init - PoC works

This commit is contained in:
Caffeine Fueled 2026-03-14 10:10:25 +01:00
commit 6209600037
Signed by: cf7
GPG key ID: CA295D643074C68C
5 changed files with 483 additions and 0 deletions

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Dockerfile Normal file
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# nginxinc/nginx-unprivileged runs as uid 101 on port 8080 — no root needed
FROM docker.io/nginxinc/nginx-unprivileged:alpine
# Copy app files
COPY --chown=101:101 index.html app.js /usr/share/nginx/html/
COPY --chown=101:101 nginx-container.conf /etc/nginx/conf.d/default.conf
EXPOSE 8080

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README.md Normal file
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# Another Mermaid Thing
Early stage, but should be working.
## Features
- local only
- stores to localstorage
- preview in iFrame for some form of sandbox
## Setup
- please use reverse proxy with strict CSP options if hosted online
Download and run. Container follows.

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mermaid.initialize({ startOnLoad: false, theme: 'dark' });
const editor = document.getElementById('editor');
const status = document.getElementById('status');
const previewArea = document.getElementById('previewArea');
const panLayer = document.getElementById('pan-layer');
const svgFrame = document.getElementById('svg-frame');
const overlay = document.getElementById('overlay');
const placeholder = document.getElementById('placeholder');
const STORAGE_KEY = 'mermaid-editor-content';
const DEFAULT = `flowchart TD
A[Start] --> B{Decision}
B -->|Yes| C[Do the thing]
B -->|No| D[Skip it]
C --> E[End]
D --> E`;
editor.value = localStorage.getItem(STORAGE_KEY) ?? DEFAULT;
editor.addEventListener('input', () => {
localStorage.setItem(STORAGE_KEY, editor.value);
});
// ── Render ───────────────────────────────────────────────────────────────────
let lastSvg = null;
async function render() {
const code = editor.value.trim();
if (!code) return;
try {
const id = 'mermaid-' + Date.now();
const { svg } = await mermaid.render(id, code);
lastSvg = svg;
const { w, h } = parseSvgSize(svg);
svgFrame.width = w;
svgFrame.height = h;
// Write SVG into sandboxed iframe — scripts inside cannot reach the parent page
svgFrame.srcdoc = `<!DOCTYPE html><html><head>
<style>html,body{margin:0;padding:0;background:transparent;overflow:hidden;}svg{display:block;}</style>
</head><body>${svg}</body></html>`;
svgFrame.style.display = 'block';
overlay.style.display = 'none';
setStatus('OK', '#4ade80');
requestAnimationFrame(resetView);
} catch (err) {
showError(err.message || String(err));
}
}
function parseSvgSize(svgString) {
const doc = new DOMParser().parseFromString(svgString, 'image/svg+xml');
const svg = doc.querySelector('svg');
let w = parseFloat(svg?.getAttribute('width'));
let h = parseFloat(svg?.getAttribute('height'));
if (!w || !h) {
const vb = svg?.getAttribute('viewBox')?.trim().split(/[\s,]+/);
if (vb?.length === 4) { w = parseFloat(vb[2]); h = parseFloat(vb[3]); }
}
return { w: w || 800, h: h || 600 };
}
function showError(msg) {
const errEl = document.createElement('div');
errEl.className = 'error';
errEl.textContent = msg;
overlay.innerHTML = '';
overlay.appendChild(errEl);
overlay.style.display = 'flex';
setStatus('Error', '#f87171');
setTimeout(() => errEl.classList.add('fade-out'), 4000);
setTimeout(() => {
if (overlay.contains(errEl)) {
overlay.innerHTML = '';
overlay.appendChild(placeholder);
overlay.style.display = 'flex';
}
}, 4600);
}
// ── Toolbar actions ──────────────────────────────────────────────────────────
function clearEditor() {
editor.value = '';
localStorage.removeItem(STORAGE_KEY);
lastSvg = null;
svgFrame.srcdoc = '';
svgFrame.style.display = 'none';
overlay.innerHTML = '';
overlay.appendChild(placeholder);
overlay.style.display = 'flex';
}
function downloadSvg() {
if (!lastSvg) return;
const blob = new Blob([lastSvg], { type: 'image/svg+xml' });
const url = URL.createObjectURL(blob);
const a = document.createElement('a');
a.href = url; a.download = 'diagram.svg'; a.click();
URL.revokeObjectURL(url);
}
async function copySvg() {
if (!lastSvg) return;
await navigator.clipboard.writeText(lastSvg);
setStatus('Copied!', '#60a5fa');
}
function setStatus(msg, color) {
status.textContent = msg;
status.style.color = color;
setTimeout(() => { status.textContent = ''; }, 2000);
}
// ── Pan & zoom ───────────────────────────────────────────────────────────────
let vt = { x: 0, y: 0, scale: 1 };
let drag = null;
function applyTransform() {
panLayer.style.transform = `translate(${vt.x}px, ${vt.y}px) scale(${vt.scale})`;
}
function resetView() {
const area = previewArea.getBoundingClientRect();
vt = {
x: (area.width - svgFrame.offsetWidth) / 2,
y: (area.height - svgFrame.offsetHeight) / 2,
scale: 1,
};
applyTransform();
}
previewArea.addEventListener('wheel', e => {
e.preventDefault();
const rect = previewArea.getBoundingClientRect();
const mx = e.clientX - rect.left;
const my = e.clientY - rect.top;
const delta = e.deltaY < 0 ? 1.1 : 0.9;
vt.x = mx - (mx - vt.x) * delta;
vt.y = my - (my - vt.y) * delta;
vt.scale = Math.min(10, Math.max(0.1, vt.scale * delta));
applyTransform();
}, { passive: false });
previewArea.addEventListener('mousedown', e => {
drag = { startX: e.clientX - vt.x, startY: e.clientY - vt.y };
previewArea.classList.add('dragging');
});
window.addEventListener('mousemove', e => {
if (!drag) return;
vt.x = e.clientX - drag.startX;
vt.y = e.clientY - drag.startY;
applyTransform();
});
window.addEventListener('mouseup', () => {
drag = null;
previewArea.classList.remove('dragging');
});
// ── Keyboard shortcuts ───────────────────────────────────────────────────────
editor.addEventListener('keydown', e => {
if ((e.ctrlKey || e.metaKey) && e.key === 'Enter') {
e.preventDefault();
render();
}
if (e.key === 'Tab') {
e.preventDefault();
const s = editor.selectionStart;
editor.value = editor.value.slice(0, s) + ' ' + editor.value.slice(editor.selectionEnd);
editor.selectionStart = editor.selectionEnd = s + 2;
}
});
// ── Init ─────────────────────────────────────────────────────────────────────
render();

