'use strict';

const { specialKey } = require('../../chapter-identity');

function localizedTitle(attributes = {}) {
  const titles = attributes.title || {};
  return titles.en || titles['ja-ro'] || titles.ja || Object.values(titles).find(Boolean) || 'Untitled';
}

function chapterNumber(value) {
  const raw = String(value ?? '').trim();
  if (!/^\d+(?:\.\d+)?$/.test(raw)) return null;
  const [whole, decimal = ''] = raw.split('.');
  const normalizedWhole = whole.replace(/^0+(?=\d)/, '') || '0';
  const normalizedDecimal = decimal.replace(/0+$/, '');
  return normalizedDecimal ? `${normalizedWhole}.${normalizedDecimal}` : normalizedWhole;
}

function groupFor(resource) {
  const relation = (resource.relationships || []).find(item => item.type === 'scanlation_group');
  return relation ? { id: relation.id, name: relation.attributes?.name || 'Unknown group' } : null;
}

function releaseRank(resource) {
  const group = groupFor(resource)?.name || '';
  const credited = /official|license/i.test(group) ? 0 : group ? 1 : 2;
  const date = Date.parse(resource.attributes?.publishAt || resource.attributes?.readableAt || resource.attributes?.createdAt || '') || Number.MAX_SAFE_INTEGER;
  return [credited, date, resource.id];
}

function compareRank(left, right) {
  const a = releaseRank(left), b = releaseRank(right);
  return a[0] - b[0] || a[1] - b[1] || String(a[2]).localeCompare(String(b[2]));
}

function selectChapterReleases(resources = [], specialLabel = 'Special') {
  const selected = new Map();
  for (const resource of resources) {
    if (resource.attributes?.externalUrl || Number(resource.attributes?.pages || 0) < 1) continue;
    const number = chapterNumber(resource.attributes?.chapter) || specialKey(resource.id);
    const prior = selected.get(number);
    if (!prior || compareRank(resource, prior) < 0) selected.set(number, resource);
  }
  return [...selected.entries()].map(([number, resource]) => {
    const group = groupFor(resource);
    return {
      id: resource.id, number, title: resource.attributes?.title || '',
      ...(!chapterNumber(resource.attributes?.chapter) ? { special: true, label: specialLabel, sourceId: resource.id, sourceNumber: resource.attributes?.chapter ?? null } : {}),
      ...(resource.attributes?.volume ? { volume: chapterNumber(resource.attributes.volume) || String(resource.attributes.volume) } : {}),
      pages: Number(resource.attributes?.pages || 0),
      added: resource.attributes?.publishAt || resource.attributes?.readableAt || resource.attributes?.createdAt,
      group,
      url: `https://mangadex.org/chapter/${resource.id}`,
    };
  }).sort((a, b) => Number(!!a.special) - Number(!!b.special) || (a.special ? a.number.localeCompare(b.number) : Number(a.number) - Number(b.number) || a.number.localeCompare(b.number)));
}

function availabilitySummary(attributes, releases, chapters, externalReleases = null) {
  const numbered = chapters.filter(ref => !ref.special);
  const expected = chapterNumber(attributes.lastChapter);
  const maximum = numbered.length ? Math.max(...numbered.map(ref => Number(ref.number))) : null;
  const expectedCount = expected && /^\d+$/.test(expected) ? Number(expected) : null;
  const sparse = expectedCount && numbered.length < expectedCount;
  const reason = chapters.length ? null : externalReleases > 0 ? 'external-only'
    : Array.isArray(attributes.availableTranslatedLanguages) && !attributes.availableTranslatedLanguages.includes('en') ? 'no-english' : 'no-hosted-pages';
  const message = reason === 'external-only' ? `MangaDex lists ${externalReleases} English external-link releases, but no hosted English pages. External links are not downloaded.`
    : reason === 'no-english' ? 'This MangaDex edition has no English releases listed.'
      : reason ? 'This MangaDex edition has no hosted English releases with pages.' : null;
  return { language: 'en', hostedReleases: releases.filter(r => !r.attributes?.externalUrl && Number(r.attributes?.pages) > 0).length,
    selectedChapters: chapters.length, numberedChapters: numbered.length, specialReleases: chapters.length - numbered.length,
    externalReleases, expectedLastChapter: expected, highestHostedChapter: maximum,
    coverage: expected && (maximum === null || maximum < Number(expected) || sparse) ? 'partial' : 'unknown', reason, message };
}

function pageUrls(atHome, chapterUrl, expectedPages) {
  const base = new URL(atHome.baseUrl);
  if (base.protocol !== 'https:' || !(base.hostname === 'uploads.mangadex.org' || base.hostname.endsWith('.mangadex.network'))) {
    throw new Error(`Unexpected MangaDex@Home host: ${base.hostname}`);
  }
  const hash = String(atHome.chapter?.hash || '');
  const files = atHome.chapter?.data;
  if (!hash || !Array.isArray(files) || !files.length) throw new Error('MangaDex@Home returned no pages');
  if (expectedPages && files.length !== expectedPages) throw new Error(`MangaDex page count changed: expected ${expectedPages}, received ${files.length}`);
  return files.map(file => ({
    url: new URL(`/data/${encodeURIComponent(hash)}/${encodeURIComponent(file)}`, base).href,
    headers: { referer: chapterUrl },
  }));
}

function metadata({ data: manga }) {
  if (!manga || manga.type !== 'manga') throw new Error('MangaDex title was not found');
  const attributes = manga.attributes || {};
  const title = localizedTitle(attributes);
  const specialLabel = /pre.serialization|pilot/i.test(title) ? 'Pilot'
    : (attributes.tags || []).some(tag => tag.attributes?.name?.en === 'Oneshot') ? 'One-shot' : 'Special';
  return { title, originalLanguage: attributes.originalLanguage || null, links: attributes.links || {},
    specialLabel, availabilityAttributes: {
      lastChapter: attributes.lastChapter ?? null,
      availableTranslatedLanguages: attributes.availableTranslatedLanguages ?? null,
    } };
}

function feed({ data: releases }) {
  if (!Array.isArray(releases)) throw new Error('Invalid MangaDex feed');
  return { releases: releases.map(resource => ({
    id: resource.id,
    attributes: {
      chapter: resource.attributes?.chapter, volume: resource.attributes?.volume,
      title: resource.attributes?.title, pages: resource.attributes?.pages,
      publishAt: resource.attributes?.publishAt, readableAt: resource.attributes?.readableAt,
      createdAt: resource.attributes?.createdAt, externalUrl: resource.attributes?.externalUrl,
    },
    relationships: (resource.relationships || []).filter(relation => relation.type === 'scanlation_group'),
  })) };
}

function catalog({ data }) {
  const { attributes, releases, specialLabel, externalReleases } = data;
  if (!attributes || !Array.isArray(releases)) throw new Error('Invalid MangaDex catalog input');
  const chapters = selectChapterReleases(releases, specialLabel);
  return { chapters, availability: availabilitySummary(attributes, releases, chapters, externalReleases) };
}

function atHome({ data }) {
  const { response, chapterUrl, expectedPages } = data;
  return { pages: pageUrls(response, chapterUrl, expectedPages) };
}

module.exports = { localizedTitle, chapterNumber, selectChapterReleases, availabilitySummary,
  pageUrls, metadata, feed, catalog, atHome };