Charts: NarrativeMOL

/* -- Chart component -----------------------------------------------------

   The sizing surface + editorial frame for the ECharts mount (chart.ts owns

   the runtime: theme adapter, resize, story). The mount itself is a plain

   block with three height presets via data-size; .chart-frame is the

   card-like bordered wrapper (title/dek/source chrome) for editorial

   data-storytelling. Tokens only (AGENTS.md token boundary rule). */

@layer components {

  .chart {

    width: 100%;

    height: 20rem;

    &[data-size='sm'] {

      height: 14rem;

    }

    &[data-size='lg'] {

      height: 28rem;

    }

    /* ECharts animates internally (canvas/svg), but the mount itself never

       transitions - reduced motion is handled in the JS base option */

    @media (prefers-reduced-motion: reduce) {

      & * {

        transition: none !important;

      }

    }

  }

  /* the editorial frame: chart + headline + dek + source line, card-like */

  .chart-frame {

    display: flex;

    flex-direction: column;

    gap: 0.75rem;

    padding: 1.5rem;

    border: 1px solid var(--border);

    border-radius: var(--radius-lg);

    background: var(--card);

    color: var(--card-foreground);

  }

  .chart-title {

    margin: 0;

    font-size: 1rem;

    font-weight: 600;

    line-height: 1.25;

    letter-spacing: var(--tracking-normal);

    text-wrap: balance;

  }

  .chart-dek {

    margin: 0;

    font-size: 0.875rem;

    line-height: 1.5;

    color: var(--muted-foreground);

    text-wrap: pretty;

  }

  .chart-source {

    margin: 0;

    font-size: 0.75rem;

    line-height: 1.4;

    color: var(--muted-foreground);

  }

  @media (prefers-contrast: more) {

    .chart-frame {

      border-width: 2px;

    }

    .chart-dek,

    .chart-source {

      color: var(--foreground);

    }

  }

  /* Windows High Contrast Mode: frame + chrome fall back to system colors */

  @media (forced-colors: active) {

    .chart-frame {

      border-color: CanvasText;

      background: Canvas;

      color: CanvasText;

    }

    .chart-title,

    .chart-dek,

    .chart-source {

      color: CanvasText;

    }

  }

}

// -- Chart ---------------------------------------------------------------

// A thin runtime primitive around Apache ECharts (vendor script, loaded by

// the page - zero echarts bytes ship here). JS is the thin part: declarative

// mounting (data-chart JSON), a theme adapter that turns our design tokens

// (getComputedStyle) into an ECharts THEME object, ResizeObserver-driven

// resize, live re-theming (dark mode / preset swaps), reduced-motion

// suppression, a story driver for option transitions and the deck stage

// (one morphing chart across presentation slides). Everything visual is

// chart.css + the token file (AGENTS.md "Native web platform first").

//

// Markup contract: `.chart` mount carrying data-chart='{…}' (the ECharts

// option; the token theme supplies every default it leaves out) + role="img"

// + aria-label. State lives ON THE ELEMENT (dataset.stateName) - the bound

// `api` is the only state mutator (AGENTS.md "State API").

// Shared preamble (AGENTS.md "State API"); the implementation lives in core.js —

// build.ts rewrites this import into a df$.shadcn.shared binding in dist/.

import { defussGlobals } from '../../shared/state-api.js';

const df$ = defussGlobals();

const chartStates = ['default'];

/** The ONE vendor-load error text - same actionable message everywhere. */

const ECHARTS_NOT_LOADED =

  'chart: echarts is not loaded - add <script src="https://cdn.jsdelivr.net/npm/echarts@6.1.0/dist/echarts.min.js"></script> before chart.js';

type Option = Record<string, unknown>;

/** Minimal structural view of the vendor global (read via globalThis, never window). */

interface EChartsInstanceLike {

  setOption(option: Option, notMerge?: boolean): void;

  setTheme?(theme: Option): void;

  resize(): void;

  clear?(): void;

  dispose(): void;

  isDisposed?(): boolean;

  getOption(): Option;

}

interface EChartsLike {

  init(el: HTMLElement, theme?: unknown, opts?: { renderer?: string }): EChartsInstanceLike;

