68 lines
2.2 KiB
JavaScript
68 lines
2.2 KiB
JavaScript
// @flow
|
|
import * as REACTION_TYPES from 'constants/reactions';
|
|
import { SORT_COMMENTS_NEW, SORT_COMMENTS_BEST, SORT_COMMENTS_CONTROVERSIAL } from 'constants/comment';
|
|
|
|
// Mostly taken from Reddit's sorting functions
|
|
// https://github.com/reddit-archive/reddit/blob/master/r2/r2/lib/db/_sorts.pyx
|
|
|
|
export function sortComments(comments: ?Array<Comment>, reactionsById: {}, method: string): Array<Comment> {
|
|
if (!comments) {
|
|
return [];
|
|
}
|
|
|
|
return comments.slice().sort((a, b) => {
|
|
if (method === SORT_COMMENTS_NEW) {
|
|
return 0;
|
|
}
|
|
|
|
const aReactions = reactionsById[a.comment_id];
|
|
const bReactions = reactionsById[b.comment_id];
|
|
const aLikes = (aReactions && aReactions[REACTION_TYPES.LIKE]) || 0;
|
|
const aDislikes = (aReactions && aReactions[REACTION_TYPES.DISLIKE]) || 0;
|
|
const bLikes = (bReactions && bReactions[REACTION_TYPES.LIKE]) || 0;
|
|
const bDislikes = (bReactions && bReactions[REACTION_TYPES.DISLIKE]) || 0;
|
|
|
|
if (method === SORT_COMMENTS_CONTROVERSIAL) {
|
|
if (aLikes === 0 && aDislikes === 0) {
|
|
return 1;
|
|
} else if (bLikes === 0 && bDislikes === 0) {
|
|
return -1;
|
|
}
|
|
|
|
const aMagnitude = aLikes + aDislikes;
|
|
const bMagnitude = bLikes + bDislikes;
|
|
|
|
const aBalance = aLikes > aDislikes ? aDislikes / aLikes : aLikes / aDislikes;
|
|
const bBalance = bLikes > bDislikes ? bDislikes / bLikes : bLikes / bDislikes;
|
|
|
|
return bMagnitude ** bBalance - aMagnitude ** aBalance;
|
|
}
|
|
|
|
if (method === SORT_COMMENTS_BEST) {
|
|
const aN = aLikes + aDislikes;
|
|
const bN = bLikes + bDislikes;
|
|
|
|
if (aN === 0) {
|
|
return 1;
|
|
} else if (bN === 0) {
|
|
return -1;
|
|
}
|
|
|
|
const z = 1.281551565545; // 80% confidence
|
|
const aP = aLikes / aN;
|
|
const bP = bLikes / bN;
|
|
|
|
const aLeft = aP + (1 / (2 * aN)) * z * z;
|
|
const aRight = z * Math.sqrt((aP * (1 - aP)) / aN + (z * z) / (4 * aN * aN));
|
|
const aUnder = 1 + (1 / aN) * z * z;
|
|
|
|
const bLeft = bP + (1 / (2 * bN)) * z * z;
|
|
const bRight = z * Math.sqrt((bP * (1 - bP)) / bN + (z * z) / (4 * bN * bN));
|
|
const bUnder = 1 + (1 / bN) * z * z;
|
|
|
|
return (bLeft - bRight) / bUnder - (aLeft - aRight) / aUnder;
|
|
}
|
|
|
|
return 0;
|
|
});
|
|
}
|