cognis_core/wrappers/
configurable.rs

1//! `Configurable<R>` — runtime swap between named alternative runnables.
2//!
3//! V1 had `configurable_fields()` and `configurable_alternatives()` listed
4//! as one of the P1 affordances. The Rust-native implementation:
5//! - One enum-like wrapper, `Configurable<I, O>`.
6//! - Caller registers alternatives by name.
7//! - Per-call selection via `RunnableConfig::extras::<ConfigKey>()`.
8//!
9//! ```ignore
10//! let model = Configurable::new(default_model)
11//!     .alternative("smaller", smaller_model)
12//!     .alternative("bigger", bigger_model);
13//!
14//! // Default behaviour:
15//! model.invoke(input, RunnableConfig::default()).await?;
16//!
17//! // Switch at runtime:
18//! let mut cfg = RunnableConfig::default();
19//! cfg.extras.insert(ConfigKey::new("bigger"));
20//! model.invoke(input, cfg).await?;
21//! ```
22
23use std::collections::HashMap;
24use std::marker::PhantomData;
25use std::sync::Arc;
26
27use async_trait::async_trait;
28
29use crate::runnable::{Runnable, RunnableConfig};
30use crate::Result;
31
32/// Key inserted into `RunnableConfig::extras` to choose an alternative.
33#[derive(Debug, Clone, PartialEq, Eq, Hash)]
34pub struct ConfigKey {
35    /// Name of the alternative to use.
36    pub name: String,
37}
38
39impl ConfigKey {
40    /// Construct.
41    pub fn new(name: impl Into<String>) -> Self {
42        Self { name: name.into() }
43    }
44}
45
46/// Runtime-swappable runnable. Holds a default plus N named alternatives.
47pub struct Configurable<I, O> {
48    default: Arc<dyn Runnable<I, O>>,
49    alternatives: HashMap<String, Arc<dyn Runnable<I, O>>>,
50    _phantom: PhantomData<fn(I) -> O>,
51}
52
53impl<I, O> Configurable<I, O>
54where
55    I: Send + 'static,
56    O: Send + 'static,
57{
58    /// Build with a default runnable.
59    pub fn new(default: Arc<dyn Runnable<I, O>>) -> Self {
60        Self {
61            default,
62            alternatives: HashMap::new(),
63            _phantom: PhantomData,
64        }
65    }
66
67    /// Add an alternative under `name`. Selection is via
68    /// `cfg.extras.insert(ConfigKey::new("name"))` at invoke time.
69    pub fn alternative(mut self, name: impl Into<String>, r: Arc<dyn Runnable<I, O>>) -> Self {
70        self.alternatives.insert(name.into(), r);
71        self
72    }
73}
74
75#[async_trait]
76impl<I, O> Runnable<I, O> for Configurable<I, O>
77where
78    I: Send + 'static,
79    O: Send + 'static,
80{
81    async fn invoke(&self, input: I, config: RunnableConfig) -> Result<O> {
82        let chosen = config
83            .extras
84            .get::<ConfigKey>()
85            .and_then(|k| self.alternatives.get(&k.name))
86            .cloned()
87            .unwrap_or_else(|| self.default.clone());
88        chosen.invoke(input, config).await
89    }
90    fn name(&self) -> &str {
91        "Configurable"
92    }
93}
94
95#[cfg(test)]
96mod tests {
97    use super::*;
98
99    struct Const(u32);
100
101    #[async_trait]
102    impl Runnable<u32, u32> for Const {
103        async fn invoke(&self, _: u32, _: RunnableConfig) -> Result<u32> {
104            Ok(self.0)
105        }
106    }
107
108    #[tokio::test]
109    async fn picks_default_when_no_key() {
110        let c: Configurable<u32, u32> =
111            Configurable::new(Arc::new(Const(1))).alternative("alt", Arc::new(Const(2)));
112        assert_eq!(c.invoke(0, RunnableConfig::default()).await.unwrap(), 1);
113    }
114
115    #[tokio::test]
116    async fn picks_alternative_when_keyed() {
117        let c: Configurable<u32, u32> =
118            Configurable::new(Arc::new(Const(1))).alternative("alt", Arc::new(Const(2)));
119        let mut cfg = RunnableConfig::default();
120        cfg.extras.insert(ConfigKey::new("alt"));
121        assert_eq!(c.invoke(0, cfg).await.unwrap(), 2);
122    }
123
124    #[tokio::test]
125    async fn unknown_key_falls_back_to_default() {
126        let c: Configurable<u32, u32> = Configurable::new(Arc::new(Const(1)));
127        let mut cfg = RunnableConfig::default();
128        cfg.extras.insert(ConfigKey::new("missing"));
129        assert_eq!(c.invoke(0, cfg).await.unwrap(), 1);
130    }
131}
cognis_core/wrappers/configurable.rs

cognis_core/wrappers/
configurable.rs
