import absFloor from '../utils/abs-floor';
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import { cloneWithOffset } from '../units/offset';
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import { normalizeUnits } from '../units/aliases';
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export function diff(input, units, asFloat) {
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var that, zoneDelta, output;
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if (!this.isValid()) {
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return NaN;
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}
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that = cloneWithOffset(input, this);
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if (!that.isValid()) {
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return NaN;
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}
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zoneDelta = (that.utcOffset() - this.utcOffset()) * 6e4;
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units = normalizeUnits(units);
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switch (units) {
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case 'year':
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output = monthDiff(this, that) / 12;
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break;
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case 'month':
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output = monthDiff(this, that);
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break;
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case 'quarter':
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output = monthDiff(this, that) / 3;
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break;
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case 'second':
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output = (this - that) / 1e3;
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break; // 1000
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case 'minute':
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output = (this - that) / 6e4;
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break; // 1000 * 60
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case 'hour':
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output = (this - that) / 36e5;
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break; // 1000 * 60 * 60
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case 'day':
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output = (this - that - zoneDelta) / 864e5;
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break; // 1000 * 60 * 60 * 24, negate dst
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case 'week':
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output = (this - that - zoneDelta) / 6048e5;
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break; // 1000 * 60 * 60 * 24 * 7, negate dst
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default:
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output = this - that;
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}
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return asFloat ? output : absFloor(output);
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}
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function monthDiff(a, b) {
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if (a.date() < b.date()) {
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// end-of-month calculations work correct when the start month has more
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// days than the end month.
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return -monthDiff(b, a);
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}
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// difference in months
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var wholeMonthDiff = (b.year() - a.year()) * 12 + (b.month() - a.month()),
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// b is in (anchor - 1 month, anchor + 1 month)
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anchor = a.clone().add(wholeMonthDiff, 'months'),
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anchor2,
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adjust;
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if (b - anchor < 0) {
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anchor2 = a.clone().add(wholeMonthDiff - 1, 'months');
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// linear across the month
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adjust = (b - anchor) / (anchor - anchor2);
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} else {
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anchor2 = a.clone().add(wholeMonthDiff + 1, 'months');
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// linear across the month
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adjust = (b - anchor) / (anchor2 - anchor);
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}
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//check for negative zero, return zero if negative zero
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return -(wholeMonthDiff + adjust) || 0;
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}
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