// ---------------------------------------------------------------------------
// viz / chartData.ts  (was customer-grid/chartData.ts — EXIT wave 2, W2-5/Y3:
// a MOVE, not a rewrite. The arithmetic below is byte-identical to what shipped
// in the grid; only the three import lines changed, because the engine now
// serves TWO callers — the customer grid's Dashboard mode and the Y1 page
// envelope the Sales page renders.)
//
// Wave-8 I19c (contract C2) — the Dashboard mode's ARITHMETIC, pure and
// React-free so verify_charts.py can run it under node.
//
// The contract's key sentence: charts "compute CLIENT-SIDE from the SAME
// pipeline rows the grid paints (filters + cohort scope apply by construction —
// that is the point)". So there is no fetching here and no second definition of
// what a row is: this module takes the rows the grid already has and buckets
// them. If the grid says 412 rows, every chart on the dashboard is describing
// those 412 rows.
//
// Honesty rules (rule 8b) live in the RETURN VALUE, not in the renderer:
//   - `omitted` counts buckets past the display cap, so the card can say "+N
//     more" instead of quietly drawing the top 12;
//   - `blanks` counts rows whose x value is empty — they become a real
//     "(blank)" bucket rather than vanishing from a total;
//   - `missingY` counts rows the aggregate could not use, so an average can
//     never silently be an average of a different denominator than the count
//     beside it.
// ---------------------------------------------------------------------------

import type { Field, Row } from "./types";
// ⚠ from `display`, NOT `cells`: cells.ts also exports the glide rating renderer, and
// importing it would drag the whole canvas library into a gate that runs under bare node.
//
// ⚠ These two still come FROM customer-grid, deliberately (Y3 amendment,
// 2026-07-30). `formatDisplay` is the ONE formatter charts and cells share —
// C2 §4, restated at `chartValueText` below: a revenue figure must not read one
// way in a row and another in the chart hovering over it, so a second copy here
// would be the bug, not the fix. The two family predicates are likewise a single
// definition; `viz/types.ts` pins the vocabulary in lock-step so a drift is a
// red build rather than a silently mis-typed axis.
import { formatDisplay } from "../customer-grid/display";
import {
  TS_BUCKETS,
  TS_MAX_LAST_N,
  isDateFamilyType,
  isGroupableField,
  isNumericFieldType,
} from "../customer-grid/types";

export const CHART_KINDS = ["bar", "line", "area", "donut", "kpi", "table"] as const;
export type ChartKind = (typeof CHART_KINDS)[number];

export const CHART_AGGS = ["sum", "avg", "count", "min", "max"] as const;
export type ChartAgg = (typeof CHART_AGGS)[number];

/** Wave-16 C-CHARTCAP — plain words for the aggregates, ONE copy. The card's auto-title and
 *  the table kind's column headers both read this, so "Sum of Revenue" cannot drift into
 *  "Total Revenue" between a chart and the table beside it. (Was DashboardView-local.) */
export const CHART_AGG_LABELS: Record<ChartAgg, string> = {
  sum: "Sum of",
  avg: "Average of",
  count: "Count of records",
  min: "Smallest",
  max: "Largest",
};

/** C2's per-chart spec. `id` is a client uuid; `y` omitted means count of rows. */
/**
 * Wave-9 I11 (contract C2) — chart customisation. The CLIENT mirror of
 * `aios_grid.CHART_PALETTES` / `CHART_FORMATS`.
 *
 * A palette names a colour JOB, never a colour. The browser must not be able to post a raw
 * hex: these four resolve to brand ramps client-side, so a tenant restyle cannot be defeated
 * by a literal somebody stored last year. STATUS colours are deliberately absent — they are
 * reserved signal, and reusing them as "series 4" is how a chart starts lying.
 */
export const CHART_PALETTES = ["brand", "categorical", "sequential", "diverging"] as const;
export type ChartPalette = (typeof CHART_PALETTES)[number];

export const CHART_FORMATS = ["auto", "number", "currency", "percent", "compact"] as const;
export type ChartFormat = (typeof CHART_FORMATS)[number];

export const MAX_AXIS_LABEL = 40;
/** The I10 drag. Width in GRID COLUMNS on a 12-column board, height in px. */
export const CHART_W_RANGE: readonly [number, number] = [1, 12];
export const CHART_H_RANGE: readonly [number, number] = [120, 800];

