegative = false;

    /**

     * Return true if the represented number is zero.

     */

    boolean isZero() {

        for (int i=0; i < count; ++i) {

            if (digits[i] != '0') {

                return false;

            }

        }

        return true;

    }

    /**

     * Set the rounding mode

     */

    void setRoundingMode(RoundingMode r) {

        roundingMode = r;

    }

    /**

     * Clears out the digits.

     * Use before appending them.

     * Typically, you set a series of digits with append, then at the point

     * you hit the decimal point, you set myDigitList.decimalAt = myDigitList.count;

     * then go on appending digits.

     */

    public void clear () {

        decimalAt = 0;

        count = 0;

    }

    /**

     * Appends a digit to the list, extending the list when necessary.

     */

    public void append(char digit) {

        if (count == digits.length) {

            char[] data = new char[count + 100];

            System.arraycopy(digits, 0, data, 0, count);

            digits = data;

        }

        digits[count++] = digit;

    }

    /**

     * Utility routine to get the value of the digit list

     * If (count == 0) this throws a NumberFormatException, which

     * mimics Long.parseLong().

     */

    public final double getDouble() {

        if (count == 0) {

            return 0.0;

        }

        StringBuffer temp = getStringBuffer();

        temp.append('.');

        temp.append(digits, 0, count);

        temp.append('E');

        temp.append(decimalAt);

        return Double.parseDouble(temp.toString());

    }

    /**

     * Utility routine to get the value of the digit list.

     * If (count == 0) this returns 0, unlike Long.parseLong().

     */

    public final long getLong() {

        // for now, simple implementation; later, do proper IEEE native stuff

        if (count == 0) {

            return 0;

        }

        // We have to check for this, because this is the one NEGATIVE value

        // we represent.  If we tried to just pass the digits off to parseLong,

        // we'd get a parse failure.

        if (isLongMIN_VALUE()) {

            return Long.MIN_VALUE;

        }

        StringBuffer temp = getStringBuffer();

        temp.append(digits, 0, count);

        for (int i = count; i < decimalAt; ++i) {

            temp.append('0');

        }

        return Long.parseLong(temp.toString());

    }

    public final BigDecimal getBigDecimal() {

        if (count == 0) {

            if (decimalAt == 0) {

                return BigDecimal.ZERO;

            } else {

                return new BigDecimal("0E" + decimalAt);

            }

        }

       if (decimalAt == count) {

           return new BigDecimal(digits, 0, count);

       } else {

           return new BigDecimal(digits, 0, count).scaleByPowerOfTen(decimalAt - count);

       }

    }

    /**

     * Return true if the number represented by this object can fit into

     * a long.

     * @param isPositive true if this number should be regarded as positive

     * @param ignoreNegativeZero true if -0 should be regarded as identical to

     * +0; otherwise they are considered distinct

     * @return true if this number fits into a Java long

     */

    boolean fitsIntoLong(boolean isPositive, boolean ignoreNegativeZero) {

        // Figure out if the result will fit in a long.  We have to

        // first look for nonzero digits after the decimal point;

        // then check the size.  If the digit count is 18 or less, then

        // the value can definitely be represented as a long.  If it is 19

        // then it may be too large.

        // Trim trailing zeros.  This does not change the represented value.

        while (count > 0 && digits[count - 1] == '0') {

            --count;

        }

        if (count == 0) {

            // Positive zero fits into a long, but negative zero can only

            // be represented as a double. - bug 4162852

            return isPositive || ignoreNegativeZero;

        }

        if (decimalAt < count || decimalAt > MAX_COUNT) {

            return false;

        }

        if (decimalAt < MAX_COUNT) return true;

        // At this point we have decimalAt == count, and count == MAX_COUNT.

        // The number will overflow if it is larger than 9223372036854775807

        // or smaller than -9223372036854775808.

        for (int i=0; i<count; ++i) {

            char dig = digits[i], max = LONG_MIN_REP[i];

            if (dig > max) return false;

            if (dig < max) return true;

        }

        // At this point the first count digits match.  If decimalAt is less

        // than count, then the remaining digits are zero, and we return true.

        if (count < decimalAt) return true;

        // Now we have a representation of Long.MIN_VALUE, without the leading

        // negative sign.  If this represents a positive value, then it does

        // not fit; otherwise it fits.

        return !isPositive;

    }

    /**

     * Set the digit list to a representation of the given double value.

     * This method supports fixed-point notation.

     * @param isNegative Boolean value indicating whether the number is negative.