}

/** Handle returned by df$.chart.mount() - the imperative lifecycle surface. */

export interface ChartMount {

  instance: EChartsInstanceLike;

  setOption(option: Option, notMerge?: boolean): void;

  dispose(): void;

}

/** The vendor runtime or the one actionable load-order error (query.ts style). */

function echartsRuntime(): EChartsLike {

  const echarts = (globalThis as { echarts?: EChartsLike }).echarts;

  if (!echarts) throw new Error(ECHARTS_NOT_LOADED);

  return echarts;

}

const isPlain = (v: unknown): v is Option => typeof v === 'object' && v !== null && !Array.isArray(v);

/** Recursive merge: plain objects combine, arrays/scalars are replaced. */

function deepMerge(base: Option, over: Option): Option {

  const out: Option = { ...base };

  for (const [key, value] of Object.entries(over)) {

    out[key] = isPlain(value) && isPlain(out[key]) ? deepMerge(out[key] as Option, value) : value;

  }

  return out;

}

const reducedMotion = (): boolean => matchMedia('(prefers-reduced-motion: reduce)').matches;

// -- color resolution ------------------------------------------------------

/** One 1×1 canvas resolves ANY CSS color the browser understands. */

let probe: CanvasRenderingContext2D | null = null;

/**

 * Why: tokens are oklch() (and themes may use color-mix/lab/…); ECharts

 * parses only hex/rgb/hsl - it would pass oklch through to SVG fills but

 * silently break every color interpolation (hover emphasis, visualMap

 * gradients, the morph between states). Painting one pixel and reading it

 * back is the browser's own conversion to sRGB. Returns [r, g, b, a] or

 * null for empty/invalid input.

 */

function rgba(css: string): [number, number, number, number] | null {

  if (!css || css === 'none') return null;

  probe ??= document.createElement('canvas').getContext('2d', { willReadFrequently: true });

  if (!probe) return null;

  probe.clearRect(0, 0, 1, 1);

  probe.fillStyle = 'rgba(1, 2, 3, 0.5)'; // sentinel: an invalid color keeps it

  probe.fillStyle = css;

  if (probe.fillStyle === 'rgba(1, 2, 3, 0.5)') return null;

  probe.fillRect(0, 0, 1, 1);

  const [r, g, b, a] = probe.getImageData(0, 0, 1, 1).data;

  return [r, g, b, a / 255];

}

/** CSS color → 'rgb()/rgba()' ECharts can interpolate ('' when unresolvable). */

function toRgb(css: string, alpha = 1): string {

  const c = rgba(css);

  if (!c) return '';

  const a = +(c[3] * alpha).toFixed(3);

  return a >= 1 ? `rgb(${c[0]}, ${c[1]}, ${c[2]})` : `rgba(${c[0]}, ${c[1]}, ${c[2]}, ${a})`;

}

/**

 * Why: page and deck options that pick token colors themselves (a highlight

 * bar, a visualMap gradient) need ECharts-parseable colors too. Resolves a

 * token name ('--chart-2', read off the element) or any CSS color to

 * rgb()/rgba(), optionally at an alpha. '' when unresolvable.

 */

export function chartColor(el: HTMLElement, value: string, alpha = 1): string {

  const css = value.startsWith('--') ? getComputedStyle(el).getPropertyValue(value).trim() : value;

  return toRgb(css, alpha);

}

/** The first opaque background up the tree - the surface the chart sits on

 * (card, slide, page); pie/sunburst separators are drawn in it. */

function surfaceOf(el: HTMLElement): string {

  for (let node: HTMLElement | null = el; node; node = node.parentElement) {

    const c = rgba(getComputedStyle(node).backgroundColor);

    if (c && c[3] > 0.5) return `rgb(${c[0]}, ${c[1]}, ${c[2]})`;

  }

  return toRgb(getComputedStyle(document.documentElement).getPropertyValue('--background').trim()) || '#ffffff';

}

// -- the theme adapter ------------------------------------------------------

/**

 * Why: the theme adapter - the chart reads the DESIGN TOKENS off its own

 * computed style and returns an ECharts THEME object (passed to init() and

 * setTheme()). A theme, unlike a merged base option, is only defaults: it

 * survives setOption(…, notMerge) (stories, deck stages), applies per

 * component type (categoryAxis/valueAxis only style axes that EXIST - no

 * phantom axes on pies/treemaps) and per series type (bar radius, line

 * width, pie separators).

