// ============================================================
// DECK REVIEW
// ============================================================
// Render the deck, look at it, and fix what only looking can catch.
//
// The model that writes a deck never sees it. It cannot tell that slide four
// overflowed, that a figure landed on the wrong slide, or that a nine-item list
// would read better as two columns — those are facts about the rendered page,
// not about the text. So the deck is rendered to images and a vision model is
// asked to correct the layout.
//
// It may only move things. Same words, same figures: the reviewer returns a
// deck whose body text is the same multiset it was given, or its answer is
// discarded. That is checked rather than asked for, because a model told not to
// rewrite will still occasionally improve a sentence, and a silent edit to
// clinical text is the one thing this must never introduce.
//
// Off unless an administrator names a model. One pass, on generation only:
// a second pass costs as much as the first and fixes much less.

var fsp = require('fs/promises');
var os = require('os');
var pathMod = require('path');
var { execFile } = require('child_process');

var MAX_SLIDES = 20;          // a review pass is one image per slide
var RENDER_DPI = 70;          // legible to a model, small enough to send
var CONVERT_TIMEOUT = 60000;
// The reply restates the whole deck, so it needs room for one.
var MAX_REPLY_TOKENS = 2000;   // a list of fixes, not a deck
var MAX_CHANGES = 12;

function run(command, args, cwd) {
  return new Promise(function (resolve, reject) {
    execFile(command, args, { cwd: cwd, timeout: CONVERT_TIMEOUT, maxBuffer: 4 * 1024 * 1024 },
      function (err, stdout, stderr) {
        if (err) return reject(new Error(command + ': ' + (stderr || err.message).toString().slice(0, 300)));
        resolve(stdout);
      });
  });
}

/** One PNG per slide, in order. */
async function slideImages(pptx, gotenbergUrl, mime) {
  var dir = await fsp.mkdtemp(pathMod.join(os.tmpdir(), 'review-'));
  try {
    var form = new FormData();
    form.append('files', new File([pptx], 'deck.pptx', { type: mime }));
    var response = await fetch(gotenbergUrl + '/forms/libreoffice/convert', {
      method: 'POST', body: form, signal: AbortSignal.timeout(90000)
    });
    if (!response.ok) throw new Error('PDF conversion failed (' + response.status + ')');
    await fsp.writeFile(pathMod.join(dir, 'deck.pdf'), Buffer.from(await response.arrayBuffer()));

    await run('pdftoppm', ['-png', '-r', String(RENDER_DPI), 'deck.pdf', 'slide'], dir);
    var files = (await fsp.readdir(dir)).filter(function (f) { return /^slide-?\d+\.png$/.test(f); }).sort();
    var images = [];
    for (var i = 0; i < files.length && i < MAX_SLIDES; i++) {
      images.push({
        mimeType: 'image/png',
        dataBase64: (await fsp.readFile(pathMod.join(dir, files[i]))).toString('base64')
      });
    }
    return images;
  } finally {
    await fsp.rm(dir, { recursive: true, force: true }).catch(function () {});
  }
}

// Everything the reviewer is forbidden to change, in a form two decks can be
// compared by. Headings are held separately because splitting an overfull slide
// legitimately repeats one.
function fingerprint(deck) {
  var body = [];
  var headings = [];
  var figures = [];
  (deck.slides || []).forEach(function (slide) {
    if (slide.heading) headings.push(slide.heading.trim());
    if (slide.image_job) figures.push(slide.image_job);
    // Every place a bullet can live: one list, two columns, or two labelled
    // columns. Missing one of them makes a legitimate re-layout look like a
    // rewrite — which it did, for the two-column case.
    [slide.bullets, slide.left, slide.right].forEach(function (list) {
      (list || []).forEach(function (b) { body.push(String(b.text || '').trim()); });
    });
    (slide.columns || []).forEach(function (c) {
      (c.bullets || []).forEach(function (b) { body.push(String(b.text || '').trim()); });
    });
    (slide.header || []).forEach(function (cell) { if (cell) body.push(String(cell).trim()); });
    (slide.rows || []).forEach(function (row) {
      row.forEach(function (cell) { if (cell) body.push(String(cell).trim()); });
    });
    if (slide.text) body.push(slide.text.trim());
    if (slide.caption) body.push(slide.caption.trim());
  });
  return { body: body.sort(), headings: headings, figures: figures.sort() };
}

function sameMultiset(a, b) {
  return a.length === b.length && a.every(function (value, i) { return value === b[i]; });
}

