// Minimal syntax highlighter for the docs (shared).
// - CSS: converts plain-text CSS inside `.css-view`
// - JS:  converts plain-text JS inside `.code-view`
// - HTML: converts plain-text HTML inside `.html-view`
//
// It uses the existing demo.css token classes:
// .kwd .str .num .punc .com .attr .val .fun .tag

(function () {
  function escapeHtml(s) {
    return String(s)
      .replace(/&/g, '&')
      .replace(/</g, '&lt;')
      .replace(/>/g, '&gt;');
  }

  function highlightCSS(input) {
    // IMPORTANT:
    // Do not insert `<span ...>` too early, otherwise later regex passes
    // will re-match inside those tags (e.g. `class="com"`) and break HTML.
    // We use placeholders then restore.
    let s = escapeHtml(input);

    const comments = [];
    const strings = [];

    // Comments (placeholder)
    s = s.replace(/\/\*[\s\S]*?\*\//g, (m) => {
      const i = comments.length;
      comments.push(m);
      return `@@COM${i}@@`;
    });

    // Strings (placeholder)
    s = s.replace(/("(?:\\.|[^"\\])*"|'(?:\\.|[^'\\])*')/g, (m) => {
      const i = strings.length;
      strings.push(m);
      return `@@STR${i}@@`;
    });

    // @rules
    s = s.replace(/(^|\s)(@[\w-]+)/g, (m, p1, p2) => `${p1}<span class="kwd">${p2}</span>`);

    // Hex colors
    s = s.replace(/(#(?:[0-9a-fA-F]{3}|[0-9a-fA-F]{6}|[0-9a-fA-F]{8}))/g, (m) => `<span class="num">${m}</span>`);

    // Numbers with units (very rough, but good enough visually)
    s = s.replace(/(\b\d+(?:\.\d+)?)(%|px|rem|em|vh|vw|vmin|vmax|deg|turn|s|ms)?\b/g, (m, n, unit) => {
      return `<span class="num">${n}</span>${unit || ''}`;
    });

    // Property names: "prop: value"
    s = s.replace(/(^|\n)(\s*)([a-zA-Z_-][\w-]*)(\s*):/g, (m, p1, ws, prop, ws2) => {
      return `${p1}${ws}<span class="attr">${prop}</span>${ws2}<span class="punc">:</span>`;
    });

    // Highlight braces / punctuation
    s = s.replace(/([{}();,])/g, (m) => `<span class="punc">${m}</span>`);

    // Selectors (line before "{"), skip @rules
    s = s.replace(/(^|\n)([^\n{]+?)(\s*)(<span class="punc">\{<\/span>)/g, (m, p1, sel, ws, brace) => {
      const trimmed = sel.trimStart();
      if (trimmed.startsWith('@')) return `${p1}${sel}${ws}${brace}`;
      return `${p1}<span class="fun">${sel}</span>${ws}${brace}`;
    });

    // Values: after ":" until ";" or "}" (best-effort, runs after punctuation)
    s = s.replace(/(<span class="punc">:<\/span>)([^;\n}]+)(?=(<span class="punc">;|<span class="punc">\}))/g, (m, colon, val) => {
      // avoid re-highlighting spans
      if (val.includes('<span')) return `${colon}${val}`;
      return `${colon}<span class="val">${val}</span>`;
    });

    // Restore placeholders
    s = s.replace(/@@COM(\d+)@@/g, (m, idx) => `<span class="com">${comments[Number(idx)] || ''}</span>`);
    s = s.replace(/@@STR(\d+)@@/g, (m, idx) => `<span class="str">${strings[Number(idx)] || ''}</span>`);

    return s;
  }

  function highlightJS(input) {
    let s = escapeHtml(input);

    // Protect strings and comments first (placeholders), so later regexes won't touch them.
    const strings = [];
    const comments = [];

    // Strings (", ', `)
    s = s.replace(/("(?:\\.|[^"\\])*"|'(?:\\.|[^'\\])*'|`(?:\\.|[^`\\])*`)/g, (m) => {
      const i = strings.length;
      strings.push(m);
      return `@@STR${i}@@`;
    });

    // Comments (/* */ and //)
    s = s.replace(/\/\*[\s\S]*?\*\/|\/\/[^\n]*/g, (m) => {
      const i = comments.length;
      comments.push(m);
      return `@@COM${i}@@`;
    });

    // Keywords (small set, enough for docs)
    const KW = new Set([
      'const', 'let', 'var', 'function', 'return',
      'if', 'else', 'for', 'while', 'do', 'switch', 'case', 'break', 'continue',
      'try', 'catch', 'finally', 'throw',
      'new', 'class', 'extends', 'super',
      'import', 'from', 'export', 'default',
      'async', 'await',
      'true', 'false', 'null', 'undefined'
    ]);

    s = s.replace(/\b([A-Za-z_$][\w$]*)\b/g, (m, id) => {
      if (KW.has(id)) return `<span class="kwd">${id}</span>`;
      return m;
    });

