// Aggregates runtime stats for the admin dashboard.
//
// Stat sources:
//   - In-memory (free): IMDb ratings Map size, IMDb mapping Map sizes, search workers count
//   - File reads (cheap, cached 30s): cron.txt, lastcron.txt tail
//   - Streaming line counts (cached 5min): tmdbintegral/movie.json, tv.json
//   - Disk usage via du (lazy, cached 10min): movie/, tv/, justwatchmovie/, justwatchtv/
//   - Prometheus counters: HTTP totals, search cache hits/misses

import { execFile as execFileCb } from 'node:child_process';
import { createReadStream, existsSync, statSync } from 'node:fs';
import { readFile } from 'node:fs/promises';
import { join } from 'node:path';
import { createInterface } from 'node:readline';
import { promisify } from 'node:util';
import {
  CRON_TXT,
  IMDB_RATINGS,
  JUSTWATCH_MOVIE_DIR,
  JUSTWATCH_TV_DIR,
  LASTCRON_TXT,
  MOVIE_DIR,
  TMDBINTEGRAL_DIR,
  TV_DIR,
} from '../config.js';
import { preloadMappings } from './imdbMapping.js';
import { getRatings } from './imdbRatings.js';
import { registry } from './metrics.js';

const execFile = promisify(execFileCb);

// ---------- TTL cache helpers ----------

const ttlCache = new Map();
async function cached(key, ttlMs, fn) {
  const now = Date.now();
  const hit = ttlCache.get(key);
  if (hit && now - hit.t < ttlMs) return hit.v;
  const v = await fn();
  ttlCache.set(key, { t: now, v });
  return v;
}

// ---------- Cheap helpers ----------

async function countLines(file) {
  if (!existsSync(file)) return 0;
  let n = 0;
  const rl = createInterface({ input: createReadStream(file), crlfDelay: Infinity });
  for await (const _ of rl) n++;
  return n;
}

async function tailLines(file, n) {
  if (!existsSync(file)) return [];
  // Read whole file — log files are < 1 MB usually. If they grow, switch to a
  // backwards-stream chunk reader.
  const text = await readFile(file, 'utf8');
  const lines = text.split('\n');
  return lines.slice(-n - 1, -1);
}

async function diskUsage(dir) {
  if (!existsSync(dir)) return 0;
  try {
    const { stdout } = await execFile('du', ['-sb', dir], { maxBuffer: 1024 * 1024 });
    const bytes = parseInt(stdout.split('\t')[0], 10);
    return Number.isFinite(bytes) ? bytes : 0;
  } catch {
    return 0;
  }
}

// ---------- Cron parsing ----------

function parseCronTxt(text) {
  if (!text) return { started: null, finished: null, duration_s: null, status: 'unknown' };
  const startMatch = text.match(/Started At (.+)/);
  const finishMatch = text.match(/Finished At (.+)/);
  const started = startMatch ? new Date(startMatch[1]).getTime() || null : null;
  const finished = finishMatch ? new Date(finishMatch[1]).getTime() || null : null;
  const duration_s = started && finished ? Math.round((finished - started) / 1000) : null;
  const status = finished ? 'ok' : started ? 'running_or_failed' : 'unknown';
  return { started, finished, duration_s, status };
}

function summarizeLogTail(lines) {
  const counts = { downloading: 0, updating: 0, removing: 0, failed: 0, writing: 0 };
  for (const l of lines) {
    if (l.startsWith('Downloading:')) counts.downloading++;
    else if (l.startsWith('Updating:')) counts.updating++;
    else if (l.startsWith('Removing:')) counts.removing++;
    else if (l.startsWith('Writing ')) counts.writing++;
    else if (l.startsWith('Failed')) counts.failed++;
  }
  return counts;
}

