Accordion

/**
 * Whether the viewer asked for less motion. Script-driven animations have to check this
 * themselves; a media query only switches off CSS ones.
 */
export function prefersReducedMotion(): boolean {
    return globalThis.matchMedia?.('(prefers-reduced-motion: reduce)').matches ?? false;
}

/**
 * Whether the viewer asked for less motion. Script-driven animations have to check this
 * themselves; a media query only switches off CSS ones.
 */
export function prefersReducedMotion() {
    return globalThis.matchMedia?.('(prefers-reduced-motion: reduce)').matches ?? false;
}

/**
 * Text that arrives word by word and leaves in one piece.
 *
 * `revealText()` fades the words in as a wave: several are in flight at once. `concealText()`
 * slides the whole block down without fading; the box around it is expected to clip it.
 * This module only moves the text, the caller owns the box.
 */
import { prefersReducedMotion } from './reduced-motion.ts';

/** First word starting to last word finished, whatever the word count. */
const REVEAL_MS = 500;

/**
 * How much of the run one word spends fading. Higher means a softer, more overlapping wave;
 * lower means words arrive more one at a time.
 */
const FADE_SHARE = 0.3;

const FADE_EASE = 'ease-out';

const CONCEAL_MS = 300;

/** Pixels the block travels down. Enough to read as leaving, short enough to stay clipped. */
const CONCEAL_DISTANCE = 32;

const MOVE_EASING = 'cubic-bezier(0.3, 0, 0.2, 1)';

export type RevealOptions = {
    duration?: number;
    fadeShare?: number;
    easing?: string;
    /** Wait before the first word, for text arriving into a box that is still opening. */
    delay?: number;
};

export type ConcealOptions = {
    duration?: number;
    /** Pixels, downwards. */
    distance?: number;
    easing?: string;
};

/**
 * Wraps every word of `element` in its own span. Walks text nodes rather than rewriting
 * innerHTML, so inline markup inside the paragraph survives. Runs once; later calls return
 * the spans already there.
 */
export function splitWords(element: HTMLElement): HTMLElement[] {
    const already = element.querySelectorAll<HTMLElement>('[data-word]');
    if (already.length) return [...already];

    const walker = document.createTreeWalker(element, NodeFilter.SHOW_TEXT);
    const texts: Text[] = [];
    while (walker.nextNode()) texts.push(walker.currentNode as Text);

    for (const text of texts) {
        if (!text.data.trim()) continue;

        const pieces = document.createDocumentFragment();
        // The capturing split keeps the whitespace, so copied text reads as before.
        for (const part of text.data.split(/(\s+)/)) {
            if (!part) continue;

            if (!part.trim()) {
                pieces.append(part);
                continue;
            }

            const word = document.createElement('span');
            word.dataset.word = '';
            word.textContent = part;
            pieces.append(word);
        }

        text.replaceWith(pieces);
    }

    return [...element.querySelectorAll<HTMLElement>('[data-word]')];
}

/**
 * Cancels whatever this block and its words have running. Scoped on purpose: a subtree
 * search from an ancestor would also cancel the box's own animation.
 */
export function settleText(element: HTMLElement): void {
    for (const animation of element.getAnimations()) animation.cancel();

    for (const word of element.querySelectorAll<HTMLElement>('[data-word]')) {
        for (const animation of word.getAnimations()) animation.cancel();
    }
}

/**
 * Fades the words in one after another. The run always takes `duration`; more words mean
 * a tighter stagger.
 */
export function revealText(element: HTMLElement, options: RevealOptions = {}): Animation[] {
    const { duration = REVEAL_MS, fadeShare = FADE_SHARE, easing = FADE_EASE, delay = 0 } = options;

    const words = splitWords(element);
    settleText(element);
    if (prefersReducedMotion()) return [];

    const solo = words.length < 2;
    const fade = solo ? duration : duration * fadeShare;
    const step = solo ? 0 : (duration - fade) / (words.length - 1);

    return words.map((word, index) =>
        // `backwards` keeps a word invisible through its delay. No forwards fill, so a
        // finished wave leaves nothing to undo.
        word.animate(
            { opacity: [0, 1] },
            { duration: fade, delay: delay + index * step, easing, fill: 'backwards' },
        ),
    );
}

/**
 * Slides the block down as one, without fading. Fills forwards so the text stays down
 * until the box has closed; the next reveal cancels it.
 */
export function concealText(element: HTMLElement, options: ConcealOptions = {}): Animation | null {
    const { duration = CONCEAL_MS, distance = CONCEAL_DISTANCE, easing = MOVE_EASING } = options;

    settleText(element);
    if (prefersReducedMotion()) return null;

    return element.animate(
        { transform: ['translateY(0)', `translateY(${distance}px)`] },
        { duration, easing, fill: 'forwards' },
    );
}

