138 lines
3.3 KiB
JavaScript
138 lines
3.3 KiB
JavaScript
// @flow
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import * as React from 'react';
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import { darken } from 'polished';
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import breakpoint from 'styled-components-breakpoint';
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import useWindowScrollPosition from '@rehooks/window-scroll-position';
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import HelpText from 'components/HelpText';
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import styled from 'styled-components';
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import Document from 'models/Document';
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import Revision from 'models/Revision';
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const HEADING_OFFSET = 20;
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type Props = {
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document: Revision | Document,
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};
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export default function Contents({ document }: Props) {
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const headings = document.headings;
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// $FlowFixMe
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const [activeSlug, setActiveSlug] = React.useState();
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const position = useWindowScrollPosition({ throttle: 100 });
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// $FlowFixMe
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React.useEffect(
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() => {
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for (let key = 0; key < headings.length; key++) {
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const heading = headings[key];
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const element = window.document.getElementById(
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decodeURIComponent(heading.slug)
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);
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if (element) {
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const bounding = element.getBoundingClientRect();
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if (bounding.top > HEADING_OFFSET) {
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const last = headings[Math.max(0, key - 1)];
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setActiveSlug(last.slug);
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break;
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}
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}
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}
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},
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[position]
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);
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// calculate the minimum heading level and adjust all the headings to make
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// that the top-most. This prevents the contents from being weirdly indented
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// if all of the headings in the document are level 3, for example.
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const minHeading = headings.reduce(
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(memo, heading) => (heading.level < memo ? heading.level : memo),
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Infinity
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);
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const headingAdjustment = minHeading - 1;
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return (
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<div>
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<Wrapper>
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<Heading>Contents</Heading>
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{headings.length ? (
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<List>
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{headings.map(heading => (
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<ListItem
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key={heading.slug}
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level={heading.level - headingAdjustment}
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active={activeSlug === heading.slug}
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>
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<Link href={`#${heading.slug}`}>{heading.title}</Link>
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</ListItem>
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))}
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</List>
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) : (
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<Empty>Headings you add to the document will appear here</Empty>
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)}
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</Wrapper>
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</div>
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);
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}
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const Wrapper = styled('div')`
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display: none;
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position: sticky;
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top: 80px;
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box-shadow: 1px 0 0 ${props => darken(0.05, props.theme.sidebarBackground)};
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margin-top: 40px;
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margin-right: 2em;
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min-height: 40px;
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${breakpoint('desktopLarge')`
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margin-left: -16em;
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`};
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${breakpoint('tablet')`
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display: block;
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`};
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`;
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const Heading = styled('h3')`
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font-size: 11px;
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font-weight: 600;
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text-transform: uppercase;
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color: ${props => props.theme.sidebarText};
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letter-spacing: 0.04em;
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`;
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const Empty = styled(HelpText)`
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margin: 1em 0 4em;
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padding-right: 2em;
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min-width: 16em;
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width: 16em;
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font-size: 14px;
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`;
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const ListItem = styled('li')`
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margin-left: ${props => (props.level - 1) * 10}px;
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margin-bottom: 8px;
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padding-right: 2em;
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line-height: 1.3;
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border-right: 3px solid
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${props => (props.active ? props.theme.textSecondary : 'transparent')};
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`;
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const Link = styled('a')`
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color: ${props => props.theme.text};
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font-size: 14px;
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&:hover {
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color: ${props => props.theme.primary};
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}
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`;
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const List = styled('ol')`
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min-width: 14em;
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width: 14em;
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padding: 0;
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list-style: none;
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`;
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