// ============================================================
// DOCUMENT EXPORT
// Markdown in, PowerPoint / Word / PDF out.
//
// Markdown is the artifact everywhere: it is what the model writes, what a
// refinement edits, and what is stored. Every format here is rendered from it
// on demand, so nothing ever has to patch a binary to change a slide.
//
// pandoc does pptx and docx in the image. PDF needs a renderer pandoc does not
// ship, so it goes to Gotenberg, which is LibreOffice behind an HTTP API. That
// is a network call, and it is the one export allowed to fail: if Gotenberg is
// down the deck and the document still download, and only PDF is unavailable.
// ============================================================

var fsp = require('fs/promises');
var os = require('os');
var pathMod = require('path');
var { execFile, spawn } = require('child_process');
var JSZip = require('jszip');
var slideSpec = require('./slideSpec');
var docSpec = require('./docSpec');

var REFERENCE_DECK = pathMod.join(__dirname, '..', '..', 'assets', 'learning', 'slides-reference.pptx');
var DECK_RENDERER = pathMod.join(__dirname, '..', '..', 'scripts', 'render_pptx.py');
var DOC_RENDERER = pathMod.join(__dirname, '..', '..', 'scripts', 'render_docx.py');
var GOTENBERG = process.env.GOTENBERG_URL || 'http://gotenberg:3000';

var FORMATS = {
  pptx: { ext: 'pptx', mime: 'application/vnd.openxmlformats-officedocument.presentationml.presentation' },
  docx: { ext: 'docx', mime: 'application/vnd.openxmlformats-officedocument.wordprocessingml.document' },
  pdf:  { ext: 'pdf',  mime: 'application/pdf' }
};

function isSupported(format) { return Object.hasOwn(FORMATS, String(format)); }
function mimeFor(format) { return (FORMATS[format] || {}).mime; }

/**
 * Let a slide shrink its own text rather than spilling off the bottom.
 *
 * pandoc writes a bare <a:bodyPr/> on every shape, which leaves the body with no
 * autofit even though the slide master has one — so a slide with too much on it
 * is simply cut off mid-sentence, and the remaining bullets are not rendered at
 * all. Verified by rendering one: three of eight bullets survived.
 *
 * <a:normAutofit/> with no scale asks the renderer to work out the reduction
 * itself, which means a slide that already fits is untouched. A fixed
 * fontScale would shrink every slide whether it needed it or not.
 *
 * This is a floor, not a substitute for slides that are the right length — the
 * prompt still asks for one idea per slide. It stops a long one becoming
 * unreadable rather than making overcrowding acceptable.
 */
async function fitSlideText(bytes) {
  try {
    var zip = await JSZip.loadAsync(bytes);
    var slides = Object.keys(zip.files).filter(function (name) {
      return /^ppt\/slides\/slide\d+\.xml$/.test(name);
    });
    if (!slides.length) return bytes;
    for (var i = 0; i < slides.length; i++) {
      var xml = await zip.file(slides[i]).async('string');
      if (xml.indexOf('normAutofit') !== -1) continue;
      zip.file(slides[i], xml.replace(/<a:bodyPr\s*\/>/g, '<a:bodyPr><a:normAutofit/></a:bodyPr>'));
    }
    return await zip.generateAsync({ type: 'nodebuffer', compression: 'DEFLATE' });
  } catch (e) {
    // A deck that renders imperfectly beats no deck at all.
    console.warn('[export] could not apply slide autofit:', e.message);
    return bytes;
  }
}

function runPandoc(args, cwd) {
  return new Promise(function (resolve, reject) {
    execFile('pandoc', args, { cwd: cwd, timeout: 60000, maxBuffer: 1024 * 1024 },
      function (err, stdout, stderr) {
        if (err) return reject(new Error(String(stderr || err.message).slice(0, 400)));
        resolve();
      });
  });
}

