marg 0.3.4

# marg

Meta config for apps from args
Use to connect to DB to pull other configs


support external app execution (az acc) for a password (token) acquisition

## ArgConfig


Parses app startup arguments into a structured config. 

### Priority order:

1. command-line args: 
   1. prefixed with --name
   2. positional or heuristic 
2. environment variables
3. config file.

### Arguments


Arguments can be passed positionally (auto-detected by format) or with explicit `--flag value` prefixes:

| Flag | Positional detection | Description | Default |
|------|----------------------|-------------|---------|
| `--db` | URL prefix (e.g. `postgres://`) | Database connection URL | `postgres://` with current `$USER` |
| `--config` | `schema.table` format (contains `.`) | Config table name | `public.<appname>` |
| `--uuid` | UUID-formatted string | Node/instance ID | Auto-generated (see `uuid_gen`) |
| `--token` | 3rd unmatched arg | Script name to acquire DB password | _(none)_ |
| `--ttl` | Numeric string | Token lifetime in minutes | `1` |
| `--key` | _(explicit only)_ | RSA/AES private key file path (feature `rsa`) | _(none)_ |
| `--secret` | _(explicit only)_ | AES cipher secret (prefer env `SECRET`) | _(none)_ |
| `--file` | _(explicit only)_ | Config file to load key=value pairs from | _(none)_ |

### Environment Variables


- `PGPASSWORD` — PostgreSQL password (used to connect to DB)
- `PASSPHRASE` — Passphrase for RSA private key
- `SECRET` — AES cipher secret; removed from env after reading (unless compiled with `keep_env_secret` feature)
- `$USER` — Substituted into DB URL where `$USER` appears

### Config File Format


Lines parsed as `key: value` or `key= value`. Blank lines and lines starting with `#`, `;`, `/`, `[` are ignored.

```
db: postgres://host/dbname
config: myschema.settings
uuid: 550e8400-e29b-41d4-a716-446655440000
token: get-token.sh
ttl: 15
pk: /path/to/private.key
```

### Fields


```rust
pub struct ArgConfig {
    pub uuid: Uuid,         // instance ID (auto-generated if not provided)
    pub uuid_gen: bool,     // true if uuid was auto-generated
    pub db_url: String,     // database connection string
    pub table: String,      // schema.table for config lookup
    pub cfg: HashMap<String, String>, // key=value pairs from config file
    pub token: Token,       // token script + TTL for dynamic DB passwords
    pub pk: Option<KeyFile>,// RSA/AES private key file
    pub secret: Option<String>, // AES cipher secret
}
```

### Usage


```rust
let config = ArgConfig::from_args()?;
let url = config.db_url(); // resolves $PWD placeholder with token value
```