74 lines
2.5 KiB
JavaScript
74 lines
2.5 KiB
JavaScript
// This is designed to exactly mimic Mastodon's ordering for threads. As described by Gargron:
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// "statuses are ordered in the postgresql query and then any of OP's self-replies bubble to the top"
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// Source: https://github.com/tootsuite/mastodon/blob/ef15246/app/models/concerns/status_threading_concern.rb
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import { concat } from './arrays.js'
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import { compareTimelineItemSummaries } from './statusIdSorting.js'
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import { mapBy, multimapBy } from './maps.js'
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export function sortItemSummariesForThread (summaries, statusId) {
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const ancestors = []
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const descendants = []
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const summariesById = mapBy(summaries, _ => _.id)
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const summariesByReplyId = multimapBy(summaries, _ => _.replyId)
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const status = summariesById.get(statusId)
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if (!status) {
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// bail out, for some reason we can't find the status (should never happen)
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return summaries
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}
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// find ancestors
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let currentStatus = status
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do {
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currentStatus = summariesById.get(currentStatus.replyId)
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if (currentStatus) {
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ancestors.unshift(currentStatus)
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}
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} while (currentStatus)
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// find descendants
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// This mirrors the depth-first ordering used in the Postgres query in the Mastodon implementation
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const stack = [status]
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while (stack.length) {
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const current = stack.shift()
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const newChildren = (summariesByReplyId.get(current.id) || []).sort(compareTimelineItemSummaries)
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Array.prototype.unshift.apply(stack, newChildren)
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if (current.id !== status.id) { // the status is not a descendant of itself
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descendants.push(current)
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}
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}
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// Normally descendants are sorted in depth-first order, via normal ID sorting
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// but replies that come from the account they're actually replying to get promoted
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// This only counts if it's an unbroken self-reply, e.g. in the case of
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// A -> A -> A -> B -> A -> A
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// B has broken the chain, so only the first three As are considered unbroken self-replies
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const isUnbrokenSelfReply = (descendant) => {
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let current = descendant
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while (true) {
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if (current.accountId !== status.accountId) {
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return false
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}
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const parent = summariesById.get(current.replyId)
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if (!parent) {
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break
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}
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current = parent
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}
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return current.id === statusId
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}
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const promotedDescendants = []
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const otherDescendants = []
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for (const descendant of descendants) {
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(isUnbrokenSelfReply(descendant) ? promotedDescendants : otherDescendants).push(descendant)
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}
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return concat(
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ancestors,
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[status],
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promotedDescendants,
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otherDescendants
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)
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}
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