 *

 * Sources: the --chart-1..5 palette (resolved to rgb; empty tokens dropped),

 * the element's own `color` for text (so a chart inherits card, slide or

 * page foreground; muted/axis/grid are fixed mixes of it), --popover* for

 * the tooltip, --font-sans for type, and `--chart-font-size` (component-

 * local, default 13px; decks raise it to artboard scale) for the type scale

 * every size here derives from. prefers-reduced-motion disables animation.

 */

export function chartTheme(el: HTMLElement): Option {

  const cs = getComputedStyle(el);

  const tok = (name: string): string => cs.getPropertyValue(name).trim();

  const fs = parseFloat(tok('--chart-font-size')) || 13;

  const k = fs / 13; // every length scales with the type

  const px = (n: number): number => Math.round(n * k * 10) / 10;

  const fg = toRgb(cs.color) || toRgb(tok('--foreground')) || '#111111';

  const muted = toRgb(cs.color, 0.62) || fg;

  const axis = toRgb(cs.color, 0.28) || fg;

  const grid = toRgb(cs.color, 0.1) || fg;

  const surface = surfaceOf(el);

  const palette = [1, 2, 3, 4, 5].map((n) => toRgb(tok(`--chart-${n}`))).filter(Boolean);

  // the chart speaks its container's typeface (a deck's display face, a

  // card's body face) - --font-sans only when nothing resolves

  const font = cs.fontFamily || tok('--font-sans') || 'system-ui, sans-serif';

  const label = { color: muted, fontSize: fs, fontFamily: font };

  const reduce = reducedMotion();

  const axisBase = {

    nameTextStyle: { ...label },

    nameGap: px(14),

    axisLabel: { ...label, margin: px(10) },

    axisTick: { show: false },

    splitArea: { show: false },

  };

  return {

    ...(palette.length > 0 ? { color: palette } : {}),

    backgroundColor: 'transparent',

    aria: { enabled: true },

    animation: !reduce,

    animationDuration: reduce ? 0 : 750,

    animationEasing: 'cubicOut',

    animationDurationUpdate: reduce ? 0 : 900,

    animationEasingUpdate: 'cubicInOut',

    textStyle: { fontFamily: font, color: fg, fontSize: fs },

    title: {

      textStyle: { color: fg, fontSize: px(16), fontWeight: 600, fontFamily: font },

      subtextStyle: { ...label },

    },

    // tight defaults (ECharts' own are 15%/10% gutters): outerBounds keeps

    // axis labels inside the box, the top leaves room for a legend row

    grid: { left: px(8), right: px(20), top: px(40), bottom: px(14) },

    legend: {

      top: 0,

      icon: 'roundRect',

      itemWidth: px(12),

      itemHeight: px(12),

      itemGap: px(18),

      textStyle: { color: muted, fontSize: fs, fontFamily: font },

      inactiveColor: grid,

      pageTextStyle: { color: muted },

    },

    tooltip: {

      ...(toRgb(tok('--popover')) ? { backgroundColor: toRgb(tok('--popover')) } : {}),

      borderColor: toRgb(tok('--border')) || axis,

      borderWidth: 1,

      padding: [px(8), px(12)],

      textStyle: { color: toRgb(tok('--popover-foreground')) || fg, fontSize: fs, fontFamily: font },

      extraCssText: 'border-radius: var(--radius-md, 8px); box-shadow: var(--shadow-md, 0 6px 16px rgba(0,0,0,.12));',

