#!/usr/bin/env node
// Banner image generator for docs.techswan.online
// Usage:
//   node scripts/generate-banner.js <slug>          # single article
//   node scripts/generate-banner.js --all           # all missing
//   node scripts/generate-banner.js --all --force   # regenerate all

const { createCanvas, registerFont } = require('canvas');
const matter = require('gray-matter');
const fs = require('fs');
const path = require('path');

// --- Config ---
const W = 1200, H = 630;
const MAX_TITLE_WIDTH = 1000;
const FONT_SIZES = [52, 44, 38];
const MAX_LINES = 3;

const FONT_PATH = '/usr/share/fonts/opentype/noto/NotoSansCJK-Bold.ttc';
if (fs.existsSync(FONT_PATH)) {
  registerFont(FONT_PATH, { family: 'Noto Sans CJK JP', weight: 'bold' });
}
const FONT_REGULAR = '/usr/share/fonts/opentype/noto/NotoSansCJK-Regular.ttc';
if (fs.existsSync(FONT_REGULAR)) {
  registerFont(FONT_REGULAR, { family: 'Noto Sans CJK JP', weight: 'normal' });
}

const CATEGORIES = {
  'docs': { label: 'Blog', color: '#0ea5e9' },
  'docs-tech': { label: 'Tech', color: '#10b981' },
};

const ROOT = path.resolve(__dirname, '..');

// --- Text wrapping ---
function tokenize(text) {
  // Split into tokens: consecutive ASCII word chars as one token, each CJK char as one token
  const tokens = [];
  const re = /([A-Za-z0-9._\-]+)|(\s+)|([\s\S])/g;
  let m;
  while ((m = re.exec(text)) !== null) {
    if (m[1]) tokens.push({ text: m[1], breakable: false });
    else if (m[2]) tokens.push({ text: ' ', breakable: true });
    else if (m[3]) tokens.push({ text: m[3], breakable: true });
  }
  return tokens;
}

function wrapText(ctx, text, maxWidth, fontSize, fontFamily) {
  ctx.font = `bold ${fontSize}px "${fontFamily}", sans-serif`;
  const tokens = tokenize(text);
  const lines = [];
  let currentLine = '';

  for (const token of tokens) {
    if (token.text === ' ' && currentLine === '') continue; // skip leading space
    const testLine = currentLine + token.text;
    const metrics = ctx.measureText(testLine);
    if (metrics.width > maxWidth && currentLine !== '') {
      lines.push(currentLine);
      currentLine = token.breakable && token.text === ' ' ? '' : token.text;
    } else {
      currentLine = testLine;
    }
  }
  if (currentLine) lines.push(currentLine);
  return lines;
}

// --- Drawing ---
function drawBanner(title, category) {
  const canvas = createCanvas(W, H);
  const ctx = canvas.getContext('2d');
  const cat = CATEGORIES[category] || CATEGORIES['docs'];

  // Background gradient
  const grad = ctx.createLinearGradient(0, 0, W, H);
  grad.addColorStop(0, '#1a1a2e');
  grad.addColorStop(1, '#16213e');
  ctx.fillStyle = grad;
  ctx.fillRect(0, 0, W, H);

  // Decorative circles
  ctx.fillStyle = 'rgba(233,69,96,0.15)';
  ctx.beginPath(); ctx.arc(1100, 100, 150, 0, Math.PI * 2); ctx.fill();
  ctx.fillStyle = 'rgba(14,165,233,0.1)';
  ctx.beginPath(); ctx.arc(1050, 500, 200, 0, Math.PI * 2); ctx.fill();

  // Accent line
  ctx.fillStyle = '#e94560';
  ctx.fillRect(60, 80, 6, 120);

  // Title - try font sizes until it fits
  ctx.fillStyle = '#ffffff';
  ctx.textBaseline = 'top';
  let lines, fontSize;
  for (fontSize of FONT_SIZES) {
    lines = wrapText(ctx, title, MAX_TITLE_WIDTH, fontSize, 'Noto Sans CJK JP');
    if (lines.length <= MAX_LINES) break;
  }
  // If still too many lines, truncate
  if (lines.length > MAX_LINES) {
    lines = lines.slice(0, MAX_LINES);
    lines[MAX_LINES - 1] = lines[MAX_LINES - 1].replace(/.$/, '…');
  }

  const lineHeight = Math.round(fontSize * 1.35);
  const titleStartY = 90;
  ctx.font = `bold ${fontSize}px "Noto Sans CJK JP", sans-serif`;
  lines.forEach((line, i) => {
    ctx.fillText(line, 90, titleStartY + i * lineHeight);
  });

