SpreadMatrix

import { cn } from "cn"
import { memo, useMemo, useRef } from "react"
import { useFlash } from "@/hooks/use-flash"
import { useRow } from "@/hooks/use-row-store"
import { NULL_TOKEN, NUMERIC_CLASS, formatBps, formatTicks, ticksBetween, type InstrumentConvention, type Nullable } from "@/lib/format"
import type { RowId, RowStore } from "@/lib/row-store"

// A spread matrix: instruments down the side and across the top, each cell the spread of the row over the
// column, in ticks of price or basis points of yield, printed with its sign and flashing by the direction it
// moved. Every row reads its own quote and every cell the column's, so a quote that moves wakes the cells it
// is part of and nothing else. Given a list of structures (curves and butterflies as weighted legs) the matrix
// lists those as rows instead of the full grid. It reads quotes and prints spreads; it stages and sends nothing.

/** What a spread is measured in: ticks of price, or basis points of yield. */
export type SpreadBasis = "ticks" | "bps"

/** One axis entry of the matrix. */
export interface SpreadInstrument {
  /** The quote's row id in the store. */
  id: RowId
  /** The header text. */
  label: string
  /** The tick a spread in ticks is counted in when this instrument is the row. */
  convention: InstrumentConvention
}

/**
 * A quote as the default reader expects it: `price` for a spread in ticks, `yield` in percent for one in basis
 * points. Pass `value` to read other fields.
 */
export interface SpreadQuote {
  price?: number | null
  yield?: number | null
}

/** A curve or a butterfly: two or three legs, each an instrument's id, with a weight per leg. */
export interface SpreadStructure {
  id: string
  label: string
  legs: readonly [RowId, RowId] | readonly [RowId, RowId, RowId]
  /** One weight per leg. Default `[-1, 1]` for two legs (the second less the first) and `[-1, 2, -1]` for three (the belly against the wings). */
  weights?: readonly number[]
  /** The tick a spread in ticks is counted in. Default: the first leg's instrument. */
  tick?: number
}

export interface SpreadMatrixLabels {
  /** The corner header of the matrix, followed by the unit. */
  instrument: string
  /** Headers of the structures list. */
  structure: string
  legs: string
  spread: string
  /** The unit words. */
  ticks: string
  bps: string
  /** Read to a screen reader as the table's caption: which side of a cell is which. */
  rule: string
}

export const DEFAULT_SPREAD_MATRIX_LABELS: SpreadMatrixLabels = {
  instrument: "Instrument",
  structure: "Structure",
  legs: "Legs",
  spread: "Spread",
  ticks: "ticks",
  bps: "bp",
  rule: "Each cell is the row less the column.",
}

export interface SpreadMatrixProps<T extends object = SpreadQuote> {
  /** Quotes keyed by instrument id. */
  store: RowStore<T>
  /** The rows, and the columns unless `columns` is given, in this order. */
  instruments: readonly SpreadInstrument[]
  /** A different set across the top, for a matrix of one set against another. */
  columns?: readonly SpreadInstrument[]
  /** Ticks of price or basis points of yield. Default `ticks`. */
  basis?: SpreadBasis
  /** Curves and butterflies. When given, the matrix lists these as rows instead of the full grid. */
  structures?: readonly SpreadStructure[]
  /** Read a quote's value in the basis. Default: `price` for ticks, `yield` for basis points. Keep it stable between renders. */
  value?: (quote: T, basis: SpreadBasis) => Nullable
  /** Print a spread. `formatSpread` by default. Keep it stable between renders. */
  format?: (value: number, basis: SpreadBasis) => string
  /** Accessible name of the table. */
  label: string
  labels?: Partial<SpreadMatrixLabels>
  /** Cell flash duration in ms. Default 900. */
  flashWindowMs?: number
  className?: string
}

const FILL_CLASSES = "data-[direction=up]:bg-up-soft data-[direction=down]:bg-down-soft data-[direction=flat]:bg-flat-soft"
const CELL = "h-7 px-2 text-right whitespace-nowrap"
const HEAD = "h-7 px-2 font-normal text-muted-foreground whitespace-nowrap"

function isNumber(v: Nullable): v is number {
  return typeof v === "number" && Number.isFinite(v)
}

/** The default weights of a structure: the second leg less the first, or the belly against the wings. Empty for any other count. */
export function defaultWeights(legs: number): readonly number[] {
  return legs === 2 ? [-1, 1] : legs === 3 ? [-1, 2, -1] : []
}

/** A difference of values in the basis: ticks of `tick`, to the nearest eighth, or basis points from yields in percent, to a thousandth. */
function toBasis(diff: number, basis: SpreadBasis, tick: number): number | null {
  if (basis === "ticks") {
    const ticks = ticksBetween(diff, 0, tick)
    return Number.isNaN(ticks) ? null : ticks
  }
  return Math.round(diff * 100 * 1000) / 1000
}

/** The spread of `a` over `b`: `a − b` in ticks of `tick` or in basis points. Null when a side is missing. */
export function spreadBetween(a: Nullable, b: Nullable, basis: SpreadBasis, tick: number): number | null {
  if (!isNumber(a) || !isNumber(b)) return null
  return toBasis(a - b, basis, tick)
}

/** A structure's spread: each leg's value times its weight, summed, in the basis. Null when a leg is missing or the weights do not match the legs. */
export function structureSpread(values: readonly Nullable[], weights: readonly number[] | undefined, basis: SpreadBasis, tick: number): number | null {
  const w = weights ?? defaultWeights(values.length)
  if (w.length !== values.length || values.length === 0) return null
  let sum = 0
  for (let i = 0; i < values.length; i++) {
    const v = values[i]
    if (!isNumber(v)) return null
    sum += w[i]! * v
  }
  return toBasis(sum, basis, tick)
}

/** A spread with its sign: `+1.5`, `−0.5`, `0` in ticks; `+12.3`, `−0.8` in basis points. The unit is in the header, not the cell. */
export function formatSpread(value: Nullable, basis: SpreadBasis): string {
  return basis === "ticks" ? formatTicks(value) : formatBps(value, { signed: true, unit: "" })
}

/** The default reader: `price` for a spread in ticks, `yield` for one in basis points. */
function defaultValue(quote: object, basis: SpreadBasis): Nullable {
  if (basis === "bps") return "yield" in quote && typeof quote.yield === "number" ? quote.yield : null
  return "price" in quote && typeof quote.price === "number" ? quote.price : null
}

interface CellProps<T extends object> {
  store: RowStore<T>
  rowId: RowId
  columnId: RowId
  /** The row's value in the basis, or null while its quote is missing. */
  rowValue: number | null
  tick: number
  basis: SpreadBasis
  read: (quote: T, basis: SpreadBasis) => Nullable
  format: (value: number, basis: SpreadBasis) => string
  windowMs: number
}

function MatrixCellInner<T extends object>(p: CellProps<T>) {
  const quote = useRow(p.store, p.columnId)
  const diagonal = p.rowId === p.columnId
  const spread = diagonal ? null : spreadBetween(p.rowValue, quote === undefined ? null : p.read(quote, p.basis), p.basis, p.tick)
  const ref = useRef<HTMLTableCellElement>(null)
  // One flash per move: the spread between these two instruments changed.
  useFlash(ref, spread, { windowMs: p.windowMs, variant: "fill", disabled: diagonal })
  return (
    <td ref={ref} data-row={p.rowId} data-column={p.columnId} data-diagonal={diagonal ? "" : undefined} data-numeric="" className={cn(CELL, NUMERIC_CLASS, FILL_CLASSES, diagonal && "bg-muted/40")}>
      {diagonal ? "" : spread === null ? NULL_TOKEN : p.format(spread, p.basis)}
    </td>
  )
}
const MatrixCell = memo(MatrixCellInner) as typeof MatrixCellInner

