// SPDX-License-Identifier: LGPL-3.0-or-later
// See Notices.txt for copyright information
pub(crate) trait DoFold<State: ?Sized + syn::fold::Fold> {
    fn do_fold(self, state: &mut State) -> Self;
}

impl<T: DoFold<State>, State: ?Sized + syn::fold::Fold> DoFold<State> for Box<T> {
    fn do_fold(mut self, state: &mut State) -> Self {
        *self = T::do_fold(*self, state);
        self
    }
}

impl<T: DoFold<State>, State: ?Sized + syn::fold::Fold> DoFold<State> for Option<T> {
    fn do_fold(self, state: &mut State) -> Self {
        self.map(|v| T::do_fold(v, state))
    }
}

impl<T: DoFold<State>, State: ?Sized + syn::fold::Fold> DoFold<State> for Vec<T> {
    fn do_fold(self, state: &mut State) -> Self {
        Vec::from_iter(self.into_iter().map(|v| T::do_fold(v, state)))
    }
}

impl<T: DoFold<State>, P: DoFold<State>, State: ?Sized + syn::fold::Fold> DoFold<State>
    for Punctuated<T, P>
{
    fn do_fold(self, state: &mut State) -> Self {
        Punctuated::from_iter(self.into_pairs().map(|v| {
            let (v, p) = v.into_tuple().do_fold(state);
            Pair::new(v, p)
        }))
    }
}

macro_rules! impl_fold_tuple {
    ($($var0:ident: $T0:ident, $($var:ident: $T:ident,)*)?) => {
        $(impl_fold_tuple!($($var: $T,)*);)?
        impl_fold_tuple!(@impl $($var0: $T0, $($var: $T,)*)?);
    };
    (@impl $($var:ident: $T:ident,)*) => {
        impl<State: ?Sized + syn::fold::Fold, $($T: DoFold<State>,)*> DoFold<State> for ($($T,)*) {
            #[allow(clippy::unused_unit)]
            fn do_fold(self, state: &mut State) -> Self {
                let _ = state;
                let ($($var,)*) = self;
                $(let $var = $var.do_fold(state);)*
                ($($var,)*)
            }
        }
    };
}

impl_fold_tuple!(
    v0: T0,
    v1: T1,
    v2: T2,
    v3: T3,
    v4: T4,
    v5: T5,
    v6: T6,
    v7: T7,
    v8: T8,
    v9: T9,
    v10: T10,
    v11: T11,
);

macro_rules! no_op_fold {
    ($ty:ty) => {
        impl<State: ?Sized + syn::fold::Fold> $crate::fold::DoFold<State> for $ty {
            fn do_fold(self, _state: &mut State) -> Self {
                self
            }
        }
    };
}

pub(crate) use no_op_fold;

