Replace `?zip=1` / `?convert=docx|html|pdf` query forms with path-suffix
URLs that look like ordinary files. `<dir>.zip` and `<file>.docx` /
`.html` / `.pdf` are virtual files served by the dispatcher when stat
fails at the requested path AND the corresponding base resource exists:
GET /Project-1/archive.zip ← if archive/ is a real directory
GET /Project-1/notes.docx ← if notes.md exists
Real on-disk files always win — a genuine archive.zip in the tree
serves its bytes normally. The virtual forms only fire when nothing
real is there.
Why: the URL form lets clients emit plain <a href> without query-
string handling; `curl -O` writes a sensible filename; mirror tools
pick up the path through normal recursion; the protocol surface
becomes "every URL is a file". Bash + filesystem mental model.
Server:
- New helpers handler.RecognizeVirtualSubtreeZip /
RecognizeVirtualConvert (in subtreezip.go and converthandler.go).
- Dispatcher's stat-fails branch checks them between IsDefaultMdlSpec
and MatchAppHTML. ACL is enforced on the base resource (the source
directory for zip, the .md source for convert).
- Three legacy query-form branches removed from main.go.
Client:
- browse/js/download.js: `dir + '.zip'` instead of `dir + '/?zip=1'`.
- browse/js/preview-markdown.js: convert anchor hrefs become
`<mdUrl-minus-.md>.<fmt>` instead of `<mdUrl>?convert=<fmt>`.
- shared/zddc-source.js downloadConverted: same transform.
Tests: subtreezip_test.go test URLs cosmetically updated to the new
shape (the handler is exercised directly, so the URL is metadata only,
but the test reads better).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
New endpoint GET /<path>/foo.md?convert=docx|html|pdf renders a markdown
source on demand. Surfaced as the Download buttons in browse's markdown
editor (separate commit).
Execution model — two upstream container images, lazy-pulled:
• docker.io/pandoc/latex:latest — MD→DOCX, MD→HTML (entrypoint pandoc)
• docker.io/zenika/alpine-chrome — HTML→PDF (entrypoint chromium-browser)
No custom image build. The runner passes --pull=missing on every podman/
docker invocation so the operator only needs the runtime installed —
first request pulls the image, subsequent requests use the local cache.
Overrides: --convert-pandoc-image / --convert-chromium-image (and the
matching ZDDC_CONVERT_* env vars). Engine: --convert-engine (podman
preferred, docker fallback). Resource caps: --convert-mem-mib (512),
--convert-cpus (2), --convert-pids (100), --convert-timeout (30s).
PDF flow is two-stage: pandoc renders the markdown through the embedded
viewer-template.html to standalone HTML, then chromium prints that HTML
via --print-to-pdf. Preserves the print-media CSS already authored in
viewer-template.html rather than going through pandoc's LaTeX template.
Each conversion runs in a throw-away container with --rm --network=none
--read-only --tmpfs=/tmp --cap-drop=ALL --security-opt=no-new-privileges
--env=HOME=/tmp plus a bind-mounted scratch dir for I/O. Pandoc reads
markdown from stdin / writes to stdout; the viewer template lives at
/tpl (ro). Chromium reads HTML from a read-write bind mount at /pdf
and writes the PDF to the same mount; the host reads it back. No shell
wrappers, no shell quoting — argv flows straight into each image's
entrypoint.
On-disk cache at <dir>/.converted/<base>.<ext> with mtime synced to the
source. Fast path is a stat-and-serve with no exec; slow path
singleflights concurrent requests for the same target. PUT/DELETE/MOVE
on the source .md purges the .converted/ sidecars.
Per-project template variables (client/project/contractor/project_number)
come from a new .zddc `convert:` cascade block, walked leaf→root with
per-key latest-wins. Filename-derived variables (title, tracking_number,
revision, status, is_draft) come from a new zddc.ParseFilename helper.
If neither podman nor docker is on PATH, the endpoint serves 503 with
a clear Retry-After. The rest of the server keeps working.
This is the first os/exec site in the codebase. The hardening in
internal/convert/runner.go — context.CancelFunc → process kill,
cmd.WaitDelay, platform-specific SysProcAttr (Setpgid + Pdeathsig on
Linux), minimal env, stdout cap via limitWriter, stderr ring buffer —
sets the pattern for any future shell-outs.
Public surface:
convert.ToDocx(ctx, source, meta) / .ToHTML / .ToPDF
convert.Probe(ctx, engineOverride) → install Runner if engine present
convert.SetImages(pandoc, chromium)
convert.ConfigureLimits(memMiB, cpus, pids, timeout)
convert.Available()
Container handler at internal/handler/converthandler.go; dispatcher
branch in cmd/zddc-server/main.go inserts the convert lookup after the
existing ACL gate, reusing the source file's read policy verbatim.