interface RowProps<T extends object> {
  store: RowStore<T>
  instrument: SpreadInstrument
  columns: readonly SpreadInstrument[]
  basis: SpreadBasis
  read: (quote: T, basis: SpreadBasis) => Nullable
  format: (value: number, basis: SpreadBasis) => string
  windowMs: number
}

function MatrixRowInner<T extends object>(p: RowProps<T>) {
  const quote = useRow(p.store, p.instrument.id)
  const raw = quote === undefined ? null : p.read(quote, p.basis)
  const rowValue = isNumber(raw) ? raw : null
  return (
    <tr data-row={p.instrument.id} className="border-t border-border/60">
      <th scope="row" className={cn(HEAD, "text-left text-foreground")}>
        {p.instrument.label}
      </th>
      {p.columns.map((column) => (
        <MatrixCell key={column.id} store={p.store} rowId={p.instrument.id} columnId={column.id} rowValue={rowValue} tick={p.instrument.convention.tick} basis={p.basis} read={p.read} format={p.format} windowMs={p.windowMs} />
      ))}
    </tr>
  )
}
const MatrixRow = memo(MatrixRowInner) as typeof MatrixRowInner

interface StructureRowProps<T extends object> {
  store: RowStore<T>
  structure: SpreadStructure
  instruments: ReadonlyMap<RowId, SpreadInstrument>
  basis: SpreadBasis
  read: (quote: T, basis: SpreadBasis) => Nullable
  format: (value: number, basis: SpreadBasis) => string
  windowMs: number
}

function StructureRowInner<T extends object>(p: StructureRowProps<T>) {
  const legs = p.structure.legs
  const a = legs[0]
  const b = legs[1]
  const c = legs.length === 3 ? legs[2] : undefined
  // Three subscriptions whatever the leg count, so the hook count never changes; a curve's third reads its second again.
  const qa = useRow(p.store, a)
  const qb = useRow(p.store, b)
  const qc = useRow(p.store, c ?? b)
  const values = (c === undefined ? [qa, qb] : [qa, qb, qc]).map((quote) => (quote === undefined ? null : p.read(quote, p.basis)))
  const tick = p.structure.tick ?? p.instruments.get(a)?.convention.tick ?? NaN
  const spread = structureSpread(values, p.structure.weights, p.basis, tick)
  const ref = useRef<HTMLTableCellElement>(null)
  useFlash(ref, spread, { windowMs: p.windowMs, variant: "fill" })
  const legLabels = legs.map((id) => p.instruments.get(id)?.label ?? id).join(" / ")
  const weights = (p.structure.weights ?? defaultWeights(legs.length)).join(" ")
  return (
    <tr data-structure={p.structure.id} data-weights={weights} className="border-t border-border/60">
      <th scope="row" className={cn(HEAD, "text-left text-foreground")}>
        {p.structure.label}
      </th>
      <td data-legs="" className={cn(HEAD, "text-left")}>
        {legLabels}
      </td>
      <td ref={ref} data-spread="" data-numeric="" className={cn(CELL, NUMERIC_CLASS, FILL_CLASSES)}>
        {spread === null ? NULL_TOKEN : p.format(spread, p.basis)}
      </td>
    </tr>
  )
}
const StructureRow = memo(StructureRowInner) as typeof StructureRowInner

export function SpreadMatrix<T extends object = SpreadQuote>({ store, instruments, columns, basis = "ticks", structures, value, format = formatSpread, label, labels: labelsProp, flashWindowMs = 900, className }: SpreadMatrixProps<T>) {
  const labels = useMemo<SpreadMatrixLabels>(() => ({ ...DEFAULT_SPREAD_MATRIX_LABELS, ...labelsProp }), [labelsProp])
  const read: (quote: T, basis: SpreadBasis) => Nullable = value ?? defaultValue
  const across = columns ?? instruments
  const byId = useMemo(() => new Map(instruments.concat(columns ?? []).map((i) => [i.id, i])), [instruments, columns])
  const unit = labels[basis]
  const mode = structures ? "structures" : "matrix"
  return (
    <div data-slot="tradecn-spread-matrix" data-basis={basis} data-mode={mode} className={cn("overflow-auto rounded-md border border-border bg-background text-xs text-foreground lining-nums tabular-nums", className)}>
      <table aria-label={label} className="w-full border-collapse">
        <caption className="sr-only">{mode === "matrix" ? `${labels.rule} ${unit}.` : `${labels.spread}: ${unit}.`}</caption>
        <thead>
          {mode === "matrix" ? (
            <tr>
              <th scope="col" data-unit={basis} className={cn(HEAD, "text-left")}>
                {labels.instrument} <span className="text-muted-foreground/80">({unit})</span>
              </th>
              {across.map((column) => (
                <th key={column.id} scope="col" data-column={column.id} className={HEAD}>
                  {column.label}
                </th>
              ))}
            </tr>
          ) : (
            <tr>
              <th scope="col" className={cn(HEAD, "text-left")}>
                {labels.structure}
              </th>
              <th scope="col" className={cn(HEAD, "text-left")}>
                {labels.legs}
              </th>
              <th scope="col" data-unit={basis} className={HEAD}>
                {labels.spread} <span className="text-muted-foreground/80">({unit})</span>
              </th>
            </tr>
          )}
        </thead>
        <tbody>
          {structures
            ? structures.map((structure) => <StructureRow key={structure.id} store={store} structure={structure} instruments={byId} basis={basis} read={read} format={format} windowMs={flashWindowMs} />)
            : instruments.map((instrument) => <MatrixRow key={instrument.id} store={store} instrument={instrument} columns={across} basis={basis} read={read} format={format} windowMs={flashWindowMs} />)}
        </tbody>
      </table>
    </div>
  )
}

import { useLayoutEffect, useRef, type RefObject } from "react"

// Flash a cell when its value changes, colored by direction, without a React re-render per tick.
//
// The previous value lives outside React (per cell, or in a shared FlashMemory keyed by cell so a
// virtualized row that scrolls back within the window resumes its flash instead of losing it).
// The flash itself is a Web Animations API animation on the existing element: retriggering cancels
// the previous one for free, and nothing is remounted.

export type Direction = "up" | "down" | "flat"

export interface FlashRecord {
  value: unknown
  /** Clock time of the last flash, or -Infinity when the cell has never flashed. */
  at: number
  dir: Direction
}

export interface FlashMemory {
  get(key: string): FlashRecord | undefined
  set(key: string, record: FlashRecord): void
  /** Drop every record whose key starts with `prefix` (a grid calls it with the row id on remove). */
  forget(prefix: string): void
  readonly size: number
}

/** Bounded, least-recently-set memory. `max` records; oldest are evicted first. */
export function createFlashMemory(max = 50_000): FlashMemory {
  const map = new Map<string, FlashRecord>()
  return {
    get: (key) => map.get(key),
    set(key, record) {
      if (map.has(key)) map.delete(key)
      map.set(key, record)
      if (map.size > max) map.delete(map.keys().next().value!)
    },
    forget(prefix) {
      for (const key of map.keys()) if (key.startsWith(prefix)) map.delete(key)
    },
    get size() {
      return map.size
    },
  }
}

export type Compare = (prev: unknown, next: unknown) => number | null

/** Numeric difference when both sides are finite numbers; 0 when identical; null for any other change. */
export const compareValues: Compare = (prev, next) => {
  if (typeof prev === "number" && typeof next === "number" && Number.isFinite(prev) && Number.isFinite(next)) return next - prev
  return Object.is(prev, next) ? 0 : null
}

