# Project Qingtian / FRO — Detailed Development & Consultation Report
## Date: 2026-09-11
## Module: FRO Share File — Resumable Individual File Downloads

## 1. Objective
Implement genuine interrupted-download recovery for individual files while keeping the original QNAP/NAS files intact. FRO must not physically split large files.

Required flow: start download → interrupt/cancel → retain partial local file → request same file again → determine local byte count → send HTTP Range → server returns HTTP 206 → append remaining bytes → Completed.

## 2. Existing Backend Review
`app/filedrop.py` already contained server-side HTTP Range capability, but this alone did not provide reliable FRO-managed resume.

Issues identified included browser flow not explicitly controlling the resume offset, interrupted streams potentially remaining `Downloading`, stale active records, insufficient session binding, concurrent status-update risks, and the need to detect a changed source file before appending resumed data.

## 3. Implementation
Backend changes included `RLock` protection, a 10-minute stale threshold, recipient/share-session binding, source ETag validation, `X-FRO-Source-ETag`, opaque `X-FRO-Download-Id`, resume validation, concurrent-resume protection, and improved cancellation handling. Incomplete transfers can become `Interrupted`; stale records can become `Stale`; changed sources can invalidate resume instead of risking corruption.

A new client controller was added:
`static/js/share-file-download.js`

The managed path uses the File System Access API for the destination file, IndexedDB for persisted handle/metadata state, actual local file size as the resume offset, `fetch()` with same-origin credentials, `Range: bytes=<local-size>-`, response validation, and safe append. Partial state is retained after interruption. Unsupported environments retain a native-download fallback.

## 4. Git Safety Investigation
Git initially reported:
```text
2941    26    app/filedrop.py
```
Ignoring end-of-line whitespace produced the same result. Line-count comparison showed:
```text
HEAD lines: 464
WORKING lines: 3379
```
Therefore Git HEAD is substantially older than the current working FRO application. The large diff contains accumulated earlier development and does not mean today's work rewrote about 3000 lines.

Critical rule until a clean baseline is deliberately established:
```text
DO NOT git reset --hard
DO NOT restore app/filedrop.py from HEAD
DO NOT git add .
```

## 5. Safety Checkpoints
Pre-deployment checkpoints used `checkpoint_20260911_before_resume_deploy`. Post-verification checkpoints used `checkpoint_20260911_resume_verified`.

Protected key files:
- `app/filedrop.py`
- `static/js/share-file-download.js`
- `tests/test_filedrop_resumable_downloads.py`

## 6. Verification
Host compilation:
```text
python3 -m compileall -q app tests
compile_exit=0
```

A host-side unittest attempt stopped before test execution because `/nas/Qingtian/Trash` is a container/NAS environment path and the host process lacked `/nas` access. This was an environment mismatch, not a resumable-download failure.

Correct container test:
```text
docker exec remoteoffice python -m unittest tests/test_filedrop_resumable_downloads.py
.....
----------------------------------------------------------------------
Ran 5 tests in 0.119s

OK
```
Result: **5/5 tests passed.**

## 7. Runtime Deployment
Mount inspection confirmed:
```text
/home/foo/RemoteOffice -> /app
/opt/remoteoffice-data -> /data
/mnt/qnap-multimedia -> /mnt/qnap-multimedia
/mnt/qnap-survey -> /nas
/home/foo/.ssh/fro_windows -> /root/.ssh/fro_windows
/mnt/qnap-survey/Share File -> /share-file
```
The source tree is bind-mounted into `/app`, so an image rebuild was unnecessary.

Uvicorn command:
```text
["uvicorn","app.main:app","--host","0.0.0.0","--port","8000"]
```
There is no `--reload`, so the service was restarted with `docker compose restart remoteoffice`.

Logs confirmed clean shutdown/startup, `Application startup complete`, and Uvicorn running on port 8000. Subsequent `/dashboard` requests returned HTTP 200.

## 8. Real Client Interruption Test
A real interrupted download was correctly recorded as `Interrupted` instead of remaining indefinitely `Downloading`. Older inactive records were also observed as `Stale`, showing the new stale handling was active.

## 9. Resume to Completion
A real file showed approximately:
```text
20260905_150427.mp4
106.00 MB / 226.81 MB
46.74%
Interrupted
```
After resume:
```text
226.81 MB / 226.81 MB
100.00%
Completed
```

## 10. Definitive HTTP Range Proof
A separate test used `20260905_194041.mp4`. The initial request returned HTTP 200 and advertised `Accept-Ranges: bytes`. The transfer was cancelled after roughly 51 MB, and the partial file was retained.

The second request contained:
```text
Range: bytes=51658752-
```
The server returned:
```text
Status Code: 206 Partial Content
Content-Range: bytes 51658752-203181465/203181466
```

This proves the resumed transfer started at byte **51,658,752**, not byte 0. It is genuine HTTP byte-range resumable downloading, not merely progress-record recovery.

## 11. Final Assessment
- Original NAS file intact: **PASS**
- No physical splitting: **PASS**
- HTTP Range support: **PASS**
- Initial HTTP 200: **PASS**
- Partial local file retained: **PASS**
- Interrupted status: **PASS**
- Resume from local partial byte count: **PASS**
- HTTP 206 Partial Content: **PASS**
- Correct Content-Range: **PASS**
- Resume reaches Completed: **PASS**
- Container unit tests: **5/5 PASS**
- Runtime restart/startup: **PASS**
- Dashboard after deployment: **HTTP 200 PASS**

## 12. Known Limitation
FRO-managed resume depends on browser support for the File System Access API and an appropriate secure browser context, normally HTTPS. Unsupported environments use native browser downloading and cannot provide the same FRO-controlled resume guarantee.

## 13. Recommended Next Session
Treat the current version as the verified baseline. Do not add more functionality to this module immediately.

The next session should address repository housekeeping and establish a safe Git baseline without losing existing uncommitted FRO/Qingtian development. Future resume changes should start from the `checkpoint_20260911_resume_verified` copies.

## End-of-Day Status
**Project Qingtian / FRO Share File — Individual File Resumable Download**

**STATUS: VERIFIED SUCCESS / COMPLETE — 2026-09-11**