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function normalize(processable) {
const { entry } = processable;
const offset = entry.rootBounds.bottom - entry.boundingClientRect.top;
const direction =
offset < 0 ? 'Up' : 'Down'; /* eslint-disable-line @gitlab/require-i18n-strings */
return {
...processable,
entry: {
time: entry.time,
type: entry.isIntersecting ? 'intersection' : `scroll${direction}`,
},
};
}
function sort({ entry: alpha }, { entry: beta }) {
const diff = alpha.time - beta.time;
let order = 0;
if (diff < 0) {
order = -1;
} else if (diff > 0) {
order = 1;
} else if (alpha.type === 'intersection' && beta.type === 'scrollUp') {
order = 2;
} else if (alpha.type === 'scrollUp' && beta.type === 'intersection') {
order = -2;
}
return order;
}
function filter(entry) {
return entry.type !== 'scrollDown';
}
export function discussionIntersectionObserverHandlerFactory() {
let unprocessed = [];
let timer = null;
return (processable) => {
unprocessed.push(processable);
if (timer) {
clearTimeout(timer);
}
timer = setTimeout(() => {
unprocessed
.map(normalize)
.filter(filter)
.sort(sort)
.forEach((discussionObservationContainer) => {
const {
entry: { type },
currentDiscussion,
isFirstUnresolved,
isDiffsPage,
functions: { setCurrentDiscussionId, getPreviousUnresolvedDiscussionId },
} = discussionObservationContainer;
if (type === 'intersection') {
setCurrentDiscussionId(currentDiscussion.id);
} else if (type === 'scrollUp') {
setCurrentDiscussionId(
isFirstUnresolved
? null
: getPreviousUnresolvedDiscussionId(currentDiscussion.id, isDiffsPage),
);
}
});
unprocessed = [];
}, 0);
};
}
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