/** Direction of a change. Zero is flat, never up. A non-numeric change is flat. */
export function directionOf(prev: unknown, next: unknown, compare: Compare = compareValues): Direction {
  const d = compare(prev, next)
  if (d === null || d === 0) return "flat"
  return d > 0 ? "up" : "down"
}

export interface FlashOptions {
  /** How long a flash lasts, and how long a scrolled-away cell remembers it. Default 900. */
  windowMs?: number
  /** `fill` tints the background; `ring` draws an inset outline, for cells that already carry a bar. */
  variant?: "fill" | "ring"
  /** Paint with this instead of the direction's token: `var(--primary)` for an acknowledgement that has no direction. */
  color?: string
  compare?: Compare
  /**
   * Flash flat when the same value arrives again. Needs `revision` to know it arrived: pass the row object
   * or the batch version, since an equal `value` alone looks unchanged to React. Default false.
   */
  flashOnEqual?: boolean
  /** Anything that changes identity when a new reading arrives (the row object, a store version). */
  revision?: unknown
  /** Shared memory across mounts; requires `cellKey`. */
  memory?: FlashMemory
  cellKey?: string
  disabled?: boolean
  /** Injectable clock in ms; defaults to performance.now. */
  now?: () => number
}

export const FILL_COLORS: Record<Direction, string> = {
  up: "var(--up-soft)",
  down: "var(--down-soft)",
  flat: "var(--flat-soft)",
}

export const RING_COLORS: Record<Direction, string> = {
  up: "var(--up)",
  down: "var(--down)",
  flat: "var(--flat)",
}

/** Tailwind classes for coloring a value by direction: text-up, text-down, text-flat. */
export function directionClass(dir: Direction | null | undefined): string {
  return dir === "up" ? "text-up" : dir === "down" ? "text-down" : "text-flat"
}

const animations = new WeakMap<Element, Animation>()
const clearTimers = new WeakMap<Element, ReturnType<typeof setTimeout>>()
let reducedMotion: boolean | null = null

function prefersReducedMotion(): boolean {
  if (reducedMotion === null) {
    reducedMotion = typeof matchMedia === "function" ? matchMedia("(prefers-reduced-motion: reduce)").matches : false
  }
  return reducedMotion
}

/** Test hook: forget the cached media query. */
export function resetReducedMotionCache() {
  reducedMotion = null
}

function keyframes(dir: Direction, variant: "fill" | "ring", color?: string): Keyframe[] {
  if (variant === "ring") return [{ boxShadow: `inset 0 0 0 1px ${color ?? RING_COLORS[dir]}` }, { boxShadow: "inset 0 0 0 1px transparent" }]
  return [{ backgroundColor: color ?? FILL_COLORS[dir] }, { backgroundColor: "transparent" }]
}

/** Start (or resume, `elapsed` ms in) a flash on an element. */
export function playFlash(el: HTMLElement, dir: Direction, opts: { windowMs: number; variant: "fill" | "ring"; color?: string; elapsed?: number }) {
  const elapsed = Math.max(0, Math.min(opts.elapsed ?? 0, opts.windowMs))
  animations.get(el)?.cancel()
  const pending = clearTimers.get(el)
  if (pending) clearTimeout(pending)
  el.dataset.direction = dir
  const done = () => {
    if (el.dataset.direction === dir) delete el.dataset.direction
  }
  if (prefersReducedMotion() || typeof el.animate !== "function") {
    // Static color from the data-direction styles, cleared when the window ends.
    clearTimers.set(el, setTimeout(done, opts.windowMs - elapsed))
    return
  }
  const anim = el.animate(keyframes(dir, opts.variant, opts.color), { duration: opts.windowMs, easing: "ease-out", fill: "none" })
  anim.currentTime = elapsed
  anim.onfinish = () => {
    if (animations.get(el) === anim) animations.delete(el)
    done()
  }
  animations.set(el, anim)
}

const NEVER: FlashRecord = { value: undefined, at: -Infinity, dir: "flat" }

export function useFlash<E extends HTMLElement>(ref: RefObject<E | null>, value: unknown, opts: FlashOptions = {}): void {
  const { windowMs = 900, variant = "fill", color, compare = compareValues, flashOnEqual = false, memory, cellKey, disabled = false, revision } = opts
  const now = opts.now ?? (() => performance.now())
  const local = useRef<FlashRecord | undefined>(undefined)
  const key = memory ? cellKey : undefined
  if (memory && !cellKey) throw new Error("useFlash: a shared memory needs a cellKey")

  const read = (): FlashRecord | undefined => (key !== undefined ? memory!.get(key) : local.current)
  const write = (record: FlashRecord) => {
    if (key !== undefined) memory!.set(key, record)
    else local.current = record
  }

  useLayoutEffect(() => {
    const el = ref.current
    if (!el || disabled) return
    const t = now()
    const prev = read()
    if (!prev) {
      // First sight of this cell: remember, do not flash.
      write({ ...NEVER, value })
      return
    }
    const changed = !Object.is(prev.value, value)
    if (changed || flashOnEqual) {
      const dir = changed ? directionOf(prev.value, value, compare) : "flat"
      write({ value, at: t, dir })
      playFlash(el, dir, { windowMs, variant, color })
      return
    }
    // Same value on a fresh mount (a virtualized row scrolled back): resume a flash still in its window.
    const elapsed = t - prev.at
    if (elapsed < windowMs) playFlash(el, prev.dir, { windowMs, variant, color, elapsed })
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [value, revision, ref, disabled, windowMs, variant, color, flashOnEqual, compare, memory, key])

  useLayoutEffect(() => {
    const el = ref.current
    return () => {
      if (!el) return
      animations.get(el)?.cancel()
      animations.delete(el)
      const pending = clearTimers.get(el)
      if (pending) clearTimeout(pending)
    }
  }, [ref])
}

import { useCallback, useEffect, useRef, useState, useSyncExternalStore } from "react"
import type { RowId, RowStore, RowView, StoreMeta, ViewOptions } from "@/lib/row-store"

/** One row. The component re-renders when this row is replaced or patched, and for nothing else. */
export function useRow<T>(store: RowStore<T>, id: RowId): T | undefined {
  const subscribe = useCallback((cb: () => void) => store.subscribeRow(id, cb), [store, id])
  const get = useCallback(() => store.getRow(id), [store, id])
  return useSyncExternalStore(subscribe, get, get)
}

/** The ids of a store (insertion or authoritative order) or of a view (filtered, sorted, held). */
export function useRowIds<T>(source: RowStore<T> | RowView<T>): readonly RowId[] {
  const subscribe = useCallback((cb: () => void) => ("subscribeOrder" in source ? source.subscribeOrder(cb) : source.subscribe(cb)), [source])
  const get = useCallback(() => source.getIds(), [source])
  return useSyncExternalStore(subscribe, get, get)
}

