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use std::{
    sync::mpsc::Receiver,
    cell::Cell
};



/// Water Bottle.
///
/// The Bottle ***must*** be held and used, otherwise it will [`Shatter`].
///
/// Allows to access Water that was produced by melting Ice.
///
/// [`Shatter`]: struct.Bottle.html#impl-Drop
pub struct Bottle<W>(Receiver<W>, Cell<bool>);

impl<W> Bottle<W> {
    pub(crate) fn new(water: Receiver<W>) -> Bottle<W> {
        Bottle(water, Cell::new(false))
    }

    /// Opens the Bottle, granting access to Water.
    ///
    /// The Bottle is consumed in the process.
    ///
    /// # Blocking
    ///
    /// This operation blocks till the Heater is done melting Ice.
    ///
    /// # Panics
    ///
    /// * When the Bottle has already been opened.
    /// * When the Bottle is Poisoned<sup>1</sup>. Poisoning<sup>1</sup> happens when Heater
    /// melting the Ice fails. Irrecoverable.
    ///
    /// ---
    ///
    /// <sup>1</sup> - Not to be confused with [`Poisoning of the Mutex`], although Bottle is
    /// Poisoned because of a very similar reason - panic in a thread.
    ///
    /// [`Poisoning of the Mutex`]: https://doc.rust-lang.org/std/sync/struct.Mutex.html#poisoning
    pub fn open(&self) -> W {
        if self.1.get() {
            panic!("Tried to open an already opened bottle");
        } else {
            self.1.set(true);
        }

        self.0
            .recv()
            .expect("Tried to open a Poisoned bottle")
    }
}

impl<T> Drop for Bottle<T> {
    /// Drops the Bottle.
    ///
    /// # Panics
    ///
    /// When Bottle is dropped without ever being used. This causes it to shatter.
    ///
    /// It is completely user's responsibility to ensure that bottle is not dropped without
    /// being used.
    fn drop(&mut self) {
        assert!(self.1.get(), "Bottle dropped without ever being opened *Shatters*");
    }
}