mirror of
https://github.com/vale981/Vulcan
synced 2025-03-08 19:11:38 -05:00
59 lines
2.1 KiB
JavaScript
59 lines
2.1 KiB
JavaScript
export const updateScore = ({collection, item, forceUpdate}) => {
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// Status Check
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if (!!item.status && item.status !== 2) // if item has a status and is not approved, don't update its score
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return 0;
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// Age Check
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// If for some reason item doesn't have a "postedAt" property, abort
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if (!item.postedAt)
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return 0;
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const postedAt = item.postedAt.valueOf();
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const now = new Date().getTime();
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const age = now - postedAt;
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const ageInHours = age / (60 * 60 * 1000);
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if (postedAt > now) // if post has been scheduled in the future, don't update its score
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return 0;
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// For performance reasons, the database is only updated if the difference between the old score and the new score
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// is meaningful enough. To find out, we calculate the "power" of a single vote after n days.
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// We assume that after n days, a single vote will not be powerful enough to affect posts' ranking order.
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// Note: sites whose posts regularly get a lot of votes can afford to use a lower n.
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// n = number of days after which a single vote will not have a big enough effect to trigger a score update
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// and posts can become inactive
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const n = 30;
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// x = score increase amount of a single vote after n days (for n=100, x=0.000040295)
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const x = 1/Math.pow(n*24+2,1.3);
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// time decay factor
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const f = 1.3;
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// use baseScore if defined, if not just use 0
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const baseScore = item.baseScore || 0;
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// HN algorithm
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const newScore = baseScore / Math.pow(ageInHours + 2, f);
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// console.log(now)
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// console.log(age)
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// console.log(ageInHours)
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// console.log(baseScore)
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// console.log(newScore)
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// Note: before the first time updateScore runs on a new item, its score will be at 0
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const scoreDiff = Math.abs(item.score - newScore);
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// only update database if difference is larger than x to avoid unnecessary updates
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if (forceUpdate || scoreDiff > x) {
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collection.update(item._id, {$set: {score: newScore, inactive: false}});
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return 1;
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} else if(ageInHours > n*24) {
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// only set a post as inactive if it's older than n days
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collection.update(item._id, {$set: {inactive: true}});
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}
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return 0;
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};
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