# SEN: CLI Engine
[](https://www.rust-lang.org/)
[](LICENSE)
A type-safe, macro-powered CLI framework.
## ๐ฏ Philosophy
SEN transforms CLI development from ad-hoc scripts into systematic applications with:
- **Compile-time safety**: Enum-based routing with exhaustiveness checking
- **Zero boilerplate**: Derive macros generate all wiring code
- **Type-driven DI**: Handler parameters injected based on type signature
- **Fixed workflows**: Predictable behavior for humans and AI agents
- **Strict separation**: Prevents the "1000-line main.rs" problem
## ๐ Quick Start
### Installation
Add to your `Cargo.toml`:
```toml
[dependencies]
sen = "0.1"
```
Or use `cargo add`:
```bash
cargo add sen
```
### Example (Router API - Recommended)
```rust
use sen::{CliResult, State, Router};
// 1. Define application state
#[derive(Clone)]
pub struct AppState {
pub config: String,
}
// 2. Implement handlers as async functions
mod handlers {
use super::*;
pub async fn status(state: State<AppState>) -> CliResult<String> {
let app = state.read().await;
Ok(format!("Config: {}", app.config))
}
pub async fn build(state: State<AppState>) -> CliResult<()> {
println!("Building...");
Ok(())
}
}
// 3. Wire it up with Router (< 20 lines of main.rs)
#[tokio::main]
async fn main() {
let state = AppState {
config: "production".to_string(),
};
let router = Router::new()
.route("status", handlers::status)
.route("build", handlers::build)
.with_state(state);
let response = router.execute().await;
if !response.output.is_empty() {
println!("{}", response.output);
}
std::process::exit(response.exit_code);
}
```
### Example (Enum API - Type-safe alternative)
```rust
use sen::{CliResult, State, SenRouter};
// 1. Define application state
pub struct AppState {
pub config: String,
}
// 2. Define commands with derive macro
#[derive(SenRouter)]
#[sen(state = AppState)]
enum Commands {
#[sen(handler = handlers::status)]
Status,
#[sen(handler = handlers::build)]
Build(BuildArgs),
}
pub struct BuildArgs {
pub release: bool,
}
// 3. Implement handlers as async functions
mod handlers {
use super::*;
pub async fn status(state: State<AppState>) -> CliResult<String> {
let app = state.read().await;
Ok(format!("Config: {}", app.config))
}
pub async fn build(state: State<AppState>, args: BuildArgs) -> CliResult<()> {
let mode = if args.release { "release" } else { "debug" };
println!("Building in {} mode", mode);
Ok(())
}
}
// 4. Wire it up (< 50 lines of main.rs)
#[tokio::main]
async fn main() {
let state = State::new(AppState {
config: "production".to_string(),
});
let cmd = Commands::parse(); // Your arg parsing logic
let response = cmd.execute(state).await; // Macro-generated async execute!
if !response.output.is_empty() {
println!("{}", response.output);
}
std::process::exit(response.exit_code);
}
```
That's it! The `#[derive(SenRouter)]` macro generates the `execute()` method that:
- Routes commands to handlers
- Injects `State<T>` and args automatically
- Converts results into responses with proper exit codes
## ๐ Project Structure
SEN enforces clean file separation from day one:
```
my-cli/
โโโ src/
โ โโโ main.rs # Entry point only (< 50 lines)
โ โโโ handlers/ # One file per command
โ โ โโโ mod.rs
โ โ โโโ status.rs
โ โ โโโ build.rs
โ โ โโโ test.rs
โ โโโ workflows/ # Multi-task operations
โ โ โโโ preflight.rs # fmt โ lint โ test
โ โโโ tasks/ # Atomic operations
โ โ โโโ fmt.rs
โ โ โโโ lint.rs
โ โโโ lib.rs # Re-exports
```
**Why?**
- Each command is independently testable
- No `println!` debugging (handlers return structured data)
- Impossible to create "1000-line main.rs"
- AI agents can understand and modify specific commands easily
## ๐จ Key Features
### 1. Flexible Routing - Choose Your Style
**Router API (Axum-style)** - Dynamic and flexible:
```rust
// Register handlers dynamically
let router = Router::new()
.route("status", handlers::status)
.route("build", handlers::build)
.with_state(app_state);
// Easy to integrate with existing CLIs
let response = router.execute(&args).await;
```
**Enum API** - Compile-time safety:
```rust
#[derive(SenRouter)]
#[sen(state = AppState)]
enum Commands {
#[sen(handler = handlers::status)] // Typo? Compile error!
