---
layout: post
---

<label>
  <input type="checkbox" id="fullscreen">
  Fullscreen
</label>

<script>
  const body = document.body;
  const checkbox = document.getElementById("fullscreen");
  const properties = ["margin", "max-width", "padding"];

  // Save each property's original inline value and priority.
  const originalStyles = Object.fromEntries(
      properties.map(property => [
	  property,
	  {
              value: body.style.getPropertyValue(property),
              priority: body.style.getPropertyPriority(property)
	  }
      ])
  );

  checkbox.addEventListener("change", () => {
      if (checkbox.checked) {
	  body.style.setProperty("margin", "0");
	  body.style.setProperty("max-width", "none");
	  body.style.setProperty("padding", "0");
      } else {
	  for (const property of properties) {
              const { value, priority } = originalStyles[property];

              if (value) {
		  body.style.setProperty(property, value, priority);
              } else {
		  body.style.removeProperty(property);
              }
	  }
      }
  });
</script>


<div id="loading">
  <div class="spinner"></div>
  <div>Loading editor…</div>
</div>

<style>
  :root {
      --bg-color: #ffffff;
      --border-color: #d0d7de;
      --text-color: #24292f;
      --tab-bg: #f6f8fa;
      --tab-active-bg: #ffffff;
  }

  #loading {
      position: absolute;
      inset: 0;
      z-index: 10;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      gap: 12px;
      background: var(--bg-color);
      font-size: 14px;
  }
  #loading .spinner {
      width: 28px;
      height: 28px;
      border: 3px solid var(--border-color);
      border-top-color: #0969da;
      border-radius: 50%;
      animation: spin 0.8s linear infinite;
  }
  @keyframes spin { to { transform: rotate(360deg); } }

  /* Match highlights (bottom editor) */
  .cm-regex-match-0 { background-color: rgba(9, 105, 218, 0.15); border-bottom: 2px solid #0969da; border-radius: 2px; }
  .cm-regex-match-1 { background-color: rgba(45, 164, 78, 0.15); border-bottom: 2px solid #2da44e; border-radius: 2px; }
  .cm-regex-match-2 { background-color: rgba(207, 34, 46, 0.15); border-bottom: 2px solid #cf222e; border-radius: 2px; }
  .cm-regex-match-3 { background-color: rgba(154, 103, 0, 0.15); border-bottom: 2px solid #9a6700; border-radius: 2px; }
  .cm-regex-match-4 { background-color: rgba(130, 80, 223, 0.15); border-bottom: 2px solid #8250df; border-radius: 2px; }

  /* Line fringe highlights (top editor) */
  .cm-regex-line-0 { border-left: 4px solid #0969da; background-color: rgba(9, 105, 218, 0.05); }
  .cm-regex-line-1 { border-left: 4px solid #2da44e; background-color: rgba(45, 164, 78, 0.05); }
  .cm-regex-line-2 { border-left: 4px solid #cf222e; background-color: rgba(207, 34, 46, 0.05); }
  .cm-regex-line-3 { border-left: 4px solid #9a6700; background-color: rgba(154, 103, 0, 0.05); }
  .cm-regex-line-4 { border-left: 4px solid #8250df; background-color: rgba(130, 80, 223, 0.05); }

  .tab-bar-container {
      display: flex;
      align-items: center;
      background: var(--border-color);
      padding: 1px 1px 0 1px;
      overflow: hidden;
  }
  .tab-bar {
      display: flex;
      gap: 1px;
      overflow-x: auto;
      flex: 1;
  }
  .tab-btn {
      background: var(--tab-bg);
      color: var(--text-color);
      border: none;
      padding: 6px 10px 6px 14px;
      cursor: pointer;
      font-size: 13px;
      display: flex;
      align-items: center;
      gap: 8px;
      white-space: nowrap;
      user-select: none;
  }
  .tab-btn input {
      font: inherit;
      padding: 0 2px;
      border: 1px solid #0969da;
      outline: none;
      background: #fff;
  }
  .tab-btn.active {
      background: var(--tab-active-bg);
      border-bottom: 2px solid #0969da;
      font-weight: 500;
  }
  .tab-close {
      background: transparent;
      border: none;
      color: #8c959f;
      cursor: pointer;
      font-size: 14px;
      padding: 0 4px;
      border-radius: 4px;
  }
  .tab-close:hover {
      background: rgba(0, 0, 0, 0.1);
      color: var(--text-color);
  }
  .tab-add-btn {
      background: var(--tab-bg);
      color: var(--text-color);
      border: none;
      cursor: pointer;
      font-size: 16px;
      font-weight: bold;
  }
  .tab-add-btn:hover {
      background: var(--tab-active-bg);
  }

