#[cfg(feature = "test-support")]
pub mod test;

use futures::Future;
use std::{
    cmp::Ordering,
    ops::AddAssign,
    pin::Pin,
    task::{Context, Poll},
};

pub fn post_inc<T: From<u8> + AddAssign<T> + Copy>(value: &mut T) -> T {
    let prev = *value;
    *value += T::from(1);
    prev
}

/// Extend a sorted vector with a sorted sequence of items, maintaining the vector's sort order and
/// enforcing a maximum length. Sort the items according to the given callback. Before calling this,
/// both `vec` and `new_items` should already be sorted according to the `cmp` comparator.
pub fn extend_sorted<T, I, F>(vec: &mut Vec<T>, new_items: I, limit: usize, mut cmp: F)
where
    I: IntoIterator<Item = T>,
    F: FnMut(&T, &T) -> Ordering,
{
    let mut start_index = 0;
    for new_item in new_items {
        if let Err(i) = vec[start_index..].binary_search_by(|m| cmp(m, &new_item)) {
            let index = start_index + i;
            if vec.len() < limit {
                vec.insert(index, new_item);
            } else if index < vec.len() {
                vec.pop();
                vec.insert(index, new_item);
            }
            start_index = index;
        }
    }
}

pub trait ResultExt {
    type Ok;

    fn log_err(self) -> Option<Self::Ok>;
    fn warn_on_err(self) -> Option<Self::Ok>;
}

impl<T, E> ResultExt for Result<T, E>
where
    E: std::fmt::Debug,
{
    type Ok = T;

    fn log_err(self) -> Option<T> {
        match self {
            Ok(value) => Some(value),
            Err(error) => {
                log::error!("{:?}", error);
                None
            }
        }
    }

    fn warn_on_err(self) -> Option<T> {
        match self {
            Ok(value) => Some(value),
            Err(error) => {
                log::warn!("{:?}", error);
                None
            }
        }
    }
}

pub trait TryFutureExt {
    fn log_err(self) -> LogErrorFuture<Self>
    where
        Self: Sized;
    fn warn_on_err(self) -> LogErrorFuture<Self>
    where
        Self: Sized;
}

impl<F, T> TryFutureExt for F
where
    F: Future<Output = anyhow::Result<T>>,
{
    fn log_err(self) -> LogErrorFuture<Self>
    where
        Self: Sized,
    {
        LogErrorFuture(self, log::Level::Error)
    }

    fn warn_on_err(self) -> LogErrorFuture<Self>
    where
        Self: Sized,
    {
        LogErrorFuture(self, log::Level::Warn)
    }
}

pub struct LogErrorFuture<F>(F, log::Level);

impl<F, T> Future for LogErrorFuture<F>
where
    F: Future<Output = anyhow::Result<T>>,
{
    type Output = Option<T>;

    fn poll(self: std::pin::Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        let level = self.1;
        let inner = unsafe { Pin::new_unchecked(&mut self.get_unchecked_mut().0) };
        match inner.poll(cx) {
            Poll::Ready(output) => Poll::Ready(match output {
                Ok(output) => Some(output),
                Err(error) => {
                    log::log!(level, "{:?}", error);
                    None
                }
            }),
            Poll::Pending => Poll::Pending,
        }
    }
}

struct Defer<F: FnOnce()>(Option<F>);

impl<F: FnOnce()> Drop for Defer<F> {
    fn drop(&mut self) {
        self.0.take().map(|f| f());
    }
}

pub fn defer<F: FnOnce()>(f: F) -> impl Drop {
    Defer(Some(f))
}

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

    #[test]
    fn test_extend_sorted() {
        let mut vec = vec![];

        extend_sorted(&mut vec, vec![21, 17, 13, 8, 1, 0], 5, |a, b| b.cmp(a));
        assert_eq!(vec, &[21, 17, 13, 8, 1]);

        extend_sorted(&mut vec, vec![101, 19, 17, 8, 2], 8, |a, b| b.cmp(a));
        assert_eq!(vec, &[101, 21, 19, 17, 13, 8, 2, 1]);

        extend_sorted(&mut vec, vec![1000, 19, 17, 9, 5], 8, |a, b| b.cmp(a));
        assert_eq!(vec, &[1000, 101, 21, 19, 17, 13, 9, 8]);
    }
}