     * @param source Value to be converted; must not be Inf, -Inf, Nan,

     * or a value <= 0.

     * @param maximumFractionDigits The most fractional digits which should

     * be converted.

     */

    final void set(boolean isNegative, double source, int maximumFractionDigits) {

        set(isNegative, source, maximumFractionDigits, true);

    }

    /**

     * Set the digit list to a representation of the given double value.

     * This method supports both fixed-point and exponential notation.

     * @param isNegative Boolean value indicating whether the number is negative.

     * @param source Value to be converted; must not be Inf, -Inf, Nan,

     * or a value <= 0.

     * @param maximumDigits The most fractional or total digits which should

     * be converted.

     * @param fixedPoint If true, then maximumDigits is the maximum

     * fractional digits to be converted.  If false, total digits.

     */

    final void set(boolean isNegative, double source, int maximumDigits, boolean fixedPoint) {

        FloatingDecimal.BinaryToASCIIConverter fdConverter  = FloatingDecimal.getBinaryToASCIIConverter(source);

        boolean hasBeenRoundedUp = fdConverter.digitsRoundedUp();

        boolean valueExactAsDecimal = fdConverter.decimalDigitsExact();

        assert !fdConverter.isExceptional();

        String digitsString = fdConverter.toJavaFormatString();

        set(isNegative, digitsString,

            hasBeenRoundedUp, valueExactAsDecimal,

            maximumDigits, fixedPoint);

    }

    /**

     * Generate a representation of the form DDDDD, DDDDD.DDDDD, or

     * DDDDDE+/-DDDDD.

     * @param roundedUp whether or not rounding up has already happened.

     * @param valueExactAsDecimal whether or not collected digits provide

     * an exact decimal representation of the value.

     */

    private void set(boolean isNegative, String s,

                     boolean roundedUp, boolean valueExactAsDecimal,

                     int maximumDigits, boolean fixedPoint) {

        this.isNegative = isNegative;

        int len = s.length();

        char[] source = getDataChars(len);

        s.getChars(0, len, source, 0);

        decimalAt = -1;

        count = 0;

        int exponent = 0;

        // Number of zeros between decimal point and first non-zero digit after

        // decimal point, for numbers < 1.

        int leadingZerosAfterDecimal = 0;

        boolean nonZeroDigitSeen = false;

        for (int i = 0; i < len; ) {

            char c = source[i++];

            if (c == '.') {

                decimalAt = count;

            } else if (c == 'e' || c == 'E') {

                exponent = parseInt(source, i, len);

                break;

            } else {

                if (!nonZeroDigitSeen) {

                    nonZeroDigitSeen = (c != '0');

                    if (!nonZeroDigitSeen && decimalAt != -1)

                        ++leadingZerosAfterDecimal;

                }

                if (nonZeroDigitSeen) {

                    digits[count++] = c;

                }

            }

        }

        if (decimalAt == -1) {

            decimalAt = count;

        }

        if (nonZeroDigitSeen) {

            decimalAt += exponent - leadingZerosAfterDecimal;

        }

        if (fixedPoint) {

            // The negative of the exponent represents the number of leading

            // zeros between the decimal and the first non-zero digit, for

            // a value < 0.1 (e.g., for 0.00123, -decimalAt == 2).  If this

            // is more than the maximum fraction digits, then we have an underflow

            // for the printed representation.

            if (-decimalAt > maximumDigits) {

                // Handle an underflow to zero when we round something like

                // 0.0009 to 2 fractional digits.

                count = 0;

                return;

            } else if (-decimalAt == maximumDigits) {

                // If we round 0.0009 to 3 fractional digits, then we have to

                // create a new one digit in the least significant location.

                if (shouldRoundUp(0, roundedUp, valueExactAsDecimal)) {

                    count = 1;

                    ++decimalAt;

                    digits[0] = '1';

                } else {

                    count = 0;

                }

                return;

            }

            // else fall through

        }

        // Eliminate trailing zeros.

        while (count > 1 && digits[count - 1] == '0') {

            --count;

        }

        // Eliminate digits beyond maximum digits to be displayed.

        // Round up if appropriate.

        round(fixedPoint ? (maximumDigits + decimalAt) : maximumDigits,

              roundedUp, valueExactAsDecimal);

     }

    /**

     * Round the representation to the given number of digits.

     * @param maximumDigits The maximum number of digits to be shown.

     * @param alreadyRounded whether or not rounding up has already happened.

     * @param valueExactAsDecimal whether or not collected digits provide

     * an exact decimal representation of the value.