  #regex-editor {
      margin-bottom: 1rem;
      border: 1px solid var(--border-color);
      overflow: hidden;
      background: #ffffff;
  }

  #cm6-editor {
      flex: 1;
      display: flex;
      flex-direction: column;
      border: 1px solid var(--border-color);
      overflow: hidden;
      background: #ffffff;
  }

  #regex-editor .cm-editor,
  #cm6-editor .cm-editor {
      height: 100%;
  }

  #regex-editor .cm-scroller,
  #cm6-editor .cm-scroller {
      overflow: auto;
  }

  .cm-editor.cm-focused, 
  .cm-scroller:focus, 
  .cm-content:focus {
  outline: none !important;
  }
</style>

<div id="regex-editor"></div>

<div class="tab-bar-container">
  <div class="tab-bar" id="tab-bar">
    <!-- Tabs will be rendered dynamically -->
  </div>
  <button class="tab-add-btn" id="add-tab-btn" title="Add New Tab">+</button>
</div>
<div id="cm6-editor"></div>

<script type="module">
  import { EditorState, StateField, StateEffect, RangeSetBuilder } from 'https://esm.sh/@codemirror/state@6.7.6';
  import { EditorView, Decoration, keymap, lineNumbers, highlightActiveLineGutter, highlightSpecialChars, drawSelection, highlightActiveLine } from 'https://esm.sh/@codemirror/view@6.43.14';
  import { defaultKeymap, history, historyKeymap } from 'https://esm.sh/@codemirror/commands@6.11.1';
  import { syntaxHighlighting, defaultHighlightStyle, bracketMatching } from 'https://esm.sh/@codemirror/language@6.13.1';

  // Top Editor Line Fringe Decorations
  const topEditorLineDecos = [
  Decoration.line({ class: 'cm-regex-line-0' }),
  Decoration.line({ class: 'cm-regex-line-1' }),
  Decoration.line({ class: 'cm-regex-line-2' }),
  Decoration.line({ class: 'cm-regex-line-3' }),
  Decoration.line({ class: 'cm-regex-line-4' })
  ];

  const topEditorField = StateField.define({
  create: state => buildTopDecorations(state),
  update: (decorations, tr) => tr.docChanged ? buildTopDecorations(tr.state) : decorations,
  provide: f => EditorView.decorations.from(f)
  });

  function buildTopDecorations(state) {
  const builder = new RangeSetBuilder();
  for (let i = 1; i <= state.doc.lines; i++) {
		       const line = state.doc.line(i);
		       builder.add(line.from, line.from, topEditorLineDecos[(i - 1) % topEditorLineDecos.length]);
		       }
		       return builder.finish();
		       }

		       

		       // Load saved regex patterns or fallback to default
		       const savedRegex = localStorage.getItem('regex_patterns') || "/([a-zA-Z0-9._-]+)@([a-zA-Z0-9._-]+)\\.([a-zA-Z]{2,5})/\n/([0-9]{4}-[0-9]{2}-[0-9]{2})/";

		       // Load saved tabs/documents or fallback to defaults
		       let documents = JSON.parse(localStorage.getItem('regex_documents')) || [
		       `Welcome to CodeMirror 6 Regex Visualizer!

		       Test email addresses:
		       - Support Team: support@example.com
		       - Main Info: info@domain.co.uk
		       - Developer: dev.team@service.org
		       - Invalid attempt: test@@domain..com

		       System parameters:
		       - User ID: 1042 | Session Token: abc123XYZ
		       - Created on: 2026-10-17`,

		       `function testAuth() {
		       const token = "Bearer eyJhbGciOiJIUzI1NiIsIn";
		       let userId = 9921;
		       // TODO: sanitize input
		       const email = "admin@system.local";
		       }
		       const date = "2026-10-18";`,

