use crate::flow::comparator::*;
use crate::flow::traversible::*;
use crate::func::fail::*;

fn and(_l: (), _r: ()) {}

struct SubsetContext<'a, T: MonadFail<'a, ()>, A: 'a, D: 'a + PartialEq> {
    comparator: &'a dyn Comparator<A>,
    n_subset: Arc<dyn TraversibleBinaryNode<'a, T, A, D>>,
    n_superset: Arc<dyn TraversibleBinaryNode<'a, T, A, D>>,
    k_l: Option<A>,
    k_r: Option<A>,
    t_superl: Arc<dyn TraversibleBinaryTree<'a, T, A, D>>,
    t_superr: Arc<dyn TraversibleBinaryTree<'a, T, A, D>>,
    k_super: A,
}

impl<'a, T: 'a + MonadFail<'a, ()>, A: 'a + Send + Clone, D: 'a + PartialEq>
    SubsetContext<'a, T, A, D>
{
    fn on_l(self, (t_subl, t_subr, k_sub): Split<'a, T, A, D>) -> T::F<()> {
        T::la2(
            algorithms::contains::t_contains(self.comparator, self.t_superl.clone(), k_sub.clone()),
            T::la2(
                t_subset_of_t(
                    self.comparator,
                    t_subl,
                    self.t_superl,
                    self.k_l,
                    Some(k_sub.clone()),
                ),
                t_subset_of_t(
                    self.comparator,
                    t_subr,
                    self.n_superset.to_tree(),
                    Some(k_sub),
                    self.k_r,
                ),
                and,
            ),
            and,
        )
    }

    fn on_e(self, (t_subl, t_subr, k_sub): Split<'a, T, A, D>) -> T::F<()> {
        T::la2(
            t_subset_of_t(
                self.comparator,
                t_subl,
                self.t_superl,
                self.k_l,
                Some(k_sub.clone()),
            ),
            t_subset_of_t(
                self.comparator,
                t_subr,
                self.t_superr,
                Some(k_sub),
                self.k_r,
            ),
            and,
        )
    }

    fn on_r(self, (t_subl, t_subr, k_sub): Split<'a, T, A, D>) -> T::F<()> {
        T::la2(
            algorithms::contains::t_contains(self.comparator, self.t_superr.clone(), k_sub.clone()),
            T::la2(
                t_subset_of_t(
                    self.comparator,
                    t_subl,
                    self.n_superset.to_tree(),
                    self.k_l,
                    Some(k_sub.clone()),
                ),
                t_subset_of_t(
                    self.comparator,
                    t_subr,
                    self.t_superr,
                    Some(k_sub),
                    self.k_r,
                ),
                and,
            ),
            and,
        )
    }

    fn test_unoptimised(self) -> T::F<()> {
        let split = self.n_subset.split();
        match self.comparator.compare(&split.2, &self.k_super) {
            Comparison::L => self.on_l(split),
            Comparison::E => self.on_e(split),
            Comparison::R => self.on_r(split),
        }
    }

    fn outside_l(&self) -> bool {
        outside_l(self.comparator, &self.k_l, &self.k_super)
    }

    fn outside_r(&self) -> bool {
        outside_r(self.comparator, &self.k_r, &self.k_super)
    }

    fn test_r_only(self) -> T::F<()> {
        t_subset_of_t(
            self.comparator,
            self.n_subset.to_tree(),
            self.t_superr,
            self.k_l,
            self.k_r,
        )
    }

    fn test_l_only(self) -> T::F<()> {
        t_subset_of_t(
            self.comparator,
            self.n_subset.to_tree(),
            self.t_superl,
            self.k_l,
            self.k_r,
        )
    }

    fn test_optimised(self) -> T::F<()> {
        if self.outside_l() {
            self.test_r_only()
        } else if self.outside_r() {
            self.test_l_only()
        } else {
            self.test_unoptimised()
        }
    }
}

fn outside_l<A>(comparator: &dyn Comparator<A>, k_l: &Option<A>, k_super: &A) -> bool {
    if let Some(a_l) = k_l {
        comparator.compare(a_l, k_super) == Comparison::R
    } else {
        false
    }
}

fn outside_r<A>(comparator: &dyn Comparator<A>, k_r: &Option<A>, k_super: &A) -> bool {
    if let Some(a_r) = k_r {
        comparator.compare(a_r, k_super) == Comparison::L
    } else {
        false
    }
}

pub fn n_subset_of_n<'a, T: MonadFail<'a, ()>, A: 'a + Send + Clone, D: 'a + PartialEq>(
    comparator: &'a dyn Comparator<A>,
    n_subset: Arc<dyn TraversibleBinaryNode<'a, T, A, D>>,
    n_superset: Arc<dyn TraversibleBinaryNode<'a, T, A, D>>,
    k_l: Option<A>,
    k_r: Option<A>,
) -> T::F<()> {
    let (t_superl, t_superr, k_super) = n_superset.split();
    SubsetContext {
        comparator,
        n_subset,
        n_superset,
        k_l,
        k_r,
        t_superl,
        t_superr,
        k_super,
    }
    .test_optimised()
}

pub fn r_subset_of_r_unoptimised<
    'a,
    T: MonadFail<'a, ()>,
    A: 'a + Send + Clone,
    D: 'a + PartialEq,
>(
    comparator: &'a dyn Comparator<A>,
    r_subset: Arc<dyn TraversibleBinaryReference<'a, T, A, D>>,
    r_superset: Arc<dyn TraversibleBinaryReference<'a, T, A, D>>,
    k_l: Option<A>,
    k_r: Option<A>,
) -> T::F<()> {
    T::bind2(
        r_subset.resolve(),
        r_superset.resolve(),
        move |n_subset, n_superset| n_subset_of_n(comparator, n_subset, n_superset, k_l, k_r),
    )
}

fn r_subset_of_r_optimised<'a, T: MonadFail<'a, ()>, A: 'a + Send + Clone, D: 'a + PartialEq>(
    r_subset: Arc<dyn TraversibleBinaryReference<'a, T, A, D>>,
    r_superset: Arc<dyn TraversibleBinaryReference<'a, T, A, D>>,
    comparator: &'a dyn Comparator<A>,
    k_l: Option<A>,
    k_r: Option<A>,
) -> <T as WeakFunctor<'a>>::F<()> {
    if r_subset.data() == r_superset.data() {
        T::pure(())
    } else {
        r_subset_of_r_unoptimised(comparator, r_subset, r_superset, k_l, k_r)
    }
}

pub fn t_subset_of_t<'a, T: MonadFail<'a, ()>, A: 'a + Send + Clone, D: 'a + PartialEq>(
    comparator: &'a dyn Comparator<A>,
    t_subset: Arc<dyn TraversibleBinaryTree<'a, T, A, D>>,
    t_superset: Arc<dyn TraversibleBinaryTree<'a, T, A, D>>,
    k_l: Option<A>,
    k_r: Option<A>,
) -> T::F<()> {
    match (t_subset.refer(), t_superset.refer()) {
        (None, _) => T::pure(()),
        (Some(_), None) => T::fail(()),
        (Some(r_subset), Some(r_superset)) => {
            r_subset_of_r_optimised(r_subset, r_superset, comparator, k_l, k_r)
        }
    }
}