'use strict';

const INPUT_TYPES = ['mouse', 'touch', 'keyboard'];
const MAX_RECENT_SESSIONS = 8;

const whole = (value, max = Number.MAX_SAFE_INTEGER) => Math.min(max, Math.max(0, Math.round(Number(value) || 0)));

function rangeSet(ranges, pageCount = Number.MAX_SAFE_INTEGER) {
  const out = new Set();
  for (const pair of Array.isArray(ranges) ? ranges : []) {
    if (!Array.isArray(pair) || pair.length < 2) continue;
    const start = whole(pair[0], pageCount - 1), end = whole(pair[1], pageCount - 1);
    for (let i = Math.min(start, end); i <= Math.max(start, end); i++) out.add(i);
  }
  return out;
}

function compactRanges(values) {
  const sorted = [...new Set(values)].filter(Number.isInteger).sort((a, b) => a - b);
  const ranges = [];
  for (const value of sorted) {
    const last = ranges[ranges.length - 1];
    if (last && value <= last[1] + 1) last[1] = Math.max(last[1], value);
    else ranges.push([value, value]);
  }
  return ranges;
}

function eligiblePages(version, settings) {
  const eligible = [];
  for (let i = 0; i < version.pages.length; i++) {
    const tags = version.pages[i].t || [];
    if (settings.skipExtras && tags.includes('extra')) continue;
    if (settings.skipCovers && tags.includes('cover')) continue;
    eligible.push(i);
  }
  return eligible.length ? eligible : version.pages.map((_, i) => i);
}

function emptyRecord() {
  return {
    schema: 1,
    totalActiveMs: 0,
    firstCompleteMs: null,
    lastCompleteMs: null,
    loadingMs: 0,
    sessions: 0,
    completedPasses: 0,
    inputMs: { mouse: 0, touch: 0, keyboard: 0 },
    fastBursts: 0,
    rejectedPageViews: 0,
    maxObservedPps: 0,
    currentPass: null,
    recentSessions: [],
    updatedAt: 0,
  };
}

function normalizeRecord(record) {
  const base = emptyRecord(), out = record && typeof record === 'object' ? record : {};
  for (const [key, value] of Object.entries(base)) if (out[key] === undefined) out[key] = value;
  out.inputMs = { ...base.inputMs, ...(out.inputMs || {}) };
  out.recentSessions = Array.isArray(out.recentSessions) ? out.recentSessions : [];
  return out;
}

function publicSummary(record, version, eligible) {
  const r = normalizeRecord(record || emptyRecord());
  const pass = r.currentPass && r.currentPass.version === version ? r.currentPass : null;
  const allowed = new Set(eligible);
  const seen = pass ? [...rangeSet(pass.seenRanges)].filter(x => allowed.has(x)) : [];
  const predominantInput = INPUT_TYPES.reduce((best, key) => r.inputMs[key] > r.inputMs[best] ? key : best, 'mouse');
  const hasInput = INPUT_TYPES.some(key => r.inputMs[key] > 0);
  return {
    schema: 1,
    totalActiveMs: whole(r.totalActiveMs),
    firstCompleteMs: r.firstCompleteMs == null ? null : whole(r.firstCompleteMs),
    lastCompleteMs: r.lastCompleteMs == null ? null : whole(r.lastCompleteMs),
    loadingMs: whole(r.loadingMs),
    sessions: whole(r.sessions),
    completedPasses: whole(r.completedPasses),
    inputMs: Object.fromEntries(INPUT_TYPES.map(key => [key, whole(r.inputMs[key])])),
    predominantInput: hasInput ? predominantInput : null,
    fastBursts: whole(r.fastBursts),
    rejectedPageViews: whole(r.rejectedPageViews),
    maxObservedPps: whole(r.maxObservedPps),
    eligiblePages: eligible.length,
    currentPass: {
      version,
      activeMs: whole(pass && pass.activeMs),
      seenRanges: compactRanges(seen),
      seenPages: seen.length,
      complete: !!(pass && pass.completedAt),
      startedAt: pass ? whole(pass.startedAt) : null,
      protocol: pass?.protocol || 1,
      requiredPages: Math.ceil(eligible.length * (pass?.protocol === 2 ? 0.6 : 1)),
    },
    updatedAt: whole(r.updatedAt),
  };
}