Status,
}
```
Both approaches are supported - choose based on your needs:
- **Router API**: Better for gradual migration, dynamic routes, existing CLIs
- **Enum API**: Better for new projects, compile-time exhaustiveness checking
### 2. Axum-Style Handler Signatures
```rust
// Order doesn't matter!
pub async fn handler1(state: State<App>, args: Args) -> CliResult<String>
pub async fn handler2(args: Args, state: State<App>) -> CliResult<String>
// State optional
pub async fn handler3(args: Args) -> CliResult<()>
```
### 3. Smart Error Handling
```rust
pub enum CliError {
User(UserError), // Exit code 1: user can fix
System(SystemError), // Exit code 101: bug/system failure
}
```
Errors automatically format with helpful hints:
```
Error: Invalid argument '--foo'
The value 'bar' is not supported.
Hint: Use one of: baz, qux
```
### 4. No Println! in Handlers
Handlers return structured data, framework handles output:
```rust
// โ Bad: Can't test, can't redirect
pub async fn status() -> CliResult<()> {
println!("Status: OK");
Ok(())
}
// โ
Good: Testable, flexible
pub async fn status() -> CliResult<StatusReport> {
Ok(StatusReport { status: "OK" })
}
```
## ๐ค Agent Mode (Machine-Readable Output)
SEN provides **automatic** AI agent integration through built-in `--agent-mode` flag support.
### Automatic Agent Mode (Recommended)
Simply call `.with_agent_mode()` and the framework handles everything:
```rust
use sen::Router;
#[tokio::main]
async fn main() {
let router = Router::new()
.route("build", handlers::build)
.with_agent_mode() // Enable automatic --agent-mode support
.with_state(state);
let response = router.execute().await;
// Automatically outputs JSON if --agent-mode was passed
if response.agent_mode {
println!("{}", response.to_agent_json());
} else {
if !response.output.is_empty() {
println!("{}", response.output);
}
}
std::process::exit(response.exit_code);
}
```
**User runs:**
```bash
myapp build # Normal text output
myapp --agent-mode build # JSON output
```
### How It Works
1. **Router detects** `--agent-mode` flag automatically
2. **Strips the flag** before passing args to handlers
3. **Sets `response.agent_mode = true`** for your output logic
4. **Zero boilerplate** - no manual arg parsing needed
### Example Output
```json
{
"result": "success",
"exit_code": 0,
"output": "Build completed successfully",
"tier": "safe",
"tags": ["build", "production"],
"sensors": {
"timestamp": "2024-01-15T10:30:00Z",
"os": "macos",
"cwd": "/Users/user/project"
}
}
```
### Advanced: Manual Agent Mode
For complex scenarios with global options, you can still manually implement agent mode (see `examples/practical-cli`).
### Features
- **Automatic `--agent-mode` detection**: Framework handles flag parsing
- **`to_agent_json()`**: Converts `Response` to structured JSON
- **Environment Sensors**: Automatic collection of system metadata (requires `sensors` feature)
- **Tier & Tags**: Safety tier and command categorization metadata
- **Structured Errors**: Exit codes and error messages in machine-readable format
## ๐ก Argument Parsing: `FromArgs` vs Global Options
SEN provides multiple approaches for argument parsing, each suited for different use cases.
### Simple Cases: Use `FromArgs`
For per-command arguments without global flags:
```rust
use sen::{Args, FromArgs, CliError};
#[derive(Debug)]
struct BuildArgs {
release: bool,
}
impl FromArgs for BuildArgs {
fn from_args(args: &[String]) -> Result<Self, CliError> {
Ok(BuildArgs {
release: args.contains(&"--release".to_string()),
})
}
}
async fn build(Args(args): Args<BuildArgs>) -> CliResult<String> {
let mode = if args.release { "release" } else { "debug" };
Ok(format!("Building in {} mode", mode))
}
```
**Use `FromArgs` when:**
- โ
You have simple per-command arguments
- โ
No global flags needed (`--verbose`, `--config`, etc.)
