// Novel requests over HTTP, for the "request a novel" page (served through the
// illustrator at /library). Searches and downloads run as short-lived child processes
// of find-novel.js / fetch-novel.js, so their memory (plugins carry their own
// libraries) is returned as soon as they finish; the server itself stays small.
//   GET  /health
//   GET  /find?q=<title>           -> [{source, id, name, path, url, exact}] (cached 10 min)
//   POST /fetch {id, path, name}   -> job; one download at a time
//   GET  /jobs                     -> recent jobs, newest first
//   GET  /info?id=&path=           -> {name, cover, author, status, genres, summary,
//                                      chapters, free, latest} (cached 1 h, 3 at a time)
//   GET  /library                  -> titles already in the library
// Nightly (UPDATE_HOUR, local time) update-novels.js appends new free chapters.
// Env: LIBRARY (novels dir, writable), PORT, NOVEL_PLUGIN_CACHE, UPDATE_HOUR.
import { spawn } from 'child_process';
import fs from 'fs';
import http from 'http';
import os from 'os';
import path from 'path';
import { fileURLToPath } from 'url';

const HERE = path.dirname(fileURLToPath(import.meta.url));
const LIBRARY = process.env.LIBRARY || '/library';
const PORT = Number(process.env.PORT || 8090);
const UPDATE_HOUR = Number(process.env.UPDATE_HOUR || 4);
const FIND_TTL_MS = 10 * 60 * 1000;
const INFO_TTL_MS = 60 * 60 * 1000;
const INFO_CONCURRENCY = 3;
const MAX_JOBS = 50;

const found = new Map(); // query -> {at, results}
const infos = new Map(); // id\npath -> {at, info}
let infoRunning = 0;
const infoWaiting = [];

// At most INFO_CONCURRENCY detail lookups at once: each is a child process and a request
// to the source site.
async function info(id, novelPath) {
  const cacheKey = `${id}\n${novelPath}`;
  const hit = infos.get(cacheKey);
  if (hit && Date.now() - hit.at < INFO_TTL_MS) return hit.info;
  if (infoRunning >= INFO_CONCURRENCY)
    await new Promise(resolve => infoWaiting.push(resolve));
  infoRunning++;
  try {
    const { code, out, err } = await run('novel-info.js', [id, novelPath]);
    if (code !== 0) throw new Error(errorLine(err, code));
    const result = JSON.parse(out.trim().split('\n').pop());
    infos.set(cacheKey, { at: Date.now(), info: result });
    return result;
  } finally {
    infoRunning--;
    infoWaiting.shift()?.();
  }
}
const jobs = []; // newest first
let running = null;

function run(script, args) {
  return new Promise(resolve => {
    const child = spawn(process.execPath, [path.join(HERE, script), ...args], {
      stdio: ['ignore', 'pipe', 'pipe'],
    });
    let out = '';
    let err = '';
    child.stdout.on('data', d => (out += d));
    child.stderr.on('data', d => {
      err += d;
      if (err.length > 20000) err = err.slice(-10000);
    });
    child.on('close', code => resolve({ code, out, err }));
  });
}

// Node ends a crash with its version line; report the line that names the error.
function errorLine(err, code) {
  const lines = err.trim().split('\n').filter(Boolean);
  return (lines.findLast(l => /error/i.test(l)) || lines[0] || `exit ${code}`)
    .trim()
    .slice(0, 200);
}

const safeName = s => s.replace(/[/\\:*?"<>|]/g, '-').trim();

// One folder per series, named after the book: Kavita groups by folder.
function place(file) {
  const name = safeName(path.basename(file, '.epub'));
  const dir = path.join(LIBRARY, name);
  const target = path.join(dir, `${name}.epub`);
  if (fs.existsSync(target)) throw new Error(`already in the library: ${name}`);
  fs.mkdirSync(dir, { recursive: true, mode: 0o2775 });
  fs.copyFileSync(file, target);
  return name;
}

async function work() {
  if (running) return;
  running = jobs.findLast(j => j.status === 'queued');
  if (!running) return;
  const job = running;
  job.status = 'running';
  job.started = Date.now();
  const tmp = fs.mkdtempSync(path.join(os.tmpdir(), 'novel-'));
  try {
    const { code, out, err } = await run('fetch-novel.js', [
      job.id,
      job.path,
      tmp,
    ]);
    const file = out.trim().split('\n').pop();
    if (code !== 0 || !file || !fs.existsSync(file)) {
      throw new Error(errorLine(err, code));
    }
    job.progress = err.trim().split('\n')[0] || '';
    job.title = place(file);
    job.status = 'done';
  } catch (e) {
    job.status = 'failed';
    job.error = String(e.message || e).slice(0, 300);
  } finally {
    fs.rmSync(tmp, { recursive: true, force: true });
    job.finished = Date.now();
    running = null;
    setImmediate(work);
  }
}

