# Clean URLs and hosting

MD-CMS gives pages whose filename matches a nav `section-id` a clean URL — `example.com/timesheet` instead of `example.com/#pages/timesheet.md`. This page explains why clean URLs need help from the web server, and how to set that up on every kind of host.

## The problem

Clean URLs are *virtual*: there is no file called `timesheet` on the server. The mapping from `/timesheet` to `pages/timesheet.md` exists only in the renderer's JavaScript inside `index.html`.

Navigation *within* the site always works — clicking a nav link never asks the server for `/timesheet`. But three things do ask the server directly:

- **Reloading** the page (Ctrl-R / F5)
- **Opening a shared link** to a clean URL in a fresh tab
- **Bookmarks** pointing at a clean URL

In all three cases the browser sends `GET /timesheet` to the server *before any JavaScript runs*. A plain static server looks for a file at that path, finds nothing, and returns **404** — `index.html` is never served, so the router that knows how to resolve the slug never executes.

The fix is always the same idea: get the server (or the browser) to answer unknown extension-less paths with `index.html`, so the client-side router can take over.

## Solutions by environment

| Environment | Solution | Setup |
|---|---|---|
| Local preview | `mdcms serve` | nothing — built in |
| Any host, PWA enabled | service worker app-shell fallback | `pwa: yes` in `config.yml` + `mdcms build` |
| GitHub Pages | `404.html` redirect | ships with the starter template |
| Netlify / Cloudflare Pages | `_redirects` file | one line, see below |
| nginx | `try_files` rule | see below |
| Apache | `.htaccess` rewrite | see below |
| Caddy | `try_files` rule | see below |

### Local preview: `mdcms serve`

`python3 -m http.server` is a "dumb" static server: no rewrites, no custom 404 page. Use the built-in preview server instead:

```
mdcms serve                   # serve the current directory
mdcms serve mysite            # serve a registered site
mdcms serve --path ./site     # serve an explicit path
mdcms serve --port 9000       # custom port (default: 8800)
```

Then open `http://localhost:8800`. The server rewrites unknown extension-less paths (like `/timesheet`) to `index.html`, while requests *with* an extension (like a missing `pages/timesheet.nb.md` category variant) still return 404 — the renderer depends on that for its category-fallback logic. It also serves `.md` files with the correct `text/markdown` type.

Never open `index.html` directly from disk — browsers block local file access due to CORS.

### Any host: the service worker (PWA)

If `pwa: yes` is set in `config.yml`, the service worker generated by `mdcms build` answers every navigation request with the cached `index.html` app shell — the request never reaches the server. This makes clean-URL reloads work on **any** host, including ones where you can't configure rewrites, and it works offline.

Caveat: the service worker is only installed after the first visit, so the *very first* request for a clean URL in a fresh browser still hits the server. Pair it with one of the server-side solutions below for full coverage.

### GitHub Pages: `404.html`

The starter template ships an `app/404.html`. GitHub Pages serves it as the body of any 404 response; it encodes the intended path as `?_route=/timesheet` and redirects to the app root, where `index.html` picks the route up and cleans the URL. No configuration needed — just deploy the file with the rest of the site.

### Netlify and Cloudflare Pages: `_redirects`

Create a file called `_redirects` in the site root (next to `index.html`) with this single line:

```
/*    /index.html    200
```

The `200` makes it a *rewrite* (the URL stays the same), not a redirect. The renderer detects these rewrites: a missing `.md` file that comes back as `index.html` is recognised by its `text/html` content type and treated as not found, so category fallback still works.

### nginx

Add a `try_files` rule to the site's `location` block:

```nginx
server {
    listen 80;
    server_name example.com;
    root /var/www/mysite;
    index index.html;

    # Serve real files when they exist; otherwise hand the request
    # to index.html so the MD-CMS router can resolve the clean URL.
    location / {
        try_files $uri $uri/ /index.html;
    }

    # Correct content type for markdown (optional but recommended —
    # the renderer rejects text/html responses for .md requests).
    types {
        text/markdown md;
    }
}
```

### Apache

Create an `.htaccess` file in the site root (requires `mod_rewrite`):

```apache
RewriteEngine On
RewriteBase /

# Serve existing files and directories as-is
RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]

# Everything else goes to index.html for the client-side router
RewriteRule ^ index.html [L]

# Correct content type for markdown
AddType text/markdown .md
```

### Caddy

```caddyfile
example.com {
    root * /var/www/mysite
    try_files {path} {path}/ /index.html
    file_server
}
```

## Sample script: standalone preview server

If `mdcms` is not installed (for example on a machine that only has Python), this standalone script reproduces what `mdcms serve` does. Save it as `serve.py` in the site root and run `python3 serve.py`:

```python
#!/usr/bin/env python3
"""Minimal static server with SPA clean-URL fallback for MD-CMS sites.

Unknown extension-less paths (e.g. /timesheet) are served index.html so the
MD-CMS client-side router can resolve them. Requests with a file extension
that don't exist (e.g. a missing .md category variant) still return 404,
which the renderer relies on.
"""
import http.server
from pathlib import Path

PORT = 8800


class SpaHandler(http.server.SimpleHTTPRequestHandler):
    extensions_map = {
        **http.server.SimpleHTTPRequestHandler.extensions_map,
        ".md": "text/markdown; charset=utf-8",
        ".yml": "text/yaml; charset=utf-8",
        ".json": "application/json; charset=utf-8",
    }

    def _rewrite_spa(self):
        if Path(self.translate_path(self.path)).exists():
            return
        clean = self.path.split("?", 1)[0].split("#", 1)[0]
        last = clean.rstrip("/").rsplit("/", 1)[-1]
        if "." not in last:
            self.path = "/index.html"

    def do_GET(self):
        self._rewrite_spa()
        super().do_GET()

    def do_HEAD(self):
        self._rewrite_spa()
        super().do_HEAD()


if __name__ == "__main__":
    with http.server.ThreadingHTTPServer(("127.0.0.1", PORT), SpaHandler) as httpd:
        print(f"Serving on http://localhost:{PORT}/  (Ctrl-C to stop)")
        try:
            httpd.serve_forever()
        except KeyboardInterrupt:
            print("\nStopped.")
```

## How the pieces interact

A request for a clean URL is resolved by the first layer that catches it:

1. **Service worker** (if installed) — serves the cached shell, even offline.
2. **Server rewrite** (`_redirects`, nginx, Apache, Caddy, `mdcms serve`) — serves `index.html` with status 200.
3. **`404.html`** (GitHub Pages) — redirects to the app root with `?_route=`.

Whichever layer answers, `index.html` boots, reads the path (or `?_route=`), matches the last segment against the nav `section-id` list, and renders the right page. If the segment matches nothing, the renderer shows its normal page-not-found message.