ifcurl/README.md

# ifcurl

**ifcurl** is a Forgejo mod that adds 3D model awareness to BIM workflows on git. When IFC files are committed or compared, diff pages show colour-coded visual renders of what changed. Paste an `ifc://` URL into any issue, PR comment, or markdown file and Forgejo renders it as a linked preview image. Every preview is a clickable link that opens the model in an interactive WebGL viewer at the exact viewpoint encoded in the URL.

---

## What you get

### Visual diffs on commit and PR pages

When an `.ifc` file changes in a commit or pull request, the diff page automatically shows a rendered snapshot of the change — added geometry in green, removed in red. The image links directly to the 3D viewer at the head version of the file, and the `ifc://` URL for that view is shown below the image.

### Inline previews in markdown

Paste a bare `ifc://` URL or write `[label](ifc://…)` in any issue, PR comment, or `.md` file:

```
ifc://github.com/brunopostle/simple-ifc@heads/main?path=building.ifc&selector=IfcWall&fov=60
```

Forgejo renders it as a `<figure>` with a preview image linked to the interactive viewer, and the `ifc://` URL shown below as a clickable link.

### "View in 3D" button

A **View in 3D** button appears on every `.ifc` file page alongside Raw / Permalink / History.

### Browser viewer

A self-contained WebGL IFC viewer (`viewer.html`) served as a Forgejo asset at `/assets/viewer.html`.

**Features:**

- Toolbar with raw ifc:// URL input and structured fields (repo, ref, path, selector) — editing any field reloads the model; ref input has branch/tag autocomplete
- Selector filtering — `IfcWall`, `IfcWall+IfcSlab`; visibility dropdown (`highlight` / `ghost` / `isolate`) for non-selected elements
- Clipping planes — **✂ clip** button, double-click on model surface to place; drag handles to adjust; planes serialised back into the URL
- FOV control, camera sync — the URL in the browser bar always reflects the current view and is shareable
- **Model overview panel** — type counts and storey list; click any storey to isolate it, click again to show all
- **Click to identify** — click any element to see its IFC type, name, and GlobalId; copy GlobalId to clipboard for use in selectors
- **⎘ copy** button — copies the current ifc:// URL to clipboard
- **Issue** button — opens a new issue on the git host with the ifc:// URL pre-filled
- **BCF export** — exports the current view as a BCF 2.1 file for import into Revit, Navisworks, etc.
- Drag-and-drop ifc:// URLs onto the page
- Download progress for large IFC files

### Collaboration workflow

`ifc://` URLs function as view permalinks that can be embedded anywhere: Forgejo issues and comments, pull request discussions, markdown documentation, Slack, or email.

1. Open the viewer and navigate to the view you want to share
2. Add clipping planes or a selector to isolate the relevant geometry
3. Click **⎘** to copy the ifc:// URL, or **Issue** to open a pre-filled issue
4. Paste the URL into a Forgejo issue, PR comment, or any markdown file

**Referencing specific elements:** click any element to see its GlobalId, then paste it directly as `selector=325Q7Fhnf67OZC$$r43uzK`. Use `visibility=highlight`, `ghost`, or `isolate` to control how the selection is displayed.

**BCF export for external tools:** the **BCF** button exports a BCF 2.1 file that can be attached to a Forgejo issue or imported into Revit, Navisworks, Solibri, or any BCF-compatible tool.

---

## Forgejo integration

A source patch and set of assets for Forgejo. See [`forgejo/README.md`](forgejo/README.md) for full apply, build, and deployment instructions.

### Quick setup

```bash
# Apply the Go source patch
cp forgejo/modules/markup/markdown/ifc_url{,_test}.go /path/to/forgejo/modules/markup/markdown/
cd /path/to/forgejo && git apply /path/to/ifcurl/forgejo/go.patch

# Build Forgejo
go build -tags 'sqlite sqlite_unlock_notify' \
  -ldflags "-X 'forgejo.org/modules/setting.StaticRootPath=/usr/share/forgejo'" \
  -o forgejo . && sudo cp forgejo /usr/bin/forgejo

# Deploy assets (no rebuild needed)
sudo cp forgejo/custom/public/assets/viewer*.* /var/lib/forgejo/custom/public/assets/
sudo cp forgejo/custom/public/assets/ifcurl.js /var/lib/forgejo/custom/public/assets/
sudo cp forgejo/templates/custom/footer.tmpl /var/lib/forgejo/custom/templates/custom/
sudo systemctl restart forgejo

# Install and start preview service as a systemd unit
sudo cp forgejo/server-config/ifcurl-preview.service /etc/systemd/system/
# edit ExecStart --allowed-hosts to match your Forgejo hostname, then:
sudo systemctl enable --now ifcurl-preview
```

Add to `/etc/forgejo/conf/app.ini`:

```ini
[ifcurl]
PREVIEW_SERVICE_URL = http://localhost:8000
; Optional: Forgejo API token for a read-only machine user.
; The preview service will use this token to fetch IFC files from private
; repositories on this Forgejo instance.  The token is appended as a query
; parameter in the <img src> URL generated by the markdown extension, so it
; is visible in page source.  Only set this on trusted private instances.
; SERVICE_TOKEN = <forgejo-api-token>
```

**Private repositories:** create a machine user with read access and set `SERVICE_TOKEN` to its API token. Alternatively, configure credentials in `~/.config/ifcurl/tokens.json` under the service user account.

### Authentication in the viewer

When the viewer is served from the same Forgejo instance (`https://git.example.com/assets/viewer.html`), it shares the browser session cookie — private repositories work automatically for authenticated users.