/**
 * Text that arrives word by word and leaves in one piece.
 *
 * `revealText()` fades the words in as a wave: several are in flight at once. `concealText()`
 * slides the whole block down without fading; the box around it is expected to clip it.
 * This module only moves the text, the caller owns the box.
 */
import { prefersReducedMotion } from './reduced-motion.js';

/** First word starting to last word finished, whatever the word count. */
const REVEAL_MS = 500;

/**
 * How much of the run one word spends fading. Higher means a softer, more overlapping wave;
 * lower means words arrive more one at a time.
 */
const FADE_SHARE = 0.3;

const FADE_EASE = 'ease-out';

const CONCEAL_MS = 300;

/** Pixels the block travels down. Enough to read as leaving, short enough to stay clipped. */
const CONCEAL_DISTANCE = 32;

const MOVE_EASING = 'cubic-bezier(0.3, 0, 0.2, 1)';

/**
 * Wraps every word of `element` in its own span. Walks text nodes rather than rewriting
 * innerHTML, so inline markup inside the paragraph survives. Runs once; later calls return
 * the spans already there.
 */
export function splitWords(element) {
    const already = element.querySelectorAll('[data-word]');
    if (already.length) return [...already];

    const walker = document.createTreeWalker(element, NodeFilter.SHOW_TEXT);
    const texts = [];
    while (walker.nextNode()) texts.push(walker.currentNode);

    for (const text of texts) {
        if (!text.data.trim()) continue;

        const pieces = document.createDocumentFragment();
        // The capturing split keeps the whitespace, so copied text reads as before.
        for (const part of text.data.split(/(\s+)/)) {
            if (!part) continue;

            if (!part.trim()) {
                pieces.append(part);
                continue;
            }

            const word = document.createElement('span');
            word.dataset.word = '';
            word.textContent = part;
            pieces.append(word);
        }

        text.replaceWith(pieces);
    }

    return [...element.querySelectorAll('[data-word]')];
}

/**
 * Cancels whatever this block and its words have running. Scoped on purpose: a subtree
 * search from an ancestor would also cancel the box's own animation.
 */
export function settleText(element) {
    for (const animation of element.getAnimations()) animation.cancel();

    for (const word of element.querySelectorAll('[data-word]')) {
        for (const animation of word.getAnimations()) animation.cancel();
    }
}

/**
 * Fades the words in one after another. The run always takes `duration`; more words mean
 * a tighter stagger.
 */
export function revealText(element, options = {}) {
    const { duration = REVEAL_MS, fadeShare = FADE_SHARE, easing = FADE_EASE, delay = 0 } = options;

    const words = splitWords(element);
    settleText(element);
    if (prefersReducedMotion()) return [];

    const solo = words.length < 2;
    const fade = solo ? duration : duration * fadeShare;
    const step = solo ? 0 : (duration - fade) / (words.length - 1);

    return words.map((word, index) =>
        // `backwards` keeps a word invisible through its delay. No forwards fill, so a
        // finished wave leaves nothing to undo.
        word.animate(
            { opacity: [0, 1] },
            { duration: fade, delay: delay + index * step, easing, fill: 'backwards' },
        ),
    );
}

/**
 * Slides the block down as one, without fading. Fills forwards so the text stays down
 * until the box has closed; the next reveal cancels it.
 */
export function concealText(element, options = {}) {
    const { duration = CONCEAL_MS, distance = CONCEAL_DISTANCE, easing = MOVE_EASING } = options;

    settleText(element);
    if (prefersReducedMotion()) return null;

    return element.animate(
        { transform: ['translateY(0)', `translateY(${distance}px)`] },
        { duration, easing, fill: 'forwards' },
    );
}

/*
 * Fonts, reset and default typography. Nothing control-specific: every demo styles its
 * own control. Only the UI face is here; the mono face is the portal's.
 */
@font-face {
    font-family: 'Figtree';
    font-style: normal;
    font-weight: 300 900;
    font-display: swap;
    src: url('../fonts/figtree-latin.woff2') format('woff2');
    unicode-range:
        U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+0304, U+0308,
        U+0329, U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;
}

@font-face {
    font-family: 'Figtree';
    font-style: normal;
    font-weight: 300 900;
    font-display: swap;
    src: url('../fonts/figtree-latin-ext.woff2') format('woff2');
    unicode-range:
        U+0100-02BA, U+02BD-02C5, U+02C7-02CC, U+02CE-02D7, U+02DD-02FF, U+0304, U+0308, U+0329,
        U+1D00-1DBF, U+1E00-1E9F, U+1EF2-1EFF, U+2020, U+20A0-20AB, U+20AD-20C0, U+2113,
        U+2C60-2C7F, U+A720-A7FF;
}

