'use strict';

// Anchors are the titles a user has shown taste for; their tags steer the wider AniList pool.
const ANCHOR_WEIGHTS = { flame: 5, good: 3, interested: 4, maybe: 2, read: 3, owned: 1 };
const MAX_ANCHORS = 15;
const MIN_TAG_RANK = 60;
const MAX_TOP_TAGS = 3;

function anchorsFor({ user, db, library, greatest }) {
  if (!user?.settings?.discoveryEnabled) return [];
  const byId = new Map();
  const add = (anilistId, source, title) => {
    if (!Number.isSafeInteger(anilistId) || anilistId <= 0) return;
    const weight = ANCHOR_WEIGHTS[source];
    const prior = byId.get(anilistId);
    if (!prior || weight > prior.weight) byId.set(anilistId, { anilistId, weight, source, title: title ?? null });
  };

  const ratings = db?.greatestRatings?.[user.name] || {};
  for (const entry of greatest?.entries || []) {
    const vote = ratings[entry.id];
    if (vote === 'flame' || vote === 'good') add(Number(entry.metadata?.id), vote, entry.title);
  }

  const feedback = db?.discoveryFeedback?.[user.name] || {};
  for (const [key, value] of Object.entries(feedback)) {
    const match = /^anilist:(\d+)$/.exec(key);
    if (match && (value === 'interested' || value === 'maybe')) add(Number(match[1]), value, null);
  }

  const progress = db?.progress?.[user.name] || {};
  const reading = Boolean(user.settings.discoveryReadingActivity);
  for (const manga of library || []) {
    const id = Number(manga.meta?.['x-anilist']?.id);
    if (!id) continue;
    const chapters = progress[manga.id];
    const done = reading && chapters && Object.values(chapters).some(chapter => chapter?.done);
    add(id, done ? 'read' : 'owned', manga.title);
  }

  return [...byId.values()]
    .sort((a, b) => b.weight - a.weight || a.anilistId - b.anilistId)
    .slice(0, MAX_ANCHORS);
}

function topTagsFor(anchors, recordOf, { mature = false } = {}) {
  const scores = new Map();
  for (const anchor of anchors) {
    const record = recordOf(anchor.anilistId);
    for (const tag of Array.isArray(record?.tags) ? record.tags : []) {
      // A tag without a rank is no evidence of taste, so it must not pass the rank filter.
      if (!tag || typeof tag !== 'object' || typeof tag.name !== 'string') continue;
      if (!(tag.rank >= MIN_TAG_RANK) || (tag.isAdult && !mature)) continue;
      const entry = scores.get(tag.name) || { name: tag.name, kind: tag.kind, score: 0 };
      entry.score += anchor.weight;
      scores.set(tag.name, entry);
    }
  }
  return [...scores.values()]
    .sort((a, b) => b.score - a.score || (a.name < b.name ? -1 : a.name > b.name ? 1 : 0))
    .slice(0, MAX_TOP_TAGS)
    .map(({ name, kind }) => ({ name, kind }));
}

module.exports = { ANCHOR_WEIGHTS, MAX_ANCHORS, anchorsFor, topTagsFor };