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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Simple Mermaid Editor</title>
<script src="https://cdn.jsdelivr.net/npm/mermaid@11/dist/mermaid.min.js"></script>
<style>
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
body {
font-family: system-ui, sans-serif;
background: #0f1117;
color: #e0e0e0;
height: 100vh;
display: flex;
flex-direction: column;
}
header {
padding: 12px 20px;
border-bottom: 1px solid #2a2d3a;
display: flex;
align-items: center;
gap: 12px;
flex-shrink: 0;
}
header h1 { font-size: 1.1rem; font-weight: 600; color: #fff; }
.badge {
font-size: 0.7rem;
background: #1e3a5f;
color: #60a5fa;
padding: 2px 8px;
border-radius: 999px;
}
.main { display: flex; flex: 1; overflow: hidden; }
.editor-pane {
display: flex;
flex-direction: column;
width: 40%;
border-right: 1px solid #2a2d3a;
}
.pane-label {
font-size: 0.7rem;
font-weight: 600;
letter-spacing: 0.08em;
text-transform: uppercase;
color: #666;
padding: 8px 16px;
border-bottom: 1px solid #2a2d3a;
flex-shrink: 0;
display: flex;
align-items: center;
}
textarea {
flex: 1;
background: #0f1117;
color: #c9d1d9;
border: none;
outline: none;
resize: none;
padding: 16px;
font-family: "JetBrains Mono", "Fira Code", "Courier New", monospace;
font-size: 0.85rem;
line-height: 1.6;
tab-size: 2;
}
.toolbar {
border-top: 1px solid #2a2d3a;
padding: 8px 12px;
display: flex;
align-items: center;
gap: 8px;
flex-shrink: 0;
flex-wrap: wrap;
}
.toolbar span { font-size: 0.75rem; color: #555; margin-left: auto; }
button {
padding: 5px 14px;
border-radius: 6px;
border: none;
cursor: pointer;
font-size: 0.8rem;
font-weight: 500;
transition: opacity 0.15s;
}
button:hover { opacity: 0.85; }
.btn-render { background: #2563eb; color: #fff; }
.btn-muted { background: #2a2d3a; color: #aaa; }
.btn-sm { padding: 2px 10px; font-size: 0.7rem; margin-left: auto; }
/* ── Preview ── */
.preview-pane { flex: 1; display: flex; flex-direction: column; overflow: hidden; }
.preview-area {
flex: 1;
overflow: hidden;
position: relative;
cursor: grab;
}
.preview-area.dragging { cursor: grabbing; }
#pan-layer {
position: absolute;
top: 0; left: 0;
transform-origin: 0 0;
}
#svg-frame {
display: block;
border: none;
background: transparent;
}
/* Placeholder / error overlay — centred, outside the pan layer */
#overlay {
position: absolute;
inset: 0;
display: flex;
align-items: center;
justify-content: center;
pointer-events: none;
}
.placeholder {
color: #333;
font-size: 0.9rem;
text-align: center;
pointer-events: none;
}
.placeholder p { margin-top: 6px; font-size: 0.78rem; color: #2a2d3a; }
.error {
background: #2d1b1b;
border: 1px solid #5c2626;
border-radius: 8px;
padding: 12px 16px;
color: #f87171;
font-family: monospace;
font-size: 0.8rem;
white-space: pre-wrap;
max-width: 560px;
opacity: 1;
transition: opacity 0.6s ease;
pointer-events: none;
}
.error.fade-out { opacity: 0; }
</style>
</head>
<body>
<header>
<h1>Simple Mermaid Editor</h1>
<span class="badge">live preview</span>
</header>
<div class="main">
<div class="editor-pane">
<div class="pane-label">Diagram Source</div>
<textarea id="editor" spellcheck="false" placeholder="Type your Mermaid diagram here…"></textarea>
<div class="toolbar">
<button class="btn-render" onclick="render()">Render</button>
<button class="btn-muted" onclick="clearEditor()">Clear</button>
<button class="btn-muted" onclick="copySvg()">Copy SVG</button>
<button class="btn-muted" onclick="downloadSvg()">Download SVG</button>
<span id="status"></span>
</div>
</div>
<div class="preview-pane">
<div class="pane-label">
Preview
<button class="btn-muted btn-sm" onclick="resetView()">Reset view</button>
</div>
<div class="preview-area" id="previewArea">
<div id="pan-layer">
<iframe id="svg-frame" sandbox="" scrolling="no"></iframe>
</div>
<div id="overlay">
<div class="placeholder" id="placeholder">
← Write a diagram and click Render
<p>or press Ctrl+Enter</p>
</div>
</div>
</div>
</div>
</div>
<script src="app.js"></script>
</body>
</html>