/* Arial with Figtree's measurements, for the moment before Figtree arrives, so the text does
   not move when it does. Measured on Figtree at 400 and 500. */
@font-face {
    font-family: 'Figtree fallback';
    src: local('Arial'), local('Liberation Sans');
    size-adjust: 100.3%;
    ascent-override: 94.7%;
    descent-override: 24.9%;
    line-gap-override: 0%;
}

*,
*::before,
*::after {
    box-sizing: border-box;
}

/* An author `display` on a component would beat the UA rule for [hidden], and then
   `el.hidden = true` would stop working. Settled once here. */
[hidden] {
    display: none !important;
}

body {
    margin: 0;
    background: var(--surface);
    color: var(--ink);
    --icon-filter: var(--filter-ink);
    font-family: var(--font-ui);
    font-size: var(--text-base);
    line-height: var(--leading-base);
    -webkit-font-smoothing: antialiased;
}

button,
input,
textarea,
select {
    font: inherit;
    color: inherit;
}

/* A second click on a button would otherwise select its label. */
button {
    -webkit-user-select: none;
    user-select: none;
}

:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 2px;
}

/*
 * In the accessibility tree but not on screen: labels and legends that the visual design
 * has no room for. Clipped rather than `display: none`, which would remove it from the
 * tree too, and it also hides live radio inputs that must stay reachable by keyboard.
 */
.visually-hidden {
    position: absolute;
    width: 1px;
    height: 1px;
    overflow: hidden;
    clip-path: inset(50%);
    white-space: nowrap;
}

/*
 * Until the script defines <lord-icon> it is an unknown inline element with no size. These
 * rules give it the box it will have, so nothing moves when it is defined.
 */
lord-icon {
    display: inline-block;
    width: var(--icon-size-32);
    height: var(--icon-size-32);
}

/* A placeholder inside the icon fills it until the icon is ready. */
lord-icon:not(:defined) > img {
    display: block;
    width: 100%;
    height: 100%;
}

/* Placeholders are black. Set --icon-filter wherever an icon's colour is set. */
lord-icon > img {
    filter: var(--icon-filter);
}

/* The one stylesheet a demo imports. */
@import './palette.css';
@import './tokens.css';
@import './base.css';

/*
 * Generated from the Figma token export.
 * Raw values only — roles live in tokens.css. Edit the Figma variables, not this file.
 */
:root {
    /* color/ink */
    --gray-0: #FFFFFF;
    --gray-50: #F7F8FA;
    --gray-100: #EEF0F3;
    --gray-200: #DEE1E6;
    --gray-300: #C3C7D0;
    --gray-400: #9BA1AD;
    --gray-500: #767C89;
    --gray-600: #565C68;
    --gray-700: #3D414B;
    --gray-800: #282B33;
    --gray-900: #16181D;
    --gray-950: #0A0B0E;

    /* color/signal */
    --brand-100: #FFEEE9;
    --brand-200: #FFD7CA;
    --brand-300: #FFB199;
    --brand-400: #FF7D5C;
    --brand-500: #FF5A36;
    --brand-600: #E8431F;
    --brand-700: #C2340F;

    /* color/success */
    --green-100: #EDF9F1;
    --green-300: #A7D9BC;
    --green-700: #15803D;

    /* color/error */
    --red-100: #FDECEC;
    --red-300: #F5B5B5;
    --red-700: #DC2626;

    /* typography/font */
    --font-ui-name: 'Figtree';
    --font-mono-name: 'JetBrains Mono';

    /* typography/size */
    --text-xs: 12px;
    --text-sm: 14px;
    --text-base: 16px;
    --text-lg: 20px;
    --text-xl: 24px;
    --text-2xl: 32px;
    --text-3xl: 40px;

    /* typography/lineHeight */
    --leading-xs: 16px;
    --leading-sm: 20px;
    --leading-base: 24px;
    --leading-lg: 28px;
    --leading-xl: 32px;
    --leading-2xl: 40px;
    --leading-3xl: 48px;

    /* spacing (named after the value, the Figma scale is non-linear) */
    --space-4: 4px;
    --space-8: 8px;
    --space-12: 12px;
    --space-16: 16px;
    --space-24: 24px;
    --space-32: 32px;
    --space-48: 48px;
    --space-64: 64px;
    --space-96: 96px;

    /* size/icon */
    --icon-size-16: 16px;
    --icon-size-20: 20px;
    --icon-size-24: 24px;
    --icon-size-32: 32px;
    --icon-size-40: 40px;
    --icon-size-48: 48px;
    --icon-size-64: 64px;
    --icon-size-96: 96px;