function chapterInsight(record) {
  if (!record || typeof record !== 'object') return null;
  const r = normalizeRecord(record);
  const totalActiveMs = whole(r.totalActiveMs);
  if (!totalActiveMs && !whole(r.completedPasses) && (!whole(r.updatedAt) || r.currentPass?.protocol === 2)) return null;
  return {
    totalActiveMs,
    firstCompleteMs: r.firstCompleteMs == null ? null : whole(r.firstCompleteMs),
    lastCompleteMs: r.lastCompleteMs == null ? null : whole(r.lastCompleteMs),
    completedPasses: whole(r.completedPasses),
    currentPassMs: whole(r.currentPass && r.currentPass.activeMs),
    currentPassComplete: !!(r.currentPass && r.currentPass.completedAt),
    updatedAt: whole(r.qualifiedUpdatedAt || r.updatedAt),
  };
}

function median(values) {
  const sorted = values.filter(value => Number.isFinite(value) && value > 0).sort((a, b) => a - b);
  if (!sorted.length) return null;
  const middle = Math.floor(sorted.length / 2);
  return sorted.length % 2 ? whole(sorted[middle]) : whole((sorted[middle - 1] + sorted[middle]) / 2);
}

function mangaInsight(records, chapterIds) {
  const source = records && typeof records === 'object' ? records : {};
  const ids = Array.isArray(chapterIds) ? chapterIds : Object.keys(source);
  const chapters = ids.map(id => ({ id, reading: chapterInsight(source[id]) })).filter(item => item.reading);
  const latest = chapters.reduce((best, item) => !best || item.reading.updatedAt > best.reading.updatedAt ? item : best, null);
  const completed = chapters.filter(item => item.reading.completedPasses > 0);
  return {
    activeMs: chapters.reduce((sum, item) => sum + item.reading.totalActiveMs, 0),
    timedChapters: chapters.filter(item => item.reading.totalActiveMs > 0).length,
    completedChapters: completed.length,
    completedPasses: completed.reduce((sum, item) => sum + item.reading.completedPasses, 0),
    rereads: completed.reduce((sum, item) => sum + Math.max(0, item.reading.completedPasses - 1), 0),
    typicalChapterMs: median(completed.map(item => item.reading.lastCompleteMs)),
    lastChapterId: latest ? latest.id : null,
    updatedAt: latest ? latest.reading.updatedAt : 0,
  };
}

function libraryInsight(mangas) {
  const tracked = (Array.isArray(mangas) ? mangas : []).filter(item => item && item.reading && item.reading.activeMs > 0);
  const most = tracked.reduce((best, item) => !best || item.reading.activeMs > best.reading.activeMs ? item : best, null);
  const latest = tracked.reduce((best, item) => !best || item.reading.updatedAt > best.reading.updatedAt ? item : best, null);
  return {
    activeMs: tracked.reduce((sum, item) => sum + item.reading.activeMs, 0),
    timedChapters: tracked.reduce((sum, item) => sum + item.reading.timedChapters, 0),
    completedPasses: tracked.reduce((sum, item) => sum + item.reading.completedPasses, 0),
    rereads: tracked.reduce((sum, item) => sum + item.reading.rereads, 0),
    timedMangas: tracked.length,
    mostTimeMangaId: most ? most.id : null,
    lastMangaId: latest ? latest.id : null,
    lastChapterId: latest ? latest.reading.lastChapterId : null,
    updatedAt: latest ? latest.reading.updatedAt : 0,
  };
}

