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/*

 * This file is available under and governed by the GNU General Public

 * License version 2 only, as published by the Free Software Foundation.

 * However, the following notice accompanied the original version of this

 * file:

 *

 * Copyright (c) 2009-2012, Stephen Colebourne & Michael Nascimento Santos

 *

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions are met:

 *

 *  * Redistributions of source code must retain the above copyright notice,

 *    this list of conditions and the following disclaimer.

 *

 *  * Redistributions in binary form must reproduce the above copyright notice,

 *    this list of conditions and the following disclaimer in the documentation

 *    and/or other materials provided with the distribution.

 *

 *  * Neither the name of JSR-310 nor the names of its contributors

 *    may be used to endorse or promote products derived from this software

 *    without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

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 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 */

package java.time;

import java.time.format.DateTimeParseException;

/**

 * A period parser that creates an instance of {@code Period} from a string.

 * This parses the ISO-8601 period format {@code PnYnMnDTnHnMn.nS}.

 * <p>

 * This class is mutable and intended for use by a single thread.

 *

 * @since 1.8

 */

final class PeriodParser {

    /**

     * Used to validate the correct sequence of tokens.

     */

    private static final String TOKEN_SEQUENCE = "PYMDTHMS";

    /**

     * The standard string representing a zero period.

     */

    private static final String ZERO = "PT0S";

    /**

     * The number of years.

     */

    private int years;

    /**

     * The number of months.

     */

    private int months;

    /**

     * The number of days.

     */

    private int days;

    /**

     * The number of hours.

     */

    private int hours;

    /**

     * The number of minutes.

     */

    private int minutes;

    /**

     * The number of seconds.

     */

    private int seconds;

    /**

     * The number of nanoseconds.

     */

    private long nanos;

    /**

     * Whether the seconds were negative.

     */

    private boolean negativeSecs;

    /**

     * Parser position index.

     */

    private int index;

    /**

     * Original text.

     */

    private CharSequence text;

    /**

     * Constructor.

     *

     * @param text  the text to parse, not null

     */

    PeriodParser(CharSequence text) {

        this.text = text;

    }

    //-----------------------------------------------------------------------

    /**

     * Performs the parse.

     * <p>

     * This parses the text set in the constructor in the format PnYnMnDTnHnMn.nS.

     *

     * @return the created Period, not null

     * @throws DateTimeParseException if the text cannot be parsed to a Period

     */

    Period parse() {

        // force to upper case and coerce the comma to dot

        String s = text.toString().toUpperCase().replace(',', '.');

        // check for zero and skip parse

        if (ZERO.equals(s)) {

            return Period.ZERO;

        }

        if (s.length() < 3 || s.charAt(0) != 'P') {

            throw new DateTimeParseException("Period could not be parsed: " + text, text, 0);

        }

        validateCharactersAndOrdering(s, text);

        // strip off the leading P

        String[] datetime = s.substring(1).split("T");

        switch (datetime.length) {

            case 2:

                parseDate(datetime[0], 1);

                parseTime(datetime[1], datetime[0].length() + 2);

                break;

            case 1:

                parseDate(datetime[0], 1);

                break;

        }

        return toPeriod();

    }

    private void parseDate(String s, int baseIndex) {

        index = 0;

        while (index < s.length()) {

            String value = parseNumber(s);

            if (index < s.length()) {

                char c = s.charAt(index);

                switch(c) {

                    case 'Y': years = parseInt(value, baseIndex) ; break;

                    case 'M': months = parseInt(value, baseIndex) ; break;

                    case 'D': days = parseInt(value, baseIndex) ; break;

                    default:

                        throw new DateTimeParseException("Period could not be parsed, unrecognized letter '" +

                                c + ": " + text, text, baseIndex + index);

                }

                index++;

            }

        }

    }

    private void parseTime(String s, int baseIndex) {

        index = 0;

        s = prepareTime(s, baseIndex);

        while (index < s.length()) {

            String value = parseNumber(s);

            if (index < s.length()) {

                char c = s.charAt(index);

                switch(c) {

                    case 'H': hours = parseInt(value, baseIndex) ; break;

                    case 'M': minutes = parseInt(value, baseIndex) ; break;

                    case 'S': seconds = parseInt(value, baseIndex) ; break;

                    case 'N': nanos = parseNanos(value, baseIndex); break;

                    default:

                        throw new DateTimeParseException("Period could not be parsed, unrecognized letter '" +

                                c + "': " + text, text, baseIndex + index);

                }

                index++;

            }

        }

    }

    private long parseNanos(String s, int baseIndex) {

        if (s.length() > 9) {

            throw new DateTimeParseException("Period could not be parsed, nanosecond range exceeded: " +

                    text, text, baseIndex + index - s.length());

        }

        // pad to the right to create 10**9, then trim

        return Long.parseLong((s + "000000000").substring(0, 9));

    }

    private String prepareTime(String s, int baseIndex) {

        if (s.contains(".")) {

            int i = s.indexOf(".") + 1;

            // verify that the first character after the dot is a digit

            if (Character.isDigit(s.charAt(i))) {

                i++;

            } else {

                throw new DateTimeParseException("Period could not be parsed, invalid decimal number: " +

                        text, text, baseIndex + index);

            }

            // verify that only digits follow the decimal point followed by an S

            while (i < s.length()) {

                // || !Character.isDigit(s.charAt(i))

                char c = s.charAt(i);

                if (Character.isDigit(c) || c == 'S') {

                    i++;

                } else {

                    throw new DateTimeParseException("Period could not be parsed, invalid decimal number: " +

                            text, text, baseIndex + index);

                }

            }

            s = s.replace('S', 'N').replace('.', 'S');

            if (s.contains("-0S")) {

                negativeSecs = true;

                s = s.replace("-0S", "0S");

            }

        }

        return s;

    }

    private int parseInt(String s, int baseIndex) {

        try {

            int value = Integer.parseInt(s);

            if (s.charAt(0) == '-' && value == 0) {

                throw new DateTimeParseException("Period could not be parsed, invalid number '" +

                        s + "': " + text, text, baseIndex + index - s.length());

            }

            return value;

        } catch (NumberFormatException ex) {

            throw new DateTimeParseException("Period could not be parsed, invalid number '" +

                    s + "': " + text, text, baseIndex + index - s.length());

        }

    }

    private String parseNumber(String s) {

        int start = index;

        while (index < s.length()) {

            char c = s.charAt(index);

            if ((c < '0' || c > '9') && c != '-') {

                break;

            }

            index++;

        }

        return s.substring(start, index);

    }

    private void validateCharactersAndOrdering(String s, CharSequence text) {

        char[] chars = s.toCharArray();

        int tokenPos = 0;

        boolean lastLetter = false;

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

            if (tokenPos >= TOKEN_SEQUENCE.length()) {

                throw new DateTimeParseException("Period could not be parsed, characters after last 'S': " + text, text, i);

            }

            char c = chars[i];

            if ((c < '0' || c > '9') && c != '-' && c != '.') {

                tokenPos = TOKEN_SEQUENCE.indexOf(c, tokenPos);

                if (tokenPos < 0) {

                    throw new DateTimeParseException("Period could not be parsed, invalid character '" + c + "': " + text, text, i);

                }

                tokenPos++;

                lastLetter = true;

            } else {

                lastLetter = false;

            }

        }

        if (lastLetter == false) {

            throw new DateTimeParseException("Period could not be parsed, invalid last character: " + text, text, s.length() - 1);

        }

    }

    private Period toPeriod() {

        return Period.of(years, months, days, hours, minutes, seconds, negativeSecs || seconds < 0 ? -nanos : nanos);

    }

}