import crypto from 'node:crypto';

const STOPWORDS = new Set([
  '的', '了', '在', '是', '我', '你', '他', '她', '它', '我们', '你们', '他们',
  '这', '那', '有', '和', '与', '或', '就', '也', '都', '还', '要', '会', '能',
  '一个', '什么', '怎么', '可以', '没有', '不是', '如果', '因为', '所以', '但是',
  '然后', '已经', '还是', '自己', '现在', '今天', '明天', '这个', '那个', '一下',
  'the', 'and', 'for', 'with', 'this', 'that', 'from', 'have', 'are', 'was', 'not',
]);

function newId() {
  return crypto.randomUUID();
}

function nowMs() {
  return Date.now();
}

function extractTerms(text) {
  const terms = [];
  const cjk = String(text).match(/[\u4e00-\u9fff]{2,12}/g) ?? [];
  terms.push(...cjk);
  const en = String(text).match(/[a-zA-Z][a-zA-Z0-9]{2,}/g) ?? [];
  terms.push(...en.map((w) => w.toLowerCase()));
  return terms.filter((t) => !STOPWORDS.has(t));
}

function dayStartUtc(date) {
  const d = new Date(date);
  return new Date(Date.UTC(d.getUTCFullYear(), d.getUTCMonth(), d.getUTCDate()));
}

function dayEndUtc(date) {
  const start = dayStartUtc(date);
  return new Date(start.getTime() + 24 * 60 * 60 * 1000 - 1);
}

function hashSignal(userId, signalType, dimensionKey, windowStart, windowEnd, valueJson) {
  const raw = `${userId}|${signalType}|${dimensionKey}|${windowStart}|${windowEnd}|${JSON.stringify(valueJson)}`;
  return crypto.createHash('sha256').update(raw).digest('hex');
}

/**
 * @param {object} envelope Evidence Envelope v1
 * @returns {Array<object>} signal drafts
 */
export function extractSignalsFromEnvelope(envelope) {
  if (envelope.evidence_type !== 'expression_segment') return [];
  const payload = envelope.payload ?? {};
  const text = payload.text ?? '';
  const occurredAt = envelope.occurred_at;
  const windowStart = dayStartUtc(occurredAt).toISOString().slice(0, 23).replace('T', ' ');
  const windowEnd = dayEndUtc(occurredAt).toISOString().slice(0, 23).replace('T', ' ');
  const signals = [];

  for (const term of extractTerms(text)) {
    const key = /^[a-z]/.test(term) ? `term:${term}` : `term:${term}`;
    signals.push({
      signal_type: 'term_frequency',
      dimension_key: key,
      window_start: windowStart,
      window_end: windowEnd,
      value_json: { count: 1, chars: text.length },
      evidence_ids: [envelope.evidence_id],
    });
  }

  const appId = payload.context?.app_bundle_id;
  if (appId) {
    signals.push({
      signal_type: 'app_usage',
      dimension_key: `app:${appId}`,
      window_start: windowStart,
      window_end: windowEnd,
      value_json: { count: 1, app_name: payload.context?.app ?? null },
      evidence_ids: [envelope.evidence_id],
    });
  }

  const hour = new Date(occurredAt).getUTCHours();
  signals.push({
    signal_type: 'segment_count',
    dimension_key: `window:daily:${windowStart.slice(0, 10)}`,
    window_start: windowStart,
    window_end: windowEnd,
    value_json: { segments: 1, hour },
    evidence_ids: [envelope.evidence_id],
  });

  return signals;
}

export async function upsertSignals(pool, userId, signalDrafts) {
  let touched = 0;
  const ts = nowMs();
  for (const draft of signalDrafts) {
    const contentHash = hashSignal(
      userId,
      draft.signal_type,
      draft.dimension_key,
      draft.window_start,
      draft.window_end,
      draft.value_json,
    );
    const [existing] = await pool.query(
      `SELECT signal_id, value_json, evidence_ids FROM um_signals
       WHERE user_id = ? AND signal_type = ? AND dimension_key = ?
         AND window_start = ? AND window_end = ?
       LIMIT 1`,
      [userId, draft.signal_type, draft.dimension_key, draft.window_start, draft.window_end],
    );
    if (existing[0]) {
      const prev = existing[0];
      const prevValue = typeof prev.value_json === 'string' ? JSON.parse(prev.value_json) : prev.value_json;
      const prevEvidence =
        typeof prev.evidence_ids === 'string' ? JSON.parse(prev.evidence_ids) : prev.evidence_ids;
      const mergedEvidence = [...new Set([...(prevEvidence ?? []), ...draft.evidence_ids])];
      const mergedValue = {
        ...prevValue,
        count: Number(prevValue.count ?? 0) + Number(draft.value_json.count ?? 1),
        segments: Number(prevValue.segments ?? 0) + Number(draft.value_json.segments ?? 0),
        chars: Number(prevValue.chars ?? 0) + Number(draft.value_json.chars ?? 0),
      };
      await pool.query(
        `UPDATE um_signals SET value_json = ?, evidence_ids = ?, computed_at = ?, content_hash = ?
         WHERE signal_id = ?`,
        [JSON.stringify(mergedValue), JSON.stringify(mergedEvidence), ts, contentHash, prev.signal_id],
      );
    } else {
      await pool.query(
        `INSERT INTO um_signals
         (signal_id, user_id, signal_type, dimension_key, window_start, window_end,
          value_json, evidence_ids, computed_at, content_hash)
         VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
        [
          newId(),
          userId,
          draft.signal_type,
          draft.dimension_key,
          draft.window_start,
          draft.window_end,
          JSON.stringify(draft.value_json),
          JSON.stringify(draft.evidence_ids),
          ts,
          contentHash,
        ],
      );
    }
    touched += 1;
  }
  return touched;
}

export { extractTerms, STOPWORDS };