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use crate::nodes::{LazyNode, Node, PersistentNode};

/// Implementation of range min for generic type T, it implements [Node], [LazyNode] and [PersistentNode].
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct Min<T>
where
    T: Ord + Clone,
{
    value: T,
    lazy_value: Option<T>,
    left: usize,
    right: usize,
}

impl<T> Node for Min<T>
where
    T: Ord + Clone,
{
    type Value = T;
    fn initialize(v: &Self::Value) -> Self {
        Min {
            value: v.clone(),
            lazy_value: None,
            left: 0,
            right: 0,
        }
    }
    fn combine(a: &Self, b: &Self) -> Self {
        Min {
            value: a.value.clone().min(b.value.clone()),
            lazy_value: None,
            left: 0,
            right: 0,
        }
    }
    fn value(&self) -> &Self::Value {
        &self.value
    }
}

/// Implementation for minimum range query, the update sets each item in the range to the given value.
impl<T> LazyNode for Min<T>
where
    T: Ord + Clone,
{
    fn lazy_update(&mut self, _i: usize, _j: usize) {
        if let Some(value) = self.lazy_value.take() {
            self.value = value
        }
    }

    fn update_lazy_value(&mut self, v: &<Self as Node>::Value) {
        self.lazy_value = Some(v.clone());
    }

    fn lazy_value(&self) -> Option<&<Self as Node>::Value> {
        self.lazy_value.as_ref()
    }
}

/// This is a pretty generic implementation of [PersistentNode] for a struct.
impl<T> PersistentNode for Min<T>
where
    T: Ord + Clone,
{
    fn left_child(&self) -> usize {
        self.left
    }

    fn right_child(&self) -> usize {
        self.right
    }

    fn set_children(&mut self, left: usize, right: usize) {
        self.left = left;
        self.right = right;
    }
}