      axisPointer: {

        lineStyle: { color: axis, width: 1 },

        crossStyle: { color: axis },

        shadowStyle: { color: toRgb(cs.color, 0.05) },

        label: { backgroundColor: fg, color: surface, fontSize: fs },

      },

    },

    categoryAxis: {

      ...axisBase,

      axisLine: { show: true, lineStyle: { color: axis, width: 1 } },

      splitLine: { show: false },

    },

    valueAxis: {

      ...axisBase,

      axisLine: { show: false },

      splitLine: { show: true, lineStyle: { color: grid, width: 1 } },

    },

    logAxis: {

      ...axisBase,

      axisLine: { show: false },

      splitLine: { show: true, lineStyle: { color: grid, width: 1 } },

    },

    timeAxis: {

      ...axisBase,

      axisLine: { show: true, lineStyle: { color: axis, width: 1 } },

      splitLine: { show: false },

    },

    bar: {

      barMaxWidth: px(56),

      itemStyle: { borderRadius: px(4) },

      label: { color: fg, fontSize: fs, fontFamily: font },

    },

    line: {

      symbol: 'circle',

      symbolSize: px(7),

      lineStyle: { width: px(2.5), cap: 'round', join: 'round' },

      label: { color: fg, fontSize: fs, fontFamily: font, textBorderWidth: 0 },

      // ECharts outlines end labels in the series color by default - a halo

      // that smears on dark surfaces; plain foreground text reads cleaner

      endLabel: { color: fg, fontSize: fs, fontFamily: font, textBorderWidth: 0 },

    },

    scatter: { symbolSize: px(12), label: { color: fg, fontSize: fs, fontFamily: font } },

    pie: {

      itemStyle: { borderColor: surface, borderWidth: px(2), borderRadius: px(4) },

      label: { color: fg, fontSize: fs, fontFamily: font },

      labelLine: { lineStyle: { color: axis } },

    },

    sunburst: { itemStyle: { borderColor: surface, borderWidth: px(1.5) }, label: { fontSize: fs } },

    treemap: {

      itemStyle: { borderColor: surface, borderWidth: px(2), gapWidth: px(2) },

      label: { fontSize: fs },

      breadcrumb: { show: false },

    },

    sankey: { label: { color: fg, fontSize: fs }, lineStyle: { opacity: 0.35 } },

    radar: { axisName: { color: muted, fontSize: fs } },

    visualMap: { textStyle: { color: muted, fontSize: fs, fontFamily: font } },

  };

}

// -- live instances -----------------------------------------------------------

/** Live instances + their resize observers, keyed by element (never module state). */

const instances = new WeakMap<HTMLElement, EChartsInstanceLike>();

const observers = new WeakMap<HTMLElement, ResizeObserver>();

/** The mounted elements, iterable for re-theming (pruned when disconnected). */

const live = new Set<HTMLElement>();

/** Reduced motion is re-evaluated per apply: animation off wins over the option. */

function withMotion(option: Option): Option {

  return reducedMotion() ? { ...option, animation: false } : option;

}

/** Strings the canvas probe cannot read directly: token references and

 * CSS Color 4/5 functions ECharts cannot parse. */

const CSS_COLOR = /var\(--|^\s*(?:oklch|oklab|lch|lab|hwb|color-mix|color)\(/;

/**

 * Why: options may name design tokens - color: 'var(--primary)', a visualMap

 * range of ['var(--card)', 'var(--chart-2)'], even color-mix() over them —

 * so they stay declarative (data-chart JSON included) AND theme-proof. Every

 * such string is resolved against the element to rgb() at apply time; the

 * raw option is kept, so a theme change re-resolves it (see retheme()).

 */

function resolveColors(el: HTMLElement, value: unknown, cs?: CSSStyleDeclaration): unknown {

  if (typeof value === 'string') {

    if (!CSS_COLOR.test(value)) return value;

    const style = cs ?? getComputedStyle(el);

    const css = value.replace(/var\((--[\w-]+)\s*(?:,\s*([^()]*))?\)/g, (_m, name: string, fallback?: string) =>

      style.getPropertyValue(name).trim() || (fallback ?? '').trim(),

    );

    return toRgb(css) || value;

  }

  if (Array.isArray(value)) {

    const style = cs ?? getComputedStyle(el);

    return value.map((v) => resolveColors(el, v, style));

  }

  if (isPlain(value)) {

    const style = cs ?? getComputedStyle(el);

    const out: Option = {};

    for (const [k, v] of Object.entries(value)) out[k] = resolveColors(el, v, style);

    return out;