export interface ChartAxisSide {
  label?: string;
  format?: ChartFormat;
}

export interface ChartSpec {
  id: string;
  kind: ChartKind;
  x?: string;
  y?: string;
  agg: ChartAgg;
  title?: string;
  /** I11 — the field whose values become the SERIES. ⚠ Named `splitBy`, NOT `colorBy`:
   *  that name already means row colouring (`config.colorBy`) and map pin colour
   *  (`display.colorField`), and a third sense would be unreadable. HOST's ruling. */
  splitBy?: string;
  /** I11 — only meaningful WITH `splitBy` and only for bar/area. Dropped anywhere else
   *  rather than stored as a lie the renderer would have to re-decide. */
  stacked?: boolean;
  palette?: ChartPalette;
  /** ⛔ ONE y-scale, always. There is no second-axis key and there must never be: two
   *  y-scales on one frame can manufacture any correlation you like by rescaling. Ruled in
   *  C2 against the "Tableau versatility" brief — two charts, small multiples, or index to
   *  a common base. */
  axis?: { x?: ChartAxisSide; y?: ChartAxisSide };
  /** I10 — the drag. `{w}` in grid columns, `{h}` in px. Clamped at both ends. */
  size?: { w?: number; h?: number };
  /**
   * Wave-14 R3 (item 18) — this card is a TREND over time buckets, not a category chart.
   *
   * Present ⇒ the series comes from the time-series channel (one `date_trunc` query per
   * metric, the metric's own window slid across bucket ends) instead of from `chartData`'s
   * grouping of the view's rows. Absent ⇒ every path below behaves byte-identically to
   * before, which is the property that makes this safe to add to a shipped renderer.
   *
   * Typed as a plain `string` for the same reason `agg` is: the vocabulary is `TS_BUCKETS` in
   * `customer-grid/types.ts`, and that module is a deliberate LEAF — importing it here to
   * nominally type one key would invert the dependency the whole viz layer is arranged
   * around. The host validates it against the real vocabulary (C-ACC) and keeps it only when
   * `y` is measure-backed.
   */
  bucket?: string;
  /** R3 — how many buckets back. Meaningful only beside `bucket`; 1..120, host-clamped. */
  span?: { lastN?: number };
  /**
   * Wave-16 C-CHARTCAP (owner R3) — the YoY companion. On a PERIOD chart it draws a second
   * series: the same metric read `TS_YOY_BACK[bucket]` buckets earlier, aligned to the same
   * x (`timeSeriesData.buildTsCompare`'s law). On a `kpi` card it puts a delta line under the
   * number: the pooled metric at the latest month-end against the same month-end a year
   * earlier (`salesParity.kpiYoyFromSeries`).
   *
   * Kept ONLY where it can mean something — beside a `bucket`, or on a sum-of-metric KPI —
   * mirroring `aios_grid._clean_chart` exactly. The single value is deliberate: "prior_year"
   * is the one comparison pages_sales drew, and a second vocabulary entry should arrive with
   * its own law, not ride this key.
   */
  compare?: "prior_year";
}

/** C2: at most 12 charts per view. */
export const MAX_CHARTS = 12;
/** Buckets drawn per chart before the card states what it left out. */
export const MAX_BUCKETS = 12;

/**
 * Wave-14 R3 — the chart kinds a PERIOD may be drawn over.
 *
 * A donut of months is a part-of-whole claim about time that nobody makes, and a
 * single-number card has no axis to put periods on. Narrowing is a design call, so it is
 * stated here rather than left implicit in a JSX condition.
 */
export const PERIOD_KINDS: readonly ChartKind[] = ["bar", "line", "area"];

/** A metric field — the only kind with a time dimension of its own (C-TS v1 eligibility). */
export function isMetricKey(key: string | undefined): boolean {
  return !!key && key.startsWith("measure_");
}

/**
 * Does this spec ask for a TREND over time buckets?
 *
 * ⚠ THIS PREDICATE DECIDES WHICH CAP APPLIES, which is why it lives here beside the cap and
 * not in the component. `true` routes the card's series through the time-series channel, where
 * `MAX_BUCKETS` must NEVER be applied: dropping the 13th of 24 months leaves an axis that
 * still reads like a complete run while two years of history quietly become one. `false` is
 * the category path, unchanged, where the same cap is correct and the card discloses it.
 *
 * The bucket vocabulary is checked by the caller and by the host (C-ACC keeps `bucket` only
 * when `y` is measure-backed); what is checked HERE is everything this module can see, so a
 * spec that is half-a-trend — a bucket on a donut, a bucket on a plain number column — takes
 * the category path rather than a broken one.
 */
export function isPeriodChart(spec: ChartSpec): boolean {
  return !!spec.bucket && isMetricKey(spec.y) && PERIOD_KINDS.includes(spec.kind);
}

