marg 0.4.0

# 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.

### Flags


Boolean flags that control runtime behaviour. Check `cfg.verbose.is_set()` etc. in your application.

| Flag | Aliases | Description                                                  |
|------|---------|--------------------------------------------------------------|
| `-v` | `--verbose`, `--debug` | Enable verbose output                                        |
| `-q` | `--quiet`, `--batch` | Suppress non-essential output or focus on non-interractive   |
| `-h` | `--help`, `--info` | Caller should print help                                     |
| `-V` | `--version` | Prints `<name> <version>` and exits (handled by `from_args`) |

Flags also accept explicit values: `--verbose=true` / `--verbose=false`.

### 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
    pub verbose: Opt,            // -v / --verbose / --debug
    pub quiet: Opt,              // -q / --quiet / --batch
    pub help: Opt,               // -h / --help / --info
    // -V / --version: prints version and exits inside from_args()
}
```

### Usage


```rust
let config = ArgConfig::from_args()?;

// -V / --version is handled inside from_args() — prints and exits automatically

if config.help.is_set() {
    println!("Usage: myapp [OPTIONS] [db-url] [schema.table] [uuid] [token] [ttl]");
    return Ok(());
}

let url = config.db_url(); // resolves $PWD placeholder with token value
```