Ticker-Change Chain Resolution

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/** Point-in-time ticker-chain resolution for a normalized security master. */

type RecordMap = Record<string, unknown>;
type Direction = "listing_to_symbol" | "symbol_to_listing";

type ParsedAssignment = RecordMap & {
  assignmentId: string;
  revision: number;
  status: "active" | "cancelled";
  changeKind: "initial_listing" | "administrative" | "corporate_action";
  listingId: string;
  symbol: string;
  sourceId: string;
  announcedAt: string;
  availableAt: string;
  effectiveAt: string;
  validTo: string | null;
  _announced: number;
  _available: number;
  _effective: number;
  _validTo: number | null;
};

const ISO_INSTANT = /^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}Z$/;
const MIC = /^[A-Z0-9]{4}$/;
const CURRENCY = /^[A-Z]{3}$/;
const CHANGE_KINDS = new Set(["initial_listing", "administrative", "corporate_action"]);
const STATUSES = new Set(["active", "cancelled"]);
const DIRECTIONS = new Set(["listing_to_symbol", "symbol_to_listing"]);

export class ResolutionError extends Error {
  constructor(message: string) {
    super(message);
    this.name = "ResolutionError";
  }
}

function objectValue(value: unknown, name: string): RecordMap {
  if (value === null || typeof value !== "object" || Array.isArray(value)) throw new TypeError(`${name} must be an object`);
  return value as RecordMap;
}

function objects(value: unknown, name: string): RecordMap[] {
  if (!Array.isArray(value)) throw new TypeError(`${name} must be a list`);
  return value.map((item, index) => objectValue(item, `${name}[${index}]`));
}

function textValue(value: unknown, name: string): string {
  if (typeof value !== "string" || value.length === 0 || value.trim() !== value) throw new TypeError(`${name} must be a non-empty, trimmed string`);
  return value;
}

function instant(value: unknown, name: string): [string, number] {
  const text = textValue(value, name);
  if (!ISO_INSTANT.test(text)) throw new TypeError(`${name} must be an ISO 8601 UTC instant ending in Z`);
  const parsed = Date.parse(text);
  if (!Number.isFinite(parsed) || new Date(parsed).toISOString() !== text.replace("Z", ".000Z")) {
    throw new RangeError(`${name} is not a valid calendar instant`);
  }
  return [text, parsed];
}

function unique(records: RecordMap[], key: string, name: string): Map<string, RecordMap> {
  const indexed = new Map<string, RecordMap>();
  records.forEach((record, index) => {
    const identifier = textValue(record[key], `${name}[${index}].${key}`);
    if (indexed.has(identifier)) throw new RangeError(`duplicate ${key}: ${identifier}`);
    indexed.set(identifier, record);
  });
  return indexed;
}

function normalizeEntities(data: RecordMap): [Map<string, RecordMap>, Map<string, RecordMap>, Map<string, RecordMap>] {
  const issuers = unique(objects(data.issuers, "issuers"), "issuerId", "issuers");
  const instruments = unique(objects(data.instruments, "instruments"), "instrumentId", "instruments");
  const listings = unique(objects(data.listings, "listings"), "listingId", "listings");

  for (const [instrumentId, instrument] of instruments) {
    const issuerId = textValue(instrument.issuerId, `instrument ${instrumentId}.issuerId`);
    textValue(instrument.shareClassId, `instrument ${instrumentId}.shareClassId`);
    if (!issuers.has(issuerId)) throw new RangeError(`instrument ${instrumentId} references unknown issuer ${issuerId}`);
  }
  for (const [listingId, listing] of listings) {
    const instrumentId = textValue(listing.instrumentId, `listing ${listingId}.instrumentId`);
    const venueMic = textValue(listing.venueMic, `listing ${listingId}.venueMic`);
    const currency = textValue(listing.currency, `listing ${listingId}.currency`);
    if (!instruments.has(instrumentId)) throw new RangeError(`listing ${listingId} references unknown instrument ${instrumentId}`);
    if (!MIC.test(venueMic)) throw new RangeError(`listing ${listingId}.venueMic must be a four-character MIC`);
    if (!CURRENCY.test(currency)) throw new RangeError(`listing ${listingId}.currency must be a three-letter code`);
  }
  return [issuers, instruments, listings];
}

