import { marked, Renderer } from 'marked';

function escapeHtml(value: string): string {
  return value
    .replaceAll('&', '&')
    .replaceAll('<', '&lt;')
    .replaceAll('>', '&gt;')
    .replaceAll('"', '&quot;')
    .replaceAll("'", '&#39;');
}

function safeUrl(value: string): string | null {
  const trimmed = value.trim();
  if (trimmed.startsWith('#') || trimmed.startsWith('/')) return trimmed;

  try {
    const url = new URL(trimmed);
    return ['http:', 'https:'].includes(url.protocol) ? url.href : null;
  } catch {
    return null;
  }
}

const renderer = new Renderer();

renderer.html = ({ text }) => escapeHtml(text);
renderer.link = function ({ href, title, tokens }) {
  const label = this.parser.parseInline(tokens);
  const url = safeUrl(href);
  if (!url) return label;
  const titleAttribute = title ? ` title="${escapeHtml(title)}"` : '';
  return `<a href="${escapeHtml(url)}"${titleAttribute} target="_blank" rel="noreferrer">${label}</a>`;
};
renderer.image = ({ href, title, text }) => {
  const url = safeUrl(href);
  if (!url) return escapeHtml(text);
  const titleAttribute = title ? ` title="${escapeHtml(title)}"` : '';
  return `<img src="${escapeHtml(url)}" alt="${escapeHtml(text)}"${titleAttribute} loading="lazy">`;
};

export function renderReleaseMarkdown(markdown: string): string {
  const options = {
    async: false,
    breaks: true,
    gfm: true,
    renderer
  } as const;
  const tokens = marked.lexer(markdown, options);
  let html = '';
  let entryOpen = false;
  for (const token of tokens) {
    const boundary = token.type === 'hr' || (token.type === 'heading' && token.depth <= 3);
    if (boundary && entryOpen) {
      html += '</section>\n';
      entryOpen = false;
    }
    if (token.type === 'heading' && token.depth === 3) {
      html += '<section class="update-entry">\n';
      entryOpen = true;
    }
    html += marked.parser([token], options);
  }
  return html + (entryOpen ? '</section>\n' : '');
}