  }

  return value;

}

/** The raw ops since the last full (notMerge) apply, per element - replayed

 * after a theme change so token references re-resolve. A long-running merge

 * stream (a bar race ticking setOption) stops recording past the cap; such a

 * chart still re-themes its chrome, just not its per-series token colors. */

interface Journal { ops: [Option, unknown, unknown][]; overflow: boolean }

const journals = new WeakMap<HTMLElement, Journal>();

const JOURNAL_CAP = 64;

/** setOption's second argument is either a boolean or an opts object. */

const isNotMerge = (arg: unknown): boolean => arg === true || (isPlain(arg) && arg.notMerge === true);

/**

 * Why: ONE apply path for every caller - mount(), the returned handle, the

 * State API, stories, the deck stage AND authors holding the raw instance

 * (instance(el).setOption is wrapped): token references resolve, reduced

 * motion applies, and the op is journaled for re-theming.

 */

function wrapSetOption(el: HTMLElement, inst: EChartsInstanceLike): void {

  const raw = inst.setOption.bind(inst) as (o: Option, a?: unknown, b?: unknown) => void;

  const journal: Journal = { ops: [], overflow: false };

  journals.set(el, journal);

  (inst as { _rawSetOption?: typeof raw })._rawSetOption = raw;

  inst.setOption = ((option: Option, arg?: unknown, lazy?: unknown) => {

    if (isNotMerge(arg)) {

      journal.ops = [];

      journal.overflow = false;

    }

    if (journal.ops.length < JOURNAL_CAP) journal.ops.push([option, arg, lazy]);

    else journal.overflow = true;

    raw(withMotion(resolveColors(el, option) as Option), arg, lazy);

  }) as EChartsInstanceLike['setOption'];

}

/**

 * Why: the one mount path (declarative and imperative converge here). The

 * token theme goes to init(); the option carries only what the author said.

 * The renderer is SVG (crisp at any density, selectable, small); a

 * ResizeObserver keeps the canvas honest - never a window resize listener.

 */

export function mount(el: HTMLElement, option: Option = {}): ChartMount {

  const echarts = echartsRuntime();

  observers.get(el)?.disconnect();

  instances.get(el)?.dispose();

  const instance = echarts.init(el, chartTheme(el), { renderer: 'svg' });

  wrapSetOption(el, instance);

  instances.set(el, instance);

  live.add(el);

  watchTheme();

  instance.setOption(option, true);

  // resize on the next frame, not inside the observer: a synchronous resize

  // changes layout mid-delivery and the browser reports "ResizeObserver loop

  // completed with undelivered notifications" (a view switch, a sidebar

  // collapsing beside the chart)

  let frame = 0;

  const ro = new ResizeObserver(() => {

    cancelAnimationFrame(frame);

    frame = requestAnimationFrame(() => { if (!instance.isDisposed?.()) instance.resize(); });

  });

  ro.observe(el);

  observers.set(el, ro);

  replayOnSlide(el);

  replayOnView(el);

  return {

    instance,

    setOption: (opt, notMerge = false) => instance.setOption(opt, notMerge),

    dispose: () => {

      viewObserver?.unobserve(el);

      ro.disconnect();

      observers.delete(el);

      instances.delete(el);

      live.delete(el);

      instance.dispose();

    },

  };

}

/** The stored instance for an element (undefined until mounted). */

export function instance(el: HTMLElement): EChartsInstanceLike | undefined {

  return instances.get(el);

}

/** Re-apply the journal from scratch (clear first): the chart's entrance

 * animation plays again. */

function replay(el: HTMLElement, inst: EChartsInstanceLike): void {

  const journal = journals.get(el);

  const raw = (inst as { _rawSetOption?: (o: Option, a?: unknown, b?: unknown) => void })._rawSetOption;

  if (!journal || !raw || journal.overflow || journal.ops.length === 0) return;

  // ECharts' clear() is itself setOption({ series: [] }, true) - through the

  // wrapper it would RESET the journal; keep the ops and restore them after

  const ops = journal.ops.slice();

  inst.clear?.();

  journal.ops = ops;

  journal.overflow = false;

  for (const [option, arg, lazy] of ops) raw(withMotion(resolveColors(el, option) as Option), arg, lazy);

