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use crate::{
gen_parser::{
GenParserError,
GenParserRequirement,
},
Parser,
};
use either::{
Left,
Right,
};
use std::fmt::{
Debug,
Formatter,
Result as FmtResult,
};
pub struct GenParser<'a, P1, P2>
where
P1: 'a + Parser<'a>,
P2: Parser<'a>,
{
requirement: P1,
generator: &'a Fn(&P1::Output) -> P2,
}
impl<'a, P1, P2> GenParser<'a, P1, P2>
where
P1: Parser<'a>,
P2: Parser<'a>,
{
pub fn new(requirement: P1, generator: &'a Fn(&P1::Output) -> P2) -> Self
{
Self {
requirement,
generator,
}
}
}
impl<'a, P1, P2> Debug for GenParser<'a, P1, P2>
where
P1: Debug + Parser<'a>,
P2: Parser<'a>,
{
fn fmt(&self, f: &mut Formatter) -> FmtResult
{
f.debug_struct("GenParser")
.field("requirement", &self.requirement)
.field("generator", &"..")
.finish()
}
}
impl<'a, P1, P2> Parser<'a> for GenParser<'a, P1, P2>
where
P1: Parser<'a>,
P2: Parser<'a>,
{
type Error = GenParserError<'a, P1, P2>;
type Output = (P1::Output, P2::Output);
type Requirement = GenParserRequirement<'a, P1, P2>;
type RequirementContext = P2;
fn parse(&self, src: &'a str, pos: &mut usize) -> Result<Self::Output, Self::Error>
{
let from = *pos;
let res1 = self
.requirement
.parse(src, pos)
.map_err(|err| GenParserError::new(from, self.requirement(None), Left(err)))?;
let parser = (self.generator)(&res1);
let res2 = parser.parse(src, pos).map_err(|err| {
GenParserError::new(from, self.requirement(Some(&parser)), Right(err))
})?;
Ok((res1, res2))
}
fn skip(&self, src: &'a str, pos: &mut usize) -> Result<(), Self::Error>
{
let from = *pos;
let res1 = match self.requirement.parse(src, pos)
{
Ok(ok) => ok,
Err(err) => return Err(GenParserError::new(from, self.requirement(None), Left(err))),
};
let parser = (self.generator)(&res1);
parser
.skip(src, pos)
.map_err(|err| GenParserError::new(from, self.requirement(None), Right(err)))
}
fn requirement(&self, context: Option<&Self::RequirementContext>) -> Self::Requirement
{
if let Some(context) = context
{
GenParserRequirement::new(
self.requirement.requirement(None),
Some(context.requirement(None)),
)
}
else
{
GenParserRequirement::new(self.requirement.requirement(None), None)
}
}
}