import { logger } from '../utils/logger.js';
import dbManager from './databaseManager.js';

class PartitionManager {
  /**
   * Calculate the start and end timestamps (milliseconds) for a given date.
   * @param {Date} date - The date to calculate for.
   * @returns {Object} { startMs, endMs, partitionSuffix }
   */
  getPartitionInfo(date) {
    const yyyy = date.getFullYear();
    const mm = String(date.getMonth() + 1).padStart(2, '0');
    const dd = String(date.getDate()).padStart(2, '0');
    const partitionSuffix = `${yyyy}${mm}${dd}`;

    const start = new Date(date);
    start.setHours(0, 0, 0, 0);
    const startMs = start.getTime();

    const end = new Date(date);
    end.setDate(end.getDate() + 1);
    end.setHours(0, 0, 0, 0);
    const endMs = end.getTime();

    return { startMs, endMs, partitionSuffix };
  }

  /**
   * Ensure partitions exist for the next N days.
   * @param {number} daysAhead - Number of days to pre-create.
   */
  async ensurePartitions(daysAhead = 30) {
    const client = await dbManager.pool.connect();
    try {
      logger.info(`Starting partition check for the next ${daysAhead} days...`);
      const now = new Date();

      for (let i = 0; i < daysAhead; i++) {
        const targetDate = new Date(now);
        targetDate.setDate(now.getDate() + i);

        const { startMs, endMs, partitionSuffix } = this.getPartitionInfo(targetDate);
        const partitionName = `rcu_action.rcu_action_events_${partitionSuffix}`;

        // Check if partition exists
        const checkSql = `
          SELECT to_regclass($1) as exists;
        `;
        const checkRes = await client.query(checkSql, [partitionName]);
        
        if (!checkRes.rows[0].exists) {
          logger.info(`Creating partition ${partitionName} for range [${startMs}, ${endMs})`);
          const createSql = `
            CREATE TABLE IF NOT EXISTS ${partitionName}
            PARTITION OF rcu_action.rcu_action_events
            FOR VALUES FROM (${startMs}) TO (${endMs});
          `;
          await client.query(createSql);
        }
      }
      logger.info('Partition check completed.');
    } catch (err) {
      logger.error('Error ensuring partitions:', err);
      throw err;
    } finally {
      client.release();
    }
  }
}

export default new PartitionManager();