/**
 * Pure helpers for the live futures quote feed (lib/live-quotes.ts): reading
 * what TopstepX's market hub and Tradovate's market-data socket send, and
 * turning the top of the book into the spread an entry pays.
 *
 * No imports, so scripts/check-instruments.mjs can test them directly.
 */

export interface BookTop {
    bid?: number;
    ask?: number;
}

const price = (v: unknown): number | undefined => (typeof v === 'number' && Number.isFinite(v) && v > 0 ? v : undefined);

/**
 * A TopstepX GatewayQuote laid over the last one. The hub sends only the
 * fields that changed, so a side it leaves out keeps its last price.
 */
export function mergeTopstepxQuote(prev: BookTop | undefined, raw: unknown): BookTop {
    const r = raw as Record<string, unknown> | null;
    const data = r && typeof r === 'object' && 'data' in r && typeof r.data === 'object' && r.data !== null
        ? (r.data as Record<string, unknown>)
        : r;
    const bid = price(data?.bestBid);
    const ask = price(data?.bestAsk);
    return { ...prev, ...(bid !== undefined ? { bid } : {}), ...(ask !== undefined ? { ask } : {}) };
}

export interface TradovateFrame {
    /** Replies to requests: request id, HTTP-like status, payload. */
    responses: { id: number; status: number; data?: unknown }[];
    /** Quote updates by contract id; a side left out didn't change. */
    quotes: { contractId: number; bid?: number; ask?: number }[];
}

/** One frame off Tradovate's market-data socket ('a[...]'; 'o', 'h' and 'c'
 *  frames carry nothing to read). */
export function parseTradovateFrame(frame: unknown): TradovateFrame {
    const out: TradovateFrame = { responses: [], quotes: [] };
    if (typeof frame !== 'string' || frame[0] !== 'a') return out;
    let items: unknown;
    try { items = JSON.parse(frame.slice(1)); } catch { return out; }
    if (!Array.isArray(items)) return out;
    for (const item of items) {
        if (!item || typeof item !== 'object') continue;
        const it = item as { e?: unknown; d?: unknown; i?: unknown; s?: unknown };
        if (typeof it.i === 'number' && typeof it.s === 'number') {
            out.responses.push({ id: it.i, status: it.s, data: it.d });
            continue;
        }
        if (it.e !== 'md') continue;
        const quotes = (it.d as { quotes?: unknown } | undefined)?.quotes;
        if (!Array.isArray(quotes)) continue;
        for (const q of quotes) {
            const quote = q as { contractId?: unknown; entries?: Record<string, { price?: unknown } | undefined> } | null;
            if (typeof quote?.contractId !== 'number') continue;
            const bid = price(quote.entries?.Bid?.price);
            const ask = price(quote.entries?.Offer?.price);
            out.quotes.push({ contractId: quote.contractId, ...(bid !== undefined ? { bid } : {}), ...(ask !== undefined ? { ask } : {}) });
        }
    }
    return out;
}

/**
 * What crossing the book costs on one contract: the width between bid and
 * ask, in dollars and in ticks. null for a book missing a side or crossed
 * (ask below bid) — not a spread anyone can enter on.
 */
export function bookSpread(book: BookTop | undefined, pointValue: number, tickSize: number): { dollars: number; ticks: number } | null {
    if (!book || book.bid === undefined || book.ask === undefined || book.ask < book.bid) return null;
    if (!(pointValue > 0)) return null;
    const width = book.ask - book.bid;
    return {
        dollars: Math.round(width * pointValue * 100) / 100,
        ticks: tickSize > 0 ? Math.round(width / tickSize) : NaN,
    };
}