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acdb1ff749
Unfortunately we have no way to calculate the number of comment posts that are previous to the current viewing position of the discussion, without loading all of the posts which is going to be too expensive (even if we do it selectively somehow).
448 lines
15 KiB
JavaScript
448 lines
15 KiB
JavaScript
import Component from 'flarum/Component';
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import icon from 'flarum/helpers/icon';
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import ScrollListener from 'flarum/utils/ScrollListener';
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import SubtreeRetainer from 'flarum/utils/SubtreeRetainer';
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import computed from 'flarum/utils/computed';
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import formatNumber from 'flarum/utils/formatNumber';
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/**
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* The `PostStreamScrubber` component displays a scrubber which can be used to
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* navigate/scrub through a post stream.
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*
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* ### Props
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*
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* - `stream`
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* - `className`
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*/
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export default class PostStreamScrubber extends Component {
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init() {
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this.handlers = {};
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/**
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* The index of the post that is currently at the top of the viewport.
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*
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* @type {Number}
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*/
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this.index = 0;
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/**
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* The number of posts that are currently visible in the viewport.
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*
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* @type {Number}
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*/
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this.visible = 1;
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/**
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* The description to render on the scrubber.
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*
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* @type {String}
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*/
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this.description = '';
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// When the post stream begins loading posts at a certain index, we want our
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// scrubber scrollbar to jump to that position.
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this.props.stream.on('unpaused', this.handlers.streamWasUnpaused = this.streamWasUnpaused.bind(this));
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// Define a handler to update the state of the scrollbar to reflect the
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// current scroll position of the page.
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this.scrollListener = new ScrollListener(this.onscroll.bind(this));
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// Create a subtree retainer that will always cache the subtree after the
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// initial draw. We render parts of the scrubber using this because we
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// modify their DOM directly, and do not want Mithril messing around with
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// our changes.
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this.subtree = new SubtreeRetainer(() => true);
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}
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view() {
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const retain = this.subtree.retain();
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const count = this.count();
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const unreadCount = this.props.stream.discussion.unreadCount();
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const unreadPercent = count ? Math.min(count - this.index, unreadCount) / count : 0;
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const viewing = app.translator.transChoice('core.forum.post_scrubber.viewing_text', count, {
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index: <span className="Scrubber-index">{retain || formatNumber(Math.ceil(this.index + this.visible))}</span>,
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count: <span className="Scrubber-count">{formatNumber(count)}</span>
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});
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function styleUnread(element, isInitialized, context) {
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const $element = $(element);
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const newStyle = {
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top: (100 - unreadPercent * 100) + '%',
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height: (unreadPercent * 100) + '%'
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};
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if (context.oldStyle) {
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$element.stop(true).css(context.oldStyle).animate(newStyle);
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} else {
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$element.css(newStyle);
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}
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context.oldStyle = newStyle;
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}
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return (
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<div className={'PostStreamScrubber Dropdown ' + (this.disabled() ? 'disabled ' : '') + (this.props.className || '')}>
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<button className="Button Dropdown-toggle" data-toggle="dropdown">
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{viewing} {icon('sort')}
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</button>
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<div className="Dropdown-menu dropdown-menu">
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<div className="Scrubber">
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<a className="Scrubber-first" onclick={this.goToFirst.bind(this)}>
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{icon('angle-double-up')} {app.translator.trans('core.forum.post_scrubber.original_post_link')}
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</a>
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<div className="Scrubber-scrollbar">
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<div className="Scrubber-before"/>
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<div className="Scrubber-handle">
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<div className="Scrubber-bar"/>
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<div className="Scrubber-info">
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<strong>{viewing}</strong>
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<span class="Scrubber-description">{retain || this.description}</span>
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</div>
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</div>
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<div className="Scrubber-after"/>
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<div className="Scrubber-unread" config={styleUnread}>
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{app.translator.trans('core.forum.post_scrubber.unread_text', {count: unreadCount})}
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</div>
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</div>
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<a className="Scrubber-last" onclick={this.goToLast.bind(this)}>
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{icon('angle-double-down')} {app.translator.trans('core.forum.post_scrubber.now_link')}
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</a>
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</div>
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</div>
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</div>
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);
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}
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/**
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* Go to the first post in the discussion.
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*/
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goToFirst() {
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this.props.stream.goToFirst();
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this.index = 0;
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this.renderScrollbar(true);
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}
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/**
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* Go to the last post in the discussion.
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*/
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goToLast() {
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this.props.stream.goToLast();
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this.index = this.props.stream.count();
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this.renderScrollbar(true);
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}
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/**
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* Get the number of posts in the discussion.
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*
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* @return {Integer}
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*/
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count() {
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return this.props.stream.count();
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}
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/**
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* When the stream is unpaused, update the scrubber to reflect its position.
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*/
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streamWasUnpaused() {
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this.update(window.pageYOffset);
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this.renderScrollbar(true);
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}
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/**
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* Check whether or not the scrubber should be disabled, i.e. if all of the
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* posts are visible in the viewport.
