import type { InstrumentHint, NormalizedObservation, ObservationType, RealtimeStatus, RightsStatus, TimestampTrust } from "@market-atlas/market-model";
import { cryptoHint, type TickerFields } from "./crypto.js";
import { conventionalPair, fxHint } from "../ecb-frankfurter/index.js";

export const FIAT = new Set(["USD", "EUR", "GBP", "JPY", "CAD", "AUD", "CHF", "NZD", "SGD", "HKD", "BRL", "MXN", "TRY", "ZAR", "ARS", "AED", "PLN", "SEK", "NOK", "DKK", "CZK", "HUF", "RON", "UAH", "INR", "KRW", "CNY"]);
export const STABLES = new Set(["USDT", "USDC", "USD1", "FDUSD", "TUSD", "DAI"]);

export interface PairPlan {
  /** Instrument hint to resolve/create. */
  hint: InstrumentHint;
  /** Nature of the LAST_PRICE value. */
  type: ObservationType;
  /** Multiply venue prices by -1 exponent: when true, canonical value = 1 / venue price. */
  invert: boolean;
  currency: string;
}

/**
 * Decide what a venue pair *means* for Market Atlas:
 *  - fiat/fiat (Kraken EUR/USD, Bitstamp EURUSD)  → FOREX instrument, TRADE (a real fiat market)
 *  - stable/fiat or fiat/stable (USDT-EUR, EURUSDT) → FOREX instrument, STABLECOIN_PROXY (USDT ≈ USD)
 *  - anything else                                  → CRYPTO instrument, TRADE
 */
export function planPair(base: string, quote: string, exchangeId: string): PairPlan {
  const b = base.toUpperCase();
  const q = quote.toUpperCase();
  if (FIAT.has(b) && FIAT.has(q)) {
    const [cb, cq] = conventionalPair(b, q);
    return { hint: fxHint(cb, cq), type: "TRADE", invert: cb !== b, currency: cq };
  }
  const bStable = STABLES.has(b);
  const qStable = STABLES.has(q);
  if ((bStable && FIAT.has(q) && q !== "USD") || (qStable && FIAT.has(b) && b !== "USD")) {
    const fb = bStable ? "USD" : b;
    const fq = qStable ? "USD" : q;
    const [cb, cq] = conventionalPair(fb, fq);
    return { hint: fxHint(cb, cq), type: "STABLECOIN_PROXY", invert: cb !== fb, currency: cq };
  }
  return { hint: cryptoHint(b, q, exchangeId), type: "TRADE", invert: false, currency: q };
}

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

/**
 * Venue ticker → observations for whatever the pair means (crypto, live FX, stablecoin proxy).
 * Inverted pairs swap bid/ask and drop venue-specific volumes (they would be in the wrong unit).
 */
export function pairObservations(
  symbol: string,
  base: string,
  quote: string,
  exchangeId: string,
  f: TickerFields,
  meta: { sourceTimestamp: number | null; timestampTrust: TimestampTrust; sequence?: number | string | null; rightsStatus: RightsStatus; realtimeStatus: RealtimeStatus },
): NormalizedObservation[] {
  const plan = planPair(base, quote, exchangeId);
  const out: NormalizedObservation[] = [];
  const conv = (v: number) => (plan.invert ? 1 / v : v);
  const push = (field: NormalizedObservation["field"], v: unknown, type: ObservationType) => {
    const n = num(v);
    if (n == null) return;
    if (field !== "VOLUME" && field !== "BID_SIZE" && field !== "ASK_SIZE" && n <= 0) return;
    const value = field === "VOLUME" || field === "BID_SIZE" || field === "ASK_SIZE" ? n : Number(conv(n).toPrecision(10));
    out.push({ symbol, instrumentHint: plan.hint, field, value, currency: plan.currency, observationType: type, sourceTimestamp: meta.sourceTimestamp, timestampTrust: meta.timestampTrust, sequence: meta.sequence ?? null, rightsStatus: meta.rightsStatus, realtimeStatus: meta.realtimeStatus, meta: plan.type === "STABLECOIN_PROXY" ? { venue_pair: `${base}/${quote}`, proxy: true } : undefined });
  };
  const quoteType: ObservationType = plan.type === "STABLECOIN_PROXY" ? "STABLECOIN_PROXY" : "QUOTE";
  push("LAST_PRICE", f.last, plan.type);
  if (plan.invert) {
    // 1/x flips the order: venue ask becomes our bid.
    push("BID", f.ask, quoteType);
    push("ASK", f.bid, quoteType);
    push("HIGH", f.low, plan.type);
    push("LOW", f.high, plan.type);
    push("OPEN", f.open, plan.type);
  } else {
    push("BID", f.bid, quoteType);
    push("ASK", f.ask, quoteType);
    push("HIGH", f.high, plan.type);
    push("LOW", f.low, plan.type);
    push("OPEN", f.open, plan.type);
    push("BID_SIZE", f.bidSize, quoteType);
    push("ASK_SIZE", f.askSize, quoteType);
    if (plan.type !== "STABLECOIN_PROXY") push("VOLUME", f.volume, plan.type);
    if (plan.type === "TRADE" && plan.hint.assetClass === "CRYPTO") push("VWAP", f.vwap, plan.type);
  }
  return out;
}

/** Split a venue symbol using an explicit separator or a list of known quote currencies. */
export function splitVenueSymbol(symbol: string, sep: string | null, quotes: string[] = ["USDT", "USDC", "USD", "EUR", "GBP", "JPY", "BTC", "ETH", "TRY", "BRL", "MXN", "ZAR", "ARS", "AUD", "SGD", "AED", "CAD", "CHF"]): [string, string] | null {
  if (sep) {
    const [b, q] = symbol.split(sep);
    return b && q ? [b.toUpperCase(), q.toUpperCase()] : null;
  }
  const s = symbol.toUpperCase();
  for (const q of quotes.sort((a, b) => b.length - a.length)) if (s.endsWith(q) && s.length > q.length) return [s.slice(0, -q.length), q];
  return null;
}