}

/** One shared observer for every chart still waiting to be seen. */

let viewObserver: IntersectionObserver | undefined;

/**

 * Why: a chart mounts as soon as its script runs - during page load, or far

 * below the fold - so its entrance animation (a gauge sweeping 0 → 77%, bars

 * growing) plays while nobody is looking. The first time a chart is actually

 * on screen (30% visible), its journal replays once, so the entrance plays

 * in view. Slide charts are excluded (replayOnSlide owns them), and so is

 * reduced motion (there is no animation to show).

 */

function replayOnView(el: HTMLElement): void {

  if (reducedMotion() || el.closest('[data-slide]') || typeof IntersectionObserver !== 'function') return;

  viewObserver ??= new IntersectionObserver(

    (entries) => {

      for (const entry of entries) {

        if (!entry.isIntersecting) continue;

        const chartEl = entry.target as HTMLElement;

        viewObserver?.unobserve(chartEl);

        const i = instances.get(chartEl);

        if (i && chartEl.isConnected && !i.isDisposed?.()) replay(chartEl, i);

      }

    },

    { threshold: 0.3 },

  );

  viewObserver.observe(el);

}

/** Slides whose charts replay on activation (one observer per slide). */

const slideCharts = new WeakMap<HTMLElement, Set<HTMLElement>>();

/**

 * Why: a chart inside a presentation slide mounts while the slide is still

 * hidden (slides keep their full artboard size), so its entrance animation

 * would play unseen. Every activation of its slide ([data-active] appears)

 * replays the chart's entrance instead - each chart animates whenever its

 * slide comes on stage. The deck stage (.presentation-stage) morphs between

 * states instead and is excluded.

 */

function replayOnSlide(el: HTMLElement): void {

  if (el.classList.contains('presentation-stage')) return;

  const slide = el.closest<HTMLElement>('[data-slide]');

  if (!slide) return;

  let charts = slideCharts.get(slide);

  if (!charts) {

    charts = new Set();

    slideCharts.set(slide, charts);

    const set = charts;

    let wasActive = slide.hasAttribute('data-active');

    new MutationObserver(() => {

      const active = slide.hasAttribute('data-active');

      if (active && !wasActive) {

        for (const chartEl of set) {

          const i = instances.get(chartEl);

          if (i && chartEl.isConnected) replay(chartEl, i);

        }

      }

      wasActive = active;

    }).observe(slide, { attributes: true, attributeFilter: ['data-active'] });

  }

  charts.add(el);

}

/** Re-derive one chart's theme, then replay its journal so token

 * references in the option resolve against the new tokens too. */

function retheme(el: HTMLElement, inst: EChartsInstanceLike): void {

  inst.setTheme?.(chartTheme(el));

  const journal = journals.get(el);

  const raw = (inst as { _rawSetOption?: (o: Option, a?: unknown, b?: unknown) => void })._rawSetOption;

  if (!journal || !raw || journal.overflow) return;

  for (const [option, arg, lazy] of journal.ops) raw(withMotion(resolveColors(el, option) as Option), arg, lazy);

}

/**

 * Why: themes are live - dark mode toggles a class on <html>, the theme

 * switcher writes token overrides into <html style> or swaps a token

 * <style>. One document-level observer re-derives every live chart

 * (ECharts' setTheme re-renders from the stored option - no remount, no

 * lost state). Debounced to one pass per burst of mutations.

