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0f936e8528
Switch the default DOCX render path from server-side mammoth → flat
HTML to client-side `docx-preview` loaded inside the Sandpack iframe.
Mammoth becomes the fallback for files above the cap.
Why
---
The Sandpack iframe is a real browser DOM. Server-side rendering
ceiling for DOCX→HTML is well below the source's visual fidelity —
mammoth strips cell shading, run colors, banners, and column layouts
because Word's layout model doesn't fit HTML's flow model. Pushing the
render into the iframe lifts that ceiling without paying the
server-side cost of jsdom or LibreOffice.
What
----
- New `wordDocToHtmlViaCdn(buffer)` builds a self-contained HTML doc
that embeds the binary as base64 and lets `docx-preview@0.3.7`
render it on load. CSS preserves dark/light mode handoff via
`prefers-color-scheme`. Bootstrap script falls back to a "preview
unavailable, please download" message if the CDN is unreachable or
the parse throws.
- `docx-preview` and its `jszip` peer dep are pinned to specific
versions on jsdelivr with SRI sha384 integrity hashes and
`crossorigin="anonymous"`. Refresh: re-fetch the file, run
`openssl dgst -sha384 -binary FILE | openssl base64 -A`.
- CSP locked down on the iframe: `default-src 'none'`, scripts only
from jsdelivr (no eval), `connect-src 'none'` so a parser bug in
docx-preview can't be turned into exfiltration of the embedded
document, `base-uri 'none'`, `form-action 'none'`. Defense in depth
on top of the Sandpack cross-origin sandbox.
- `wordDocToHtml` dispatches by size: ≤ 350 KB binary → CDN path
(high fidelity), larger → mammoth fallback (preserves the size cap
on `attachment.text`). 350 KB chosen so worst-case base64-inflated
output (~478 KB) plus wrapper overhead (~5 KB) fits under
MAX_TEXT_CACHE_BYTES (512 KB) with 40 KB headroom.
- Internal renderers exported as `_internal` for tests. Public API
unchanged — callers still go through `wordDocToHtml`.
PPTX intentionally NOT switched
-------------------------------
Surveyed the available client-side PPTX libraries:
- `pptx-preview@1.0.7` ships an ESM-only main entry plus a 1.36 MB
UMD that references `require("stream"/"events"/"buffer"/"util")` —
bundled for Node, not browser-clean. Could work but the runtime
references to undefined Node globals are a fragility risk worth
more validation than this PR can absorb.
- `pptxjs` is jQuery-era, requires four separate UMD scripts in a
specific order, less actively maintained.
- The honest answer for PPTX is the LibreOffice sidecar (DOCX/XLSX/
PPTX → PDF → PDF.js), which is the architecture every major
product (Google Drive, Claude.ai, ChatGPT) effectively uses and
the only path to ~5/5 fidelity for arbitrary user decks.
PPTX stays on the existing slide-list extraction for now. Open a
follow-up issue for the LibreOffice/Gotenberg sidecar.
Tests
-----
- 6 new in CDN-rendered describe block: wrapper structure, base64
round-trip, SRI integrity + crossorigin, CSP locks
(connect-src/eval/base-uri/form-action), fallback message wiring,
size-threshold lock.
- Adjusted 2 existing tests that asserted on mammoth-path artifacts
(literal document text in `<article class="lc-docx">`) — those
assertions move to the mammoth-fallback test that calls
`_internal.wordDocToHtmlViaMammoth` directly. Dispatcher tests now
assert CDN-path signatures instead.
packages/api files: 434/434 ✅, full unit suite 4473/4473 ✅.
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| babel.config.cjs | ||
| jest.config.mjs | ||
| jest.setup.cjs | ||
| package.json | ||
| rollup.config.js | ||
| tsconfig-paths-bootstrap.mjs | ||
| tsconfig.build.json | ||
| tsconfig.json | ||
| tsconfig.spec.json | ||