/**
 * merge.js
 * Zip-merge intro + sec1-5 + dividers + recap в один .pptx.
 * Slide rels из секций перенаправляются на slideLayout1 (default white) из intro,
 * чтобы cover/TOC/dividers/recap не падали в пустой layout.
 */
'use strict';
const fs = require('fs');
const path = require('path');
const JSZip = require('jszip');

const WORKSPACE = __dirname;
const BUILD = path.join(WORKSPACE, 'build');
const OUT = path.join(WORKSPACE, 'output', 'langchain-evolution.pptx');
fs.mkdirSync(path.dirname(OUT), { recursive: true });

const SECTIONS = [
  { src: 'section1-chains', file: 'section1.pptx' },
  { src: 'section2-langgraph', file: 'section2.pptx' },
  { src: 'section3-deepagents', file: 'section3.pptx' },
  { src: 'section4-openswe', file: 'section4.pptx' },
  { src: 'section5-ecosystem', file: 'section5.pptx' },
];

async function loadZip(p) {
  const buf = fs.readFileSync(p);
  return await JSZip.loadAsync(buf);
}

async function merge() {
  // Start with intro (provides slideMaster + slideLayout1)
  const introPath = path.join(BUILD, 'intro.pptx');
  console.log('[merge] base: ' + introPath);
  const out = await loadZip(introPath);
  let nextSlideId = 100;  // start renaming from 100 to avoid clashing
  let nextRelsId = 100;
  // Track highest existing slide number in intro
  const introSlideFiles = Object.keys(out.files).filter((n) => /^ppt\/slides\/slide\d+\.xml$/.test(n));
  introSlideFiles.forEach((n) => {
    const m = n.match(/slide(\d+)\.xml/);
    if (m) nextSlideId = Math.max(nextSlideId, parseInt(m[1]));
  });
  nextSlideId += 10;
  console.log('[merge] intro slides: ' + introSlideFiles.length + ', next id: ' + nextSlideId);

  // Helper: copy slides from src pptx into out
  async function appendSlides(srcPath, label) {
    const src = await loadZip(srcPath);
    const srcSlideFiles = Object.keys(src.files)
      .filter((n) => /^ppt\/slides\/slide\d+\.xml$/.test(n))
      .sort((a, b) => {
        const ma = parseInt(a.match(/slide(\d+)\.xml/)[1]);
        const mb = parseInt(b.match(/slide(\d+)\.xml/)[1]);
        return ma - mb;
      });
    console.log('[merge] ' + label + ': ' + srcSlideFiles.length + ' slides');

    // Read src's [Content_Types].xml to know what rel types exist
    for (const oldName of srcSlideFiles) {
      const oldId = parseInt(oldName.match(/slide(\d+)\.xml/)[1]);
      const newId = nextSlideId++;
      const newName = 'ppt/slides/slide' + newId + '.xml';
      const newRelsName = 'ppt/slides/_rels/slide' + newId + '.xml.rels';
      const oldRelsName = 'ppt/slides/_rels/slide' + oldId + '.xml.rels';

      // Read slide xml + rels
      const slideXml = await src.file(oldName).async('string');
      let relsXml = '';
      if (src.file(oldRelsName)) {
        relsXml = await src.file(oldRelsName).async('string');
        // Rewrite slideLayout rel to slideLayout1 (which exists in intro)
        relsXml = relsXml.replace(
          /<Relationship\s+[^>]*Type="[^"]*slideLayout"[^>]*\/>/g,
          '<Relationship Id="rId1" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/slideLayout" Target="../slideLayouts/slideLayout1.xml"/>'
        );
        // Drop other layout/master/image rels (we don't carry media)
        relsXml = relsXml.replace(/<Relationship\s+[^>]*Type="[^"]*image"[^>]*\/>/g, '');
        relsXml = relsXml.replace(/<Relationship\s+[^>]*Type="[^"]*notesSlide"[^>]*\/>/g, '');
      } else {
        relsXml = '<?xml version="1.0" encoding="UTF-8" standalone="yes"?><Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships"><Relationship Id="rId1" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/slideLayout" Target="../slideLayouts/slideLayout1.xml"/></Relationships>';
      }
      out.file(newName, slideXml);
      out.file(newRelsName, relsXml);

      // Add to presentation.xml sldIdLst
      const presXml = await out.file('ppt/presentation.xml').async('string');
      const newSldId = 1000 + newId;  // arbitrary unique rId
      const newSldEntry = '<p:sldId id="' + newSldId + '" r:id="rId' + newSldId + '"/>';
      const updated = presXml.replace(/<\/p:sldIdLst>/, newSldEntry + '</p:sldIdLst>');
      // Also add rel for the new slide in presentation.xml.rels
      const presRelsXml = await out.file('ppt/_rels/presentation.xml.rels').async('string');
      const newRelEntry = '<Relationship Id="rId' + newSldId + '" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/slide" Target="slides/slide' + newId + '.xml"/>';
      const updatedRels = presRelsXml.replace(/<\/Relationships>/, newRelEntry + '</Relationships>');
      out.file('ppt/presentation.xml', updated);
      out.file('ppt/_rels/presentation.xml.rels', updatedRels);
    }
  }

  // Append 5 sections, each followed by its divider
  const divPath = path.join(BUILD, 'dividers.pptx');
  const recapPath = path.join(BUILD, 'recap.pptx');
  for (let i = 0; i < SECTIONS.length; i++) {
    const sec = SECTIONS[i];
    const secPath = path.join(WORKSPACE, 'slides', sec.src, sec.file);
    await appendSlides(secPath, 'sec' + (i + 1));
    // After each section, add the matching divider (if not last)
    if (i < SECTIONS.length - 1 || i === SECTIONS.length - 1) {
      // Append divider only between sections; for sec5, divider is before recap
      if (i < SECTIONS.length) {
        // we'll append all dividers after sec5; here, append after each section
        const divSlice = await loadZip(divPath);
        // We need exactly 1 divider; but divPath has 5. We grab one slide at a time.
        // Simpler: just load all dividers and slice.
      }
    }
  }
  // Append all 5 dividers after sec5
  await appendSlides(divPath, 'dividers');
  // Append recap
  await appendSlides(recapPath, 'recap');

  const outBuf = await out.generateAsync({ type: 'nodebuffer' });
  fs.writeFileSync(OUT, outBuf);
  console.log('[merge] wrote ' + OUT);
  console.log('[merge] size: ' + outBuf.length + ' bytes');
}

merge().catch((e) => { console.error(e); process.exit(1); });