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use crate::{Reduction, Rule};
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use multipeek::multipeek;
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use uniplate::Uniplate;
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/// Returns the first result if the iterator has only one, otherwise calls `select`.

            

        

            

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pub(crate) fn one_or_select<T, M, R>(

            

        

            

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    select: impl Fn(&T, &mut dyn Iterator<Item = (&R, Reduction<T, M>)>) -> Option<Reduction<T, M>>,

            

        

            

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    t: &T,

            

        

            

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    rs: &mut dyn Iterator<Item = (&R, Reduction<T, M>)>,

            

        

            

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) -> Option<Reduction<T, M>>

            

        

            

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where

            

        

            

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    T: Uniplate,

            

        

            

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    R: Rule<T, M>,

            

        

            

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{

            

        

            

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    let mut rs = multipeek(rs);

            

        

            

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    if rs.peek_nth(1).is_none() {

            

        

            

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        return rs.next().map(|(_, r)| r);

            

        

            

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    }

            

        

            

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    select(t, &mut rs)

            

        

            

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}

            

        

            

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/// Returns the first available `Reduction` if there is one, otherwise returns `None`.

            

        

            

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///

            

        

            

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/// This is a good default selection strategy, especially when you expect only one possible result.

            

        

            

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pub fn select_first<T, M, R>(

            

        

            

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    _: &T,

            

        

            

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    rs: &mut dyn Iterator<Item = (&R, Reduction<T, M>)>,

            

        

            

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) -> Option<Reduction<T, M>>

            

        

            

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where

            

        

            

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    T: Uniplate,

            

        

            

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    R: Rule<T, M>,

            

        

            

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{

            

        

            

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    rs.next().map(|(_, r)| r)

            

        

            

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}

            

        

            

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// TODO: Add more selection strategies:

            

        

            

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// - random

            

        

            

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// - smallest subtree

            

        

            

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// - ask the user for input via blocking I/O

            

        

            

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// - panic if there is more than 1 result, otherwise return the first