IFC files on other platforms (GitHub, GitLab, a different Forgejo instance) are fetched directly from the browser; only public repositories work for external hosts.

### Preview service

An HTTP service that renders `ifc://` URLs to PNG, intended for co-location with a Forgejo instance.

```bash
pip install "ifcurl[service]"
ifcurl serve --allowed-hosts git.example.com     # restrict to your Forgejo host
ifcurl serve --host 0.0.0.0 --port 9000 --allowed-hosts git.example.com
```

| Endpoint | Description |
|---|---|
| `POST /preview` | Render an ifc:// URL to PNG |
| `GET /preview?url=ifc://…` | Same, via query string (used by Forgejo `<img>` tags) |
| `POST /bcf` | Generate a BCF 2.1 zip from an ifc:// URL viewpoint |
| `GET /select?url=ifc://…` | Resolve a complex selector server-side; returns JSON list of GlobalIds |
| `GET /render_diff?base=ifc://…&head=ifc://…` | Render a colour-coded diff PNG (added green, removed red) |

**Caching:**

| Tier | Key | Contents | Notes |
|---|---|---|---|
| 2 | commit hash + path | IFC bytes | In-memory LRU |
| 3 | commit hash + path + selector | Resolved element set | In-memory LRU |
| 4 | SHA-256 of full URL | Rendered PNG | Filesystem; immutable refs only |

Tier 4 is never written for mutable refs (`@heads/`, `@HEAD`).

---

## ifc:// URL scheme

An `ifc://` URL encodes everything needed to reproduce a specific model view: the git source, the file, which elements to show, and the camera position. Like a permalink for BIM — paste it, share it, embed it in documentation.

Full specification: [`SPECIFICATION.md`](SPECIFICATION.md)

```
ifc://[user@]host/org/repo@<ref>?<parameters>
```

Transport is inferred from the URL structure:

| URL form | Transport |
|---|---|
| `ifc://host/org/repo` | HTTPS |
| `ifc://git@host/org/repo` | SSH |
| `ifc:///path/to/repo` | Local file |

Refs follow git namespace form to avoid branch/tag ambiguity:

| Form | Meaning |
|---|---|
| `@heads/main` | Branch tip |
| `@tags/v1.2` | Tag |
| `@abc123def` | Commit hash |
| `@HEAD` | Default branch |

Key query parameters:

| Parameter | Description |
|---|---|
| `path=` | IFC file path within the repository |
| `selector=IfcWall` | [IfcOpenShell selector](https://docs.ifcopenshell.org/ifcopenshell-python/selector_syntax.html) — filter elements; `+` for union |
| `camera=px,py,pz,dx,dy,dz,ux,uy,uz` | Camera position, direction, up in IFC world coordinates |
| `fov=60` | Perspective field of view in degrees |
| `scale=50` | Orthographic view-to-world scale |
| `clip=px,py,pz,nx,ny,nz` | Clipping plane — point + normal in IFC coords (repeatable) |
| `visibility=` | `highlight` · `ghost` · `isolate` |

---

## Python library and CLI

Fetch an IFC file from a git repository and render it to PNG.

```bash
pip install "ifcurl[render]"
ifcurl render "ifc://github.com/brunopostle/simple-ifc@heads/main?path=_test_simple.ifc"
ifcurl render "ifc://..." -o output.png

# Manage the local git repository cache
ifcurl cache list           # show cached repos with size and last-access time
ifcurl cache prune --max 5  # remove oldest repos until cache is under 5 GB
ifcurl cache clear          # remove all cached repos
```

Use as a library:

```python
import ifcopenshell
from ifcurl import IfcUrl, fetch_ifc
from ifcurl.render import render

url = IfcUrl.parse(
    "ifc://example.com/org/repo@heads/main"
    "?path=models/building.ifc&selector=IfcWall&visibility=ghost"
)
hexsha, ifc_bytes = fetch_ifc(url)   # hexsha is stable even for mutable refs
model = ifcopenshell.file.from_string(ifc_bytes.decode())

png = render(model, selector=url.selector, clips=url.clips or None,
             camera=url.camera, fov=url.fov, visibility=url.visibility)
```

Remote repositories are cloned as bare repos to the OS cache directory (`~/.cache/ifcurl/` on Linux) on first use. Mutable refs (`@heads/`, `@HEAD`) trigger a `git fetch`; immutable refs (commit hashes, tags) use the cache as-is.

For private repositories, configure tokens per host in `~/.config/ifcurl/tokens.json`:

```json
{ "hosts": { "github.com": "ghp_…", "gitlab.example.com": "glpat_…" } }
```

---

## Development

```bash
git clone https://github.com/brunopostle/ifcurl
cd ifcurl
pip install -e ".[service]"

# Python tests
python -m pytest tests/

# JavaScript tests (Node 18+)
node --test tests/test_viewer_url.mjs

# Go tests (requires Forgejo source tree with patch applied)
cd /path/to/forgejo
go test ./modules/markup/markdown/ -run TestIfcURL -v
```

### Roadmap

| Phase | Status | Description |
|---|---|---|
| 1 — Python core | ✓ done | URL parsing, git fetch, render |
| 2 — Preview service | ✓ done | HTTP service with caching |
| 3 — Forgejo integration | ✓ done | Go patch, viewer, markdown extension |
| 4 — Bonsai integration | planned | Protocol handler + "Copy view URL" |
| 5 — IFC Viewer integration | planned | Plugin for the open-source IFC Viewer |
| 6 — Federation | planned | `IFCDOCUMENTREFERENCE` cross-repo links |

Development tasks are tracked with [beads](https://github.com/brunopostle/beads): `bd ready`.

---

## Licence

LGPL-3.0-or-later