export interface Bucket {
  key: string;
  label: string;
  value: number;
  /** Rows in this bucket — the denominator behind `value`, always available so
   *  a card can show "n = ..." rather than an unexplained number. */
  n: number;
}

export interface ChartData {
  buckets: Bucket[];
  /** Buckets not drawn because of MAX_BUCKETS. Never silently dropped. */
  omitted: number;
  /** Value of the omitted buckets, so "+N more" can carry its weight. */
  omittedValue: number;
  /** Rows whose x value was empty (they form the "(blank)" bucket). */
  blanks: number;
  /** Rows the aggregate could not use (non-numeric/empty y under sum/avg/...). */
  missingY: number;
  /** Total rows considered — always the grid's row count for this view. */
  rows: number;
  /** Aggregate buckets across the FULL domain, before the display cap. */
  negativeBuckets?: number;
  negativeValue?: number;
  zeroBuckets?: number;
  /** Populated when the spec cannot be drawn; the card shows this verbatim. */
  problem?: string;
  /**
   * wave17 GRID — item 3 / owner R6. **Waiting is not a problem.**
   *
   * The period-series chart used to report its wait by writing "Loading the periods…" INTO
   * `problem`, which meant a card that was merely early and a card that is refusing were the
   * same state to every reader. R6 asks for a spinner and no words, and you cannot render a
   * spinner from a string field — so the two states are now distinct, and the card checks this
   * FIRST. A `problem` set beside it still says what went wrong once the wait ends.
   */
  pending?: boolean;
}

/**
 * The renderer-neutral data model consumed by Chart View.
 *
 * This is intentionally not a Vega-Lite type. Saved views persist `ChartSpec`,
 * the arithmetic produces this small table, and the current renderer translates
 * it at the final boundary. Replacing Vega later therefore changes one adapter
 * rather than every saved view and every aggregation rule.
 */
export interface ChartPoint extends Bucket {
  seriesKey: string;
  seriesLabel: string;
}

export interface ChartModel extends Omit<ChartData, "buckets"> {
  points: ChartPoint[];
  xOrder: string[];
  seriesOrder: string[];
  omittedSeries: number;
  omittedSeriesValue: number;
  /** Donut-only: zero/negative groups cannot be represented as angular share. */
  nonPositive: number;
  nonPositiveValue: number;
}

/** A legend with dozens of entries is a data dump, not a chart. */
export const MAX_CHART_SERIES = 12;

/** A date value bucketed to its month, the only date bucket wave 8 offers. */
function monthOf(v: unknown): string | null {
  const s = String(v ?? "");
  return /^\d{4}-\d{2}/.test(s) ? s.slice(0, 7) : null;
}

function monthLabel(ym: string): string {
  const y = Number(ym.slice(0, 4));
  const m = Number(ym.slice(5, 7));
  if (!Number.isFinite(y) || !Number.isFinite(m)) return ym;
  return new Date(Date.UTC(y, m - 1, 1)).toLocaleDateString(undefined, {
    month: "short",
    year: "numeric",
    timeZone: "UTC",
  });
}

function numOf(v: unknown): number | null {
  if (v == null || v === "") return null;
  const n = typeof v === "number" ? v : Number(v);
  return Number.isFinite(n) ? n : null;
}

/** Reduce a bucket's collected values to the aggregate. */
function reduce(agg: ChartAgg, vals: number[], n: number): number {
  if (agg === "count") return n;
  if (vals.length === 0) return 0;
  switch (agg) {
    case "sum":
      return vals.reduce((a, b) => a + b, 0);
    case "avg":
      return vals.reduce((a, b) => a + b, 0) / vals.length;
    case "min":
      return Math.min(...vals);
    case "max":
      return Math.max(...vals);
  }
}

/** The numeric coercion the aggregates use — exported for item 4's calendar summaries so the
 *  two surfaces agree on what counts as a number. */
export { numOf as asChartNumber };

/**
 * Owner item 4 (C-DISP) — the aggregate, for callers OUTSIDE a chart card.
 *
 * ⚠ Deliberately a different return type from the private `reduce` above, and the difference
 * is honesty, not style. `reduce` answers `0` when a bucket collected no usable values,
 * because a bar chart needs a height and the card states its `missingY` separately. A calendar
 * day cell has no such companion disclosure: a lone "0" in a Wednesday IS the whole claim, and
 * "the average of nothing is zero" is false. So this returns **null** for an empty
 * sum/avg/min/max bucket, which the caller renders as "—".
 *
 * `count` is exempt — the count of no rows really is 0, and that is a fact rather than a
 * substitute for one.
 *
 * `reduce` itself is untouched: `verify_charts.py` holds 12 negative controls against its
 * behaviour, and changing the shared function to suit a second caller is how a gated rule
 * quietly stops being the rule.
 */
export function aggregateOrNull(agg: ChartAgg, vals: number[], n: number): number | null {
  if (agg === "count") return n;
  if (vals.length === 0) return null;
  return reduce(agg, vals, n);
}

