/*
 *  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
 *
 *      https://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.
 *
 */

package org.apache.tools.ant.taskdefs;

import java.text.SimpleDateFormat;
import java.time.Instant;
import java.util.Calendar;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Optional;
import java.util.StringTokenizer;
import java.util.TimeZone;
import java.util.Vector;
import java.util.function.BiFunction;
import java.util.function.Function;

import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.Location;
import org.apache.tools.ant.MagicNames;
import org.apache.tools.ant.Project;
import org.apache.tools.ant.Task;
import org.apache.tools.ant.types.EnumeratedAttribute;

/**
 * Sets properties to the current time, or offsets from the current time.
 * The default properties are TSTAMP, DSTAMP and TODAY;
 *
 * @since Ant 1.1
 * @ant.task category="utility"
 */
public class Tstamp extends Task {

    private static final String ENV_SOURCE_DATE_EPOCH = "SOURCE_DATE_EPOCH";

    private List<CustomFormat> customFormats = new Vector<>();
    private String prefix = "";

    /**
     * Set a prefix for the properties. If the prefix does not end with a "."
     * one is automatically added.
     * @param prefix the prefix to use.
     * @since Ant 1.5
     */
    public void setPrefix(String prefix) {
        this.prefix = prefix;
        if (!this.prefix.endsWith(".")) {
            this.prefix += ".";
        }
    }

    /**
     * create the timestamps. Custom ones are done before
     * the standard ones, to get their retaliation in early.
     * @throws BuildException on error.
     */
    @Override
    public void execute() throws BuildException {
        try {
            Date d = getNow();
            // Honour reproducible builds https://reproducible-builds.org/specs/source-date-epoch/#idm55
            final String epoch = System.getenv(ENV_SOURCE_DATE_EPOCH);
            try {
                if (epoch != null) {
                    // Value of SOURCE_DATE_EPOCH will be an integer, representing seconds.
                    d = new Date(Integer.parseInt(epoch) * 1000);
                    log("Honouring environment variable " + ENV_SOURCE_DATE_EPOCH + " which has been set to " + epoch);
                }
            } catch(NumberFormatException e) {
                // ignore
                log("Ignoring invalid value '" + epoch + "' for " + ENV_SOURCE_DATE_EPOCH
                        + " environment variable", Project.MSG_DEBUG);
            }
            final Date date = d;
            customFormats.forEach(cts -> cts.execute(getProject(), date, getLocation()));

            SimpleDateFormat dstamp = new SimpleDateFormat("yyyyMMdd");
            setProperty("DSTAMP", dstamp.format(d));

            SimpleDateFormat tstamp = new SimpleDateFormat("HHmm");
            setProperty("TSTAMP", tstamp.format(d));

            SimpleDateFormat today
                = new SimpleDateFormat("MMMM d yyyy", Locale.US);
            setProperty("TODAY", today.format(d));

        } catch (Exception e) {
            throw new BuildException(e);
        }
    }

    /**
     * create a custom format with the current prefix.
     * @return a ready to fill-in format
     */
    public CustomFormat createFormat() {
        CustomFormat cts = new CustomFormat();
        customFormats.add(cts);
        return cts;
    }

    /**
     * helper that encapsulates prefix logic and property setting
     * policy (i.e. we use setNewProperty instead of setProperty).
     */
    private void setProperty(String name, String value) {
        getProject().setNewProperty(prefix + name, value);
    }

    /**
     * Return the {@link Date} instance to use as base for DSTAMP, TSTAMP and TODAY.
     *
     * @return Date
     */
    protected Date getNow() {
        Optional<Date> now = getNow(
            MagicNames.TSTAMP_NOW_ISO,
            s -> Date.from(Instant.parse(s)),
            (k, v) -> "magic property " + k + " ignored as '" + v + "' is not in valid ISO pattern"
        );
        if (now.isPresent()) {
            return now.get();
        }

        now = getNow(
            MagicNames.TSTAMP_NOW,
            s -> new Date(1000 * Long.parseLong(s)),
            (k, v) -> "magic property " + k + " ignored as " + v + " is not a valid number"
        );
        return now.orElseGet(Date::new);
    }

    /**
     * Checks and returns a Date if the specified property is set.
     * @param propertyName name of the property to check
     * @param map conversion of the property value as string to Date
     * @param log supplier of the log message containing the property name and value if
     *     the conversion fails
     * @return Optional containing the Date or null
     */
    protected Optional<Date> getNow(String propertyName, Function<String, Date> map, BiFunction<String, String, String> log) {
        String property = getProject().getProperty(propertyName);
        if (property != null && !property.isEmpty()) {
            try {
                return Optional.ofNullable(map.apply(property));
            } catch (Exception e) {
                log(log.apply(propertyName, property));
            }
        }
        return Optional.empty();
    }

    /**
     * This nested element that allows a property to be set
     * to the current date and time in a given format.
     * The date/time patterns are as defined in the
     * Java SimpleDateFormat class.
     * The format element also allows offsets to be applied to
     * the time to generate different time values.
     * @todo consider refactoring out into a re-usable element.
     */
    public class CustomFormat {
        private TimeZone timeZone;
        private String propertyName;
        private String pattern;
        private String language;
        private String country;
        private String variant;
        private int offset = 0;
        private int field = Calendar.DATE;

        /**
         *  The property to receive the date/time string in the given pattern
         * @param propertyName the name of the property.
         */
        public void setProperty(String propertyName) {
            this.propertyName = propertyName;
        }

