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//! Scopes containing function parsers.
use std::collections::HashMap;
use std::fmt::{self, Debug, Formatter};
use crate::Pass;
use crate::func::ParseFunc;
use super::func::FuncCall;
use super::parsing::ParseState;
use super::Model;
/// A map from identifiers to function parsers.
pub struct Scope {
parsers: HashMap<String, Box<Parser>>,
fallback: Box<Parser>,
}
impl Scope {
/// Create a new empty scope with a fallback parser that is invoked when no
/// match is found.
pub fn new<F>() -> Scope
where F: ParseFunc<Meta=()> + Model + 'static {
Scope {
parsers: HashMap::new(),
fallback: parser::<F>(()),
}
}
/// Create a new scope with the standard functions contained.
pub fn with_std() -> Scope {
crate::library::std()
}
/// Associate the given name with a type that is parseable into a function.
pub fn add<F>(&mut self, name: &str)
where F: ParseFunc<Meta=()> + Model + 'static {
self.add_with_meta::<F>(name, ());
}
/// Add a parseable type with additional metadata that is given to the
/// parser (other than the default of `()`).
pub fn add_with_meta<F>(&mut self, name: &str, metadata: <F as ParseFunc>::Meta)
where F: ParseFunc + Model + 'static {
self.parsers.insert(
name.to_string(),
parser::<F>(metadata),
);
}
/// Return the parser with the given name if there is one.
pub fn get_parser(&self, name: &str) -> Option<&Parser> {
self.parsers.get(name).map(AsRef::as_ref)
}
/// Return the fallback parser.
pub fn get_fallback_parser(&self) -> &Parser {
&*self.fallback
}
}
impl Debug for Scope {
fn fmt(&self, f: &mut Formatter) -> fmt::Result {
f.debug_set()
.entries(self.parsers.keys())
.finish()
}
}
/// A function which parses the source of a function into a model type which
/// implements [`Model`].
type Parser = dyn Fn(FuncCall, &ParseState) -> Pass<Box<dyn Model>>;
fn parser<F>(metadata: <F as ParseFunc>::Meta) -> Box<Parser>
where F: ParseFunc + Model + 'static {
Box::new(move |f, s| {
F::parse(f, s, metadata.clone())
.map(|model| Box::new(model) as Box<dyn Model>)
})
}
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