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use core::marker::PhantomData;

use crate::{
    build::{Build, Builder},
    error::{BasicError, UniError},
    protocol::{
        lookup_hint, lookup_visit, AnyHint, AnyVisit, Hint, Protocol, ProtocolDescription,
        ProtocolId,
    },
    protocol_list,
    protocols::reference::{self, Reference},
    walk::{Walk, WalkMut, WalkOnce},
    walk_with_hints, HintGiven, WalkerHints,
};

use super::reference::BuilderRefValue;

pub struct Walker<'value, 'ctx: 'value>(&'value str, PhantomData<&'ctx ()>);

impl<'value, 'ctx: 'value, VisitorErr: 'ctx> crate::Walker<'value, 'ctx, VisitorErr>
    for Walker<'value, 'ctx>
{
    type Error = BasicError;

    fn walk(
        &mut self,
        visitor: &mut dyn crate::Visitor<'value, 'ctx, Self::Error, Error = VisitorErr>,
    ) -> Result<crate::WalkStatus, UniError<Self::Error, VisitorErr>> {
        match lookup_visit::<Reference<str>, _, _>(visitor).map_err(UniError::Walker)? {
            Some(visitor) => {
                visitor.visit(reference::Ref::Value(self.0))?;
                Ok(crate::WalkStatus::Continue)
            }
            None => Err(UniError::Walker(BasicError::new(
                "visitor needs the reference protocol for `str`",
            ))),
        }
    }

    fn all_protocols() -> impl Iterator<Item = ProtocolDescription>
    where
        Self: Sized,
    {
        protocol_list![Reference<str>]
    }
}

impl<'value, 'ctx: 'value, VisitorErr: 'ctx> WalkerHints<'value, 'ctx, VisitorErr>
    for Walker<'value, 'ctx>
{
    type Error = BasicError;

    fn protocol(
        &mut self,
        id: ProtocolId,
    ) -> Option<AnyHint<'_, 'value, 'ctx, Self::Error, VisitorErr>> {
        match id {
            id if id == ProtocolId::of::<Reference<str>>() => Some(AnyHint::new(self)),
            _ => None,
        }
    }
}

impl<'value, 'ctx: 'value, VisitorErr: 'ctx> Hint<'value, 'ctx, Reference<str>, VisitorErr>
    for Walker<'value, 'ctx>
{
    type Error = BasicError;

    fn hint(
        &mut self,
        visitor: &mut dyn crate::Visitor<'value, 'ctx, Self::Error, Error = VisitorErr>,
        _hint: <Reference<str> as crate::protocol::Protocol<'value, 'ctx>>::Hint,
    ) -> Result<HintGiven, UniError<Self::Error, VisitorErr>> {
        lookup_visit::<Reference<str>, _, _>(visitor)
            .map_err(UniError::Walker)?
            .ok_or_else(|| {
                UniError::Walker(BasicError::new("visitor is missing the str protocol"))
            })?
            .visit(reference::Ref::Value(self.0))?;

        Ok(HintGiven)
    }

    fn known(
        &mut self,
        _hint: &<Reference<str> as crate::protocol::Protocol<'value, 'ctx>>::Hint,
    ) -> Result<<Reference<str> as crate::protocol::Protocol<'value, 'ctx>>::Known, BasicError>
    {
        Ok(reference::Known {
            len: Some(self.0.len()),
            kind: Some(reference::Kind::Context),
        })
    }
}

impl<'value, 'ctx: 'value, VisitorErr: 'ctx> WalkMut<'value, 'ctx, VisitorErr> for str {
    type ErrorMut = BasicError;
    type WalkerMut = Walker<'value, 'ctx>;

    fn walker_mut(&'value mut self) -> Self::WalkerMut {
        Walker(self, PhantomData)
    }
}

impl<'value, 'ctx: 'value, VisitorErr: 'ctx> Walk<'value, 'ctx, VisitorErr> for str {
    type Error = BasicError;
    type Walker = Walker<'value, 'ctx>;

    fn walker(&'value self) -> Self::Walker {
        Walker(self, PhantomData)
    }
}