     *

     * Upon return, count will be less than or equal to maximumDigits.

     */

    private final void round(int maximumDigits,

                             boolean alreadyRounded,

                             boolean valueExactAsDecimal) {

        // Eliminate digits beyond maximum digits to be displayed.

        // Round up if appropriate.

        if (maximumDigits >= 0 && maximumDigits < count) {

            if (shouldRoundUp(maximumDigits, alreadyRounded, valueExactAsDecimal)) {

                // Rounding up involved incrementing digits from LSD to MSD.

                // In most cases this is simple, but in a worst case situation

                // (9999..99) we have to adjust the decimalAt value.

                for (;;) {

                    --maximumDigits;

                    if (maximumDigits < 0) {

                        // We have all 9's, so we increment to a single digit

                        // of one and adjust the exponent.

                        digits[0] = '1';

                        ++decimalAt;

                        maximumDigits = 0; // Adjust the count

                        break;

                    }

                    ++digits[maximumDigits];

                    if (digits[maximumDigits] <= '9') break;

                    // digits[maximumDigits] = '0'; // Unnecessary since we'll truncate this

                }

                ++maximumDigits; // Increment for use as count

            }

            count = maximumDigits;

            // Eliminate trailing zeros.

            while (count > 1 && digits[count-1] == '0') {

                --count;

            }

        }

    }

    /**

     * Return true if truncating the representation to the given number

     * of digits will result in an increment to the last digit.  This

     * method implements the rounding modes defined in the

     * java.math.RoundingMode class.

     * [bnf]

     * @param maximumDigits the number of digits to keep, from 0 to

     * {@code count-1}.  If 0, then all digits are rounded away, and

     * this method returns true if a one should be generated (e.g., formatting

     * 0.09 with "#.#").

     * @param alreadyRounded whether or not rounding up has already happened.

     * @param valueExactAsDecimal whether or not collected digits provide

     * an exact decimal representation of the value.

     * @throws    ArithmeticException if rounding is needed with rounding

     *            mode being set to RoundingMode.UNNECESSARY

     * @return true if digit {@code maximumDigits-1} should be

     * incremented

     */

    private boolean shouldRoundUp(int maximumDigits,

                                  boolean alreadyRounded,

                                  boolean valueExactAsDecimal) {

        if (maximumDigits < count) {

            /*

             * To avoid erroneous double-rounding or truncation when converting

             * a binary double value to text, information about the exactness

             * of the conversion result in FloatingDecimal, as well as any

             * rounding done, is needed in this class.

             *

             * - For the  HALF_DOWN, HALF_EVEN, HALF_UP rounding rules below:

             *   In the case of formating float or double, We must take into

             *   account what FloatingDecimal has done in the binary to decimal

             *   conversion.

             *

             *   Considering the tie cases, FloatingDecimal may round up the

             *   value (returning decimal digits equal to tie when it is below),

             *   or "truncate" the value to the tie while value is above it,

             *   or provide the exact decimal digits when the binary value can be

             *   converted exactly to its decimal representation given formating

             *   rules of FloatingDecimal ( we have thus an exact decimal

             *   representation of the binary value).

             *

             *   - If the double binary value was converted exactly as a decimal

             *     value, then DigitList code must apply the expected rounding

             *     rule.

             *

             *   - If FloatingDecimal already rounded up the decimal value,

             *     DigitList should neither round up the value again in any of

             *     the three rounding modes above.

             *

             *   - If FloatingDecimal has truncated the decimal value to

             *     an ending '5' digit, DigitList should round up the value in

             *     all of the three rounding modes above.

             *

             *

             *   This has to be considered only if digit at maximumDigits index

             *   is exactly the last one in the set of digits, otherwise there are

             *   remaining digits after that position and we don't have to consider

             *   what FloatingDecimal did.

             *

             * - Other rounding modes are not impacted by these tie cases.

             *

             * - For other numbers that are always converted to exact digits

             *   (like BigInteger, Long, ...), the passed alreadyRounded boolean

             *   have to be  set to false, and valueExactAsDecimal has to be set to

             *   true in the upper DigitList call stack, providing the right state

             *   for those situations..

             */

            switch(roundingMode) {

            case UP:

                for (int i=maximumDigits; i<count; ++i) {

                    if (digits[i] != '0') {

                        return true;

                    }

                }

                break;

            case DOWN:

                break;

            case CEILING:

                for (int i=maximumDigits; i<count; ++i) {

                    if (digits[i] != '0') {

                        return !isNegative;

                    }

                }