/**
 * Build one chart's data from the view's rows.
 *
 * `fieldByKey` resolves the spec's refs; a ref naming a field that no longer
 * exists yields a `problem` rather than an empty chart, because a blank card is
 * indistinguishable from "no data matched" and sends people looking in the wrong
 * place.
 */
export interface ChartDataOpts {
  /**
   * Raise (or effectively remove) the display cap.
   *
   * ⚠ Wave-15 C-CHARTCAP. `MAX_BUCKETS` is a CHART's cap — twelve bars is where an axis stops
   * being readable — and the card discloses what it dropped. A group-by TABLE has no axis to
   * run out of: it is a list, and its cap is its own row limit, which reports the total it
   * truncated from. Passing the chart's cap to a table would silently keep 12 salespeople out
   * of 40 and then let the table's own "showing 25 of 25" agree with it.
   * Absent = `MAX_BUCKETS`, i.e. every existing caller is byte-identical.
   */
  maxBuckets?: number;
}

export function chartData(
  spec: ChartSpec,
  rows: Row[],
  fieldByKey: Map<string, Field>,
  opts?: ChartDataOpts
): ChartData {
  const base: ChartData = {
    buckets: [],
    omitted: 0,
    omittedValue: 0,
    blanks: 0,
    missingY: 0,
    rows: rows.length,
  };
  const yField = spec.y ? fieldByKey.get(spec.y) : undefined;
  if (spec.y && !yField)
    return { ...base, problem: "The field this chart measured no longer exists." };
  if (yField && spec.agg !== "count" && !isNumericFieldType(yField.type))
    return {
      ...base,
      problem: `${yField.label} is not a number, so it cannot be ${spec.agg === "avg" ? "averaged" : spec.agg + "med"}.`,
    };
  if (spec.agg !== "count" && !yField)
    return { ...base, problem: "Choose a number field to measure, or switch to Count." };

  // --- KPI: one number over every row, no bucketing.
  if (spec.kind === "kpi") {
    const vals: number[] = [];
    let missingY = 0;
    for (const r of rows) {
      if (!yField) continue;
      const n = numOf(r[yField.key]);
      if (n == null) missingY += 1;
      else vals.push(n);
    }
    return {
      ...base,
      missingY,
      buckets: [
        { key: "", label: "", value: reduce(spec.agg, vals, rows.length), n: rows.length },
      ],
    };
  }

  const xField = spec.x ? fieldByKey.get(spec.x) : undefined;
  if (!spec.x) return { ...base, problem: "Choose a field to group by." };
  if (!xField)
    return { ...base, problem: "The field this chart grouped by no longer exists." };

  const byMonth = isDateFamilyType(xField.type);
  const groups = new Map<string, { label: string; vals: number[]; n: number }>();
  let blanks = 0;
  let missingY = 0;

  for (const r of rows) {
    const raw = r[xField.key];
    let key: string;
    let label: string;
    if (byMonth) {
      const m = monthOf(raw);
      if (m == null) {
        blanks += 1;
        key = "";
        label = "(no date)";
      } else {
        key = m;
        label = monthLabel(m);
      }
    } else {
      const s = String(raw ?? "").trim();
      if (s === "") {
        blanks += 1;
        key = "";
        label = "(blank)";
      } else {
        key = s;
        label = s;
      }
    }
    let g = groups.get(key);
    if (!g) {
      g = { label, vals: [], n: 0 };
      groups.set(key, g);
    }
    g.n += 1;
    if (yField) {
      const n = numOf(r[yField.key]);
      if (n == null) missingY += 1;
      else g.vals.push(n);
    }
  }

  let buckets: Bucket[] = [...groups.entries()].map(([key, g]) => ({
    key,
    label: g.label,
    value: reduce(spec.agg, g.vals, g.n),
    n: g.n,
  }));

  // Time reads chronologically; categories read biggest-first. Sorting a date
  // axis by value would turn a trend line into a sawtooth that means nothing.
  if (byMonth) {
    buckets.sort((a, b) => (a.key === "" ? 1 : b.key === "" ? -1 : a.key.localeCompare(b.key)));
  } else {
    buckets.sort((a, b) => b.value - a.value || a.label.localeCompare(b.label));
  }