/** Version, size, lane, drop count, sequence, gap, and timestamps. Changes once per batch. */
export function useStoreMeta<T>(store: RowStore<T>): StoreMeta {
  const subscribe = useCallback((cb: () => void) => store.subscribeMeta(cb), [store])
  const get = useCallback(() => store.getMeta(), [store])
  return useSyncExternalStore(subscribe, get, get)
}

/**
 * A view this component owns: made for the options given, disposed on the way out, and made again for
 * new options. Keep the options object's identity stable (a `useMemo`), since a new object is a new view.
 * Null options give null, for a component that takes a view from its props instead.
 *
 * Why a hook and not a memo with a dispose effect: React's StrictMode mounts, unmounts, and mounts a
 * component again in development, and the cleanup of that rehearsal disposes the memo's view while the
 * memo keeps handing it out, so the grid stopped following its store until something remade the view.
 * The effect here notices a disposed view and makes another.
 */
export function useView<T>(store: RowStore<T>, options: ViewOptions<T> | null): RowView<T> | null {
  const [view, setView] = useState<RowView<T> | null>(() => (options ? store.createView(options) : null))
  const made = useRef({ store, options, view })
  useEffect(() => {
    let current = made.current.view
    if (made.current.store !== store || made.current.options !== options || (current !== null && current.isDisposed())) {
      current = options ? store.createView(options) : null
      made.current = { store, options, view: current }
      // A view the rehearsal disposed, or new options: the replacement is state so the render that reads it re-runs.
      setView(current)
    }
    return () => current?.dispose()
  }, [store, options])
  return view
}

// A row store that React components subscribe to one row at a time.
//
// The consumer owns the feed. It calls `applyDeltas` once per frame with everything that changed
// (a Tauri consumer straight from its event listener; a WebSocket consumer through `createFrameBatcher`).
// A delta to one row wakes that row's subscribers and nobody else, and React batches every
// notification fired inside one `applyDeltas` into one commit, so a batch of two thousand row
// changes is one render pass over the rows that changed.
//
// Views sit on top: a filtered, sorted list of ids with an optional reorder hold so rows do not
// move under a trader's cursor while they work.

export type RowId = string

/** How the lane loses data. `coalesced` drops stale ticks and counts them; `ordered` never drops. */
export type Lane = "coalesced" | "ordered"

export interface DeltaBatch<T> {
  /** Whole rows. Replaces the row object, so every subscriber of that row wakes. */
  upsert?: readonly T[]
  /** Partial rows merged into a new object. Unknown ids are ignored. */
  patch?: readonly { id: RowId; fields: Partial<T> }[]
  remove?: readonly RowId[]
  /** Authoritative order for an ordered lane. Ids not present keep their previous relative order at the end. */
  order?: readonly RowId[]
  meta?: {
    lane?: Lane
    /** Messages the producer dropped since the last batch (coalesced lane). Accumulated. */
    dropped?: number
    /** Last sequence number applied (ordered lane). */
    seq?: number
    /** A gap was detected and replay is in progress. */
    gap?: boolean
    /** Producer timestamp of the newest message in the batch, ms since epoch. */
    producedAt?: number
  }
}

export interface StoreMeta {
  /** Increments once per applied batch. */
  version: number
  size: number
  lane: Lane
  dropped: number
  seq: number | null
  gap: boolean
  /** Wall clock of the last applied batch, ms since epoch. */
  lastBatchAt: number | null
  producedAt: number | null
}

export interface ViewOptions<T> {
  comparator?: (a: T, b: T) => number
  filter?: (row: T) => boolean
  /**
   * After `touch()` (the grid calls it on every key and pointer interaction) the order is frozen for this
   * long: new rows append, removed rows vanish, nothing moves. 0 disables the hold.
   */
  reorderHoldMs?: number
  /** Injectable clock, ms. Defaults to Date.now. */
  now?: () => number
}

export interface RowView<T> {
  /** The store this view reads from. */
  readonly store: RowStore<T>
  /** Stable array reference until the order actually changes. */
  getIds(): readonly RowId[]
  subscribe(cb: () => void): () => void
  /** The user interacted; start or extend the reorder hold. */
  touch(): void
  /** True while a hold is in force. */
  isHeld(): boolean
  dispose(): void
  /** True after `dispose`: the view no longer follows the store. */
  isDisposed(): boolean
}

export interface RowStore<T> {
  /** Stable object reference until the row is replaced or patched. */
  getRow(id: RowId): T | undefined
  /** Stable array reference until the order changes. Insertion order unless a batch carries `order`. */
  getIds(): readonly RowId[]
  /** Stable object reference until the next batch. */
  getMeta(): StoreMeta
  subscribeRow(id: RowId, cb: () => void): () => void
  subscribeOrder(cb: () => void): () => void
  subscribeMeta(cb: () => void): () => void
  /** Apply one batch synchronously. Call it once per frame. */
  applyDeltas(batch: DeltaBatch<T>): void
  createView(opts?: ViewOptions<T>): RowView<T>
  /** Drop every row (a re-snapshot is coming). Wakes every subscriber. */
  clear(): void
  readonly getRowId: (row: T) => RowId
}

export interface RowStoreOptions<T> {
  getRowId: (row: T) => RowId
  lane?: Lane
  now?: () => number
}

type Listener = () => void

export function createRowStore<T>(options: RowStoreOptions<T>): RowStore<T> {
  const { getRowId } = options
  const now = options.now ?? Date.now
  const rows = new Map<RowId, T>()
  let ids: RowId[] = []
  let idsSnapshot: readonly RowId[] = ids
  let meta: StoreMeta = { version: 0, size: 0, lane: options.lane ?? "coalesced", dropped: 0, seq: null, gap: false, lastBatchAt: null, producedAt: null }
  const rowListeners = new Map<RowId, Set<Listener>>()
  const orderListeners = new Set<Listener>()
  const metaListeners = new Set<Listener>()
  const views = new Set<ViewImpl<T>>()

  function notifyRow(id: RowId) {
    const set = rowListeners.get(id)
    if (set) for (const cb of set) cb()
  }

  function applyDeltas(batch: DeltaBatch<T>) {
    const touched = new Set<RowId>()
    const removed = new Set<RowId>()
    let orderChanged = false

    if (batch.upsert) {
      for (const row of batch.upsert) {
        const id = getRowId(row)
        if (!rows.has(id)) {
          ids.push(id)
          orderChanged = true
        }
        rows.set(id, row)
        touched.add(id)
      }
    }
    if (batch.patch) {
      for (const { id, fields } of batch.patch) {
        const existing = rows.get(id)
        if (existing === undefined) continue
        rows.set(id, { ...existing, ...fields })
        touched.add(id)
      }
    }
    if (batch.remove?.length) {
      const drop = new Set<RowId>()
      for (const id of batch.remove) {
        if (rows.delete(id)) {
          drop.add(id)
          removed.add(id)
          touched.add(id)
        }
      }
      if (drop.size) {
        ids = ids.filter((id) => !drop.has(id))
        orderChanged = true
      }
    }
    if (batch.order) {
      const next: RowId[] = []
      const seen = new Set<RowId>()
      for (const id of batch.order) {
        if (rows.has(id) && !seen.has(id)) {
          next.push(id)
          seen.add(id)
        }
      }
      for (const id of ids) if (!seen.has(id)) next.push(id)
      if (!sameOrder(ids, next)) {
        ids = next
        orderChanged = true
      }
    }