function normalizeAssignments(data: RecordMap, listings: Map<string, RecordMap>): ParsedAssignment[] {
  const versions = new Map<string, ParsedAssignment[]>();
  const seenVersions = new Set<string>();
  const normalized: ParsedAssignment[] = [];

  objects(data.assignments, "assignments").forEach((raw, index) => {
    const record = structuredClone(raw) as RecordMap;
    const assignmentId = textValue(record.assignmentId, `assignments[${index}].assignmentId`);
    const revision = record.revision;
    if (!Number.isInteger(revision) || (revision as number) < 1) throw new TypeError(`assignments[${index}].revision must be a positive integer`);
    const versionKey = `${assignmentId}\u0000${revision}`;
    if (seenVersions.has(versionKey)) throw new RangeError(`duplicate assignment revision: ${assignmentId} r${revision}`);
    seenVersions.add(versionKey);

    const status = textValue(record.status, `assignments[${index}].status`);
    const changeKind = textValue(record.changeKind, `assignments[${index}].changeKind`);
    const listingId = textValue(record.listingId, `assignments[${index}].listingId`);
    const symbol = textValue(record.symbol, `assignments[${index}].symbol`);
    const sourceId = textValue(record.sourceId, `assignments[${index}].sourceId`);
    if (!STATUSES.has(status)) throw new RangeError(`assignments[${index}].status is unsupported`);
    if (!CHANGE_KINDS.has(changeKind)) throw new RangeError(`assignments[${index}].changeKind is unsupported`);
    if (!listings.has(listingId)) throw new RangeError(`assignment ${assignmentId} references unknown listing ${listingId}`);

    const [announcedText, announcedAt] = instant(record.announcedAt, `assignments[${index}].announcedAt`);
    const [availableText, availableAt] = instant(record.availableAt, `assignments[${index}].availableAt`);
    const [effectiveText, effectiveAt] = instant(record.effectiveAt, `assignments[${index}].effectiveAt`);
    if (availableAt < announcedAt) throw new RangeError(`assignment ${assignmentId} is available before it was announced`);
    let validToText: string | null = null;
    let validTo: number | null = null;
    if (record.validTo !== null) {
      [validToText, validTo] = instant(record.validTo, `assignments[${index}].validTo`);
      if (validTo <= effectiveAt) throw new RangeError(`assignment ${assignmentId}.validTo must be after effectiveAt`);
    }

    const parsed = {
      ...record,
      assignmentId,
      revision: revision as number,
      status: status as ParsedAssignment["status"],
      changeKind: changeKind as ParsedAssignment["changeKind"],
      listingId,
      symbol,
      sourceId,
      announcedAt: announcedText,
      availableAt: availableText,
      effectiveAt: effectiveText,
      validTo: validToText,
      _announced: announcedAt,
      _available: availableAt,
      _effective: effectiveAt,
      _validTo: validTo,
    } as ParsedAssignment;
    normalized.push(parsed);
    versions.set(assignmentId, [...(versions.get(assignmentId) ?? []), parsed]);
  });

  for (const [assignmentId, records] of versions) {
    records.sort((a, b) => a.revision - b.revision);
    if (records.some((record, index) => record.revision !== index + 1)) throw new RangeError(`assignment ${assignmentId} revisions must be contiguous from 1`);
    const anchor = [records[0].listingId, records[0].symbol, records[0].effectiveAt].join("\u0000");
    let previousAvailable: number | null = null;
    for (const record of records) {
      if ([record.listingId, record.symbol, record.effectiveAt].join("\u0000") !== anchor) throw new RangeError(`assignment ${assignmentId} revision changes immutable identity fields`);
      if (previousAvailable !== null && record._available <= previousAvailable) throw new RangeError(`assignment ${assignmentId} revision availability must increase`);
      previousAvailable = record._available;
    }
  }
  return normalized;
}

function visibleAssignments(assignments: ParsedAssignment[], asOf: number): ParsedAssignment[] {
  const versions = new Map<string, ParsedAssignment[]>();
  for (const record of assignments) {
    if (record._available <= asOf) versions.set(record.assignmentId, [...(versions.get(record.assignmentId) ?? []), record]);
  }
  const selected: ParsedAssignment[] = [];
  for (const records of versions.values()) {
    const latest = records.reduce((left, right) => left.revision > right.revision ? left : right);
    if (latest.status === "active") selected.push(latest);
  }
  return selected;
}