/**
 * Render markdown to one format.
 *
 * `kind` decides how a document is laid out: a presentation becomes slides with
 * the reference deck's fonts and layouts, an article becomes a Word document.
 * PDF is produced by converting whichever of those two applies, so a PDF of a
 * presentation looks like the presentation rather than like a long page.
 *
 * Returns a Buffer. Throws with a readable message; the caller decides whether
 * a failed PDF is fatal.
 */
async function render(markdown, kind, format, options) {
  if (!isSupported(format)) throw new Error('Unsupported format: ' + format);
  options = options || {};
  var workdir = await fsp.mkdtemp(pathMod.join(os.tmpdir(), 'export-'));
  try {
    await fsp.writeFile(pathMod.join(workdir, 'doc.md'), String(markdown || ''), 'utf8');

    var office = kind === 'presentation' ? 'pptx' : 'docx';
    if (office === 'docx' || format === 'docx') {
      await buildDoc(markdown, workdir, options);
    }
    if (office === 'pptx' || format === 'pptx') {
      await buildDeck(markdown, workdir, options.images || [], options);
    }

    if (format !== 'pdf') {
      return await fsp.readFile(pathMod.join(workdir, 'doc.' + format));
    }

    // PDF: hand the office file to Gotenberg. Its LibreOffice keeps the deck's
    // layout, which is why this is not rendered from the markdown directly.
    var bytes = await fsp.readFile(pathMod.join(workdir, 'doc.' + office));
    var form = new FormData();
    form.append('files', new File([bytes], 'doc.' + office, { type: FORMATS[office].mime }));
    var response = await fetch(GOTENBERG + '/forms/libreoffice/convert', {
      method: 'POST', body: form, signal: AbortSignal.timeout(90000)
    });
    if (!response.ok) throw new Error('PDF conversion failed (' + response.status + ')');
    return Buffer.from(await response.arrayBuffer());
  } finally {
    try { await fsp.rm(workdir, { recursive: true, force: true }); }
    catch (e) { console.warn('[export] could not clean', workdir, e.message); }
  }
}

// ── Deck ────────────────────────────────────────────────────
// Built by scripts/render_pptx.py rather than pandoc. Pandoc's pptx writer maps
// markdown onto a handful of reference layouts and gives no control over
// per-slide layout, positioning, or how large an image is drawn — the reason
// every generated deck came out as bullets on a template, and the reason
// autofit had to be injected into its output by hand afterwards.
//
// If the renderer fails for any reason, pandoc still produces a deck. A plainer
// deck beats a failed download.
function runRenderer(script, out, spec, workdir) {
  return new Promise(function (resolve, reject) {
    var child = spawn('python3', [script, out], { cwd: workdir });
    var stderr = '';
    child.stderr.on('data', function (chunk) { stderr += chunk.toString().slice(0, 2000); });
    child.on('error', reject);
    child.on('close', function (code) {
      if (code === 0) return resolve();
      reject(new Error(pathMod.basename(script) + ' exited ' + code + (stderr ? ': ' + stderr.trim() : '')));
    });
    child.stdin.end(JSON.stringify(spec));
  });
}

// ── Word ────────────────────────────────────────────────────
// Also python, for the same reason as the deck. Pandoc reads markdown, so a deck
// had to be flattened to markdown first — and a deck flattened to markdown stops
// being one: a comparison became two headings and two lists, a callout became
// bold text, and a figure became nothing at all. Built from the typed spec, a
// comparison is a two-column table, a callout is a shaded box, and a figure
// keeps its caption.
//
// Pandoc remains the fallback. A plainer document beats a failed download.
async function buildDoc(markdown, workdir, options) {
  var out = pathMod.join(workdir, 'doc.docx');
  try {
    var spec = docSpec.build({
      deck: options.deck, markdown: markdown,
      images: figuresByJob(options.images, options.figureIds)
    });
    if (!spec.blocks.length) throw new Error('nothing to render');
    await runRenderer(DOC_RENDERER, out, spec, workdir);
    if (!(await fsp.readFile(out)).length) throw new Error('the renderer produced an empty file');
  } catch (err) {
    console.warn('[export] document renderer failed, falling back to pandoc:', err.message);
    await runPandoc(['doc.md', '-o', 'doc.docx'], workdir);
  }
}