    const m = batch.meta
    meta = {
      version: meta.version + 1,
      size: rows.size,
      lane: m?.lane ?? meta.lane,
      dropped: meta.dropped + (m?.dropped ?? 0),
      seq: m?.seq ?? meta.seq,
      gap: m?.gap ?? meta.gap,
      lastBatchAt: now(),
      producedAt: m?.producedAt ?? meta.producedAt,
    }

    if (orderChanged) idsSnapshot = ids.slice()
    for (const view of views) view.onBatch(touched, removed, orderChanged)
    for (const id of touched) notifyRow(id)
    if (orderChanged) for (const cb of orderListeners) cb()
    for (const cb of metaListeners) cb()
  }

  const store: RowStore<T> = {
    getRowId,
    getRow: (id) => rows.get(id),
    getIds: () => idsSnapshot,
    getMeta: () => meta,
    subscribeRow(id, cb) {
      let set = rowListeners.get(id)
      if (!set) rowListeners.set(id, (set = new Set()))
      set.add(cb)
      return () => {
        set!.delete(cb)
        if (!set!.size) rowListeners.delete(id)
      }
    },
    subscribeOrder(cb) {
      orderListeners.add(cb)
      return () => orderListeners.delete(cb)
    },
    subscribeMeta(cb) {
      metaListeners.add(cb)
      return () => metaListeners.delete(cb)
    },
    applyDeltas,
    createView(opts = {}) {
      const view = new ViewImpl<T>(store, opts, () => views.delete(view))
      views.add(view)
      return view
    },
    clear() {
      const all = ids
      rows.clear()
      ids = []
      idsSnapshot = ids
      meta = { ...meta, version: meta.version + 1, size: 0, lastBatchAt: now() }
      for (const view of views) view.onBatch(new Set(all), new Set(all), true)
      for (const id of all) notifyRow(id)
      for (const cb of orderListeners) cb()
      for (const cb of metaListeners) cb()
    },
  }
  return store
}

function sameOrder(a: readonly RowId[], b: readonly RowId[]): boolean {
  if (a.length !== b.length) return false
  for (let i = 0; i < a.length; i++) if (a[i] !== b[i]) return false
  return true
}

class ViewImpl<T> implements RowView<T> {
  private ids: readonly RowId[] = []
  private readonly listeners = new Set<Listener>()
  private holdUntil = 0
  private timer: ReturnType<typeof setTimeout> | null = null
  private disposed = false
  private readonly now: () => number
  readonly store: RowStore<T>
  private readonly opts: ViewOptions<T>
  private readonly onDispose: () => void

  constructor(store: RowStore<T>, opts: ViewOptions<T>, onDispose: () => void) {
    this.store = store
    this.opts = opts
    this.onDispose = onDispose
    this.now = opts.now ?? Date.now
    this.ids = this.compute()
  }

  getIds() {
    return this.ids
  }

  subscribe(cb: Listener) {
    this.listeners.add(cb)
    return () => {
      this.listeners.delete(cb)
    }
  }

  isHeld() {
    return this.now() < this.holdUntil
  }

  touch() {
    const hold = this.opts.reorderHoldMs ?? 0
    if (hold <= 0) return
    this.holdUntil = this.now() + hold
    if (this.timer) clearTimeout(this.timer)
    // A quiet feed still settles: recompute when the hold lapses.
    this.timer = setTimeout(() => {
      this.timer = null
      this.set(this.compute())
    }, hold)
  }

  dispose() {
    if (this.disposed) return
    this.disposed = true
    if (this.timer) clearTimeout(this.timer)
    this.listeners.clear()
    this.onDispose()
  }

  isDisposed() {
    return this.disposed
  }

  /** Called by the store inside applyDeltas, before row listeners fire. */
  onBatch(touched: Set<RowId>, removed: Set<RowId>, orderChanged: boolean) {
    if (!touched.size && !orderChanged) return
    if (this.isHeld()) {
      // Frozen order: keep what is there, drop removals and rows that no longer pass the filter, append newcomers.
      const present = new Set(this.ids)
      const kept = this.ids.filter((id) => !removed.has(id) && this.passes(id))
      const newcomers = this.store.getIds().filter((id) => !present.has(id) && this.passes(id))
      if (this.opts.comparator) newcomers.sort(this.compare)
      const next = kept.length === this.ids.length && !newcomers.length ? this.ids : [...kept, ...newcomers]
      this.set(next)
      return
    }
    // Only recompute when the batch could have changed this view.
    let relevant = orderChanged
    if (!relevant) for (const id of touched) if (this.passes(id) || this.ids.includes(id)) { relevant = true; break }
    if (relevant) this.set(this.compute())
  }

  private passes(id: RowId): boolean {
    const row = this.store.getRow(id)
    if (row === undefined) return false
    return this.opts.filter ? this.opts.filter(row) : true
  }

  private readonly compare = (a: RowId, b: RowId) => this.opts.comparator!(this.store.getRow(a)!, this.store.getRow(b)!)

  private compute(): readonly RowId[] {
    const all = this.store.getIds()
    const list = this.opts.filter ? all.filter((id) => this.passes(id)) : all.slice()
    if (this.opts.comparator) list.sort(this.compare)
    return list
  }

  private set(next: readonly RowId[]) {
    if (sameOrder(this.ids, next)) return
    this.ids = next
    for (const cb of this.listeners) cb()
  }
}

export interface FrameBatcher<T> {
  /** Queue a delta; the merged batch applies on the next animation frame. */
  push(delta: DeltaBatch<T>): void
  /** Apply now, without waiting for the frame. */
  flush(): void
  /** Drop everything queued. */
  cancel(): void
  pending(): boolean
}

/**
 * Coalesce many small deltas into one batch per frame, last write wins per row. For consumers whose
 * feed delivers messages one at a time. A consumer whose core already batches per frame calls
 * `applyDeltas` directly and skips this: another frame of latency buys nothing.
 */
export function createFrameBatcher<T>(
  apply: (batch: DeltaBatch<T>) => void,
  options: { getRowId: (row: T) => RowId; raf?: (cb: () => void) => number; caf?: (handle: number) => void },
): FrameBatcher<T> {
  const raf = options.raf ?? ((cb) => requestAnimationFrame(cb))
  const caf = options.caf ?? ((h) => (typeof cancelAnimationFrame === "function" ? cancelAnimationFrame(h) : undefined))
  const upserts = new Map<RowId, T>()
  const patches = new Map<RowId, Partial<T>>()
  const removes = new Set<RowId>()
  let order: readonly RowId[] | undefined
  let meta: NonNullable<DeltaBatch<T>["meta"]> | undefined
  let handle: number | null = null

  function reset() {
    upserts.clear()
    patches.clear()
    removes.clear()
    order = undefined
    meta = undefined
  }

  function flush() {
    if (handle !== null) {
      caf(handle)
      handle = null
    }
    if (!upserts.size && !patches.size && !removes.size && !order && !meta) return
    const batch: DeltaBatch<T> = {}
    if (upserts.size) batch.upsert = [...upserts.values()]
    if (patches.size) batch.patch = [...patches].map(([id, fields]) => ({ id, fields }))
    if (removes.size) batch.remove = [...removes]
    if (order) batch.order = order
    if (meta) batch.meta = meta
    reset()
    apply(batch)
  }

  return {
    push(delta) {
      for (const row of delta.upsert ?? []) {
        const id = options.getRowId(row)
        removes.delete(id)
        patches.delete(id)
        upserts.set(id, row)
      }
      for (const { id, fields } of delta.patch ?? []) {
        if (removes.has(id)) continue
        const pendingUpsert = upserts.get(id)
        if (pendingUpsert !== undefined) upserts.set(id, { ...pendingUpsert, ...fields })
        else patches.set(id, { ...(patches.get(id) ?? {}), ...fields })
      }
      for (const id of delta.remove ?? []) {
        upserts.delete(id)
        patches.delete(id)
        removes.add(id)
      }
      if (delta.order) order = delta.order
      if (delta.meta) {
        meta = {
          ...meta,
          ...delta.meta,
          dropped: (meta?.dropped ?? 0) + (delta.meta.dropped ?? 0),
          gap: Boolean(meta?.gap) || Boolean(delta.meta.gap),
        }
      }
      if (handle === null) {
        handle = raf(() => {
          handle = null
          flush()
        })
      }
    },
    flush,
    cancel() {
      if (handle !== null) caf(handle)
      handle = null
      reset()
    },
    pending: () => handle !== null,
  }
}