 */

let themeWatched = false;

function watchTheme(): void {

  if (themeWatched) return;

  themeWatched = true;

  let timer = 0;

  const schedule = (): void => {

    clearTimeout(timer);

    timer = setTimeout(() => {

      for (const el of live) {

        const inst = instances.get(el);

        if (!el.isConnected || !inst || inst.isDisposed?.()) {

          live.delete(el);

          continue;

        }

        retheme(el, inst);

      }

    }, 60) as unknown as number;

  };

  const mo = new MutationObserver(schedule);

  mo.observe(document.documentElement, { attributes: true, attributeFilter: ['class', 'style', 'data-theme'] });

  if (document.head) mo.observe(document.head, { childList: true, subtree: true, characterData: true });

  matchMedia('(prefers-color-scheme: dark)').addEventListener('change', schedule);

}

// -- story + deck stage -----------------------------------------------------

/** Every series joins the morph unless it opted out: universalTransition is

 * what turns a state change into one continuous shape change. Custom series

 * are left alone - ECharts cannot morph renderItem geometry; they animate

 * through their own element `transition` / `enterFrom` instead. */

function morphable(option: Option): Option {

  const series = option.series;

  if (series === undefined) return option;

  const list = (Array.isArray(series) ? series : [series]) as Option[];

  return {

    ...option,

    series: list.map((s) => (s.universalTransition === undefined && s.type !== 'custom' ? { ...s, universalTransition: { enabled: true } } : s)),

  };

}

/**

 * Why: data-storytelling - a sequence of option states driven like slides.

 * go() clamps (or wraps with { loop: true }) and applies states[i] with

 * notMerge, so each step is a full surface (the token theme persists - it

 * is the instance's theme, not part of the option). Series default to

 * universalTransition, so keeping series.id and data names stable across

 * states makes ECharts MORPH instead of redrawing. An unmounted element is

 * lazily mounted with states[0].

 */

export function chartStory(

  el: HTMLElement,

  states: Option[],

  { loop = false }: { loop?: boolean } = {},

): { next(): number; prev(): number; go(i: number): number; index(): number } {

  if (!Array.isArray(states) || states.length === 0) {

    throw new Error('chart: chartStory needs at least one option state');

  }

  if (!instances.has(el)) mount(el, morphable(states[0]));

  let i = 0;

  const go = (n: number): number => {

    i = loop ? ((n % states.length) + states.length) % states.length : Math.min(Math.max(n, 0), states.length - 1);

    instances.get(el)?.setOption(morphable(states[i]), true);

    return i;

  };

  return { next: () => go(i + 1), prev: () => go(i - 1), go, index: () => i };

}

/** Handle returned by df$.shadcn.chart.deck(). */

export interface ChartDeck {

  /** Show a named state (morphing from the current one), or hide the stage with null. */

  show(name: string | null): void;

  /** The state currently on stage (null while hidden). */

  state(): string | null;

  /** Stop following the deck and dispose the chart. */

  dispose(): void;

}

/**

 * Why: the deck stage - ONE chart instance for a whole presentation, so

 * every chart slide MORPHS into the next (bars → dots → donut …) instead of

 * cutting between separate charts. The stage is a `.chart.presentation-

 * stage` child of the `.presentation` mount, laid out in artboard

 * coordinates by presentation.css; slides name the state they show with

 * data-chart-state="name". Slides without one fade the stage out - the

 * instance keeps its last state, so the next chart slide morphs from there.

 *

 * Each state is deep-merged over `base` (shared chrome) and applied with

 * notMerge, so a state is a complete surface; series default to

 * universalTransition. The first appearance mounts the chart, so its

 * entrance animation plays on stage - never hidden at page load.

 */

/** Deck tempo: entrances and morphs take the slides' 1.5s - slow and legible

 * at presentation distance (a base or state may still override it). */

const DECK_TEMPO: Option = { animationDuration: 1500, animationEasing: 'cubicOut', animationDurationUpdate: 1500, animationEasingUpdate: 'cubicInOut' };

export function chartDeck(deck: HTMLElement, { base = {}, states }: { base?: Option; states: Record<string, Option> }): ChartDeck {

  const stage = deck.querySelector<HTMLElement>(':scope > .presentation-stage');

  if (!stage) throw new Error('chart: chart.deck() needs a <div class="chart presentation-stage"> child of the .presentation');

  if (!isPlain(states) || Object.keys(states).length === 0) throw new Error('chart: chart.deck() needs at least one named state');

  const slides = Array.from(deck.querySelectorAll<HTMLElement>(':scope > [data-slide]'));

  let current: string | null = null;

  let last: string | null = null;

  const show = (name: string | null): void => {

    if (name === null || !(name in states)) {

      stage.removeAttribute('data-visible');

      current = null;

      return;