/**
 * True when the reviewed deck moved things without changing them.
 *
 * Body text must be the same multiset — moving a bullet to another slide or into
 * a column keeps it, rewording it does not. Figures must be the same set, so a
 * review can place them but cannot invent or drop one. A heading may be reused
 * or extended, which is what splitting a slide needs, but not invented.
 */
function movedOnly(before, after) {
  if (!sameMultiset(before.body, after.body)) return 'the wording changed';
  if (!sameMultiset(before.figures, after.figures)) return 'the figures changed';
  var known = before.headings;
  var invented = after.headings.filter(function (heading) {
    return !known.some(function (original) {
      return heading === original || heading.indexOf(original) === 0;
    });
  });
  if (invented.length) return 'a heading was invented: ' + invented[0].slice(0, 60);
  return null;
}

function instructions(slides) {
  return [
    'You are looking at the rendered slides of a teaching deck, in order. Slide 1',
    'in the images is index 0 below. The JSON that produced them follows.',
    '',
    'Report layout problems only — things that are wrong about the rendered page,',
    'not about the writing:',
    '  - text running off the bottom of a slide, or too small to read',
    '  - a slide carrying so much that it should be two',
    '  - a long single-column list that would read better in two columns',
    '  - two labelled groups that would read better as a side-by-side comparison',
    '',
    'Return ONLY a JSON object of changes, nothing else:',
    '',
    '{"changes":[',
    '  {"slide":2,"action":"two"},',
    '  {"slide":4,"action":"split","after":3,"heading":"Management (continued)"},',
    '  {"slide":6,"action":"compare","at":3,"labels":["MILD","SEVERE"]},',
    '  {"slide":1,"action":"one"}',
    ']}',
    '',
    '  "two"     — lay this slide\'s bullets out in two columns',
    '  "one"     — put a two-column slide back into one column',
    '  "split"   — make a second slide from the bullets after index "after"',
    '              (0-based); "heading" must repeat or extend the original',
    '  "compare" — two labelled columns, splitting the bullets at index "at";',
    '              "labels" are two short column headings',
    '',
    'You cannot change any wording, and you are not being asked to: name the slide',
    'and the action, and the server rearranges the text it already has. Slide',
    'indices are 0 to ' + (slides - 1) + '. Return {"changes":[]} if the deck reads well.'
  ].join('\n');
}

// Apply a reviewer's changes to a copy of the deck.
//
// The reviewer names slides and split points; the text is moved by this code and
// never passes through the model, so a review cannot reword, drop or invent a
// single bullet. That is a stronger guarantee than asking it not to and checking
// afterwards — which is still done, because a bug here would be just as bad.
function applyChanges(deck, changes) {
  var slides = (deck.slides || []).map(function (slide) { return JSON.parse(JSON.stringify(slide)); });
  var applied = 0;

  // Highest index first, so splitting one slide does not renumber the next.
  var ordered = changes.slice().sort(function (a, b) { return (b.slide || 0) - (a.slide || 0); });

  ordered.forEach(function (change) {
    var index = parseInt(change.slide, 10);
    if (!(index >= 0 && index < slides.length)) return;
    var slide = slides[index];
    var action = String(change.action || '');