macro_rules! impl_fold {
    (
        struct $Struct:ident<$($T:ident,)*> $(where ($($where:tt)*))? {
            $($field:ident: $field_ty:ty,)*
        }
    ) => {
        impl<State: ?Sized + syn::fold::Fold, $($T,)*> $crate::fold::DoFold<State> for $Struct<$($T,)*>
        where
            $($T: $crate::fold::DoFold<State>,)*
            $($where)*
        {
            fn do_fold(self, state: &mut State) -> Self {
                let _ = state;
                let Self {
                    $($field,)*
                } = self;
                Self {
                    $($field: <$field_ty as $crate::fold::DoFold<State>>::do_fold($field, state),)*
                }
            }
        }
    };
    (
        struct $Struct:ident<$($T:ident,)*>(
            $field0_ty:ty $(,)?
        )
        $(where ($($where:tt)*))?;
    ) => {
        impl<State: ?Sized + syn::fold::Fold, $($T,)*> $crate::fold::DoFold<State> for $Struct<$($T,)*>
        where
            $($T: $crate::fold::DoFold<State>,)*
            $($where)*
        {
            fn do_fold(self, state: &mut State) -> Self {
                let _ = state;
                let Self(
                    v0,
                ) = self;
                Self(
                    <$field0_ty as $crate::fold::DoFold<State>>::do_fold(v0, state),
                )
            }
        }
    };
    (
        enum $Enum:ident<$($T:ident,)*> $(where ($($where:tt)*))? {
            $($Variant:ident $({
                $($brace_field:ident: $brace_field_ty:ty,)*
            })?
            $((
                $($paren_field_ty:ty),* $(,)?
            ))?,)*
        }
    ) => {
        impl<State: ?Sized + syn::fold::Fold, $($T,)*> $crate::fold::DoFold<State> for $Enum<$($T,)*>
        where
            $($T: $crate::fold::DoFold<State>,)*
            $($where)*
        {
            fn do_fold(self, state: &mut State) -> Self {
                let _ = state;
                $crate::fold::impl_fold! {
                    @enum_variants self, state => ()
                    $($Variant $({
                        $($brace_field: $brace_field_ty,)*
                    })?
                    $((
                        $($paren_field_ty,)*
                    ))?,)*
                }
            }
        }
    };
    (
        @enum_variants $self:expr, $state:expr => ($($generated_arms:tt)*)
    ) => {
        match $self {
            $($generated_arms)*
        }
    };
    (
        @enum_variants $self:expr, $state:expr => ($($generated_arms:tt)*)
        $Variant:ident {
            $($field:tt: $field_ty:ty,)*
        },
        $($rest:tt)*
    ) => {
        $crate::fold::impl_fold! {
            @enum_variants $self, $state => (
                $($generated_arms)*
                Self::$Variant {
                    $($field,)*
                } => Self::$Variant {
                    $($field: <$field_ty as $crate::fold::DoFold<State>>::do_fold($field, $state),)*
                },
            )
            $($rest)*
        }
    };
    (
        @enum_variants $self:expr, $state:expr => ($($generated_arms:tt)*)
        $Variant:ident(
            $field0_ty:ty $(,)?
        ),
        $($rest:tt)*
    ) => {
        $crate::fold::impl_fold! {
            @enum_variants $self, $state => (
                $($generated_arms)*
                Self::$Variant(v0) => Self::$Variant(
                    <$field0_ty as $crate::fold::DoFold<State>>::do_fold(v0, $state),
                ),
            )
            $($rest)*
        }
    };
}

pub(crate) use impl_fold;
use syn::punctuated::{Pair, Punctuated};

macro_rules! forward_fold {
    ($ty:ty => $fn:ident) => {
        impl<State: syn::fold::Fold + ?Sized> DoFold<State> for $ty {
            fn do_fold(self, state: &mut State) -> Self {
                <State as syn::fold::Fold>::$fn(state, self)
            }
        }
    };
}

forward_fold!(syn::Attribute => fold_attribute);
forward_fold!(syn::AttrStyle => fold_attr_style);
forward_fold!(syn::Expr => fold_expr);
forward_fold!(syn::ExprArray => fold_expr_array);
forward_fold!(syn::ExprCall => fold_expr_call);
forward_fold!(syn::ExprIf => fold_expr_if);
forward_fold!(syn::ExprMatch => fold_expr_match);
forward_fold!(syn::ExprPath => fold_expr_path);
forward_fold!(syn::ExprStruct => fold_expr_struct);
forward_fold!(syn::ExprTuple => fold_expr_tuple);
forward_fold!(syn::Ident => fold_ident);
forward_fold!(syn::Member => fold_member);
forward_fold!(syn::Path => fold_path);
forward_fold!(syn::Type => fold_type);
forward_fold!(syn::TypePath => fold_type_path);
forward_fold!(syn::WherePredicate => fold_where_predicate);
no_op_fold!(syn::parse::Nothing);
no_op_fold!(syn::token::Brace);
no_op_fold!(syn::token::Bracket);
no_op_fold!(syn::token::Paren);
no_op_fold!(syn::Token![_]);
no_op_fold!(syn::Token![,]);
no_op_fold!(syn::Token![;]);
no_op_fold!(syn::Token![:]);
no_op_fold!(syn::Token![..]);
no_op_fold!(syn::Token![.]);
no_op_fold!(syn::Token![#]);
no_op_fold!(syn::Token![=]);
no_op_fold!(syn::Token![=>]);
no_op_fold!(syn::Token![|]);
no_op_fold!(syn::Token![enum]);
no_op_fold!(syn::Token![extern]);
no_op_fold!(syn::Token![let]);
no_op_fold!(syn::Token![mut]);
no_op_fold!(syn::Token![struct]);
no_op_fold!(syn::Token![where]);