  // Category badge
  const badgeY = Math.max(titleStartY + lines.length * lineHeight + 40, 350);
  ctx.fillStyle = cat.color;
  ctx.beginPath();
  ctx.roundRect(60, badgeY, 100, 36, 8);
  ctx.fill();
  ctx.fillStyle = '#ffffff';
  ctx.font = 'bold 18px "Noto Sans CJK JP", sans-serif';
  ctx.textBaseline = 'middle';
  ctx.fillText(cat.label, 60 + 50 - ctx.measureText(cat.label).width / 2, badgeY + 18);

  // Footer
  ctx.textBaseline = 'top';
  ctx.fillStyle = 'rgba(255,255,255,0.6)';
  ctx.font = '20px "Noto Sans CJK JP", sans-serif';
  ctx.fillText('雑記 by swallow', 60, 550);
  ctx.fillStyle = 'rgba(255,255,255,0.3)';
  const siteText = 'docs.techswan.online';
  ctx.fillText(siteText, W - 60 - ctx.measureText(siteText).width, 550);

  return canvas.toBuffer('image/png');
}

// --- Article discovery ---
function findArticle(slug) {
  for (const dir of ['docs-tech', 'docs']) {
    const mdPath = path.join(ROOT, dir, slug, 'index.md');
    if (fs.existsSync(mdPath)) return { mdPath, category: dir };
  }
  return null;
}

function getAllArticles() {
  const articles = [];
  for (const dir of ['docs-tech', 'docs']) {
    const dirPath = path.join(ROOT, dir);
    if (!fs.existsSync(dirPath)) continue;
    for (const slug of fs.readdirSync(dirPath)) {
      const mdPath = path.join(dirPath, slug, 'index.md');
      if (fs.existsSync(mdPath)) {
        articles.push({ slug, mdPath, category: dir });
      }
    }
  }
  return articles;
}

// --- Frontmatter update ---
function ensureFrontmatterImage(mdPath) {
  const raw = fs.readFileSync(mdPath, 'utf-8');
  const parsed = matter(raw);
  if (parsed.data.image) return false; // already set
  parsed.data.image = './banner.png';
  const updated = matter.stringify(parsed.content, parsed.data);
  fs.writeFileSync(mdPath, updated);
  return true;
}

// --- Main ---
function generateOne(slug, force = false) {
  const article = findArticle(slug);
  if (!article) {
    console.error(`❌ Article not found: ${slug}`);
    return false;
  }
  const { mdPath, category } = article;
  const bannerPath = path.join(path.dirname(mdPath), 'banner.png');

  if (fs.existsSync(bannerPath) && !force) {
    console.log(`⏭️  Skip (exists): ${slug}`);
    return true;
  }

  const parsed = matter(fs.readFileSync(mdPath, 'utf-8'));
  const title = parsed.data.title || slug;

  const buf = drawBanner(title, category);
  fs.writeFileSync(bannerPath, buf);

  const updated = ensureFrontmatterImage(mdPath);
  console.log(`✅ ${slug} → banner.png (${(buf.length / 1024).toFixed(0)}KB)${updated ? ' + frontmatter updated' : ''}`);
  return true;
}

// --- CLI ---
const args = process.argv.slice(2);
const force = args.includes('--force');
const all = args.includes('--all');

if (all) {
  const articles = getAllArticles();
  console.log(`Found ${articles.length} articles`);
  let generated = 0;
  for (const { slug } of articles) {
    if (generateOne(slug, force)) generated++;
  }
  console.log(`\nDone: ${generated}/${articles.length}`);
} else {
  const slug = args.find(a => !a.startsWith('--'));
  if (!slug) {
    console.log('Usage: node scripts/generate-banner.js <slug> | --all [--force]');
    process.exit(1);
  }
  generateOne(slug, force);
}