		       `[2026-10-18 10:15:30] INFO: User login success (uid=402, ip=192.168.1.50)
		       [2026-10-18 10:16:02] ERROR: Invalid token provided (token=xyz_9988_abc)
		       [2026-10-18 10:17:11] WARN: Rate limit approaching for service@api.net`
		       ];

		       let tabTitles = JSON.parse(localStorage.getItem('regex_tab_titles')) || ["Emails & IDs", "Code Snippet", "Server Logs"];
		       let activeTabIndex = parseInt(localStorage.getItem('regex_active_tab')) || 0;
		       if (activeTabIndex >= documents.length) activeTabIndex = 0;

    function saveToStorage() {
    // Keep current active tab text up to date in the array before saving
    documents[activeTabIndex] = mainView.state.doc.toString();
    
    localStorage.setItem('regex_patterns', regexView.state.doc.toString());
    localStorage.setItem('regex_documents', JSON.stringify(documents));
    localStorage.setItem('regex_tab_titles', JSON.stringify(tabTitles));
    localStorage.setItem('regex_active_tab', activeTabIndex.toString());
    }

    const initialRegex = "/([a-zA-Z0-9.\-_]+)@([a-zA-Z0-9.\-_]+)\\.([a-zA-Z]{2,5})/\n/([0-9]{4}-[0-9]{2}-[0-9]{2})/";

    const regexView = new EditorView({
    state: EditorState.create({
    doc: savedRegex,
    extensions: [
    lineNumbers(),
    drawSelection(),
    keymap.of(defaultKeymap),
    topEditorField,
    EditorView.updateListener.of(update => {
    if (update.docChanged) {
    dispatchRegexUpdate();
    saveToStorage();
    }
    })
    ]
    }),
    parent: document.getElementById('regex-editor')
    });

    const tabBarEl = document.getElementById('tab-bar');

    function renderTabs() {
    tabBarEl.innerHTML = '';
    documents.forEach((_, index) => {
    const tab = document.createElement('div');
    tab.className = 'tab-btn' + (index === activeTabIndex ? ' active' : '');
    tab.setAttribute('role', 'tab');

    const label = document.createElement('span');
    label.textContent = tabTitles[index] || `Tab ${index + 1}`;
    label.title = 'Double-click to rename';
    label.addEventListener('dblclick', () => renameTab(index, label));
    tab.appendChild(label);

    if (documents.length > 1) {
    const closeBtn = document.createElement('span');
    closeBtn.className = 'tab-close';
    closeBtn.setAttribute('role', 'button');
    closeBtn.title = 'Close Tab';
    closeBtn.textContent = '×';
    closeBtn.addEventListener('click', e => { e.stopPropagation(); closeTab(index); });
    tab.appendChild(closeBtn);
    }

    tab.addEventListener('click', () => switchTab(index));
    tabBarEl.appendChild(tab);
    });
    }

    function renameTab(index, label) {
    const input = document.createElement('input');
    input.value = tabTitles[index] || '';
    input.size = Math.max(6, input.value.length);
    label.replaceWith(input);
    input.focus();
    input.select();

    let done = false;
    const finish = save => {
    if (done) return;          // blur also fires when the input is removed
    done = true;
    const name = input.value.trim();
    if (save && name) tabTitles[index] = name;   // empty name keeps the old one
    renderTabs();
    saveToStorage();
    };

    input.addEventListener('keydown', e => {
    e.stopPropagation();
    if (e.key === 'Enter') finish(true);
    if (e.key === 'Escape') finish(false);
    });
    input.addEventListener('blur', () => finish(true));
    input.addEventListener('click', e => e.stopPropagation());   // don't trigger switchTab
    }

    function loadActive() {
    renderTabs();
    mainView.setState(states[activeTabIndex]);
    dispatchRegexUpdate();   // a stashed state may hold stale regex queries
    saveToStorage();         // must run after setState so it saves the new tab's text
    }

    function switchTab(index) {
    if (index === activeTabIndex) return;
    states[activeTabIndex] = mainView.state;   // stash undo history + cursor
    activeTabIndex = index;
    loadActive();
    }

    function closeTab(index) {
    const tabName = tabTitles[index] || `Tab ${index + 1}`;
    if (!window.confirm(`Are you sure you want to close "${tabName}"?`)) return;

    states[activeTabIndex] = mainView.state;
    [documents, tabTitles, states].forEach(a => a.splice(index, 1));

    if (index < activeTabIndex) activeTabIndex--;   // also fixes the wrong-tab bug
		else activeTabIndex = Math.min(activeTabIndex, documents.length - 1);
		loadActive();
		}

		document.getElementById('add-tab-btn').addEventListener('click', () => {
      const text = "// Type or paste text here...\n";
      states[activeTabIndex] = mainView.state;
      documents.push(text);
      tabTitles.push(`Dataset ${documents.length}`);
      states.push(makeState(text));
      activeTabIndex = documents.length - 1;
      loadActive();
      });