  // Signed-domain facts are computed BEFORE the display cap. A negative group
  // that sorts below the top 12 must still block a donut; otherwise the cap
  // would turn invalid source data into a plausible positive composition.
  const negativeBuckets = buckets.filter((bucket) => bucket.value < 0);
  const zeroBuckets = buckets.filter((bucket) => bucket.value === 0).length;
  const negativeValue = negativeBuckets.reduce((sum, bucket) => sum + bucket.value, 0);

  let omitted = 0;
  let omittedValue = 0;
  const cap = opts?.maxBuckets ?? MAX_BUCKETS;
  if (buckets.length > cap) {
    const kept = buckets.slice(0, cap);
    const rest = buckets.slice(cap);
    omitted = rest.length;
    omittedValue = rest.reduce((a, b) => a + b.value, 0);
    buckets = kept;
  }

  return {
    ...base,
    buckets,
    omitted,
    omittedValue,
    blanks,
    missingY,
    negativeBuckets: negativeBuckets.length,
    negativeValue,
    zeroBuckets,
  };
}

/**
 * Expand the flat aggregation into the renderer-neutral table used at the
 * chart boundary. `splitBy` becomes a real series dimension here; saved view
 * state remains independent of Vega-Lite (or whichever renderer replaces it).
 */
export function chartModel(
  spec: ChartSpec,
  rows: Row[],
  fieldByKey: Map<string, Field>
): ChartModel {
  const base = chartData({ ...spec, splitBy: undefined }, rows, fieldByKey);
  const empty: ChartModel = {
    points: [],
    xOrder: [],
    seriesOrder: [],
    omitted: base.omitted,
    omittedValue: base.omittedValue,
    omittedSeries: 0,
    omittedSeriesValue: 0,
    nonPositive: 0,
    nonPositiveValue: 0,
    blanks: base.blanks,
    missingY: base.missingY,
    rows: base.rows,
    problem: base.problem,
  };
  if (base.problem) return empty;

  if (spec.kind === "donut") {
    // Arc length encodes a share of a positive whole. Vega (like most chart
    // engines) can accept signed theta values syntactically, but the resulting
    // geometry has no truthful business meaning. Zero groups preserve the old
    // positive-only omission (with disclosure); one negative group blocks the
    // entire composition and directs the user to a signed chart.
    const positive = base.buckets.filter((bucket) => bucket.value > 0);
    const negativeCount =
      base.negativeBuckets ?? base.buckets.filter((bucket) => bucket.value < 0).length;
    const zeroCount =
      base.zeroBuckets ?? base.buckets.filter((bucket) => bucket.value === 0).length;
    const nonPositive = negativeCount + zeroCount;
    const nonPositiveValue =
      base.negativeValue ??
      base.buckets
        .filter((bucket) => bucket.value < 0)
        .reduce((sum, bucket) => sum + bucket.value, 0);
    if (negativeCount > 0) {
      return {
        ...empty,
        nonPositive,
        nonPositiveValue,
        problem:
          "A donut cannot represent negative values without misrepresenting the whole. Use a bar or line chart for signed values.",
      };
    }
    if (base.buckets.length > 0 && positive.length === 0) {
      return {
        ...empty,
        nonPositive,
        nonPositiveValue,
        problem:
          "A donut needs at least one positive value. Zero-value groups cannot be drawn as slices.",
      };
    }
    return {
      ...empty,
      points: positive.map((bucket) => ({
        ...bucket,
        seriesKey: "",
        seriesLabel: "",
      })),
      xOrder: positive.map((bucket) => bucket.key),
      nonPositive,
      nonPositiveValue,
    };
  }

  if (!spec.splitBy || spec.kind === "kpi") {
    return {
      ...empty,
      points: base.buckets.map((bucket) => ({
        ...bucket,
        seriesKey: "",
        seriesLabel: "",
      })),
      xOrder: base.buckets.map((bucket) => bucket.key),
    };
  }

  const splitField = fieldByKey.get(spec.splitBy);
  const xField = spec.x ? fieldByKey.get(spec.x) : undefined;
  if (!splitField)
    return { ...empty, problem: "The field this chart split into series no longer exists." };
  if (!xField)
    return { ...empty, problem: "The field this chart grouped by no longer exists." };

  const xKey = (row: Row): string => {
    if (isDateFamilyType(xField.type)) return monthOf(row[xField.key]) ?? "";
    return String(row[xField.key] ?? "").trim();
  };
  const seriesKey = (row: Row): string => String(row[splitField.key] ?? "").trim();
  const xAllowed = new Set(base.buckets.map((bucket) => bucket.key));
  const bySeries = new Map<string, Row[]>();
  for (const row of rows) {
    if (!xAllowed.has(xKey(row))) continue;
    const key = seriesKey(row);
    const group = bySeries.get(key);
    if (group) group.push(row);
    else bySeries.set(key, [row]);
  }