// Cumulative visits tolerate retry and an exit beacon overtaking a regular pulse.
// Coverage belongs to THIS visit, so an old read cannot qualify a picture lookup.
// Legacy totals are preserved; unqualified visit time is a draft, not a statistic.
function applyVisit(record, pulse, { version, pageCount, eligible, now = Date.now() } = {}) {
  const r = normalizeRecord(record), session = String(pulse.session || ''), seq = whole(pulse.seq, 1e9);
  let receipt = r.recentSessions.find(item => item.id === session);
  if (receipt && seq <= whole(receipt.seq)) return { duplicate: true, record: r };
  if (!receipt) {
    if (!r.qualifiedUpdatedAt && r.totalActiveMs) r.qualifiedUpdatedAt = r.updatedAt;
    receipt = { id: session, seq: 0, at: now, pass: {
      protocol: 2, visit: session, version, pageCount, seenRanges: [], activeMs: 0,
      loadingMs: 0, inputMs: { mouse: 0, touch: 0, keyboard: 0 }, creditedMs: 0,
      startedAt: now, completedAt: null,
    } };
    r.recentSessions.push(receipt);
    r.currentPass = receipt.pass;
  }
  const pass = receipt.pass;
  if (!pass || pass.version !== version) return { duplicate: true, record: r };
  // Wall-time sanity, not a speed test or the legacy twelve-second packet cap.
  const budget = whole(pulse.elapsedMs, 24 * 60 * 60 * 1000) + 1500;
  const requestedActive = whole(pulse.activeMs, budget), requestedLoading = whole(pulse.loadingMs, budget);
  const scale = requestedActive + requestedLoading > budget ? budget / (requestedActive + requestedLoading) : 1;
  const active = Math.max(pass.activeMs, Math.round(requestedActive * scale));
  const loading = Math.max(pass.loadingMs, Math.round(requestedLoading * scale));
  r.loadingMs += loading - pass.loadingMs;
  pass.activeMs = active; pass.loadingMs = loading;
  const input = Object.fromEntries(INPUT_TYPES.map(key => [key, whole(pulse.inputMs?.[key], active)]));
  const inputTotal = INPUT_TYPES.reduce((sum, key) => sum + input[key], 0);
  const inputScale = inputTotal > active ? active / inputTotal : 1;
  for (const key of INPUT_TYPES) pass.inputMs[key] = Math.max(pass.inputMs[key], Math.round(input[key] * inputScale));
  const allowed = new Set(eligible), seen = rangeSet(pass.seenRanges, pageCount);
  for (const page of Array.isArray(pulse.seen) ? pulse.seen.slice(0, pageCount) : []) {
    if (Number.isInteger(page) && allowed.has(page)) seen.add(page);
  }
  pass.seenRanges = compactRanges(seen);
  const covered = eligible.filter(page => seen.has(page)).length;
  if (!pass.completedAt && eligible.length && covered >= Math.ceil(eligible.length * 0.6) && active > 0) {
    pass.completedAt = now;
    pass.ordinal = ++r.completedPasses;
    r.sessions++;
  }
  if (pass.completedAt) {
    r.totalActiveMs += active - pass.creditedMs;
    pass.creditedMs = active;
    pass.creditedInput = pass.creditedInput || { mouse: 0, touch: 0, keyboard: 0 };
    for (const key of INPUT_TYPES) {
      r.inputMs[key] += pass.inputMs[key] - pass.creditedInput[key];
      pass.creditedInput[key] = pass.inputMs[key];
    }
    // Duration keeps growing through the last page and departure, not just 60%.
    if (pass.ordinal === 1) r.firstCompleteMs = active;
    if (pass.ordinal === r.completedPasses) r.lastCompleteMs = active;
    r.qualifiedUpdatedAt = now;
  }
  pass.closed = !!pulse.final;
  receipt.seq = seq; receipt.at = now;
  if (r.currentPass?.visit === session) r.currentPass = pass;
  r.recentSessions.sort((a, b) => whole(b.at) - whole(a.at));
  r.recentSessions.splice(MAX_RECENT_SESSIONS);
  r.updatedAt = now;
  return { duplicate: false, record: r };
}

