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src/convert.js

/*
 * @copyright (c) 2016, Philipp Thürwächter & Pattrick Hüper
 * @license BSD-3-Clause (see LICENSE in the root directory of this source tree)
 */

import {IllegalArgumentException} from './errors';

import {LocalDate} from './LocalDate';
import {LocalDateTime} from './LocalDateTime';
import {ZonedDateTime} from './ZonedDateTime';
import {ZoneId} from './ZoneId';

class ToNativeJsConverter {
    /**
     * @param {!(LocalDate|LocalDateTime|ZonedDateTime)} temporal - a joda temporal instance
     * @param {ZoneId} [zone] - the zone of the temporal,
     *  the default value for LocalDate and LocalDateTime is ZoneId.systemDefault().
     */
    constructor(temporal, zone){
        let zonedDateTime;

        if(temporal instanceof LocalDate) {
            zone = zone == null ?  ZoneId.systemDefault() : zone;
            zonedDateTime = temporal.atStartOfDay(zone);
        } else if (temporal instanceof LocalDateTime) {
            zone = zone == null ? ZoneId.systemDefault() : zone;
            zonedDateTime = temporal.atZone(zone);
        } else if (temporal instanceof ZonedDateTime) {
            if (zone == null) {
                zonedDateTime = temporal;
            } else {
                zonedDateTime = temporal.withZoneSameInstant(zone);
            }
        } else {
            throw new IllegalArgumentException('unsupported instance for convert operation:' + temporal);
        }

        this.instant = zonedDateTime.toInstant();
    }

    /**
     *
     * @returns {Date}
     */
    toDate() {
        return new Date(this.instant.toEpochMilli());
    }

    /**
     *
     * @returns {number}
     */
    toEpochMilli() {
        return this.instant.toEpochMilli();
    }
}

/**
 * converts a LocalDate, LocalDateTime or ZonedDateTime to a native Javascript Date.
 *
 * In a first step the temporal is converted to an Instant by adding implicit values.
 * 
 * A LocalDate is implicit set to a LocalDateTime at start of day. 
 * A LocalDateTime is implicit set to a ZonedDateTime with 
 * the passed zone or if null, with the system default time zone. 
 * A ZonedDateTime is converted to an Instant, if a zone is specified the zonedDateTime is adjusted to this 
 * zone, keeping the same Instant.
 *
 * In a second step the instant is converted to a native Javascript Date
 *
 * default zone for LocalDate and LocalDateTime is ZoneId.systemDefault().
 *
 * @example
 * convert(localDate).toDate() // returns a javascript Date
 * convert(localDate).toEpochMilli()   // returns the epochMillis
 *
 * @param {!(LocalDate|LocalDateTime|ZonedDateTime)} temporal - a joda temporal instance
 * @param {ZoneId} [zone] - the zone of the temporal
 * @returns {ToNativeJsConverter}
 */
export function convert(temporal, zone){
    return new ToNativeJsConverter(temporal, zone);
}