  const computed = [...bySeries.entries()].map(([key, seriesRows]) => {
    const data = chartData(
      { ...spec, splitBy: undefined },
      seriesRows,
      fieldByKey
    );
    return {
      key,
      label: key || "(blank)",
      data,
      weight: data.buckets.reduce((sum, bucket) => sum + Math.abs(bucket.value), 0),
    };
  });
  computed.sort((a, b) => b.weight - a.weight || a.label.localeCompare(b.label));
  const kept = computed.slice(0, MAX_CHART_SERIES);
  const omittedSeries = Math.max(0, computed.length - kept.length);
  const omittedSeriesValue = computed
    .slice(MAX_CHART_SERIES)
    .reduce((sum, series) => sum + series.weight, 0);
  const xOrder = base.buckets.map((bucket) => bucket.key);
  const labelByX = new Map(base.buckets.map((bucket) => [bucket.key, bucket.label]));
  const points: ChartPoint[] = [];
  for (const series of kept) {
    const byX = new Map(series.data.buckets.map((bucket) => [bucket.key, bucket]));
    for (const key of xOrder) {
      const bucket = byX.get(key);
      points.push({
        key,
        label: labelByX.get(key) ?? key,
        value: bucket?.value ?? 0,
        n: bucket?.n ?? 0,
        seriesKey: series.key,
        seriesLabel: series.label,
      });
    }
  }
  return {
    ...empty,
    points,
    xOrder,
    seriesOrder: kept.map((series) => series.key),
    omittedSeries,
    omittedSeriesValue,
  };
}

/** The default spec for a freshly added chart — count of rows by the first
 *  groupable field, which draws something real immediately rather than an empty
 *  card the user has to configure before seeing anything. */
export function defaultChart(id: string, fields: Field[]): ChartSpec {
  const x = fields.find((f) => f.type === "status" || f.type === "select")?.key;
  return { id, kind: "bar", x, agg: "count", size: { w: 6, h: 280 } };
}

/**
 * Fields offerable as a chart's x (group-by).
 *
 * ⭐ ONE evaluator, not two. `types.isGroupableField` is the app's answer to
 * "can this column be a group key" — `Toolbar.tsx:637` has said so in those
 * words since wave 20 — and this function used to carry a SECOND, hand-kept
 * allow-list that disagreed with it about `multiselect` and `checkbox`. Nobody
 * ever decided that disagreement; two lists drifted, and the picker quietly
 * offered a different vocabulary from the grid's own group-by
 * ([[one-evaluator-per-question]]). The categorical answer now comes from
 * there and from nowhere else.
 *
 * TWO declared deltas, each with a stated cause. **A declared delta is the whole
 * difference from what stood here before**, which was an opaque parallel list
 * nobody could tell from an oversight — and the delegation means a type added
 * to `isGroupableField` tomorrow is offered here automatically instead of
 * silently missing.
 *
 * **+ the date family.** A chart buckets a date into PERIODS (`monthOf`, in
 * `chartData` below), so the one-bucket-per-day objection that keeps raw dates
 * out of the GRID's grouping simply does not apply to a chart.
 *
 * **− set-like and checkbox columns.** The grid keys these TYPE-AWARE and this
 * module does not. `useVisibleRows.ts:563-575 groupRows` expands a multi cell
 * into one bucket PER MEMBER — in its own words, *"a customer in A and in B is
 * in both groups — not in a combined 'A, B' bucket that is nobody's list"* —
 * and maps a blank checkbox to its UNCHECKED label, blank being the storage
 * contract's false rather than a missing value. `chartData` keys every non-date
 * bucket as `String(cell).trim()`, so offering them here would draw precisely
 * the combined bucket the grid refuses to draw, and label the unchecked half
 * "(blank)". ⛔ **Offering a type the renderer keys WRONG is worse than not
 * offering it at all** — a chart is the surface where a wrong bucket looks most
 * convincing. Closing this is a change to the KEYING, not to this list, and the
 * set case is not a relabel: one row landing in several buckets changes what a
 * sum means.
 *
 * ⚠ `lockedKey` is `""` deliberately. `ChartCard` has no identity column in
 * scope, and every text field INCLUDING the identity one was already offered
 * here before this change — so `""` preserves today's offer exactly. Narrowing
 * it is a product decision, not a refactor, and it does not belong in a defect
 * fix.
 */
export function chartKeyable(f: Field): boolean {
  return !f.multi && f.type !== "multiselect" && f.type !== "checkbox";
}

export function groupableForChart(fields: Field[]): Field[] {
  return fields.filter((f) => (isGroupableField(f, "") || isDateFamilyType(f.type)) && chartKeyable(f));
}