// Number formatting for trading screens. Pure functions, no React, no dependencies.
// Every formatter returns NULL_TOKEN for null, undefined, NaN, and infinities, so a grid
// never prints "NaN" or "undefined" while a feed is warming up.

export const NULL_TOKEN = "–"
const MINUS = "−"

export type Nullable = number | null | undefined

export interface Locale {
  /** BCP 47 tag; defaults to en-US. */
  locale?: string
}

export type PriceConvention =
  /** Fixed decimals, e.g. equities at 2. */
  | { kind: "decimal"; decimals: number }
  /** Decimals derived from the instrument's tick size, e.g. 0.001 gives 3. */
  | { kind: "tick"; tick: number }
  /**
   * Fractional quoting. `denominator` 32 or 64; `half` renders a half tick as "+" (99-16+) or "5" (99-165);
   * `eighths` renders eighths of a tick as a trailing digit (99-162 is 99 and 16 2/8 thirty-seconds).
   */
  | { kind: "fraction"; denominator: 32 | 64; half: "+" | "5"; eighths?: boolean }

/** What a quote is typed and read in. Bills quote on discount, most bonds on price, some on yield, credit often on a spread in basis points. */
export type QuoteBasis = "price" | "yield" | "discount" | "spread"

export interface InstrumentConvention {
  price: PriceConvention
  /** Smallest price increment, used for stepping and rounding. */
  tick: number
  yieldDecimals?: number
  quantityUnit?: "notional" | "contracts"
  /** Default price. */
  quoteBasis?: QuoteBasis
  /** What a quote steps by in its basis. Default: the tick for price, 0.001 for yield and discount, 0.1 for spread. */
  quoteStep?: number
  /** Decimals for a yield, discount, or spread quote. Default 3, 3, and 1. Price quotes follow their convention. */
  quoteDecimals?: number
}

function isNil(v: Nullable): v is null | undefined {
  return v === null || v === undefined || !Number.isFinite(v)
}

// One Intl.NumberFormat per locale and option set; construction is the expensive part.
const formatters = new Map<string, Intl.NumberFormat>()

export function numberFormat(locale: string | undefined, options: Intl.NumberFormatOptions): Intl.NumberFormat {
  const key = `${locale ?? "en-US"}|${JSON.stringify(options)}`
  let nf = formatters.get(key)
  if (!nf) {
    nf = new Intl.NumberFormat(locale ?? "en-US", options)
    formatters.set(key, nf)
  }
  return nf
}

function fixed(v: number, decimals: number, locale?: string, extra: Intl.NumberFormatOptions = {}): string {
  return numberFormat(locale, { minimumFractionDigits: decimals, maximumFractionDigits: decimals, ...extra }).format(v)
}

function typographicMinus(s: string): string {
  return s.replace(/-/g, MINUS)
}

/** Decimal places needed to show a price on this tick grid. 0.001 gives 3, 1/32 gives 5, 1 gives 0. Capped at `max`. */
export function decimalsFromTick(tick: number, max = 8): number {
  if (!Number.isFinite(tick) || tick <= 0) return 0
  for (let d = 0; d <= max; d++) {
    const scaled = tick * 10 ** d
    if (Math.abs(scaled - Math.round(scaled)) < 1e-9 * Math.max(1, scaled)) return d
  }
  return max
}

/** Nearest price on the tick grid, cleaned of float noise. */
export function roundToTick(v: number, tick: number): number {
  if (!Number.isFinite(v) || !Number.isFinite(tick) || tick <= 0) return v
  return Number((Math.round(v / tick) * tick).toFixed(decimalsFromTick(tick)))
}

/** Move `steps` ticks (negative allowed) from the nearest grid price. */
export function stepByTick(v: number, tick: number, steps: number): number {
  return roundToTick(roundToTick(v, tick) + steps * tick, tick)
}

/** Whole-number and sub-tick decomposition on an integer grid so 32nds never drift. */
function decomposeFraction(v: number, c: Extract<PriceConvention, { kind: "fraction" }>) {
  const sub = c.eighths ? 8 : 2
  const unitsPerWhole = c.denominator * sub
  const total = Math.round(Math.abs(v) * unitsPerWhole)
  const whole = Math.floor(total / unitsPerWhole)
  const rem = total - whole * unitsPerWhole
  const ticks = Math.floor(rem / sub)
  const subticks = rem - ticks * sub
  return { negative: v < 0 && total > 0, whole, ticks, subticks, sub }
}

/** 99.515625 as "99-16+" (32nds, half "+"), "99-165" (half "5"), or "99-164" with eighths. */
export function formatFraction(v: Nullable, c: Extract<PriceConvention, { kind: "fraction" }>): string {
  if (isNil(v)) return NULL_TOKEN
  const { negative, whole, ticks, subticks, sub } = decomposeFraction(v, c)
  let tail = ""
  if (subticks !== 0) {
    if (c.eighths) tail = String(subticks)
    else tail = c.half
  }
  void sub
  return `${negative ? MINUS : ""}${whole}-${String(ticks).padStart(2, "0")}${tail}`
}

export function formatPrice(v: Nullable, c: PriceConvention, l?: Locale): string {
  if (isNil(v)) return NULL_TOKEN
  switch (c.kind) {
    case "decimal":
      return typographicMinus(fixed(v, c.decimals, l?.locale))
    case "tick":
      return typographicMinus(fixed(roundToTick(v, c.tick), decimalsFromTick(c.tick), l?.locale))
    case "fraction":
      return formatFraction(v, c)
  }
}

/**
 * Inverse of formatPrice for ticket entry. Accepts the convention's own notation and a plain decimal.
 * Returns null when the text is not a price. Fraction input: "99-16+", "99-165", "99-162", "99-16", "99".
 */
export function parsePrice(s: string, c: PriceConvention): number | null {
  const text = s.trim().replace(/−/g, "-").replace(/,/g, "")
  if (!text) return null
  if (c.kind === "fraction") {
    const m = /^([+-]?)(\d+)(?:-(\d{1,2})([+0-9])?)?$/.exec(text)
    if (m) {
      const [, sign, wholeText, ticksText, tail] = m
      const ticks = ticksText ? Number(ticksText) : 0
      if (ticks >= c.denominator) return null
      let subFraction = 0
      if (tail === "+") subFraction = 0.5
      else if (tail !== undefined) {
        const digit = Number(tail)
        if (c.eighths) {
          if (digit > 7) return null
          subFraction = digit / 8
        } else if (c.half === "5" && digit === 5) subFraction = 0.5
        else if (digit === 0) subFraction = 0
        else return null
      }
      const value = Number(wholeText) + (ticks + subFraction) / c.denominator
      return sign === "-" ? -value : value
    }
  }
  if (!/^[+-]?(\d+\.?\d*|\.\d+)$/.test(text)) return null
  const n = Number(text)
  if (!Number.isFinite(n)) return null
  if (c.kind === "tick") return roundToTick(n, c.tick)
  if (c.kind === "decimal") return Number(n.toFixed(c.decimals))
  return n
}

