/**
 * Contract Resolver
 *
 * Determines the best contract for each symbol by combining:
 * 1. Tradovate's suggest API (front month)
 * 2. Tradovate's rollcontract API (next months)
 * 3. Yahoo Finance continuous contract price matching ({PRODUCT}=F)
 *
 * Results are cached and refreshed periodically (default: every 30 minutes).
 */

import axios from 'axios';

interface ContractInfo {
    id: number;
    name: string;
    tickSize: number;
    contractMaturityId?: number;
}

export interface ResolvedContract extends ContractInfo {
    /** The other candidate contracts that were not selected */
    alternative?: string;
}

// ── Yahoo Finance ticker mapping ─────────────────────────────────────────────

const EXCHANGE_MAP: Record<string, string> = {
    NQ: 'CME', MNQ: 'CME', ES: 'CME', MES: 'CME',
    YM: 'CBT', MYM: 'CBT', RTY: 'CME', M2K: 'CME',
    GC: 'CMX', MGC: 'CMX',
    SI: 'CMX', SIL: 'CMX',
    CL: 'NYM', MCL: 'NYM', NG: 'NYM',
    ZB: 'CBT', ZN: 'CBT', ZF: 'CBT',
    '6E': 'CME', '6J': 'CME', '6B': 'CME',
};

/** Convert Tradovate name to Yahoo ticker, e.g. "GCH6" → "GCH26.CMX" */
function toYahoo(tvName: string): string {
    const yearDigit = tvName.slice(-1);
    const monthLetter = tvName.slice(-2, -1);
    const product = tvName.slice(0, -2);
    const year2d = '2' + yearDigit; // assumes 2020s
    const exchange = EXCHANGE_MAP[product] ?? 'CME';
    return `${product}${monthLetter}${year2d}.${exchange}`;
}

// ── Cache ────────────────────────────────────────────────────────────────────

const cache = new Map<string, { contract: ResolvedContract; resolvedAt: number }>();
const CACHE_TTL_MS = 30 * 60 * 1000; // 30 minutes

export function getCachedContract(symbol: string): ResolvedContract | null {
    const entry = cache.get(symbol);
    if (!entry) return null;
    if (Date.now() - entry.resolvedAt > CACHE_TTL_MS) {
        cache.delete(symbol);
        return null;
    }
    return entry.contract;
}

export function getAllCachedContracts(): Record<string, ResolvedContract | null> {
    const result: Record<string, ResolvedContract | null> = {};
    for (const [symbol, entry] of cache) {
        if (Date.now() - entry.resolvedAt > CACHE_TTL_MS) {
            cache.delete(symbol);
            result[symbol] = null;
        } else {
            result[symbol] = entry.contract;
        }
    }
    return result;
}

// ── Yahoo Finance price lookup ───────────────────────────────────────────────

/** Fetch regularMarketPrice for a Yahoo ticker. Returns null on failure. */
async function getYahooPrice(ticker: string): Promise<number | null> {
    try {
        const res = await axios.get(
            `https://query1.finance.yahoo.com/v8/finance/chart/${encodeURIComponent(ticker)}`,
            { params: { range: '1d', interval: '1d' }, headers: { 'User-Agent': 'Mozilla/5.0' } }
        );
        const meta = res.data?.chart?.result?.[0]?.meta;
        return meta?.regularMarketPrice ?? null;
    } catch {
        return null;
    }
}

/** Get the continuous contract price for a product (e.g. "GC" → "GC=F"). */
async function getContinuousPrice(product: string): Promise<number | null> {
    return getYahooPrice(`${product}=F`);
}

/** Get the price for a specific Tradovate contract name (e.g. "GCM6" → "GCM26.CMX"). */
async function getCandidatePrice(tvName: string): Promise<number | null> {
    return getYahooPrice(toYahoo(tvName));
}

// ── Main resolver ────────────────────────────────────────────────────────────

/**
 * Resolve the best contract for a list of symbols using a Tradovate access token.
 * For each symbol:
 *   1. Get front month via /contract/suggest
 *   2. Get roll targets via /contract/rollcontract (up to 2 forward)
 *   3. Match candidates against Yahoo's continuous contract price ({PRODUCT}=F)
 */
export async function resolveContracts(
    symbols: string[],
    accessToken: string,
): Promise<Record<string, ResolvedContract | null>> {
    const headers = { Authorization: `Bearer ${accessToken}` };
    const results: Record<string, ResolvedContract | null> = {};