/** Fields offerable as a chart's y (the measure). */
export function measurableForChart(fields: Field[]): Field[] {
  return fields.filter((f) => isNumericFieldType(f.type));
}

/** One entry of a chart field picker's option list. */
export interface FieldOption {
  key: string;
  label: string;
}

/**
 * The options a chart's field picker must render for a STORED value.
 *
 * ⛔ THE STORED VALUE IS ALWAYS AN OPTION. A `<select>` whose `value` matches no
 * `<option>` does not complain — it deselects, so the control reads "Choose a
 * field…" while the chart is still perfectly well grouped by that column, and
 * the next edit to any other control writes back whatever the user can now see.
 * The grouping is lost without anybody choosing to lose it. This repo has paid
 * for that twice ([[cg-condition-builder-items]]);
 * `automation/CondBuilder.tsx:288-290` is the hardened precedent, and the
 * synthesised entry leads the list there too.
 *
 * ⭐ It lives here, next to the predicate that decides the offer, rather than
 * inline in the .tsx — the same reason `clientToUser` moved into
 * `mapProjection.ts` this wave: a rule written inside a component is a rule the
 * gate's compiled-artifact mutations cannot reach, and this one shipped broken
 * behind a green gate for exactly that reason.
 *
 * Two ways a stored key falls out of the offered list, and they deserve
 * different words:
 *  - **the column exists but is not offerable here** — a `user` column, or a
 *    text column somebody retyped. It carries its OWN LABEL: the chart really
 *    is grouped by it, and saying anything else would be the lie.
 *  - **the column is gone from this database** — it is named and marked, in the
 *    same words the card's own `problem` sentence uses.
 */
export function fieldOptions(
  offered: Field[],
  fields: Field[],
  stored: string | undefined
): FieldOption[] {
  const list = offered.map((f) => ({ key: f.key, label: f.label }));
  if (!stored || list.some((o) => o.key === stored)) return list;
  const known = fields.find((f) => f.key === stored);
  return [{ key: stored, label: known ? known.label : `${stored} (not in this database)` }, ...list];
}

/**
 * Wave-9 I10 (contract C2 §4) — **ONE number formatter for charts, not two.**
 *
 * C2 is explicit: hover/tooltip values use the same formatter as the CELLS (`formatDisplay`),
 * so a revenue figure never reads one way in a row and another way in a chart hovering over
 * it. `auto` (the default) therefore delegates to the field's own formatting, which already
 * knows that field's conventions.
 *
 * ⚠ An EXPLICIT format is presentation only and **never rescales the number.** In particular
 * `percent` appends the sign without multiplying by 100: semantic percentages here are 0–1
 * while transform `*_pct` values are 0–100 ([[analyst-chart-library]]), so a blanket ×100
 * would silently be wrong for half the fields it is applied to. Choosing a format changes how
 * a value is WRITTEN, never what it is.
 */
export function chartValueText(
  v: number,
  yField: Field | undefined,
  format: ChartFormat | undefined,
  fallback: (n: number) => string
): string {
  if (!format || format === "auto") {
    return yField ? formatDisplay(yField, v) : fallback(v);
  }
  if (format === "compact") return fallback(v);
  if (format === "number") return v.toLocaleString(undefined, { maximumFractionDigits: 2 });
  if (format === "percent")
    return `${v.toLocaleString(undefined, { maximumFractionDigits: 2 })}%`;
  // currency
  return v.toLocaleString(undefined, {
    style: "currency",
    currency: "USD",
    maximumFractionDigits: 0,
  });
}

function clampRange(n: number, [lo, hi]: readonly [number, number]): number {
  return Math.max(lo, Math.min(hi, n));
}