    }

    // the stage inherits its text color from the slide it plays on, once:

    // the theme is fixed at mount, states own every color after that

    const slide = slides.find((s) => s.dataset.chartState === name);

    if (!instances.has(stage) && slide) stage.style.color = getComputedStyle(slide).color;

    stage.setAttribute('data-visible', '');

    if (name === current) return;

    const returning = current === null && name === last; // same chart, stage was away

    current = name;

    last = name;

    const option = morphable(deepMerge(deepMerge(DECK_TEMPO, base), states[name]));

    const inst = instances.get(stage);

    if (!inst) mount(stage, option);

    else if (returning) {

      // nothing to morph from - replay the chart's entrance instead, so

      // every arrival on a chart slide animates

      inst.clear?.();

      inst.setOption(option, true);

    } else inst.setOption(option, true);

  };

  const sync = (): void => {

    const active = slides.find((s) => s.hasAttribute('data-active'));

    show(active?.dataset.chartState ?? null);

  };

  const mo = new MutationObserver(sync);

  slides.forEach((s) => mo.observe(s, { attributes: true, attributeFilter: ['data-active'] }));

  sync();

  return {

    show,

    state: () => current,

    dispose: () => {

      mo.disconnect();

      observers.get(stage)?.disconnect();

      instances.get(stage)?.dispose();

      instances.delete(stage);

      live.delete(stage);

      stage.removeAttribute('data-visible');

    },

  };

}

// -- State API ------------------------------------------------------------

/**

 * UI side of setState: 'default' re-applies the chart surface - config.option

 * replaces the option wholesale (notMerge), so a reset returns to exactly

 * the given surface; a bare setState('default') is a no-op on the DOM.

 * Unknown names throw.

 */

function triggerStateChange(el: HTMLElement, stateName: string, config: Option = {}): void {

  if (!chartStates.includes(stateName)) {

    throw new Error(`chart: unknown state "${stateName}" (supported: ${chartStates.join(', ')})`);

  }

  if (isPlain(config.option)) {

    const current = instances.get(el);

    if (current) current.setOption(config.option, true);

    else mount(el, config.option);

  }

}

/** Registry-level API; pass the mount explicitly. Unknown names throw. */

export const chartApi = {

  setState(el: HTMLElement, stateName: string, config: Option = {}) {

    triggerStateChange(el, stateName, config);

    // state lives on the ELEMENT, not module scope (AGENTS.md "State API")

    el.dataset.stateName = stateName;

    el._stateConfig = config;

  },

  getState(el: HTMLElement) {

    return {

      name: el.dataset.stateName || 'default',

      config: { ...el._stateConfig },

    };

  },

};

df$.chartApi = chartApi;

df$.chartStates = chartStates;

df$.chart = { mount, instance, theme: chartTheme, color: chartColor, deck: chartDeck };

df$.chartStory = chartStory;

function init(): void {

  document.querySelectorAll<HTMLElement>('.chart:not([data-init])').forEach((el) => {

    el.dataset.init = '';

    // bind-scope the api per instance: `$('#c').api.setState('default', …)`

    el.api = {

      setState: (stateName: string, config?: Option) => chartApi.setState(el, stateName, config),

      getState: () => chartApi.getState(el),

    };

    // declarative mount: data-chart JSON → echarts instance. Zero-size boxes

    // (display:none hosts, pre-layout SPA swaps) defer - the observer retries

    // once the box has real width+height; the instance guard makes it once-only.

    const boot = (): void => {

      if (instances.has(el)) return;

      const raw = el.getAttribute('data-chart');

      if (!raw) return;

      const box = el.getBoundingClientRect();

      if (box.width === 0 || box.height === 0) return;

      let option: Option;

      try {

        option = JSON.parse(raw) as Option;

      } catch (err) {

        throw new Error(`chart: invalid JSON in data-chart - ${err instanceof Error ? err.message : err}`);

      }

      mount(el, option);

    };

    new ResizeObserver(boot).observe(el);

    boot();

  });

}

init();

new MutationObserver(init).observe(document, { childList: true, subtree: true });