    // Step 1: Get front month for each symbol
    const frontMonths: Record<string, ContractInfo | null> = {};
    await Promise.all(symbols.map(async (sym) => {
        try {
            const res = await axios.get(
                `https://demo.tradovateapi.com/v1/contract/suggest?t=${encodeURIComponent(sym)}&l=5`,
                { headers }
            );
            const contracts: ContractInfo[] = res.data ?? [];
            // Match symbol exactly: after the symbol prefix, next char must be a month code (A-Z) then a digit
            const match = contracts.find((c) => {
                if (!c.name.startsWith(sym)) return false;
                const rest = c.name.slice(sym.length);
                return /^[A-Z]\d/.test(rest);
            });
            frontMonths[sym] = match ? {
                id: match.id,
                name: match.name,
                tickSize: (match as any).providerTickSize ?? 0.25,
                contractMaturityId: (match as any).contractMaturityId,
            } : null;
        } catch {
            frontMonths[sym] = null;
        }
    }));

    // Step 2: Get roll targets (up to 2 months forward to handle bi-monthly products like GC)
    const rollTargets1: Record<string, ContractInfo | null> = {};
    const rollTargets2: Record<string, ContractInfo | null> = {};
    await Promise.all(symbols.map(async (sym) => {
        const front = frontMonths[sym];
        if (!front) { rollTargets1[sym] = null; rollTargets2[sym] = null; return; }
        try {
            const res1 = await axios.post(
                'https://demo.tradovateapi.com/v1/contract/rollcontract',
                { name: front.name, forward: true, ifExpired: false },
                { headers }
            );
            const c1 = res1.data?.contract;
            if (c1 && c1.name !== front.name) {
                rollTargets1[sym] = {
                    id: c1.id, name: c1.name,
                    tickSize: c1.providerTickSize ?? 0.25,
                    contractMaturityId: c1.contractMaturityId,
                };
                // Roll a second time from the first rolled contract
                try {
                    const res2 = await axios.post(
                        'https://demo.tradovateapi.com/v1/contract/rollcontract',
                        { name: c1.name, forward: true, ifExpired: false },
                        { headers }
                    );
                    const c2 = res2.data?.contract;
                    if (c2 && c2.name !== c1.name) {
                        rollTargets2[sym] = {
                            id: c2.id, name: c2.name,
                            tickSize: c2.providerTickSize ?? 0.25,
                            contractMaturityId: c2.contractMaturityId,
                        };
                    } else {
                        rollTargets2[sym] = null;
                    }
                } catch {
                    rollTargets2[sym] = null;
                }
            } else {
                rollTargets1[sym] = null;
                rollTargets2[sym] = null;
            }
        } catch {
            rollTargets1[sym] = null;
            rollTargets2[sym] = null;
        }
    }));

    // Step 3: Match candidates against Yahoo's continuous contract price ({PRODUCT}=F)
    // This is more reliable than volume comparison — Yahoo knows the active contract.
    for (const sym of symbols) {
        const front = frontMonths[sym];
        const roll1 = rollTargets1[sym];
        const roll2 = rollTargets2[sym];

        if (!front) {
            results[sym] = null;
            continue;
        }

        const candidates: { contract: ContractInfo; label: string }[] = [
            { contract: front, label: 'front' },
        ];
        if (roll1) candidates.push({ contract: roll1, label: 'roll1' });
        if (roll2) candidates.push({ contract: roll2, label: 'roll2' });

        // Fetch continuous price and all candidate prices in parallel
        const [continuousPrice, ...candidatePrices] = await Promise.all([
            getContinuousPrice(sym),
            ...candidates.map(c => getCandidatePrice(c.contract.name)),
        ]);

        console.log(`[contract-resolver] ${sym}: continuous=${continuousPrice}, candidates=[${candidates.map((c, i) => `${c.contract.name}=$${candidatePrices[i]}`).join(', ')}]`);

        // Find the candidate with the closest price to the continuous contract
        let best = candidates[0]; // default to front
        if (continuousPrice !== null) {
            let bestDiff = Infinity;
            for (let i = 0; i < candidates.length; i++) {
                const price = candidatePrices[i];
                if (price === null) continue;
                const diff = Math.abs(price - continuousPrice);
                if (diff < bestDiff) {
                    bestDiff = diff;
                    best = candidates[i];
                }
            }
        } else {
            // Yahoo failed entirely — fall back to roll1 (nearest non-expired) if available
            if (roll1) best = candidates[1];
        }

        const alternatives = candidates.filter(c => c !== best).map(c => c.contract.name).join(', ');
        results[sym] = {
            ...best.contract,
            alternative: alternatives || undefined,
        };

        if (best.label !== 'front') {
            console.log(`[contract-resolver] ${sym}: ${front.name} → ${best.contract.name} (price match) ROLLED`);
        } else {
            console.log(`[contract-resolver] ${sym}: ${front.name} stays (price match)`);
        }

        // Update cache
        if (results[sym]) {
            cache.set(sym, { contract: results[sym]!, resolvedAt: Date.now() });
        }
    }

    return results;
}