@spalger/kibana/src/ui/public/time_buckets/calc_auto_interval.js

Kibana is an open source (Apache Licensed), browser based analytics and search dashboard for Elasticsearch. Kibana is a snap to setup and start using. Kibana strives to be easy to get started with, while also being flexible and powerful, just like Elastic

define(function (require) {
  return function DateIntervalRoundingRulesProvider() {
    var moment = require('moment');
    // these are the rounding rules used by roundInterval()
    var d = require('moment').duration;

    var roundingRules = [
      [ d(500, 'ms'), d(100, 'ms') ],
      [ d(5, 'second'), d(1, 'second') ],
      [ d(7.5, 'second'), d(5, 'second') ],
      [ d(15, 'second'), d(10, 'second') ],
      [ d(45, 'second'), d(30, 'second') ],
      [ d(3, 'minute'), d(1, 'minute') ],
      [ d(9, 'minute'), d(5, 'minute') ],
      [ d(20, 'minute'), d(10, 'minute') ],
      [ d(45, 'minute'), d(30, 'minute') ],
      [ d(2, 'hour'), d(1, 'hour') ],
      [ d(6, 'hour'), d(3, 'hour') ],
      [ d(24, 'hour'), d(12, 'hour') ],
      [ d(1, 'week'), d(1, 'd') ],
      [ d(3, 'week'), d(1, 'week') ],
      [ d(1, 'year'), d(1, 'month') ],
      [ Infinity, d(1, 'year') ]
    ];

    var revRoundingRules = roundingRules.slice(0).reverse();

    function find(rules, check, last) {
      function pick(buckets, duration) {
        var target = duration / buckets;
        var lastResp;

        for (var i = 0; i < rules.length; i++) {
          var rule = rules[i];
          var resp = check(rule[0], rule[1], target);

          if (resp == null) {
            if (!last) continue;
            if (lastResp) return lastResp;
            break;
          }

          if (!last) return resp;
          lastResp = resp;
        }

        // fallback to just a number of milliseconds, ensure ms is >= 1
        var ms = Math.max(Math.floor(target), 1);
        return moment.duration(ms, 'ms');
      }

      return function (buckets, duration) {
        var interval = pick(buckets, duration);
        if (interval) return moment.duration(interval._data);
      };
    }

    return {
      near: find(revRoundingRules, function near(bound, interval, target) {
        if (bound > target) return interval;
      }, true),

      lessThan: find(revRoundingRules, function (bound, interval, target) {
        if (interval < target) return interval;
      }),

      atLeast: find(revRoundingRules, function atLeast(bound, interval, target) {
        if (interval <= target) return interval;
      }),
    };
  };
});