// ---------- Aggregator ----------

async function getCounterValue(name) {
  const arr = await registry.getSingleMetric(name)?.get();
  if (!arr?.values) return 0;
  return arr.values.reduce((sum, v) => sum + (v.value || 0), 0);
}

export async function getStats() {
  const [
    movieTotal,
    tvTotal,
    cronText,
    cronLogTail,
    duMovie,
    duTv,
    duJwMovie,
    duJwTv,
    duRatings,
    ratings,
    mappings,
  ] = await Promise.all([
    cached('movie_total', 5 * 60_000, () => countLines(join(TMDBINTEGRAL_DIR, 'movie.json'))),
    cached('tv_total', 5 * 60_000, () => countLines(join(TMDBINTEGRAL_DIR, 'tv.json'))),
    cached('cron_txt', 30_000, async () => (existsSync(CRON_TXT) ? await readFile(CRON_TXT, 'utf8') : '')),
    cached('cron_tail', 30_000, () => tailLines(LASTCRON_TXT, 200)),
    cached('du_movie', 10 * 60_000, () => diskUsage(MOVIE_DIR)),
    cached('du_tv', 10 * 60_000, () => diskUsage(TV_DIR)),
    cached('du_jwmovie', 10 * 60_000, () => diskUsage(JUSTWATCH_MOVIE_DIR)),
    cached('du_jwtv', 10 * 60_000, () => diskUsage(JUSTWATCH_TV_DIR)),
    cached('du_ratings', 10 * 60_000, async () =>
      existsSync(IMDB_RATINGS) ? statSync(IMDB_RATINGS).size : 0,
    ),
    getRatings().catch(() => null),
    preloadMappings().catch(() => ({ movie: 0, tv: 0 })),
  ]);

  const cron = parseCronTxt(cronText);
  const cronLogSummary = summarizeLogTail(cronLogTail);

  const cacheHits = await getCounterValue('search_cache_hits_total');
  const cacheMisses = await getCounterValue('search_cache_misses_total');
  const httpRequests = await getCounterValue('http_requests_total');

  return {
    timestamp: Date.now(),
    data: {
      movies: { master: movieTotal, with_imdb: mappings.movie },
      tv: { master: tvTotal, with_imdb: mappings.tv },
      imdb_ratings: ratings ? ratings.size : 0,
      disk: {
        movie_b: duMovie,
        tv_b: duTv,
        justwatch_movie_b: duJwMovie,
        justwatch_tv_b: duJwTv,
        ratings_b: duRatings,
        total_b: duMovie + duTv + duJwMovie + duJwTv + duRatings,
      },
    },
    cron: {
      ...cron,
      log_summary: cronLogSummary,
      log_tail: cronLogTail.slice(-50),
    },
    search_cache: {
      hits: cacheHits,
      misses: cacheMisses,
      hit_rate: cacheHits + cacheMisses > 0 ? cacheHits / (cacheHits + cacheMisses) : null,
    },
    http: {
      total_requests: httpRequests,
    },
    process: {
      uptime_s: Math.round(process.uptime()),
      memory_mb: Math.round(process.memoryUsage().rss / 1024 / 1024),
      heap_mb: Math.round(process.memoryUsage().heapUsed / 1024 / 1024),
      node: process.version,
      pid: process.pid,
    },
  };
}

// Returns the parsed Prometheus metrics in a structured form for the admin UI.
// Groups by metric name + labels, returns counters as scalars and histograms
// with their bucket counts.
export async function getMetricsForUI() {
  const text = await registry.metrics();
  const groups = {};
  let currentName = null;
  let currentHelp = '';
  let currentType = '';

  for (const line of text.split('\n')) {
    if (!line) continue;
    if (line.startsWith('# HELP ')) {
      const m = line.match(/^# HELP (\S+) (.+)$/);
      if (m) {
        currentName = m[1];
        currentHelp = m[2];
      }
      continue;
    }
    if (line.startsWith('# TYPE ')) {
      const m = line.match(/^# TYPE (\S+) (\S+)$/);
      if (m) {
        currentName = m[1];
        currentType = m[2];
        groups[currentName] = { name: currentName, help: currentHelp, type: currentType, samples: [] };
      }
      continue;
    }
    if (line.startsWith('#')) continue;
    const m = line.match(/^(\S+?)(?:\{([^}]*)\})?\s+(\S+)/);
    if (!m) continue;
    const baseName = m[1].replace(/_(bucket|count|sum)$/, '');
    const labelsStr = m[2] || '';
    const value = parseFloat(m[3]);
    const labels = {};
    if (labelsStr) {
      for (const pair of labelsStr.split(',')) {
        const [k, v] = pair.split('=');
        if (k && v) labels[k.trim()] = v.replace(/^"|"$/g, '');
      }
    }
    const grp = groups[baseName] || groups[m[1]];
    if (grp) grp.samples.push({ name: m[1], labels, value });
  }
  return Object.values(groups);
}