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use std::ops::Range;

use crate::RangeMap;

#[derive(Clone)]
/// A set whose items are stored as ranges.
///
/// See [`RangeMap`]'s documentation for more details.
///
/// [`RangeMap`]: struct.RangeMap.html
pub struct RangeSet<T> {
    rm: RangeMap<T, ()>,
}

impl<T> Default for RangeSet<T>
where
    T: Ord + Clone,
{
    fn default() -> Self {
        RangeSet::new()
    }
}

impl<T> RangeSet<T>
where
    T: Ord + Clone,
{
    /// Makes a new empty `RangeSet`.
    pub fn new() -> Self {
        RangeSet {
            rm: RangeMap::new(),
        }
    }

    /// Returns a reference to the range covering the given key, if any.
    pub fn get(&self, value: &T) -> Option<&Range<T>> {
        self.rm.get_key_value(value).map(|(range, _)| range)
    }

    /// Returns `true` if any range in the set covers the specified value.
    pub fn contains(&self, value: &T) -> bool {
        self.rm.contains_key(value)
    }

    /// Gets an ordered iterator over all ranges,
    /// ordered by range.
    pub fn iter(&self) -> impl Iterator<Item = &Range<T>> {
        self.rm.iter().map(|(range, _v)| range)
    }

    /// Insert a range into the set.
    ///
    /// If the inserted range either overlaps or is immediately adjacent
    /// any existing range, then the ranges will be coalesced into
    /// a single contiguous range.
    ///
    /// # Panics
    ///
    /// Panics if range `start >= end`.
    pub fn insert(&mut self, range: Range<T>) {
        self.rm.insert(range, ());
    }

    /// Removes a range from the set, if all or any of it was present.
    ///
    /// If the range to be removed _partially_ overlaps any ranges
    /// in the set, then those ranges will be contracted to no
    /// longer cover the removed range.
    ///
    /// # Panics
    ///
    /// Panics if range `start >= end`.
    pub fn remove(&mut self, range: Range<T>) {
        self.rm.remove(range);
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    trait RangeMapExt<T> {
        fn to_vec(&self) -> Vec<Range<T>>;
    }

    impl<T> RangeMapExt<T> for RangeSet<T>
    where
        T: Ord + Clone,
    {
        fn to_vec(&self) -> Vec<Range<T>> {
            self.iter().cloned().collect()
        }
    }

    #[test]
    fn empty_set_is_empty() {
        let range_set: RangeSet<u32> = RangeSet::new();
        assert_eq!(range_set.to_vec(), vec![]);
    }

    #[test]
    fn insert_into_empty_map() {
        let mut range_set: RangeSet<u32> = RangeSet::new();
        range_set.insert(0..50);
        assert_eq!(range_set.to_vec(), vec![0..50]);
    }

    #[test]
    fn remove_partially_overlapping() {
        let mut range_set: RangeSet<u32> = RangeSet::new();
        range_set.insert(0..50);
        range_set.remove(25..75);
        assert_eq!(range_set.to_vec(), vec![0..25]);
    }
}