- โ
You want the framework to handle everything
### Complex Cases: Use Global Options + Manual Parsing
For applications with global flags that apply to all commands:
```rust
use sen::FromGlobalArgs;
#[derive(Clone)]
pub struct GlobalOpts {
pub verbose: bool,
pub config_path: String,
}
impl FromGlobalArgs for GlobalOpts {
fn from_global_args(args: &[String]) -> Result<(Self, Vec<String>), CliError> {
let mut verbose = false;
let mut config_path = "~/.config/myapp".to_string();
let mut remaining_args = Vec::new();
for arg in args {
match arg.as_str() {
"--verbose" | "-v" => verbose = true,
"--config" => { /* handle next arg */ }
_ => remaining_args.push(arg.clone()),
}
}
Ok((GlobalOpts { verbose, config_path }, remaining_args))
}
}
```
**Use Global Options when:**
- โ
You need flags that apply to **all** commands (`--verbose`, `--config`)
- โ
You want integration with `clap` or other parsers
- โ
You have complex validation or conflicting flag logic
- โ
Building a production CLI (like `practical-cli` example)
### Why practical-cli Uses Global Options
The `practical-cli` example intentionally uses `FromGlobalArgs` instead of `FromArgs`:
1. **Global flags**: `--verbose` and `--config` apply to all commands
2. **`clap` integration**: Uses `clap::Command` for help generation
3. **Flexibility**: Manual parsing allows complex validation
4. **Real-world pattern**: Mirrors production CLI tools like `kubectl`, `docker`, etc.
**Key Insight:** `FromArgs` is a convenience feature, not required. For complex CLIs, manual parsing gives you full control.
See `examples/practical-cli` for a complete implementation.
## ๐๏ธ Architecture
SEN follows a three-layer design:
```
โโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโ
โ Router Layer (Compile-time) โ
โ - Enum-based command tree โ
โ - Handler binding via proc macros โ
โ - Type-safe routing โ
โโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโ
โ
โผ
โโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโ
โ Handler Layer (Runtime) โ
โ - Dependency injection (State, Args) โ
โ - Business logic execution โ
โ - Result<T, E> return type โ
โโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโ
โ
โผ
โโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโ
โ Response Layer (Exit) โ
โ - Exit code mapping (0, 1, 101) โ
โ - Structured output (JSON/Human) โ
โ - Logging & telemetry โ
โโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโ
```
See [DESIGN.md](./docs/DESIGN.md) for full architecture details.
## ๐ Examples
Check out the [examples/simple-cli](./examples/simple-cli) directory for a working CLI with:
- Status command (no args)
- Build command (with `--release` flag)
- Test command (with optional filter)
- Proper error handling
Run it:
```bash
cd examples/simple-cli
cargo build
./target/debug/admin status
./target/debug/admin build --release
./target/debug/admin test my_test
```
## ๐งช Testing
```bash
# Run all tests
cargo test
# Test specific crate
cargo test -p sen
cargo test -p sen-rs-macros
```
## ๐ Documentation
- [DESIGN.md](./docs/DESIGN.md) - Complete design document
## ๐ฃ๏ธ Roadmap
- [x] Phase 1: Core framework (State, CliResult, IntoResponse)
- [x] Phase 2: Macro system (#[derive(SenRouter)])
- [ ] Phase 3: Advanced features (ReloadableConfig, tracing)
- [ ] Phase 4: Developer experience (CLI generator, templates)
## ๐ค Contributing
Contributions welcome! Please read [DESIGN.md](./docs/DESIGN.md) to understand the architecture first.
## ๐ License
Licensed under either of:
- Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
- MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
at your option.
## ๐ Inspiration
SEN is inspired by:
- [Axum](https://github.com/tokio-rs/axum) - Type-safe handler functions
- [Clap](https://github.com/clap-rs/clap) - CLI argument parsing
- The philosophy of Anti-Fragility and Fixed Workflows
---
**SEN** (็ท/ๅ
): The Line to Success, Leading the Future of CLI Development