function contains(record: ParsedAssignment, queryAt: number): boolean {
  return record._effective <= queryAt && (record._validTo === null || queryAt < record._validTo);
}

function buildChain(records: ParsedAssignment[], listingId: string) {
  const chain = records.filter((record) => record.listingId === listingId).sort((a, b) => a._effective - b._effective || a.assignmentId.localeCompare(b.assignmentId));
  const gaps: Array<{from: string; to: string}> = [];
  const seenSymbols = new Set<string>();
  const reusedSymbols = new Set<string>();
  chain.forEach((record, index) => {
    if (seenSymbols.has(record.symbol)) reusedSymbols.add(record.symbol);
    seenSymbols.add(record.symbol);
    if (index === 0) return;
    const previous = chain[index - 1];
    if (previous._validTo === null || previous._validTo > record._effective) throw new ResolutionError(`ambiguous chain for ${listingId}: effective intervals overlap`);
    if (previous._validTo < record._effective) gaps.push({from: previous.validTo as string, to: record.effectiveAt});
  });
  return {
    chain: chain.map((record) => ({
      assignmentId: record.assignmentId,
      revision: record.revision,
      symbol: record.symbol,
      effectiveAt: record.effectiveAt,
      validTo: record.validTo,
      changeKind: record.changeKind,
      sourceId: record.sourceId,
      announcedAt: record.announcedAt,
      availableAt: record.availableAt,
    })),
    gaps,
    reusedSymbols: [...reusedSymbols].sort(),
  };
}

export function resolveTickerChain(input: unknown) {
  const data = objectValue(input, "data");
  const [issuers, instruments, listings] = normalizeEntities(data);
  const assignments = normalizeAssignments(data, listings);
  const query = objectValue(data.query, "query");
  const direction = textValue(query.direction, "query.direction") as Direction;
  if (!DIRECTIONS.has(direction)) throw new RangeError("query.direction is unsupported");
  const [queryAtText, queryAt] = instant(query.queryAt, "query.queryAt");
  const [asOfText, asOf] = instant(query.asOf, "query.asOf");
  const visible = visibleAssignments(assignments, asOf);
  let matches: ParsedAssignment[];

  if (direction === "listing_to_symbol") {
    const listingId = textValue(query.listingId, "query.listingId");
    if (!listings.has(listingId)) throw new ResolutionError(`unknown listing: ${listingId}`);
    matches = visible.filter((record) => record.listingId === listingId && contains(record, queryAt));
  } else {
    const symbol = textValue(query.symbol, "query.symbol");
    const venueMic = textValue(query.venueMic, "query.venueMic");
    if (!MIC.test(venueMic)) throw new RangeError("query.venueMic must be a four-character MIC");
    matches = visible.filter((record) => record.symbol === symbol && listings.get(record.listingId)?.venueMic === venueMic && contains(record, queryAt));
  }
  if (matches.length === 0) throw new ResolutionError("no visible symbol assignment covers queryAt; the result is a gap, cancellation, or unavailable revision");
  if (matches.length !== 1) throw new ResolutionError("ambiguous point-in-time symbol assignment; venue, listing, and interval evidence do not resolve uniquely");

  const selected = matches[0];
  const listing = listings.get(selected.listingId) as RecordMap;
  const instrument = instruments.get(listing.instrumentId as string) as RecordMap;
  const {chain, gaps, reusedSymbols} = buildChain(visible, selected.listingId);
  return {
    status: "resolved",
    direction,
    queryAt: queryAtText,
    asOf: asOfText,
    symbol: selected.symbol,
    listingId: selected.listingId,
    instrumentId: listing.instrumentId,
    issuerId: instrument.issuerId,
    shareClassId: instrument.shareClassId,
    venueMic: listing.venueMic,
    currency: listing.currency,
    assignmentId: selected.assignmentId,
    revision: selected.revision,
    changeKind: selected.changeKind,
    sourceId: selected.sourceId,
    announcedAt: selected.announcedAt,
    availableAt: selected.availableAt,
    effectiveAt: selected.effectiveAt,
    validTo: selected.validTo,
    chain,
    diagnostics: {
      visibleAssignmentCount: visible.length,
      chainSegmentCount: chain.length,
      gapCount: gaps.length,
      gaps,
      reusedSymbolsWithinListing: reusedSymbols,
    },
  };
}

export const calculate = resolveTickerChain;