#!/usr/bin/env node

/**
 * Generate output HTML from template + data for asteroid-splitting documents.
 *
 * Usage: node generate.mjs <docId>
 * Example: node generate.mjs asteroid-splitting-1
 *
 * Reads:  docs/<docId>.template.html
 * Reads:  docs/<docId>.data.json (optional)
 * Writes: docs/<docId>.output.html
 *
 * data.json format:
 * {
 *   pages: [{
 *     page: 1,
 *     sections: [{ index: 0, scale: 1.2, rotate: 15 }]
 *   }]
 * }
 *
 * Applies transform to big asteroid img (w-[26mm] container)
 * and proportionally to small asteroid imgs (w-[12mm] containers) in formula rows.
 */

import { readFileSync, writeFileSync, existsSync } from 'fs';
import { join, dirname } from 'path';
import { fileURLToPath } from 'url';
import { postGenerate } from '../../../src/scripts/post-generate.mjs';

const __dirname = dirname(fileURLToPath(import.meta.url));
const docsDir = join(__dirname, '..', 'docs');

const docId = process.argv[2];
if (!docId) {
  console.error('Usage: node generate.mjs <docId>');
  process.exit(1);
}

const templatePath = join(docsDir, `${docId}.template.html`);
const dataPath = join(docsDir, `${docId}.data.json`);
const outputPath = join(docsDir, `${docId}.output.html`);

if (!existsSync(templatePath)) {
  console.error(`Template not found: ${templatePath}`);
  process.exit(1);
}

let html = readFileSync(templatePath, 'utf-8');

if (existsSync(dataPath)) {
  const data = JSON.parse(readFileSync(dataPath, 'utf-8'));
  html = applyData(html, data);
  console.log(`Applied data from ${data.pages?.length || 0} pages`);
}

writeFileSync(outputPath, html);
console.log(`Generated: ${outputPath}`);
await postGenerate(outputPath);

function applyData(html, data) {
  if (!data.pages) return html;

  // Split HTML into pages by w-[210mm] divs
  const pageRegex = /<div class="w-\[210mm\] h-\[297mm\]/g;
  const starts = [];
  let match;
  while ((match = pageRegex.exec(html)) !== null) {
    starts.push(match.index);
  }
  if (starts.length === 0) return html;

  // Process pages in reverse to preserve indices
  for (let i = data.pages.length - 1; i >= 0; i--) {
    const pageData = data.pages[i];
    const pageNum = pageData.page || (i + 1);
    const pageIdx = pageNum - 1;
    if (pageIdx >= starts.length) continue;

    const pageStart = starts[pageIdx];
    const pageEnd = pageIdx + 1 < starts.length ? starts[pageIdx + 1] : html.length;
    let pageHtml = html.slice(pageStart, pageEnd);

    if (pageData.sections) {
      pageHtml = applySections(pageHtml, pageData.sections);
    }

    html = html.slice(0, pageStart) + pageHtml + html.slice(pageEnd);
  }

  return html;
}

function applySections(pageHtml, sections) {
  // Find section containers: <!-- Section: N=... -->
  // Each section has a big asteroid img in .asteroid-glow and small imgs in formula rows

  // Find all asteroid-glow containers (one per section)
  const sectionBlocks = [];
  const sectionRegex = /<!-- Section: N=\d+/g;
  let match;
  while ((match = sectionRegex.exec(pageHtml)) !== null) {
    sectionBlocks.push(match.index);
  }

  // Process sections in reverse
  for (let i = sections.length - 1; i >= 0; i--) {
    const secData = sections[i];
    const secIdx = secData.index;
    if (secIdx >= sectionBlocks.length) continue;

    const secStart = sectionBlocks[secIdx];
    const secEnd = secIdx + 1 < sectionBlocks.length
      ? sectionBlocks[secIdx + 1]
      : pageHtml.length;

    let secHtml = pageHtml.slice(secStart, secEnd);

    const scale = secData.scale ?? 1;
    const rotate = secData.rotate ?? 0;

    if (scale !== 1 || rotate !== 0) {
      const transform = `transform: scale(${scale}) rotate(${rotate}deg);`;

      // Apply to big asteroid img (inside asteroid-glow container)
      // The img has class="w-full h-full object-contain"
      // Add style to the img inside asteroid-glow
      secHtml = secHtml.replace(
        /(class="w-full h-full object-contain" alt="")(>)(\s*<span class="absolute text-\[2\.2rem\])/,
        `$1 style="${transform}"$2$3`
      );

      // Apply to all small asteroid imgs (inside w-[12mm] containers)
      // These imgs also have class="w-full h-full object-contain"
      // but are inside relative w-[12mm] divs
      secHtml = secHtml.replace(
        /(<div class="relative w-\[12mm\] h-\[12mm\] shrink-0"><img src="[^"]*pack3-asteroids[^"]*" class="w-full h-full object-contain" alt="")>/g,
        `$1 style="${transform}">`
      );
    }

    pageHtml = pageHtml.slice(0, secStart) + secHtml + pageHtml.slice(secEnd);
  }

  return pageHtml;
}