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use crate::value::{Object, Value};
/// A `Document` that can be evaluated by the solver.
///
/// Rules are solved against Documents, and thus to solve against a data type it must implement
/// `Document`. Implementing `Object` gives this trait for free. Most of the time this trait will
/// not need to be implmented, it is there to enable complex use cases.
///
/// # Implementations
///
/// The implementation for `Object` will just pass the `find` call along to the `Object`
/// implementation of find. If for some reason this was undesired or just not needed below is an
/// example of how to implement `Document`.
///
/// ```
/// use std::borrow::Cow;
///
/// use tau_engine::{Document, Value};
///
/// struct Foo {
/// bar: String,
/// baz: String,
/// }
///
/// impl Document for Foo {
/// fn find(&self, key: &str) -> Option<Value<'_>> {
/// match key {
/// "bar" => Some(Value::String(Cow::Borrowed(&self.bar))),
/// "baz" => Some(Value::String(Cow::Borrowed(&self.baz))),
/// _ => None,
/// }
/// }
/// }
/// ```
pub trait Document {
/// Looks for a `Value` by key and returns it if found.
fn find(&self, key: &str) -> Option<Value<'_>>;
}
impl Document for &dyn Object {
#[inline]
fn find(&self, key: &str) -> Option<Value<'_>> {
Object::find(*self, key)
}
}
impl<O: Object> Document for O {
#[inline]
fn find(&self, key: &str) -> Option<Value<'_>> {
Object::find(self, key)
}
}
#[cfg(test)]
mod tests {
use super::*;
use std::borrow::Cow;
struct Foo {
bar: String,
}
impl Document for Foo {
fn find(&self, key: &str) -> Option<Value<'_>> {
match key {
"bar" => Some(Value::String(Cow::Borrowed(&self.bar))),
_ => None,
}
}
}
#[test]
fn find() {
let foo = Foo {
bar: "baz".to_owned(),
};
assert_eq!(foo.find("bar").unwrap().as_str().unwrap(), "baz");
}
}