import { formatMoment } from '../format/format';
import { hooks } from '../utils/hooks';
import isFunction from '../utils/is-function';

hooks.defaultFormat = 'YYYY-MM-DDTHH:mm:ssZ';
hooks.defaultFormatUtc = 'YYYY-MM-DDTHH:mm:ss[Z]';

export function toString () {
    return this.clone().locale('en').format('ddd MMM DD YYYY HH:mm:ss [GMT]ZZ');
}

export function toISOString(keepOffset) {
    if (!this.isValid()) {
        return null;
    }
    var utc = keepOffset !== true;
    var m = utc ? this.clone().utc() : this;
    if (m.year() < 0 || m.year() > 9999) {
        return formatMoment(m, utc ? 'YYYYYY-MM-DD[T]HH:mm:ss.SSS[Z]' : 'YYYYYY-MM-DD[T]HH:mm:ss.SSSZ');
    }
    if (isFunction(Date.prototype.toISOString)) {
        // native implementation is ~50x faster, use it when we can
        if (utc) {
            return this.toDate().toISOString();
        } else {
            return new Date(this.valueOf() + this.utcOffset() * 60 * 1000).toISOString().replace('Z', formatMoment(m, 'Z'));
        }
    }
    return formatMoment(m, utc ? 'YYYY-MM-DD[T]HH:mm:ss.SSS[Z]' : 'YYYY-MM-DD[T]HH:mm:ss.SSSZ');
}

/**
 * Return a human readable representation of a moment that can
 * also be evaluated to get a new moment which is the same
 *
 * @link https://nodejs.org/dist/latest/docs/api/util.html#util_custom_inspect_function_on_objects
 */
export function inspect () {
    if (!this.isValid()) {
        return 'moment.invalid(/* ' + this._i + ' */)';
    }
    var func = 'moment';
    var zone = '';
    if (!this.isLocal()) {
        func = this.utcOffset() === 0 ? 'moment.utc' : 'moment.parseZone';
        zone = 'Z';
    }
    var prefix = '[' + func + '("]';
    var year = (0 <= this.year() && this.year() <= 9999) ? 'YYYY' : 'YYYYYY';
    var datetime = '-MM-DD[T]HH:mm:ss.SSS';
    var suffix = zone + '[")]';

    return this.format(prefix + year + datetime + suffix);
}

export function format (inputString) {
    if (!inputString) {
        inputString = this.isUtc() ? hooks.defaultFormatUtc : hooks.defaultFormat;
    }
    var output = formatMoment(this, inputString);
    return this.localeData().postformat(output);
}