      // Initial Render Call
      renderTabs();
      
      const updateRegexEffect = StateEffect.define();

      const regexMatchDecos = [
      Decoration.mark({ class: 'cm-regex-match-0' }),
      Decoration.mark({ class: 'cm-regex-match-1' }),
      Decoration.mark({ class: 'cm-regex-match-2' }),
      Decoration.mark({ class: 'cm-regex-match-3' }),
      Decoration.mark({ class: 'cm-regex-match-4' })
      ];

      const regexHighlightField = StateField.define({
      create: () => ({ decorations: Decoration.none, query: [] }),
      update(value, tr) {
      let currentQueries = value.query;
      for (let effect of tr.effects) {
      if (effect.is(updateRegexEffect)) currentQueries = effect.value;
      }
      if (!tr.docChanged && tr.effects.length === 0) return value;

      const docText = tr.state.doc.toString();
      const ranges = [];

      currentQueries.forEach(q => {
      if (!q.pattern) return;
      let activeRegex;
      try {
      activeRegex = new RegExp(q.pattern, q.flags);
      } catch (err) {
      return;
      }

      let match;
      const deco = regexMatchDecos[q.lineIndex % regexMatchDecos.length];

      if (q.flags.includes('g')) {
      while ((match = activeRegex.exec(docText)) !== null) {
      const fullStart = match.index;
      const fullEnd = fullStart + match[0].length;
      if (fullStart !== fullEnd) {
      ranges.push({ from: fullStart, to: fullEnd, deco });
      }
      if (match.index === activeRegex.lastIndex) {
      activeRegex.lastIndex++;
      }
      }
      } else {
      match = activeRegex.exec(docText);
      if (match) {
      const fullStart = match.index;
      const fullEnd = fullStart + match[0].length;
      if (fullStart !== fullEnd) {
      ranges.push({ from: fullStart, to: fullEnd, deco });
      }
      }
      }
      });

      ranges.sort((a, b) => a.from - b.from || a.to - b.to);
      const builder = new RangeSetBuilder();
      ranges.forEach(r => builder.add(r.from, r.to, r.deco));

      return { decorations: builder.finish(), query: currentQueries };
      },
      provide: f => EditorView.decorations.from(f, val => val.decorations)
      });

      const mainExtensions = [
      lineNumbers(),
      highlightActiveLineGutter(),
      highlightSpecialChars(),
      history(),
      drawSelection(),
      highlightActiveLine(),
      bracketMatching(),
      syntaxHighlighting(defaultHighlightStyle, { fallback: true }),
      keymap.of([...defaultKeymap, ...historyKeymap]),
      regexHighlightField,
      EditorView.updateListener.of(u => { if (u.docChanged) saveToStorage(); })
      ];

      const makeState = doc => EditorState.create({ doc, extensions: mainExtensions });
      const states = documents.map(makeState);   // one EditorState per tab, parallel to documents/tabTitles

      const mainView = new EditorView({
      state: states[activeTabIndex],
      parent: document.getElementById('cm6-editor')
      });

      function dispatchRegexUpdate() {
      const lines = regexView.state.doc.toString().split('\n');
      const queries = [];

      lines.forEach((lineText, index) => {
      const trimmed = lineText.trim();
      if (!trimmed) return;

      let pattern = trimmed;
      let flags = 'g';

      const lastSlashIndex = trimmed.lastIndexOf('/');
      if (trimmed.startsWith('/') && lastSlashIndex > 0) {
      pattern = trimmed.substring(1, lastSlashIndex);
      flags = trimmed.substring(lastSlashIndex + 1) || 'g';
      }

      queries.push({ pattern, flags, lineIndex: index });
      });

      mainView.dispatch({
      effects: updateRegexEffect.of(queries)
      });
      }

      // Initial setup call
      dispatchRegexUpdate();

      document.getElementById('loading').remove();
</script>