    /* radius */
    --radius-sm: 4px;
    --radius-md: 8px;
    --radius-lg: 12px;
    --radius-pill: 9999px;
}

/*
 * Design tokens by role. Raw values come from palette.css (generated); which grey is a
 * border and which is muted text is decided here, and so would a dark mode be.
 */
:root {
    /* Text. `--ink*` is always a colour; `--text-*` is always a size. */
    --ink: var(--gray-950);
    /* Text that reads as done or in progress, a step lighter than a heading. */
    --ink-strong: var(--gray-800);
    /* Body copy: a step down from --ink. */
    --ink-soft: var(--gray-600);
    --ink-muted: var(--gray-500);
    --ink-subtle: var(--gray-400);
    /* What has not started yet. */
    --ink-faint: var(--gray-300);
    --ink-inverse: var(--gray-0);

    /* Backgrounds */
    --surface: var(--gray-0);
    --surface-muted: var(--gray-50);
    /* A well inside a surface: the filled shape a single icon sits in. */
    --surface-sunken: var(--gray-100);

    /* Outlines */
    --border: var(--gray-200);
    /* The edge of a box that already has a fill, such as an input. */
    --border-soft: var(--gray-100);
    --border-strong: var(--gray-300);
    --border-accent: var(--brand-400);

    /* Brand accent */
    --accent: var(--brand-500);
    --accent-strong: var(--brand-600);
    --accent-surface: var(--brand-100);
    /* The outline of a tinted box, or a small shape on one. */
    --accent-border: var(--brand-300);
    /* Text or a mark on either of the above. */
    --accent-ink: var(--brand-700);

    /* Status. Warning rides the brand ramp — that is what the designs use. */
    --success: var(--green-700);
    --success-surface: var(--green-100);
    --success-border: var(--green-300);

    --warning: var(--brand-500);
    --warning-surface: var(--brand-100);
    --warning-border: var(--brand-300);

    --danger: var(--red-700);
    --danger-surface: var(--red-100);
    --danger-border: var(--red-300);

    /* Icons. Fed straight into --lord-icon-* by the demos. */
    --icon-color: var(--gray-950);
    --icon-accent: var(--brand-500);

    /* Icon placeholders are black SVGs. Each filter turns black into the colour of the same
       name. Made with a CSS filter generator: make a new one when its colour changes. */
    --filter-ink: invert(2%) sepia(4%) saturate(4817%) hue-rotate(193deg) brightness(114%)
        contrast(96%);
    --filter-ink-soft: invert(33%) sepia(18%) saturate(323%) hue-rotate(182deg) brightness(100%)
        contrast(90%);
    --filter-ink-muted: invert(55%) sepia(23%) saturate(191%) hue-rotate(181deg) brightness(84%)
        contrast(89%);
    --filter-ink-subtle: invert(70%) sepia(11%) saturate(284%) hue-rotate(181deg) brightness(91%)
        contrast(86%);
    --filter-ink-faint: invert(76%) sepia(17%) saturate(99%) hue-rotate(184deg) brightness(99%)
        contrast(100%);
    --filter-ink-inverse: invert(100%);
    --filter-accent: invert(49%) sepia(65%) saturate(3508%) hue-rotate(337deg) brightness(106%)
        contrast(113%);
    --filter-accent-strong: invert(29%) sepia(85%) saturate(1790%) hue-rotate(350deg)
        brightness(94%) contrast(93%);
    --filter-success: invert(38%) sepia(22%) saturate(2045%) hue-rotate(94deg) brightness(92%)
        contrast(84%);
    --filter-warning: var(--filter-accent);
    --filter-danger: invert(48%) sepia(74%) saturate(7139%) hue-rotate(343deg) brightness(84%)
        contrast(105%);

    /* Type stacks. The families themselves are in palette.css. */
    --font-ui:
        var(--font-ui-name), 'Figtree fallback', -apple-system, BlinkMacSystemFont, 'Segoe UI',
        Roboto, sans-serif;
    --font-mono: var(--font-mono-name), ui-monospace, SFMono-Regular, Menlo, monospace;

    /* Side padding of a page. The portal uses the same value, so demo and text line up. */
    --gutter: clamp(var(--space-16), 5vw, var(--space-48));

    /* A card's halo: no offset, so it reads as lift rather than as a light source. */
    --shadow-sm: 0 0 7.5px color-mix(in srgb, var(--gray-400) 20%, transparent);
    /* The same halo under a brand-coloured element. */
    --shadow-accent: 0 0 7.5px color-mix(in srgb, var(--accent-strong) 40%, transparent);
}