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use crate::{Merge, Reactive};
use paste::paste;

impl<T> Merge for &Reactive<T>
where
    T: Clone + Default + Send + 'static,
{
    type Output = T;
    fn merge(self) -> Reactive<Self::Output> {
        self.clone()
    }
}

#[cfg(not(feature = "parallel-notification"))]
macro_rules! impl_merge_for_nested_tuple {
    ( $($i:literal),* ) => { paste!{
    impl < $( [<T $i>], )* > Merge for ( $( [<T $i>], )* )
    where
        $( [<T $i>]: Merge, ) *
        $( [<T $i>]::Output: Clone + Default + Send + 'static, ) *
    {
        body!($($i),*);
    }
    }};
}

#[cfg(feature = "parallel-notification")]
macro_rules! impl_merge_for_nested_tuple {
    ( $($i:literal),* ) => { paste!{
    impl < $( [<T $i>], )* > Merge for ( $( [<T $i>], )* )
    where
        $( [<T $i>]: Merge + Sync, ) *
        $( [<T $i>]::Output: Clone + Default + Send + Sync + 'static, ) *
    {
        body!($($i),*);
    }
    }};
}

macro_rules! body {
    ( $($i:literal),* ) => {paste!{
        type Output = ( $([<T $i>]::Output,)* );

        fn merge(self) -> Reactive<Self::Output> {
            let reactives = ( $(self.$i.merge(),)* );
            let values = ( $(reactives.$i.value(),)* );
            let combined = Reactive::new(values);

            $( reactives.$i.add_observer({
                let combined = combined.clone();
                // we know for sure that the value inside 'combined' did change
                // because 'combined' stores the reactive values as-is without any transformation
                // eg: (&Reactive<String>, &Reactive<usize>, ...) -> Reactive<(String, usize, ...)>
                // so if the parent reactive changes, the 'combined' will definitely change.
                // Therefore 'unchecked' is fine.
                move |val| combined.update_inplace_unchecked(|c| c.$i = val.clone())
            }); )*

            combined
        }
    }};
}

impl_merge_for_nested_tuple!(0);
impl_merge_for_nested_tuple!(0, 1);
impl_merge_for_nested_tuple!(0, 1, 2);
impl_merge_for_nested_tuple!(0, 1, 2, 3);
impl_merge_for_nested_tuple!(0, 1, 2, 3, 4);
impl_merge_for_nested_tuple!(0, 1, 2, 3, 4, 5);
impl_merge_for_nested_tuple!(0, 1, 2, 3, 4, 5, 6);
impl_merge_for_nested_tuple!(0, 1, 2, 3, 4, 5, 6, 7);
impl_merge_for_nested_tuple!(0, 1, 2, 3, 4, 5, 6, 7, 8);
impl_merge_for_nested_tuple!(0, 1, 2, 3, 4, 5, 6, 7, 8, 9);
impl_merge_for_nested_tuple!(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
impl_merge_for_nested_tuple!(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11);
impl_merge_for_nested_tuple!(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12);
impl_merge_for_nested_tuple!(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13);
impl_merge_for_nested_tuple!(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14);
impl_merge_for_nested_tuple!(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15);