/**
 * Deduplication module implementation.
 * Tracks seen item IDs to filter duplicates from feeds.
 */

import type { Kysely } from 'kysely';
import type { FeedItem } from '../../interfaces/feed.types.js';
import type { IDedup } from '../../interfaces/dedup.interface.js';
import type { Database, SeenIdTable } from '../../infrastructure/db/database.js';

export class DatabaseDedup implements IDedup {
  private readonly db: Kysely<Database>;

  constructor(db: Kysely<Database>) {
    this.db = db;
  }

  async filter(items: FeedItem[]): Promise<FeedItem[]> {
    if (items.length === 0) {
      return [];
    }

    const ids = items.map((item) => item.id);

    // Query which IDs are already in the seen table
    const seenRows = await this.db
      .selectFrom('seen_ids')
      .select('id')
      .where('id', 'in', ids)
      .execute();

    const seenIds = new Set(seenRows.map((row) => row.id));

    // Return only items NOT in seen table
    return items.filter((item) => !seenIds.has(item.id));
  }

  async markSeen(items: FeedItem[]): Promise<void> {
    if (items.length === 0) {
      return;
    }

    const rows: SeenIdTable[] = items.map((item) => ({
      id: item.id,
      seen_at: new Date().toISOString(),
    }));

    // Insert or ignore (idempotent)
    await this.db
      .insertInto('seen_ids')
      .values(rows)
      .onConflict((oc) => oc.column('id').doNothing())
      .execute();
  }
}