# Simplex.FileTransfer.Server.Env

> XFTP router environment: configuration, storage quota tracking, and request routing.

**Source**: [`FileTransfer/Server/Env.hs`](../../../../../src/Simplex/FileTransfer/Server/Env.hs)

## Non-obvious behavior

### 1. Startup storage accounting with quota warning

`newXFTPServerEnv` computes `usedStorage` by summing data packet sizes from the in-memory store at startup. If the computed usage exceeds the configured `fileSizeQuota`, a warning is logged but the router still starts. This allows the router to come up even if it's over quota (e.g., after a quota reduction), relying on expiration to reclaim space.

### 2. XFTPRequest ADT separates new data packets from commands

`XFTPRequest` has three constructors:
- `XFTPReqNew`: data packet creation (carries `FileInfo`, recipient keys, optional basic auth)
- `XFTPReqCmd`: command on an existing data packet (carries file ID, `FileRec`, and the command)
- `XFTPReqPing`: health check

This separation occurs after credential verification in `Server.hs`. `XFTPReqNew` bypasses entity lookup entirely since the data packet doesn't exist yet.

### 3. fileTimeout for upload deadline

`fileTimeout` in `XFTPServerConfig` sets the maximum time allowed for a single data packet upload (FPUT). The router wraps the receive operation in `timeout fileTimeout`. Default is 5 minutes (for 4MB chunks). This prevents slow or stalled uploads from holding router resources indefinitely.