var $ = require('../internals/export');
var log1p = require('../internals/math-log1p');

// eslint-disable-next-line es/no-math-acosh -- required for testing
var $acosh = Math.acosh;
var log = Math.log;
var sqrt = Math.sqrt;
var LN2 = Math.LN2;

var FORCED = !$acosh
  // V8 bug: https://code.google.com/p/v8/issues/detail?id=3509
  || Math.floor($acosh(Number.MAX_VALUE)) != 710
  // Tor Browser bug: Math.acosh(Infinity) -> NaN
  || $acosh(Infinity) != Infinity;

// `Math.acosh` method
// https://tc39.es/ecma262/#sec-math.acosh
$({ target: 'Math', stat: true, forced: FORCED }, {
  acosh: function acosh(x) {
    var n = +x;
    return n < 1 ? NaN : n > 94906265.62425156
      ? log(n) + LN2
      : log1p(n - 1 + sqrt(n - 1) * sqrt(n + 1));
  }
});