    if (action === 'two' && slide.type === 'bullets' && (slide.bullets || []).length > 3) {
      var half = Math.ceil(slide.bullets.length / 2);
      slides[index] = { type: 'two', heading: slide.heading, notes: slide.notes,
                        left: slide.bullets.slice(0, half), right: slide.bullets.slice(half) };
      applied++;
      return;
    }
    if (action === 'one' && slide.type === 'two') {
      slides[index] = { type: 'bullets', heading: slide.heading, notes: slide.notes,
                        bullets: (slide.left || []).concat(slide.right || []) };
      applied++;
      return;
    }
    if (action === 'compare' && slide.type === 'bullets') {
      var at = parseInt(change.at, 10);
      var labels = Array.isArray(change.labels) ? change.labels : [];
      if (!(at > 0 && at < (slide.bullets || []).length) || labels.length !== 2) return;
      slides[index] = { type: 'compare', heading: slide.heading, notes: slide.notes, columns: [
        { label: String(labels[0]).slice(0, 60), bullets: slide.bullets.slice(0, at) },
        { label: String(labels[1]).slice(0, 60), bullets: slide.bullets.slice(at) }] };
      applied++;
      return;
    }
    if (action === 'split' && slide.type === 'bullets') {
      var after = parseInt(change.after, 10);
      if (!(after >= 0 && after < (slide.bullets || []).length - 1)) return;
      // The continuation heading is the reviewer's only piece of text, and it
      // has to repeat or extend the original or it is not a continuation.
      var heading = String(change.heading || '').trim();
      var original = String(slide.heading || '').trim();
      if (!heading || heading.indexOf(original) !== 0) heading = original + ' (continued)';
      var tail = { type: 'bullets', heading: heading, bullets: slide.bullets.slice(after + 1) };
      slides[index] = Object.assign({}, slide, { bullets: slide.bullets.slice(0, after + 1) });
      slides.splice(index + 1, 0, tail);
      applied++;
    }
  });

  return { deck: Object.assign({}, deck, { slides: slides }), applied: applied };
}

/**
 * Review a deck and return a corrected one, or the original.
 *
 * Never throws and never fails a generation: a deck that could not be reviewed
 * is the deck that was written, which is what would have shipped anyway.
 */
async function review(deck, options) {
  var reasons = [];
  try {
    if (!options.model) return { deck: deck, reviewed: false, reason: 'no reviewer configured' };
    var slides = (deck.slides || []).length;
    if (!slides) return { deck: deck, reviewed: false, reason: 'nothing to review' };
    if (slides > MAX_SLIDES) return { deck: deck, reviewed: false, reason: 'deck too long to review' };

    var images = await slideImages(options.pptx, options.gotenberg, options.mime);
    if (!images.length) return { deck: deck, reviewed: false, reason: 'could not render the deck' };

    var ai = await options.callAI(
      [{ role: 'user', content: instructions(deck.slides.length) +
          '\n\nDECK JSON:\n' + JSON.stringify({ slides: deck.slides }) }],
      { model: options.model, temperature: 0.1, images: images, maxTokens: MAX_REPLY_TOKENS }
    );

    // A list of changes, not a deck. Asking for the whole deck back put the
    // reply in proportion to the deck rather than to the number of problems,
    // and a fourteen-slide deck came back cut off mid-object every time.
    var reply = options.extractJson(String((ai && ai.content) || ''));
    var changes = reply && Array.isArray(reply.changes) ? reply.changes : null;
    if (!changes) return { deck: deck, reviewed: false, reason: 'the reviewer did not return changes' };
    if (!changes.length) return { deck: deck, reviewed: false, reason: 'nothing to fix' };

    var result = applyChanges(deck, changes.slice(0, MAX_CHANGES));
    if (!result.applied) return { deck: deck, reviewed: false, reason: 'no change was applicable' };

    // The text never went through the model, so this should always hold. It is
    // checked anyway: a bug in applyChanges would be as bad as a model rewriting
    // the words, and silently worse for being trusted.
    var complaint = movedOnly(fingerprint(deck), fingerprint(result.deck));
    if (complaint) {
      console.warn('[deck-review] discarded: ' + complaint);
      return { deck: deck, reviewed: false, reason: complaint };
    }
    return { deck: result.deck, reviewed: true, reason: null,
             slides: images.length, changes: result.applied };
  } catch (err) {
    console.warn('[deck-review] skipped:', err.message);
    reasons.push(err.message);
    return { deck: deck, reviewed: false, reason: reasons[0] };
  }
}

// slideImages is exported because modifying a deck wants the same picture of it
// that reviewing does — same render path, same DPI, same per-slide cap — and two
// copies of this would drift.
module.exports = { review, slideImages, fingerprint, movedOnly, applyChanges, instructions, MAX_SLIDES, MAX_CHANGES, RENDER_DPI };