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nginx-container.conf Normal file
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# Runs inside the container — TLS and HSTS are handled by the reverse proxy.
server {
listen 8080;
server_name _;
root /usr/share/nginx/html;
index index.html;
# Disable nginx version in error pages and headers
server_tokens off;
# ── Security headers ─────────────────────────────────────────────────────
add_header Content-Security-Policy "
default-src 'none';
script-src 'self' https://cdn.jsdelivr.net;
style-src 'unsafe-inline';
img-src 'self' data: blob:;
frame-src 'self';
child-src 'self';
connect-src 'none';
font-src 'none';
object-src 'none';
base-uri 'self';
form-action 'none';
frame-ancestors 'none';
" always;
add_header X-Content-Type-Options "nosniff" always;
add_header X-Frame-Options "DENY" always;
add_header Referrer-Policy "no-referrer" always;
add_header Permissions-Policy "camera=(), microphone=(), geolocation=(), payment=()" always;
# ── Static files ─────────────────────────────────────────────────────────
location / {
try_files $uri $uri/ =404;
}
location ~* \.(js|css)$ {
expires 1y;
add_header Cache-Control "public, immutable";
# nginx overrides parent add_header inside location blocks, so repeat them
add_header Content-Security-Policy "
default-src 'none';
script-src 'self' https://cdn.jsdelivr.net;
style-src 'unsafe-inline';
img-src 'self' data: blob:;
frame-src 'self';
child-src 'self';
connect-src 'none';
font-src 'none';
object-src 'none';
base-uri 'self';
form-action 'none';
frame-ancestors 'none';
" always;
add_header X-Content-Type-Options "nosniff" always;
add_header X-Frame-Options "DENY" always;
add_header Referrer-Policy "no-referrer" always;
}
# Block hidden files (.git, .env, etc.)
location ~ /\. {
deny all;
}
}