const MODE_WEIGHTS = Object.freeze({
    algo: Object.freeze({ algorithm: 80, structure: 15, metadata: 5, laya: 0 }),
    hybrid: Object.freeze({ algorithm: 70, structure: 15, metadata: 5, laya: 10 }),
    laya: Object.freeze({ algorithm: 55, structure: 15, metadata: 5, laya: 25 })
});
const PROTECTED_TOKENS = new Set(['max', 'news', 'premium', 'extra', 'xtra', 'kids', 'movies']);
const STRONG_FAMILIES = ['bein sports', 'sky sports', 'canal plus', 'eurosport', 'espn', 'dazn'];
const LAYA_CONFIDENCE_FLOOR = 0.65;
const MERGE_THRESHOLD = 70;

function tokens(value) {
    return String(value || '').toLowerCase().split(/[^a-z0-9]+/).filter(Boolean);
}

function strongFamily(value) {
    const text = tokens(value).join(' ');
    return STRONG_FAMILIES.find(family => text.includes(family)) || null;
}

function identityNumber(value, family = strongFamily(value)) {
    const list = tokens(value);
    let start = 0;
    if (family) {
        const familyTokens = family.split(' ');
        for (let index = 0; index <= list.length - familyTokens.length; index++) {
            if (familyTokens.every((token, offset) => list[index + offset] === token)) {
                start = index + familyTokens.length;
                break;
            }
        }
    }
    return list.slice(start).find(token => /^\d+$/.test(token)) || null;
}

function identity(value) {
    const list = tokens(value);
    const family = strongFamily(value);
    return {
        family,
        number: identityNumber(value, family),
        protectedTokens: new Set(list.filter(token => PROTECTED_TOKENS.has(token)))
    };
}

function sameSet(left, right) {
    return left.size === right.size && [...left].every(value => right.has(value));
}

function hardBlock(left, right) {
    const a = identity(left.fingerprint || left.name);
    const b = identity(right.fingerprint || right.name);
    if (!sameSet(a.protectedTokens, b.protectedTokens)) return 'protected_token_mismatch';
    if (a.number && b.number && a.number !== b.number) return 'number_mismatch';
    if (a.family && b.family && a.family !== b.family) return 'strong_family_mismatch';
    return null;
}

function pairKey(left, right) {
    return [String(left.id), String(right.id)].sort().join('\0');
}

function layaSignal(hint, leftIdentity, rightIdentity) {
    if (!hint || Number(hint.confidence) < LAYA_CONFIDENCE_FLOOR) return 0;
    if (hint.number && leftIdentity.number && hint.number !== leftIdentity.number) return 0;
    if (hint.number && rightIdentity.number && hint.number !== rightIdentity.number) return 0;
    if (hint.family && leftIdentity.family && hint.family !== leftIdentity.family) return 0;
    if (hint.family && rightIdentity.family && hint.family !== rightIdentity.family) return 0;
    return Number(hint.sameIdentityProbability) >= 0.5
        ? Math.min(1, Math.max(0, Number(hint.confidence)))
        : 0;
}

function scoreCandidate(left, right, options = {}) {
    const mode = MODE_WEIGHTS[options.mode] ? options.mode : 'algo';
    const weights = MODE_WEIGHTS[mode];
    const blocker = hardBlock(left, right);
    if (blocker) return { matched: false, blocker, total: 0, signals: { algorithm: 0, structure: 0, metadata: 0, laya: 0 } };

    const leftIdentity = identity(left.fingerprint || left.name);
    const rightIdentity = identity(right.fingerprint || right.name);
    const exact = left.fingerprint === right.fingerprint;
    const sameStructure = Boolean(leftIdentity.family && leftIdentity.family === rightIdentity.family &&
        leftIdentity.number && leftIdentity.number === rightIdentity.number);
    const algorithm = exact ? 1 : (mode !== 'algo' && sameStructure ? 0.6 : 0);
    const structure = sameStructure ? 1 : 0;
    const metadata = Boolean(
        (left.category_id && left.category_id === right.category_id) ||
        (left.tvg_id && left.tvg_id === right.tvg_id)
    ) ? 1 : 0;
    const laya = exact ? 0 : layaSignal(options.layaHint, leftIdentity, rightIdentity);
    const total = algorithm * weights.algorithm + structure * weights.structure +
        metadata * weights.metadata + laya * weights.laya;
    return { matched: total >= MERGE_THRESHOLD, blocker: null, total, signals: { algorithm, structure, metadata, laya } };
}

module.exports = {
    LAYA_CONFIDENCE_FLOOR,
    MERGE_THRESHOLD,
    MODE_WEIGHTS,
    PROTECTED_TOKENS,
    hardBlock,
    identity,
    pairKey,
    scoreCandidate
};