import crypto from 'node:crypto';
import { intentDraftTtlMs } from './intent-transaction-config.mjs';

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

function rowToDraft(row) {
  if (!row) return null;
  return {
    id: row.id,
    userId: row.user_id,
    layer: row.layer,
    draftType: row.draft_type,
    actionLevel: Number(row.action_level ?? 1),
    title: row.title,
    payload: parseJson(row.payload_json),
    cardText: row.card_text,
    status: row.status,
    sourceChannel: row.source_channel,
    sourceMessageId: row.source_message_id ?? null,
    sourceText: row.source_text ?? null,
    committedRef: parseJson(row.committed_ref_json),
    eventLog: parseJson(row.event_log_json) ?? [],
    expiresAt: row.expires_at == null ? null : Number(row.expires_at),
    createdAt: Number(row.created_at),
    updatedAt: Number(row.updated_at),
  };
}

function parseJson(value) {
  if (value == null || value === '') return null;
  if (typeof value === 'object') return value;
  try { return JSON.parse(value); } catch { return null; }
}

export function createIntentDraftService(pool, { clock = { now: () => Date.now() }, ttlMs = intentDraftTtlMs() } = {}) {
  if (!pool) throw new Error('缺少数据库连接');

  const appendEvent = (events, type, detail = {}) => [
    ...(Array.isArray(events) ? events : []),
    { type, at: clock.now(), ...detail },
  ];

  const expireStaleDrafts = async (userId) => {
    const now = nowMs(clock);
    await pool.query(
      `UPDATE h5_intent_drafts
       SET status = 'expired', updated_at = ?
       WHERE user_id = ? AND status = 'draft' AND expires_at IS NOT NULL AND expires_at <= ?`,
      [now, userId, now],
    );
  };

  const getPendingDraft = async (userId) => {
    if (!userId) return null;
    await expireStaleDrafts(userId);
    const [rows] = await pool.query(
      `SELECT * FROM h5_intent_drafts
       WHERE user_id = ? AND status = 'draft'
       ORDER BY created_at DESC
       LIMIT 1`,
      [userId],
    );
    return rowToDraft(rows?.[0]);
  };

  const createDraft = async ({
    userId,
    layer,
    draftType,
    actionLevel = 1,
    title,
    payload,
    cardText,
    sourceChannel = 'wechat',
    sourceMessageId = null,
    sourceText = null,
  }) => {
    if (!userId) throw new Error('缺少用户');
    const safeTitle = String(title ?? '').trim() || '待确认任务';
    const now = nowMs(clock);
    await expireStaleDrafts(userId);
    await pool.query(
      `UPDATE h5_intent_drafts
       SET status = 'cancelled', updated_at = ?
       WHERE user_id = ? AND status = 'draft'`,
      [now, userId],
    );
    const id = crypto.randomUUID();
    const expiresAt = now + ttlMs;
    const eventLog = appendEvent([], 'draft_created', { layer, draftType });
    await pool.query(
      `INSERT INTO h5_intent_drafts
       (id, user_id, layer, draft_type, action_level, title, payload_json, card_text, status,
        source_channel, source_message_id, source_text, committed_ref_json, event_log_json,
        expires_at, created_at, updated_at)
       VALUES (?, ?, ?, ?, ?, ?, ?, ?, 'draft', ?, ?, ?, NULL, ?, ?, ?, ?)`,
      [
        id,
        userId,
        layer,
        draftType,
        actionLevel,
        safeTitle,
        JSON.stringify(payload ?? {}),
        cardText,
        sourceChannel,
        sourceMessageId,
        sourceText,
        JSON.stringify(eventLog),
        expiresAt,
        now,
        now,
      ],
    );
    const [rows] = await pool.query(`SELECT * FROM h5_intent_drafts WHERE id = ? LIMIT 1`, [id]);
    return rowToDraft(rows?.[0]);
  };

  const cancelDraft = async (draftId, userId, { reason = 'user_cancel' } = {}) => {
    const now = nowMs(clock);
    const [rows] = await pool.query(
      `SELECT * FROM h5_intent_drafts WHERE id = ? AND user_id = ? LIMIT 1`,
      [draftId, userId],
    );
    const row = rows?.[0];
    if (!row) throw new Error('草稿不存在');
    if (row.status !== 'draft') return rowToDraft(row);
    const eventLog = appendEvent(parseJson(row.event_log_json), 'draft_cancelled', { reason });
    await pool.query(
      `UPDATE h5_intent_drafts SET status = 'cancelled', event_log_json = ?, updated_at = ? WHERE id = ?`,
      [JSON.stringify(eventLog), now, draftId],
    );
    const [updated] = await pool.query(`SELECT * FROM h5_intent_drafts WHERE id = ? LIMIT 1`, [draftId]);
    return rowToDraft(updated?.[0]);
  };

  const markDraftCommitted = async (draftId, userId, committedRef = {}) => {
    const now = nowMs(clock);
    const [rows] = await pool.query(
      `SELECT * FROM h5_intent_drafts WHERE id = ? AND user_id = ? LIMIT 1`,
      [draftId, userId],
    );
    const row = rows?.[0];
    if (!row) throw new Error('草稿不存在');
    const eventLog = appendEvent(parseJson(row.event_log_json), 'draft_committed', { committedRef });
    await pool.query(
      `UPDATE h5_intent_drafts
       SET status = 'committed', committed_ref_json = ?, event_log_json = ?, updated_at = ?
       WHERE id = ?`,
      [JSON.stringify(committedRef), JSON.stringify(eventLog), now, draftId],
    );
    const [updated] = await pool.query(`SELECT * FROM h5_intent_drafts WHERE id = ? LIMIT 1`, [draftId]);
    return rowToDraft(updated?.[0]);
  };

  return {
    getPendingDraft,
    createDraft,
    cancelDraft,
    markDraftCommitted,
  };
}