//! Helper type for making configurations mutable.

use std::sync::{Arc, RwLock};

/// A mutable configuration object.

///

/// Internally, this is just a `RwLock<Arc<T>>`; this type just defines some

/// convenience wrappers for it.

#[derive(Debug, Default)]

pub struct MutCfg<T> {

    /// The interior configuration object.

    cfg: RwLock<Arc<T>>,

}

impl<T> MutCfg<T> {

    /// Return a new MutCfg with the provided value.

    /// Return the current configuration

    /// If this configuration object is still the same pointer as `old_config`,

    /// replace it with `new_config`.

    ///

    /// Returns `true` if it was in fact replaced.

        } else {

        }

    /// Replace this configuration with `new_config`.

    /// Replace the current configuration with the results of evaluating `func` on it.

    {

}

impl<T> From<T> for MutCfg<T> {

}

#[cfg(test)]

mod test {

    // @@ begin test lint list maintained by maint/add_warning @@

    #![allow(clippy::bool_assert_comparison)]

    #![allow(clippy::clone_on_copy)]

    #![allow(clippy::dbg_macro)]

    #![allow(clippy::mixed_attributes_style)]

    #![allow(clippy::print_stderr)]

    #![allow(clippy::print_stdout)]

    #![allow(clippy::single_char_pattern)]

    #![allow(clippy::unwrap_used)]

    #![allow(clippy::unchecked_time_subtraction)]

    #![allow(clippy::useless_vec)]

    #![allow(clippy::needless_pass_by_value)]

    #![allow(clippy::string_slice)] // See arti#2571

    //! <!-- @@ end test lint list maintained by maint/add_warning @@ -->

    use super::*;

    #[test]

    fn basic_constructors() {

        let m = MutCfg::new(7_u32);

        assert_eq!(*m.get(), 7);

        let m: MutCfg<u32> = MutCfg::default();

        assert_eq!(*m.get(), 0);

        let m: MutCfg<u32> = 100.into();

        assert_eq!(*m.get(), 100);

    }

    #[test]

    fn mutate_with_existing_ref() {

        let m = MutCfg::new(100_u32);

        let old_ref = m.get();

        m.replace(101);

        assert_eq!(*old_ref, 100);

        assert_eq!(*m.get(), 101);

    }

    #[test]

    fn check_and_replace() {

        let m = MutCfg::new(100_u32);

        let different_100 = Arc::new(100_u32);

        // won't replace, since it is a different arc.

        assert!(!m.check_and_replace(&different_100, 200));

        let old_100 = m.get();

        assert_eq!(*old_100, 100);

        assert!(m.check_and_replace(&old_100, 200));

        assert_eq!(*m.get(), 200);

    }

    #[test]

    fn map_and_replace() {

        let m = MutCfg::new(100_u32);

        let m_old = m.get();

        m.map_and_replace(|old_val| **old_val * 20);

        assert_eq!(*m.get(), 2000);

        assert_eq!(*m_old, 100);

    }

}