/**
 * Chart colour roles — all CSS custom properties so light/dark swap without re-render.
 * Categorical slots are assigned in FIXED order (dataviz rule: colour follows the entity, never its rank;
 * never cycle past 8 — fold to "Other" or facet).
 */
export const SERIES_MAX = 8;

export function seriesVar(index: number): string {
  const i = Math.min(Math.max(index, 0), SERIES_MAX - 1) + 1;
  return `var(--series-${i})`;
}

/** Sequential (choropleth) class fill, k ∈ 1..7 light→dark. */
export function seqVar(step: number): string {
  const i = Math.min(Math.max(step, 1), 7);
  return `var(--seq-${i})`;
}

export const CHART = {
  ink: 'var(--ink)',
  ink2: 'var(--ink-2)',
  ink3: 'var(--ink-3)',
  rule: 'var(--rule)',
  ruleStrong: 'var(--rule-strong)',
  surface: 'var(--surface)',
  accent: 'var(--accent)',
  accentSoft: 'var(--accent-soft)',
  up: 'var(--up)',
  down: 'var(--down)',
  nodata: 'var(--nodata)',
  forecast: 'var(--forecast)',
} as const;

/** Mark specs (dataviz marks-and-anatomy): thin marks, 2px lines, ≥8px end dots, 24px max bar thickness. */
export const MARK = {
  line: 2,
  dotR: 4,
  ringW: 2,
  barMax: 24,
  barRadius: 4,
  gap: 2,
  areaOpacity: 0.12,
} as const;