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*
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* @return {Boolean}
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*/
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disabled() {
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return this.visible >= this.count();
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}
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/**
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* When the page is scrolled, update the scrollbar to reflect the visible
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* posts.
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*
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* @param {Integer} top
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*/
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onscroll(top) {
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const stream = this.props.stream;
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if (stream.paused || !stream.$()) return;
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this.update(top);
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this.renderScrollbar();
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}
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/**
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* Update the index/visible/description properties according to the window's
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* current scroll position.
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*
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* @param {Integer} scrollTop
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*/
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update(scrollTop) {
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const stream = this.props.stream;
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const marginTop = stream.getMarginTop();
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const viewportTop = scrollTop + marginTop;
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const viewportHeight = $(window).height() - marginTop;
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const viewportBottom = viewportTop + viewportHeight;
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// Before looping through all of the posts, we reset the scrollbar
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// properties to a 'default' state. These values reflect what would be
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// seen if the browser were scrolled right up to the top of the page,
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// and the viewport had a height of 0.
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const $items = stream.$('> .PostStream-item[data-index]');
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let index = $items.first().data('index') || 0;
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let visible = 0;
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let period = '';
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// Now loop through each of the items in the discussion. An 'item' is
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// either a single post or a 'gap' of one or more posts that haven't
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// been loaded yet.
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$items.each(function() {
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const $this = $(this);
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const top = $this.offset().top;
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const height = $this.outerHeight(true);
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// If this item is above the top of the viewport, skip to the next
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// one. If it's below the bottom of the viewport, break out of the
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// loop.
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if (top + height < viewportTop) {
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return true;
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}
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if (top > viewportTop + viewportHeight) {
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return false;
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}
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// Work out how many pixels of this item are visible inside the viewport.
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// Then add the proportion of this item's total height to the index.
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const visibleTop = Math.max(0, viewportTop - top);
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const visibleBottom = Math.min(height, viewportTop + viewportHeight - top);
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const visiblePost = visibleBottom - visibleTop;
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if (top <= viewportTop) {
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index = parseFloat($this.data('index')) + visibleTop / height;
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}
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if (visiblePost > 0) {
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visible += visiblePost / height;
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}
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// If this item has a time associated with it, then set the
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// scrollbar's current period to a formatted version of this time.
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const time = $this.data('time');
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if (time) period = time;
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});
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this.index = index;
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this.visible = visible;
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this.description = period ? moment(period).format('MMMM YYYY') : '';
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}
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config(isInitialized, context) {
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if (isInitialized) return;
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context.onunload = this.ondestroy.bind(this);
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this.scrollListener.start();
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// Whenever the window is resized, adjust the height of the scrollbar
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// so that it fills the height of the sidebar.
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$(window).on('resize', this.handlers.onresize = this.onresize.bind(this)).resize();
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// When any part of the whole scrollbar is clicked, we want to jump to
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// that position.
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this.$('.Scrubber-scrollbar')
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.bind('click', this.onclick.bind(this))
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// Now we want to make the scrollbar handle draggable. Let's start by
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// preventing default browser events from messing things up.
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.css({ cursor: 'pointer', 'user-select': 'none' })
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.bind('dragstart mousedown touchstart', e => e.preventDefault());
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// When the mouse is pressed on the scrollbar handle, we capture some
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// information about its current position. We will store this
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// information in an object and pass it on to the document's
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// mousemove/mouseup events later.
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this.dragging = false;
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this.mouseStart = 0;
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this.indexStart = 0;
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this.$('.Scrubber-handle')
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.css('cursor', 'move')
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.bind('mousedown touchstart', this.onmousedown.bind(this))
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// Exempt the scrollbar handle from the 'jump to' click event.
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.click(e => e.stopPropagation());
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// When the mouse moves and when it is released, we pass the
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// information that we captured when the mouse was first pressed onto
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// some event handlers. These handlers will move the scrollbar/stream-
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// content as appropriate.
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$(document)
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.on('mousemove touchmove', this.handlers.onmousemove = this.onmousemove.bind(this))
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.on('mouseup touchend', this.handlers.onmouseup = this.onmouseup.bind(this));
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}
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ondestroy() {
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this.scrollListener.stop();
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this.props.stream.off('unpaused', this.handlers.streamWasUnpaused);
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$(window)
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.off('resize', this.handlers.onresize);
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$(document)
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.off('mousemove touchmove', this.handlers.onmousemove)
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.off('mouseup touchend', this.handlers.onmouseup);
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}
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/**
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* Update the scrollbar's position to reflect the current values of the
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* index/visible properties.
