import { getDatabase } from '../db/index';
import collectionsRepo from '../db/repositories/collections';
import logger from '../utils/logger';
import type { WatchLookup } from './conditions';
import { loadInProgressConfig } from './inProgress';
import type { EvaluationContext } from './engine';

/**
 * Build a ratingKey → username → Date lookup from the watch_history_cache.
 * Called once per preview/evaluation run.
 */
export function buildWatchLookup(): WatchLookup {
  const lookup: WatchLookup = new Map();
  try {
    // Snapshot the cache — pull all watched entries. For very large caches
    // this could be narrowed with a filter, but 100k rows is manageable.
    const db = getDatabase();
    const rows = db
      .prepare(
        'SELECT plex_rating_key, username, MAX(stopped_at) as stopped_at FROM watch_history_cache WHERE watched = 1 GROUP BY plex_rating_key, username'
      )
      .all() as Array<{ plex_rating_key: string; username: string; stopped_at: string }>;
    for (const r of rows) {
      let userMap = lookup.get(r.plex_rating_key);
      if (!userMap) {
        userMap = new Map();
        lookup.set(r.plex_rating_key, userMap);
      }
      userMap.set(r.username, new Date(r.stopped_at));
    }
  } catch (err) {
    logger.warn('Failed to build watch lookup:', err);
  }
  return lookup;
}

/**
 * The same watched history keyed by lower-cased show title, so a show's
 * viewers can be found from its episodes' plays.
 */
export function buildShowWatchLookup(): WatchLookup {
  const lookup: WatchLookup = new Map();
  try {
    const rows = getDatabase()
      .prepare(
        `SELECT LOWER(show_title) AS show_key, username, MAX(stopped_at) AS stopped_at
         FROM watch_history_cache
         WHERE watched = 1 AND show_title IS NOT NULL AND show_title != ''
         GROUP BY show_key, username`
      )
      .all() as Array<{ show_key: string; username: string; stopped_at: string }>;
    for (const r of rows) {
      let userMap = lookup.get(r.show_key);
      if (!userMap) {
        userMap = new Map();
        lookup.set(r.show_key, userMap);
      }
      userMap.set(r.username, new Date(r.stopped_at));
    }
  } catch (err) {
    logger.warn('Failed to build show watch lookup:', err);
  }
  return lookup;
}

/**
 * The single place an EvaluationContext is assembled. Every caller that
 * evaluates rule conditions must go through here — a context missing its
 * watchLookup silently inverts watched_by/watched_by_user conditions
 * (`is_empty` reports true for every item), which previously made the
 * scheduled scan see the whole library as never-watched.
 */
export function buildEvaluationContext(): EvaluationContext {
  return {
    collectionsRepo,
    watchLookup: buildWatchLookup(),
    showWatchLookup: buildShowWatchLookup(),
    inProgressRecentDays: loadInProgressConfig().recentDays,
    now: new Date(),
  };
}