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use Input;

/// When the window is resized
pub trait ResizeEvent: Sized {
    /// Creates a resize event.
    fn from_width_height(w: u32, h: u32, old_event: &Self) -> Option<Self>;
    /// Calls closure if this is a resize event.
    fn resize<U, F>(&self, f: F) -> Option<U> where F: FnMut(u32, u32) -> U;
    /// Returns resize arguments.
    fn resize_args(&self) -> Option<[u32; 2]> {
        self.resize(|x, y| [x, y])
    }
}

impl ResizeEvent for Input {
    fn from_width_height(w: u32, h: u32, _old_event: &Self) -> Option<Self> {
        Some(Input::Resize(w, h))
    }

    fn resize<U, F>(&self, mut f: F) -> Option<U>
        where F: FnMut(u32, u32) -> U
    {
        match *self {
            Input::Resize(w, h) => Some(f(w, h)),
            _ => None,
        }
    }
}

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

    #[test]
    fn test_input_resize() {
        use super::super::Input;

        let e = Input::Resize(0, 0);
        let x: Option<Input> = ResizeEvent::from_width_height(100, 100, &e);
        let y: Option<Input> = x.clone()
            .unwrap()
            .resize(|w, h| ResizeEvent::from_width_height(w, h, x.as_ref().unwrap()))
            .unwrap();
        assert_eq!(x, y);
    }
}