async function nightly() {
  const next = new Date();
  next.setHours(UPDATE_HOUR, 17, 0, 0);
  if (next <= new Date()) next.setDate(next.getDate() + 1);
  setTimeout(async () => {
    const { code, out, err } = await run('update-novels.js', [LIBRARY]);
    process.stdout.write(
      `nightly update (exit ${code}):\n${out}${err.slice(-2000)}\n`,
    );
    nightly();
  }, next - new Date());
}

function send(res, code, body) {
  const data = JSON.stringify(body);
  res.writeHead(code, {
    'Content-Type': 'application/json',
    'Content-Length': Buffer.byteLength(data),
    'Cache-Control': 'no-store',
  });
  res.end(data);
}

function readJson(req) {
  return new Promise((resolve, reject) => {
    let body = '';
    req.on('data', d => {
      body += d;
      if (body.length > 10000) reject(new Error('body too large'));
    });
    req.on('end', () => {
      try {
        resolve(JSON.parse(body || '{}'));
      } catch {
        reject(new Error('invalid JSON'));
      }
    });
  });
}

http
  .createServer(async (req, res) => {
    const url = new URL(req.url, 'http://localhost');
    try {
      if (req.method === 'GET' && url.pathname === '/health') {
        return send(res, 200, { ok: true });
      }
      if (req.method === 'GET' && url.pathname === '/find') {
        const q = (url.searchParams.get('q') || '').trim().slice(0, 200);
        if (q.length < 2) return send(res, 400, { error: 'q is required' });
        const hit = found.get(q.toLowerCase());
        if (hit && Date.now() - hit.at < FIND_TTL_MS)
          return send(res, 200, hit.results);
        const { code, out, err } = await run('find-novel.js', ['--json', q]);
        if (code !== 0) return send(res, 502, { error: errorLine(err, code) });
        const results = JSON.parse(out.trim().split('\n').pop() || '[]');
        found.set(q.toLowerCase(), { at: Date.now(), results });
        return send(res, 200, results);
      }
      if (req.method === 'GET' && url.pathname === '/info') {
        const id = url.searchParams.get('id') || '';
        const novelPath = url.searchParams.get('path') || '';
        if (!id || !novelPath)
          return send(res, 400, { error: 'id and path are required' });
        try {
          return send(res, 200, await info(id, novelPath));
        } catch (e) {
          return send(res, 502, {
            error: String(e.message || e).slice(0, 300),
          });
        }
      }
      if (req.method === 'GET' && url.pathname === '/library') {
        const titles = fs.existsSync(LIBRARY)
          ? fs
              .readdirSync(LIBRARY, { withFileTypes: true })
              .filter(d => d.isDirectory())
              .map(d => d.name)
          : [];
        return send(res, 200, titles);
      }
      if (req.method === 'GET' && url.pathname === '/jobs') {
        return send(res, 200, jobs);
      }
      if (req.method === 'POST' && url.pathname === '/fetch') {
        const { id, path: novelPath, name } = await readJson(req);
        if (
          typeof id !== 'string' ||
          typeof novelPath !== 'string' ||
          !id ||
          !novelPath
        )
          return send(res, 400, { error: 'id and path are required' });
        const same = jobs.find(
          j =>
            j.id === id &&
            j.path === novelPath &&
            ['queued', 'running'].includes(j.status),
        );
        if (same) return send(res, 202, same);
        const job = {
          id: id.slice(0, 100),
          path: novelPath.slice(0, 500),
          name: String(name || novelPath).slice(0, 200),
          status: 'queued',
          queued: Date.now(),
        };
        jobs.unshift(job);
        jobs.length = Math.min(jobs.length, MAX_JOBS);
        setImmediate(work);
        return send(res, 202, job);
      }
      send(res, 404, { error: 'not found' });
    } catch (e) {
      send(res, 400, { error: String(e.message || e) });
    }
  })
  .listen(PORT, () => process.stdout.write(`novel requests on :${PORT}\n`));

nightly();