        /**
         * The date/time pattern to be used. The values are as
         * defined by the Java SimpleDateFormat class.
         * @param pattern the pattern to use.
         * @see java.text.SimpleDateFormat
         */
        public void setPattern(String pattern) {
            this.pattern = pattern;
        }

        /**
         * The locale used to create date/time string.
         * The general form is "language, country, variant" but
         * either variant or variant and country may be omitted.
         * For more information please refer to documentation
         * for the java.util.Locale  class.
         * @param locale the locale to use.
         * @see java.util.Locale
         */
        public void setLocale(String locale) {
            StringTokenizer st = new StringTokenizer(locale, " \t\n\r\f,");
            try {
                language = st.nextToken();
                if (st.hasMoreElements()) {
                    country = st.nextToken();
                    if (st.hasMoreElements()) {
                        variant = st.nextToken();
                        if (st.hasMoreElements()) {
                            throw new BuildException("bad locale format", getLocation());
                        }
                    }
                } else {
                    country = "";
                }
            } catch (NoSuchElementException e) {
                throw new BuildException("bad locale format", e, getLocation());
            }
        }

        /**
         * The timezone to use for displaying time.
         * The values are as defined by the Java TimeZone class.
         * @param id the timezone value.
         * @see java.util.TimeZone
         */
        public void setTimezone(String id) {
            timeZone = TimeZone.getTimeZone(id);
        }

        /**
         * The numeric offset to the current time.
         * @param offset the offset to use.
         */
        public void setOffset(int offset) {
            this.offset = offset;
        }

        /**
         * Set the unit type (using String).
         * @param unit the unit to use.
         * @deprecated since 1.5.x.
         *             setUnit(String) is deprecated and is replaced with
         *             setUnit(Tstamp.Unit) to make Ant's
         *             Introspection mechanism do the work and also to
         *             encapsulate operations on the unit in its own
         *             class.
         */
        @Deprecated
        public void setUnit(String unit) {
            log("DEPRECATED - The setUnit(String) method has been deprecated. Use setUnit(Tstamp.Unit) instead.");
            Unit u = new Unit();
            u.setValue(unit);
            field = u.getCalendarField();
        }

        /**
         * The unit of the offset to be applied to the current time.
         * Valid Values are
         * <ul>
         *    <li>millisecond</li>
         *    <li>second</li>
         *    <li>minute</li>
         *    <li>hour</li>
         *    <li>day</li>
         *    <li>week</li>
         *    <li>month</li>
         *    <li>year</li>
         * </ul>
         * The default unit is day.
         * @param unit the unit to use.
         */
        public void setUnit(Unit unit) {
            field = unit.getCalendarField();
        }

        /**
         * validate parameter and execute the format.
         * @param project project to set property in.
         * @param date date to use as a starting point.
         * @param location line in file (for errors)
         */
        public void execute(Project project, Date date, Location location) {
            if (propertyName == null) {
                throw new BuildException("property attribute must be provided", location);
            }

            if (pattern == null) {
                throw new BuildException("pattern attribute must be provided", location);
            }

            SimpleDateFormat sdf;
            if (language == null) {
                sdf = new SimpleDateFormat(pattern);
            } else if (variant == null) {
                sdf = new SimpleDateFormat(pattern, new Locale(language, country));
            } else {
                sdf = new SimpleDateFormat(pattern, new Locale(language, country, variant));
            }
            if (offset != 0) {
                Calendar calendar = Calendar.getInstance();
                calendar.setTime(date);
                calendar.add(field, offset);
                date = calendar.getTime();
            }
            if (timeZone != null) {
                sdf.setTimeZone(timeZone);
            }
            Tstamp.this.setProperty(propertyName, sdf.format(date));
        }
    }

    /**
     * set of valid units to use for time offsets.
     */
    public static class Unit extends EnumeratedAttribute {

        private static final String MILLISECOND = "millisecond";
        private static final String SECOND = "second";
        private static final String MINUTE = "minute";
        private static final String HOUR = "hour";
        private static final String DAY = "day";
        private static final String WEEK = "week";
        private static final String MONTH = "month";
        private static final String YEAR = "year";

        private static final String[] UNITS = {
                                                MILLISECOND,
                                                SECOND,
                                                MINUTE,
                                                HOUR,
                                                DAY,
                                                WEEK,
                                                MONTH,
                                                YEAR
                                              };

        private Map<String, Integer> calendarFields = new HashMap<>();

        /** Constructor for Unit enumerated type. */
        public Unit() {
            calendarFields.put(MILLISECOND,
                    Calendar.MILLISECOND);
            calendarFields.put(SECOND, Calendar.SECOND);
            calendarFields.put(MINUTE, Calendar.MINUTE);
            calendarFields.put(HOUR, Calendar.HOUR_OF_DAY);
            calendarFields.put(DAY, Calendar.DATE);
            calendarFields.put(WEEK, Calendar.WEEK_OF_YEAR);
            calendarFields.put(MONTH, Calendar.MONTH);
            calendarFields.put(YEAR, Calendar.YEAR);
        }

        /**
         * Convert the value to int unit value.
         * @return an int value.
         */
        public int getCalendarField() {
            String key = getValue().toLowerCase(Locale.ENGLISH);
            return calendarFields.get(key);
        }

        /**
         * Get the valid values.
         * @return the value values.
         */
        @Override
        public String[] getValues() {
            return UNITS;
        }
    }
}