    // Numbers
    s = s.replace(/\b(\d+(?:\.\d+)?)\b/g, (m, n) => `<span class="num">${n}</span>`);

    // Function calls: identifier followed by "(" (skip keywords)
    s = s.replace(/\b([A-Za-z_$][\w$]*)\b(?=\s*\()/g, (m, id) => {
      if (KW.has(id)) return id;
      return `<span class="fun">${id}</span>`;
    });

    // Basic punctuation (avoid "." / "=" to not conflict with injected HTML)
    s = s.replace(/([{}()[\];,:])/g, (m) => `<span class="punc">${m}</span>`);

    // Restore comments and strings (escaped)
    s = s.replace(/@@COM(\d+)@@/g, (m, idx) => `<span class="com">${comments[Number(idx)] || ''}</span>`);
    s = s.replace(/@@STR(\d+)@@/g, (m, idx) => `<span class="str">${strings[Number(idx)] || ''}</span>`);

    return s;
  }

  function highlightHTML(input) {
    // Input comes from textContent, so it contains real "<" / ">" characters.
    let s = escapeHtml(input);

    // HTML comments
    s = s.replace(/&lt;!--[\s\S]*?--&gt;/g, (m) => `<span class="com">${m}</span>`);

    // Tags + attributes (best-effort)
    s = s.replace(/&lt;(\/?)([A-Za-z][\w:-]*)([\s\S]*?)&gt;/g, (m, slash, name, rest) => {
      // self-close
      const selfClose = /\s\/\s*$/.test(rest) || /\/\s*$/.test(rest);
      const restNoClose = rest.replace(/\/\s*$/, '');

      let out = `<span class="tag">&lt;${slash || ''}${name}</span>`;

      // attributes: key="value" / key='value' / key=value
      const attrRe = /(\s+)([^\s=\/]+)(\s*=\s*)(?:"([^"]*)"|'([^']*)'|([^\s"'>]+))/g;
      let lastIdx = 0;
      let attrs = '';
      let match;
      while ((match = attrRe.exec(restNoClose))) {
        const [full, ws, key, eq, v1, v2, v3] = match;
        const start = match.index;
        // keep any junk between attrs
        attrs += restNoClose.slice(lastIdx, start);
        lastIdx = start + full.length;

        const rawVal = (v1 !== undefined ? `"${v1}"` : (v2 !== undefined ? `'${v2}'` : (v3 !== undefined ? v3 : '')));
        attrs += `${ws}<span class="attr">${key}</span>${eq}<span class="val">${escapeHtml(rawVal)}</span>`;
      }
      attrs += restNoClose.slice(lastIdx);
      out += attrs;

      if (selfClose) out += `<span class="tag">/&gt;</span>`;
      else out += `<span class="tag">&gt;</span>`;
      return out;
    });

    return s;
  }

  function enhance() {
    const blocks = document.querySelectorAll('.css-view, .code-view, .html-view');
    blocks.forEach((el) => {
      try {
        if (el.dataset.highlighted === '1') return;
        const text = el.textContent || '';
        // If already contains spans, assume it's already highlighted.
        if (el.innerHTML.includes('<span')) {
          el.dataset.highlighted = '1';
          return;
        }
        if (el.classList.contains('css-view')) {
          el.innerHTML = highlightCSS(text);
        } else if (el.classList.contains('html-view')) {
          el.innerHTML = highlightHTML(text);
        } else {
          // `.code-view`
          el.innerHTML = highlightJS(text);
        }
        el.dataset.highlighted = '1';
      } catch (_) {
        // Never break the page; just skip highlighting if anything goes wrong.
      }
    });
  }

  // Expose for pages that want to re-run manually
  window.__highlightCssViews = enhance;

  if (document.readyState === 'loading') {
    document.addEventListener('DOMContentLoaded', enhance, { once: true });
  } else {
    enhance();
  }

  // Re-run when switching to the CSS tab (covers cases where the page
  // injects/replaces code blocks after load or during navigation).
  document.addEventListener(
    'click',
    (e) => {
      const tab = e.target && e.target.closest ? e.target.closest('.tab') : null;
      if (!tab) return;
      const label = (tab.textContent || '').trim().toLowerCase();
      if (label === 'css' || label === 'html' || label === 'javascript' || label === 'js') {
        // Defer so the tab switch can toggle DOM/classes first
        setTimeout(enhance, 0);
      }
    },
    true
  );

  // Observe DOM changes to catch dynamically added `.css-view` blocks.
  try {
    const mo = new MutationObserver(() => {
      // Cheap debounce via microtask
      Promise.resolve().then(enhance);
    });
    mo.observe(document.documentElement, {
      subtree: true,
      childList: true,
      characterData: true
    });
  } catch (_) {}
})();