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//! Align a view relative to its parent

use euclid::{Rect, Size2D};

use crate::{event::Event, unit::Cell, Printer, View as ViewTrait};

/// Content alignment
pub enum Alignment {
    /// Left or top
    Start,

    /// Obvious
    Middle,

    /// Right or bottom
    End,
}

/// The view itself
pub struct View<V> {
    inner: V,
    v: Alignment,
    h: Alignment,
}

impl<V> View<V> {
    /// Creates a new aligned view
    ///
    /// Defaults to centered vertically and horizontally.
    pub fn new(view: V) -> Self {
        Self {
            inner: view,
            v: Alignment::Middle,
            h: Alignment::Middle,
        }
    }

    /// Set horizontal alignment method
    pub fn h_align(mut self, alignment: Alignment) -> Self {
        self.h = alignment;

        self
    }

    /// Set vertical alignment method
    pub fn v_align(mut self, alignment: Alignment) -> Self {
        self.v = alignment;

        self
    }
}

/// Shorthand for [`View::new()`]
///
/// [`View::new()`]: View::new
pub fn new<V>(view: V) -> View<V> {
    View::new(view)
}

impl<T, M, V> ViewTrait<T, M> for View<V>
where
    V: ViewTrait<T, M>,
{
    fn draw(&self, printer: &Printer, focused: bool) {
        let p_size = printer.size();
        let inner_size =
            self.inner.layout((p_size.width, p_size.height).into());

        let origin = {
            let x = match self.h {
                Alignment::Start => 0,
                Alignment::Middle => {
                    (p_size.width / 2).saturating_sub(inner_size.width / 2)
                }
                Alignment::End => p_size.width.saturating_sub(inner_size.width),
            };

            let y = match self.v {
                Alignment::Start => 0,
                Alignment::Middle => {
                    (p_size.height / 2).saturating_sub(inner_size.height / 2)
                }
                Alignment::End => {
                    p_size.height.saturating_sub(inner_size.height)
                }
            };

            (x, y)
        };

        let sub =
            printer.to_sub_area(Rect::new(origin.into(), inner_size)).unwrap();

        self.inner.draw(&sub, focused);
    }

    fn width(&self) -> Size2D<u16, Cell> {
        self.inner.width()
    }

    fn height(&self) -> Size2D<u16, Cell> {
        self.inner.height()
    }

    fn layout(&self, constraint: Size2D<u16, Cell>) -> Size2D<u16, Cell> {
        self.inner.layout(constraint)
    }

    fn event(
        &mut self,
        event: &Event<T>,
        focused: bool,
    ) -> Box<dyn Iterator<Item = M>> {
        self.inner.event(event, focused)
    }

    fn interactive(&self) -> bool {
        self.inner.interactive()
    }
}

pub trait ViewExt {
    fn align(self) -> View<Self>
    where
        Self: Sized,
    {
        View::new(self)
    }
}

impl<V> ViewExt for V {}