function applyPulse(record, pulse, { version, pageCount, eligible, now = Date.now(), maxDeltaMs = 12000 } = {}) {
  const r = normalizeRecord(record);
  const session = String(pulse.session || '');
  const seq = whole(pulse.seq, 1e9);
  let receipt = r.recentSessions.find(item => item.id === session);
  if (receipt && seq <= whole(receipt.seq, 1e9)) return { duplicate: true, record: r };

  const newSession = !receipt;
  if (!receipt) {
    receipt = { id: session, seq: 0, at: now, counted: false };
    r.recentSessions.push(receipt);
  }

  const elapsed = newSession ? maxDeltaMs : Math.max(0, now - whole(receipt.at));
  const allowedDelta = Math.min(maxDeltaMs, elapsed + 1500);
  const requestedActive = whole(pulse.activeMs, maxDeltaMs * 2);
  const requestedLoading = whole(pulse.loadingMs, maxDeltaMs * 2);
  const requestedTotal = requestedActive + requestedLoading;
  const scale = requestedTotal > allowedDelta && requestedTotal ? allowedDelta / requestedTotal : 1;
  const activeMs = Math.round(requestedActive * scale);
  const loadingMs = Math.round(requestedLoading * scale);

  receipt.seq = seq;
  receipt.at = now;
  if (!receipt.counted && activeMs > 0) { receipt.counted = true; r.sessions++; }
  r.recentSessions.sort((a, b) => whole(b.at) - whole(a.at));
  r.recentSessions.splice(MAX_RECENT_SESSIONS);

  const prior = r.currentPass;
  if (!prior || prior.version !== version || (prior.completedAt && newSession)) {
    r.currentPass = {
      version,
      pageCount,
      seenRanges: [],
      activeMs: 0,
      startedAt: now,
      completedAt: null,
    };
  }
  const pass = r.currentPass;
  pass.pageCount = pageCount;
  pass.activeMs = whole(pass.activeMs) + activeMs;

  r.totalActiveMs = whole(r.totalActiveMs) + activeMs;
  r.loadingMs = whole(r.loadingMs) + loadingMs;
  const rawInput = pulse.inputMs && typeof pulse.inputMs === 'object' ? pulse.inputMs : {};
  const requestedInput = Object.fromEntries(INPUT_TYPES.map(key => [key, whole(rawInput[key], maxDeltaMs * 2)]));
  const inputTotal = INPUT_TYPES.reduce((sum, key) => sum + requestedInput[key], 0);
  const inputScale = inputTotal > activeMs && inputTotal ? activeMs / inputTotal : 1;
  for (const key of INPUT_TYPES) r.inputMs[key] = whole(r.inputMs[key]) + Math.round(requestedInput[key] * inputScale);

  const allowedPages = new Set(eligible);
  const seen = rangeSet(pass.seenRanges, pageCount);
  for (const raw of Array.isArray(pulse.seen) ? pulse.seen.slice(0, pageCount) : []) {
    const page = Number(raw);
    if (Number.isInteger(page) && allowedPages.has(page)) seen.add(page);
  }
  pass.seenRanges = compactRanges([...seen]);

  r.fastBursts = whole(r.fastBursts) + whole(pulse.fastBursts, 100);
  r.rejectedPageViews = whole(r.rejectedPageViews) + whole(pulse.rejectedPageViews, pageCount * 2);
  r.maxObservedPps = Math.max(whole(r.maxObservedPps), whole(pulse.maxPps, 1000));

  if (!pass.completedAt && eligible.length && eligible.every(page => seen.has(page))) {
    pass.completedAt = now;
    r.completedPasses = whole(r.completedPasses) + 1;
    r.lastCompleteMs = pass.activeMs;
    if (r.firstCompleteMs == null) r.firstCompleteMs = pass.activeMs;
  }
  r.updatedAt = now;
  return { duplicate: false, record: r, activeMs, loadingMs };
}

module.exports = {
  INPUT_TYPES, applyPulse, applyVisit, chapterInsight, compactRanges, eligiblePages, emptyRecord,
  libraryInsight, mangaInsight, publicSummary, rangeSet,
};