/** C2's `charts` array, normalized. Unknown kinds/aggs and dead shapes are
 *  dropped rather than rendered as a broken card; the cap is enforced here so
 *  both the writer and the reader agree on it. */
export function cleanCharts(raw: unknown): ChartSpec[] | undefined {
  if (!Array.isArray(raw)) return undefined;
  const out: ChartSpec[] = [];
  for (const item of raw) {
    if (!item || typeof item !== "object") continue;
    const d = item as Record<string, unknown>;
    const id = typeof d.id === "string" && d.id ? d.id : "";
    const kind = d.kind as ChartKind;
    const agg = d.agg as ChartAgg;
    if (!id || !CHART_KINDS.includes(kind) || !CHART_AGGS.includes(agg)) continue;
    const spec: ChartSpec = { id, kind, agg };
    if (typeof d.x === "string" && d.x) spec.x = d.x;
    if (typeof d.y === "string" && d.y) spec.y = d.y;
    if (typeof d.title === "string" && d.title) spec.title = d.title.slice(0, 60);
    // ── I11 (C2) customisation. Mirrors `aios_grid._clean_chart` key for key and RULE for
    // rule: a mirror that is merely "close" is how the picker ends up offering something the
    // host silently drops on save.
    // `splitBy` may not be the category axis itself — a series per category is one bar each
    // and no information.
    if (typeof d.splitBy === "string" && d.splitBy && d.splitBy !== spec.x)
      spec.splitBy = d.splitBy;
    if (spec.splitBy && (kind === "bar" || kind === "area") && d.stacked === true)
      spec.stacked = true;
    if (CHART_PALETTES.includes(d.palette as ChartPalette))
      spec.palette = d.palette as ChartPalette;
    if (d.axis && typeof d.axis === "object" && !Array.isArray(d.axis)) {
      const rawAxis = d.axis as Record<string, unknown>;
      const axis: { x?: ChartAxisSide; y?: ChartAxisSide } = {};
      for (const side of ["x", "y"] as const) {
        const s = rawAxis[side];
        if (!s || typeof s !== "object" || Array.isArray(s)) continue;
        const sr = s as Record<string, unknown>;
        const one: ChartAxisSide = {};
        if (typeof sr.label === "string" && sr.label.trim())
          one.label = sr.label.trim().slice(0, MAX_AXIS_LABEL);
        if (CHART_FORMATS.includes(sr.format as ChartFormat))
          one.format = sr.format as ChartFormat;
        if (one.label !== undefined || one.format !== undefined) axis[side] = one;
      }
      if (axis.x || axis.y) spec.axis = axis;
    }
    if (d.size && typeof d.size === "object" && !Array.isArray(d.size)) {
      const sz = d.size as Record<string, unknown>;
      const one: { w?: number; h?: number } = {};
      if (typeof sz.w === "number" && Number.isFinite(sz.w))
        one.w = clampRange(Math.round(sz.w), CHART_W_RANGE);
      if (typeof sz.h === "number" && Number.isFinite(sz.h))
        one.h = clampRange(Math.round(sz.h), CHART_H_RANGE);
      if (one.w !== undefined || one.h !== undefined) spec.size = one;
    }
    // ── Wave-14 R3 (item 18): the PERIOD. ⚠ This branch is not optional decoration — THIS
    // FUNCTION IS A REBUILDER. It constructs `{id, kind, agg}` and copies named keys, so a
    // key it does not name is DROPPED on every read (`CustomerGrid.tsx:2566` runs it over the
    // stored display). Without these lines the host would store the period faithfully and the
    // client would throw it away one layer later — the control would simply look like it does
    // not save, with nothing anywhere going red. Same law GRID booked from the other side of
    // `cleanDisplay`: when a validator narrows a key inside a collection, every cleaner in the
    // chain has to know the key exists.
    //
    // The rules mirror `aios_grid._clean_chart` (C-ACC) exactly: a period only means something
    // on a metric, and a span only means something beside a period.
    if (
      typeof d.bucket === "string" &&
      (TS_BUCKETS as readonly string[]).includes(d.bucket) &&
      isMetricKey(spec.y)
    ) {
      spec.bucket = d.bucket;
      if (d.span && typeof d.span === "object" && !Array.isArray(d.span)) {
        const n = (d.span as Record<string, unknown>).lastN;
        if (typeof n === "number" && Number.isFinite(n)) {
          const lastN = Math.round(n);
          if (lastN >= 1 && lastN <= TS_MAX_LAST_N) spec.span = { lastN };
        }
      }
    }
    // Wave-16 C-CHARTCAP — the YoY companion survives the rebuild ONLY where it can mean
    // something: beside a kept bucket (the compare series) or on a sum-of-metric KPI (the
    // delta line). This function rebuilds `{id, kind, agg}` and copies NAMED keys, so
    // omitting this branch would make the toggle look like it does not save — the exact
    // failure the period branch above documents. Mirrors `aios_grid._clean_chart`.
    if (
      d.compare === "prior_year" &&
      (spec.bucket || (kind === "kpi" && spec.agg === "sum" && isMetricKey(spec.y)))
    )
      spec.compare = "prior_year";
    out.push(spec);
    if (out.length >= MAX_CHARTS) break;
  }
  return out.length ? out : undefined;
}