function figuresByJob(files, figureIds) {
  var byJob = {};
  (figureIds || []).forEach(function (id, index) {
    if (files && files[index]) byJob[id] = files[index];
  });
  return byJob;
}

async function buildDeck(markdown, workdir, images, options) {
  options = options || {};
  var out = pathMod.join(workdir, 'doc.pptx');
  try {
    // A deck the model designed is rendered as designed. Only a resource made
    // before decks existed, or an article being forced into slides, falls back
    // to inferring a layout from markdown.
    var spec = options.deck
      ? attachFigures(options.deck, images, options.figureIds)
      : slideSpec.build(markdown, { images: images });
    await runRenderer(DECK_RENDERER, out, spec, workdir);
    var built = await fsp.readFile(out);
    if (built.length) return;
    throw new Error('deck renderer produced an empty file');
  } catch (err) {
    console.warn('[export] deck renderer failed, falling back to pandoc:', err.message);
    await runPandoc(['doc.md', '--reference-doc=' + REFERENCE_DECK, '-o', 'doc.pptx'], workdir);
    // pandoc leaves a bare <a:bodyPr/> on every shape, so its decks still need
    // autofit injecting or they overflow.
    await fsp.writeFile(out, await fitSlideText(await fsp.readFile(out)));
  }
}

// Put the drawn figures back on the slides that asked for them. The files
// arrive in the order the jobs were created, which is the order the slides
// requested them, so a slide is matched by its job id rather than by position.
function attachFigures(deck, files, figureIds) {
  var byJob = figuresByJob(files, figureIds);
  var slides = (deck.slides || []).map(function (slide) {
    var copy = Object.assign({}, slide);
    // A custom slide carries its figures on image shapes, under the same rule.
    if (Array.isArray(copy.shapes)) {
      copy.shapes = copy.shapes.map(function (shape) {
        var s = Object.assign({}, shape);
        delete s.image;
        if (s.image_job && byJob[s.image_job]) s.image = byJob[s.image_job];
        return s;
      });
    }
    // The renderer reads whatever path this field holds and embeds that file in
    // the download. Nothing today can put a path in a stored deck — normalise()
    // never copies one and the edit endpoint writes markdown only — but the
    // field is cleared before it is set, so the only paths that can reach the
    // renderer are the figures just fetched for this export.
    delete copy.image;
    if (copy.image_job && byJob[copy.image_job]) copy.image = byJob[copy.image_job];
    // A figure slide whose picture never arrived is still a slide of text.
    if (!copy.image && (copy.type === 'image' || copy.type === 'figure')) {
      copy.type = copy.type === 'image' ? 'section' : 'bullets';
    }
    return copy;
  });
  var out = { title: deck.title, subtitle: deck.subtitle, date: deck.date, slides: slides };
  if (deck.title && !slides.some(function (s) { return s.type === 'title'; })) {
    out.slides = [{ type: 'title', heading: deck.title, subtitle: deck.subtitle, date: deck.date }]
      .concat(slides);
  }
  return out;
}

// A filename someone can find again, without letting a title choose the path.
function filename(title, format) {
  var safe = String(title || 'resource')
    .replace(/[^a-zA-Z0-9-_\s]/g, '').replace(/\s+/g, '-').toLowerCase().slice(0, 60) || 'resource';
  return safe + '.' + (FORMATS[format] || FORMATS.pdf).ext;
}

// The deck as bytes, without writing a download. The reviewer renders the deck
// it is about to judge, and that is the same pipeline an export runs.
async function renderDeck(deck, images, figureIds) {
  var workdir = await fsp.mkdtemp(pathMod.join(os.tmpdir(), 'deck-'));
  try {
    await buildDeck('', workdir, images || [], { deck: deck, figureIds: figureIds || [] });
    return await fsp.readFile(pathMod.join(workdir, 'doc.pptx'));
  } finally {
    await fsp.rm(workdir, { recursive: true, force: true }).catch(function () {});
  }
}

module.exports = { render, renderDeck, filename, mimeFor, isSupported, FORMATS, GOTENBERG };