/** 4.2531 as "4.253%". */
export function formatYield(v: Nullable, o: { decimals?: number; suffix?: "%" | "" } & Locale = {}): string {
  if (isNil(v)) return NULL_TOKEN
  return typographicMinus(fixed(v, o.decimals ?? 3, o.locale)) + (o.suffix ?? "%")
}

/** 12.5 as "12.5 bp"; signed gives "+12.5 bp". */
export function formatBps(v: Nullable, o: { decimals?: number; signed?: boolean; unit?: "bp" | "bps" | "" } & Locale = {}): string {
  if (isNil(v)) return NULL_TOKEN
  const unit = o.unit ?? "bp"
  const body = o.signed ? formatSigned(v, { decimals: o.decimals ?? 1, locale: o.locale }) : typographicMinus(fixed(v, o.decimals ?? 1, o.locale))
  return unit ? `${body} ${unit}` : body
}

/** Dollar value of a basis point as whole currency; compact gives "$1.23K". */
export function formatDv01(v: Nullable, o: { currency?: string; compact?: boolean } & Locale = {}): string {
  if (isNil(v)) return NULL_TOKEN
  const currency = o.currency ?? "USD"
  if (o.compact) {
    const symbol = numberFormat(o.locale, { style: "currency", currency, currencyDisplay: "narrowSymbol", maximumFractionDigits: 0 })
      .formatToParts(0)
      .find((p) => p.type === "currency")?.value ?? ""
    return `${v < 0 ? MINUS : ""}${symbol}${formatNotional(Math.abs(v), { compact: true, locale: o.locale })}`
  }
  return typographicMinus(numberFormat(o.locale, { style: "currency", currency, currencyDisplay: "narrowSymbol", maximumFractionDigits: 0 }).format(v))
}

/** 1250000 as "1.25M" (compact), "1.25mm" (unit "mm", the desk's word for millions, never scaled further), or "1,250,000.00". Compact suffixes K, M, B, T. */
export function formatNotional(v: Nullable, o: { compact?: boolean; decimals?: number; unit?: "mm" } & Locale = {}): string {
  if (isNil(v)) return NULL_TOKEN
  const decimals = o.decimals ?? 2
  if (o.unit === "mm") return typographicMinus(numberFormat(o.locale, { minimumFractionDigits: 0, maximumFractionDigits: decimals }).format(v / 1e6)) + "mm"
  if (!o.compact) return typographicMinus(fixed(v, decimals, o.locale))
  const abs = Math.abs(v)
  const [divisor, suffix] = abs >= 1e12 ? [1e12, "T"] : abs >= 1e9 ? [1e9, "B"] : abs >= 1e6 ? [1e6, "M"] : abs >= 1e3 ? [1e3, "K"] : [1, ""]
  return typographicMinus(fixed(v / divisor, suffix ? decimals : 0, o.locale)) + suffix
}

/** "+0.12", "−0.12" (U+2212), and "0.00" for zero: flat carries no sign. */
export function formatSigned(v: Nullable, o: { decimals?: number } & Locale = {}): string {
  if (isNil(v)) return NULL_TOKEN
  return typographicMinus(fixed(v, o.decimals ?? 2, o.locale, { signDisplay: "exceptZero" }))
}

/** 1.234 as "1.23%"; signed gives "+1.23%". */
export function formatPercent(v: Nullable, o: { decimals?: number; signed?: boolean } & Locale = {}): string {
  if (isNil(v)) return NULL_TOKEN
  const decimals = o.decimals ?? 2
  return (o.signed ? formatSigned(v, { decimals, locale: o.locale }) : typographicMinus(fixed(v, decimals, o.locale))) + "%"
}

/** Whole quantities with grouping: 1000000 as "1,000,000". */
export function formatQuantity(v: Nullable, l?: Locale): string {
  if (isNil(v)) return NULL_TOKEN
  return typographicMinus(fixed(Math.round(v), 0, l?.locale))
}

/**
 * A coupon the way a run prints it: 4.125 as "4 1/8", 4.5 as "4 1/2", 4 as "4", 0 as "0" (coupons step in eighths).
 * One off the eighths grid prints as a plain decimal, "4.1". `style: "decimal"` prints "4.125%".
 */
export function formatCoupon(v: Nullable, o: { style?: "fraction" | "decimal"; decimals?: number } & Locale = {}): string {
  if (isNil(v)) return NULL_TOKEN
  if (o.style === "decimal") return typographicMinus(fixed(v, o.decimals ?? 3, o.locale)) + "%"
  const eighths = Math.round(Math.abs(v) * 8)
  if (Math.abs(eighths / 8 - Math.abs(v)) > 1e-9) return typographicMinus(numberFormat(o.locale, { minimumFractionDigits: 0, maximumFractionDigits: o.decimals ?? 3 }).format(v))
  const whole = Math.floor(eighths / 8)
  const rem = eighths % 8
  const fraction = rem === 0 ? "" : rem % 4 === 0 ? "1/2" : rem % 2 === 0 ? `${rem / 2}/4` : `${rem}/8`
  const body = fraction ? (whole ? `${whole} ${fraction}` : fraction) : String(whole)
  return `${v < 0 && eighths > 0 ? MINUS : ""}${body}`
}

/** A date as an instant, a millisecond count, or a string `Date` can read. A date-only string ("2034-05-15") is that day in UTC. */
export type DateLike = Date | number | string

function toDate(d: DateLike | null | undefined): Date | null {
  if (d === null || d === undefined) return null
  const date = d instanceof Date ? d : new Date(d)
  return Number.isNaN(date.getTime()) ? null : date
}

const dateFormatters = new Map<string, Intl.DateTimeFormat>()

/**
 * A maturity as a run prints it: "05/15/34", or "05/15/2034" with `year: "numeric"`. Read in UTC, so a
 * date-only string prints as that day wherever the screen is.
 */
export function formatMaturity(d: DateLike | null | undefined, o: { year?: "2-digit" | "numeric" } & Locale = {}): string {
  const date = toDate(d)
  if (!date) return NULL_TOKEN
  const key = `${o.locale ?? "en-US"}|${o.year ?? "2-digit"}`
  let f = dateFormatters.get(key)
  if (!f) {
    f = new Intl.DateTimeFormat(o.locale ?? "en-US", { month: "2-digit", day: "2-digit", year: o.year ?? "2-digit", timeZone: "UTC" })
    dateFormatters.set(key, f)
  }
  return f.format(date)
}

/** Whole UTC days from `now` (the moment, by default) to a maturity. Negative once it has passed; null when the date does not read. */
export function daysToMaturity(d: DateLike | null | undefined, now: DateLike = Date.now()): number | null {
  const maturity = toDate(d)
  const from = toDate(now)
  if (!maturity || !from) return null
  const day = (x: Date) => Date.UTC(x.getUTCFullYear(), x.getUTCMonth(), x.getUTCDate())
  return Math.round((day(maturity) - day(from)) / 86_400_000)
}