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*
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* @param {Boolean} animate
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*/
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renderScrollbar(animate) {
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const percentPerPost = this.percentPerPost();
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const index = this.index;
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const count = this.count();
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const visible = this.visible || 1;
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const $scrubber = this.$();
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$scrubber.find('.Scrubber-index').text(formatNumber(Math.ceil(index + visible)));
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$scrubber.find('.Scrubber-description').text(this.description);
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$scrubber.toggleClass('disabled', this.disabled());
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const heights = {};
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heights.before = Math.max(0, percentPerPost.index * Math.min(index, count - visible));
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heights.handle = Math.min(100 - heights.before, percentPerPost.visible * visible);
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heights.after = 100 - heights.before - heights.handle;
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const func = animate ? 'animate' : 'css';
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for (const part in heights) {
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const $part = $scrubber.find(`.Scrubber-${part}`);
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$part.stop(true, true)[func]({height: heights[part] + '%'}, 'fast');
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// jQuery likes to put overflow:hidden, but because the scrollbar handle
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// has a negative margin-left, we need to override.
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if (func === 'animate') $part.css('overflow', 'visible');
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}
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}
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/**
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* Get the percentage of the height of the scrubber that should be allocated
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* to each post.
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*
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* @return {Object}
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* @property {Number} index The percent per post for posts on either side of
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* the visible part of the scrubber.
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* @property {Number} visible The percent per post for the visible part of the
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* scrubber.
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*/
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percentPerPost() {
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const count = this.count() || 1;
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const visible = this.visible || 1;
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// To stop the handle of the scrollbar from getting too small when there
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// are many posts, we define a minimum percentage height for the handle
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// calculated from a 50 pixel limit. From this, we can calculate the
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// minimum percentage per visible post. If this is greater than the actual
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// percentage per post, then we need to adjust the 'before' percentage to
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// account for it.
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const minPercentVisible = 50 / this.$('.Scrubber-scrollbar').outerHeight() * 100;
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const percentPerVisiblePost = Math.max(100 / count, minPercentVisible / visible);
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const percentPerPost = count === visible ? 0 : (100 - percentPerVisiblePost * visible) / (count - visible);
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return {
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index: percentPerPost,
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visible: percentPerVisiblePost
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};
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}
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onresize() {
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this.scrollListener.update(true);
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// Adjust the height of the scrollbar so that it fills the height of
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// the sidebar and doesn't overlap the footer.
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const scrubber = this.$();
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const scrollbar = this.$('.Scrubber-scrollbar');
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scrollbar.css('max-height', $(window).height() -
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scrubber.offset().top + $(window).scrollTop() -
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parseInt($('#app').css('padding-bottom'), 10) -
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(scrubber.outerHeight() - scrollbar.outerHeight()));
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}
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onmousedown(e) {
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this.mouseStart = e.clientY || e.originalEvent.touches[0].clientY;
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this.indexStart = this.index;
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this.dragging = true;
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this.props.stream.paused = true;
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$('body').css('cursor', 'move');
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}
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onmousemove(e) {
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if (!this.dragging) return;
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// Work out how much the mouse has moved by - first in pixels, then
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// convert it to a percentage of the scrollbar's height, and then
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// finally convert it into an index. Add this delta index onto
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// the index at which the drag was started, and then scroll there.
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const deltaPixels = (e.clientY || e.originalEvent.touches[0].clientY) - this.mouseStart;
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const deltaPercent = deltaPixels / this.$('.Scrubber-scrollbar').outerHeight() * 100;
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const deltaIndex = (deltaPercent / this.percentPerPost().index) || 0;
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const newIndex = Math.min(this.indexStart + deltaIndex, this.count() - 1);
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this.index = Math.max(0, newIndex);
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this.renderScrollbar();
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}
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onmouseup() {
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if (!this.dragging) return;
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this.mouseStart = 0;
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this.indexStart = 0;
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this.dragging = false;
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$('body').css('cursor', '');
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this.$().removeClass('open');
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// If the index we've landed on is in a gap, then tell the stream-
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// content that we want to load those posts.
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const intIndex = Math.floor(this.index);
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this.props.stream.goToIndex(intIndex);
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this.renderScrollbar(true);
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}
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onclick(e) {
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// Calculate the index which we want to jump to based on the click position.
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// 1. Get the offset of the click from the top of the scrollbar, as a
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// percentage of the scrollbar's height.
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const $scrollbar = this.$('.Scrubber-scrollbar');
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const offsetPixels = (e.clientY || e.originalEvent.touches[0].clientY) - $scrollbar.offset().top + $('body').scrollTop();
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let offsetPercent = offsetPixels / $scrollbar.outerHeight() * 100;
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// 2. We want the handle of the scrollbar to end up centered on the click
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// position. Thus, we calculate the height of the handle in percent and
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// use that to find a new offset percentage.
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offsetPercent = offsetPercent - parseFloat($scrollbar.find('.Scrubber-handle')[0].style.height) / 2;
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// 3. Now we can convert the percentage into an index, and tell the stream-
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// content component to jump to that index.
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let offsetIndex = offsetPercent / this.percentPerPost().index;
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offsetIndex = Math.max(0, Math.min(this.count() - 1, offsetIndex));
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this.props.stream.goToIndex(Math.floor(offsetIndex));
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this.index = offsetIndex;
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this.renderScrollbar(true);
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this.$().removeClass('open');
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}
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}
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