ferogram-derive 0.3.3

Procedural macros for ferogram - #[derive(FsmState)]
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# ferogram-derive

Procedural macros for the ferogram workspace. Currently exposes `#[derive(FsmState)]`.

[![Crates.io](https://img.shields.io/crates/v/ferogram-derive?color=fc8d62)](https://crates.io/crates/ferogram-derive)
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[![docs.rs](https://img.shields.io/badge/docs.rs-ferogram--derive-5865F2)](https://docs.rs/ferogram-derive)
[![License: MIT OR Apache-2.0](https://img.shields.io/badge/license-MIT%20OR%20Apache--2.0-blue.svg)](#license)

Most users get this through `ferogram` with the `derive` feature flag. Direct usage is only needed when building on top of the FSM layer directly.

---

## Installation

Via the `ferogram` crate (recommended):

```toml
[dependencies]
ferogram = { version = "0.3", features = ["derive"] }
```

Or directly:

```toml
[dependencies]
ferogram-derive = "0.3"
```

---

## `#[derive(FsmState)]`

Implements the `ferogram::fsm::FsmState` trait for an enum.

**Restrictions:** only unit variants are supported. Tuple or struct variants produce a compile error.

**What gets generated:**

- `as_key(&self) -> String` converts the variant name to a string.
- `from_key(key: &str) -> Option<Self>` parses the variant name back into the enum.

```rust
use ferogram::FsmState;

#[derive(FsmState, Clone, Debug, PartialEq)]
enum RegistrationState {
    Start,
    WaitingName,
    WaitingPhone,
    WaitingCity,
    Done,
}
```

The generated impl:

```rust
impl ferogram::fsm::FsmState for RegistrationState {
    fn as_key(&self) -> String {
        match self {
            Self::Start       => "Start",
            Self::WaitingName => "WaitingName",
            // ...
        }
        .to_string()
    }

    fn from_key(key: &str) -> Option<Self> {
        match key {
            "Start"       => Some(Self::Start),
            "WaitingName" => Some(Self::WaitingName),
            // ...
            _ => None,
        }
    }
}
```

Keys are the variant names as written in source. Renaming a variant changes its key and breaks any stored state.

---

## Using FsmState in a dispatcher

```rust
use ferogram::{FsmState, fsm::MemoryStorage, filters::text};
use std::sync::Arc;

#[derive(FsmState, Clone, Debug, PartialEq)]
enum Form { Name, Age, Done }

dp.with_state_storage(Arc::new(MemoryStorage::new()));

dp.on_message_fsm(text(), Form::Name, |msg, state| async move {
    state.set_data("name", msg.text().unwrap()).await.ok();
    state.transition(Form::Age).await.ok();
    msg.reply("How old are you?").await.ok();
});

dp.on_message_fsm(text(), Form::Age, |msg, state| async move {
    let name = state.get_data("name").await.unwrap_or_default();
    state.transition(Form::Done).await.ok();
    msg.reply(format!("Got it, {name}!")).await.ok();
});
```

---

## Stack position

```
ferogram
└ ferogram-derive  <-- here (proc-macro crate, compile-time only)
```

---

## License

MIT or Apache-2.0, at your option. See [LICENSE-MIT](../LICENSE-MIT) and [LICENSE-APACHE](../LICENSE-APACHE).

**Ankit Chaubey** - [github.com/ankit-chaubey](https://github.com/ankit-chaubey)