/** How many ticks `a` is from `b`, signed, to the nearest eighth of a tick: 99-17 against 99-16+ on a 1/64 tick is 1. NaN when a side is not a number or the tick is not positive. */
export function ticksBetween(a: number, b: number, tick: number): number {
  if (!Number.isFinite(a) || !Number.isFinite(b) || !(tick > 0)) return NaN
  return Math.round(((a - b) / tick) * 8) / 8
}

/** A count of ticks: "+1", "−0.5", "0", up to three decimals and no trailing zeros. Signed unless told otherwise; `unit` adds a word. */
export function formatTicks(v: Nullable, o: { signed?: boolean; unit?: string } & Locale = {}): string {
  if (isNil(v)) return NULL_TOKEN
  const body = typographicMinus(numberFormat(o.locale, { minimumFractionDigits: 0, maximumFractionDigits: 3, signDisplay: o.signed === false ? "auto" : "exceptZero" }).format(v))
  return o.unit ? `${body} ${o.unit}` : body
}

/**
 * The class a number wears (contract rule 14): lining, tabular figures whatever the font, in the numeric family.
 * `--tradecn-font-numeric` is the sans by default, so letters stay proportional and only the digits take one
 * width, which is what a column of prices wants. docs/typography.md has the reasoning and the tokens.
 */
export const NUMERIC_CLASS = "font-(family-name:--tradecn-font-numeric) lining-nums tabular-nums"
/** The same figures in the mono stack, `--tradecn-font-mono`: for a fraction quote, whose dash, ticks, and tail must line up down a column. */
export const MONO_NUMERIC_CLASS = "font-(family-name:--tradecn-font-mono) lining-nums tabular-nums"

/**
 * The class for a number printed under a convention: a fraction price (99-16+) sets in the mono stack, so
 * 99-16+ over 99-17 keeps its dash and its tail in the same place; every other price, and every quote in
 * another basis, keeps the numeric family.
 */
export function numericFontClass(c?: PriceConvention | InstrumentConvention | null): string {
  const price = c && "price" in c ? (quoteBasisOf(c) === "price" ? c.price : null) : c
  return price?.kind === "fraction" ? MONO_NUMERIC_CLASS : NUMERIC_CLASS
}

/** The word for a quote field's label, per basis. */
export const QUOTE_BASIS_LABELS: Record<QuoteBasis, string> = { price: "Price", yield: "Yield", discount: "Discount", spread: "Spread" }

const QUOTE_DEFAULTS: Record<Exclude<QuoteBasis, "price">, { step: number; decimals: number }> = {
  yield: { step: 0.001, decimals: 3 },
  discount: { step: 0.001, decimals: 3 },
  spread: { step: 0.1, decimals: 1 },
}

export function quoteBasisOf(c: InstrumentConvention): QuoteBasis {
  return c.quoteBasis ?? "price"
}

/** What a quote steps by in its basis: the tick for a price, else `quoteStep` or the basis default. */
export function quoteStepOf(c: InstrumentConvention): number {
  const basis = quoteBasisOf(c)
  return basis === "price" ? c.tick : (c.quoteStep ?? QUOTE_DEFAULTS[basis].step)
}

function quoteDecimalsOf(c: InstrumentConvention): number {
  const basis = quoteBasisOf(c)
  return basis === "price" ? 0 : (c.quoteDecimals ?? QUOTE_DEFAULTS[basis].decimals)
}

/** A quote in the instrument's basis: a price by its convention, else a fixed decimal with the basis's decimals and no unit, since the field's label says the basis. */
export function formatQuote(v: Nullable, c: InstrumentConvention, l?: Locale): string {
  if (isNil(v)) return NULL_TOKEN
  if (quoteBasisOf(c) === "price") return formatPrice(v, c.price, l)
  return typographicMinus(fixed(roundToTick(v, quoteStepOf(c)), quoteDecimalsOf(c), l?.locale))
}

/** Inverse of formatQuote for a quote field. A price takes its notation or a decimal; the others take a decimal and snap to the quote step. Null when the text is not a quote. */
export function parseQuote(s: string, c: InstrumentConvention): number | null {
  if (quoteBasisOf(c) === "price") return parsePrice(s, c.price)
  const text = s.trim().replace(/−/g, "-").replace(/,/g, "")
  if (!/^[+-]?(\d+\.?\d*|\.\d+)$/.test(text)) return null
  const n = Number(text)
  return Number.isFinite(n) ? roundToTick(n, quoteStepOf(c)) : null
}

/** Move a quote by `steps` of its step, from the nearest grid value. */
export function stepQuote(v: number, c: InstrumentConvention, steps: number): number {
  return stepByTick(v, quoteStepOf(c), steps)
}

/** Bind a convention once per instrument; a grid column calls `formatters[row.instrumentId].price(v)`, a quote field its `quote`, `parseQuote`, and `stepQuote`. */
export function createInstrumentFormatter(c: InstrumentConvention, l?: Locale) {
  return {
    tick: c.tick,
    basis: quoteBasisOf(c),
    quoteStep: quoteStepOf(c),
    price: (v: Nullable) => formatPrice(v, c.price, l),
    yield: (v: Nullable) => formatYield(v, { decimals: c.yieldDecimals ?? 3, locale: l?.locale }),
    step: (v: number, steps: number) => stepByTick(v, c.tick, steps),
    parsePrice: (s: string) => parsePrice(s, c.price),
    quantity: (v: Nullable) => formatQuantity(v, l),
    quote: (v: Nullable) => formatQuote(v, c, l),
    parseQuote: (s: string) => parseQuote(s, c),
    stepQuote: (v: number, steps: number) => stepQuote(v, c, steps),
  }
}

:root {
  --down: oklch(0.46 0.19 40);
  --down-soft: oklch(0.46 0.19 40 / 18%);
  --flat: var(--color-muted-foreground);
  --flat-soft: oklch(0.55 0 0 / 14%);
  --tradecn-font-accessible: 'Atkinson Hyperlegible Next', 'Atkinson Hyperlegible', ui-sans-serif, system-ui, sans-serif;
  --tradecn-font-accessible-mono: 'Atkinson Hyperlegible Mono', ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  --tradecn-font-mono: 'JetBrains Mono', ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  --tradecn-font-numeric: var(--tradecn-font-sans);
  --tradecn-font-sans: 'Inter', ui-sans-serif, system-ui, sans-serif;
  --up: oklch(0.52 0.13 165);
  --up-soft: oklch(0.52 0.13 165 / 18%);
}

.dark {
  --down: oklch(0.66 0.19 40);
  --down-soft: oklch(0.66 0.19 40 / 18%);
  --flat: var(--color-muted-foreground);
  --flat-soft: oklch(0.7 0 0 / 14%);
  --tradecn-font-accessible: 'Atkinson Hyperlegible Next', 'Atkinson Hyperlegible', ui-sans-serif, system-ui, sans-serif;
  --tradecn-font-accessible-mono: 'Atkinson Hyperlegible Mono', ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  --tradecn-font-mono: 'JetBrains Mono', ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  --tradecn-font-numeric: var(--tradecn-font-sans);
  --tradecn-font-sans: 'Inter', ui-sans-serif, system-ui, sans-serif;
  --up: oklch(0.74 0.15 165);
  --up-soft: oklch(0.74 0.15 165 / 18%);
}

:root[data-accessibility="hyperlegible"], [data-accessibility="hyperlegible"] {
  --tradecn-font-sans: var(--tradecn-font-accessible);
  --tradecn-font-mono: var(--tradecn-font-accessible-mono);
}