//! Scrolling moves content and stops at its ends.

use iris::harness::{Harness, assert_corners};
use iris::prelude::*;

#[test]
fn scrollable_enables_a_region_node_but_raw_scroll_does_not() {
    let mut h = Harness::new((100, 100));
    let default_child = ().add(&mut h.rsc);
    let _default = default_child.scrollable().add(&mut h.rsc);
    assert!(h.rsc.widgets().is_region_node(default_child));
    h.rsc.widgets_mut().set_region_node(default_child, false);
    assert!(!h.rsc.widgets().is_region_node(default_child));

    let raw_child = ().add(&mut h.rsc);
    let _raw = Scroll::new(raw_child.add_strong(&mut h.rsc), Axis::Y).add(&mut h.rsc);
    assert!(!h.rsc.widgets().is_region_node(raw_child));

    let explicit = ().region_node().add(&mut h.rsc);
    assert!(h.rsc.widgets().is_region_node(explicit));
}

#[test]
fn a_scrollable_child_can_drop_its_region_node() {
    let mut h = Harness::new((400, 200));
    let top = rect(Color::RED).height(200).add(&mut h.rsc);
    let bottom = rect(Color::BLUE).height(200).add(&mut h.rsc);
    let content = (top, bottom).span(Dir::DOWN).add(&mut h.rsc);
    h.set_root(content.scrollable());
    h.rsc.widgets_mut().set_region_node(content, false);
    h.frame();

    h.move_to((200, 100));
    h.scroll((0, 1));
    h.frame();

    assert!(!h.rsc.widgets().is_region_node(content));
    assert_corners!(h, top, (0, -150), (400, 50));
}

#[test]
fn a_wheel_scrolls_the_content_and_stops_at_its_end() {
    let mut h = Harness::new((400, 200));
    // Twice the window's height, so there is 200 to scroll.
    let top = rect(Color::RED).height(200).add(&mut h.rsc);
    let bottom = rect(Color::BLUE).height(200).add(&mut h.rsc);
    h.set_root((top, bottom).span(Dir::DOWN).scrollable());
    h.move_to((200, 100));

    // `Scroll` starts snapped to the end.
    assert_corners!(h, top, (0, -200), (400, 0));

    // The handler scales a wheel line by 50.
    h.scroll((0, 1));
    h.frame();
    assert_corners!(h, top, (0, -150), (400, 50));

    h.scroll((0, 10));
    h.frame();
    assert_corners!(h, top, (0, 0), (400, 200));
}

#[test]
fn fixed_content_and_a_share_fill_one_viewport() {
    let mut h = Harness::new((900, 100));
    let content = rect(Color::RED)
        .width(LayoutLen {
            px: Px::from_int(600),
            rel: Rel::ZERO,
            leftover: Weight::ONE,
        })
        .add(&mut h.rsc);
    let scroll = Scroll::new(content.add_strong(&mut h.rsc), Axis::X);
    h.set_root(scroll);

    assert_corners!(h, content, (0, 0), (900, 100));
}

#[test]
fn fixed_content_wider_than_the_viewport_still_scrolls() {
    let mut h = Harness::new((900, 100));
    let content = rect(Color::RED).width(1200).add(&mut h.rsc);
    let scroll = Scroll::new(content.add_strong(&mut h.rsc), Axis::X);
    h.set_root(scroll);

    assert_corners!(h, content, (-300, 0), (900, 100));
}

#[test]
fn a_lone_share_fills_without_scrolling() {
    let mut h = Harness::new((900, 100));
    let content = rect(Color::RED).width(LayoutLen::LEFTOVER).add(&mut h.rsc);
    let scroll = Scroll::new(content.add_strong(&mut h.rsc), Axis::X);
    h.set_root(scroll);

    assert_corners!(h, content, (0, 0), (900, 100));
}

#[test]
fn wrapping_content_beside_a_fixed_length_is_stable_warm_and_cold() {
    fn plant(h: &mut Harness) -> (WidgetId, WidgetId) {
        let fixed = rect(Color::RED).width(600).add(&mut h.rsc);
        let text = wtext("Wrapping shapes one source into as many lines as the box leaves room for, so a paragraph's height is an answer and not a setting.")
            .size(16)
            .wrap(true)
            .width(LayoutLen::LEFTOVER)
            .add(&mut h.rsc);
        let content = (fixed, text).span(Dir::RIGHT).add(&mut h.rsc);
        let scroll = Scroll::new(content.add_strong(&mut h.rsc), Axis::X);
        h.set_root(scroll);
        (text.id(), content.id())
    }

    let mut warm = Harness::new((900, 300));
    let (text, content) = plant(&mut warm);
    warm.rsc.widgets_mut().get_dyn_mut(text);
    warm.frame();

    let mut cold = Harness::new((900, 300));
    let (cold_text, cold_content) = plant(&mut cold);

    assert_eq!(warm.region(&text), cold.region(&cold_text));
    assert_eq!(warm.region(&content), cold.region(&cold_content));
}

/// A widget that clips to its box may not report more than the box: its
/// parent would place the part it cut off, and the framework would put a
/// drawing longer than its box somewhere. `Masked` is the second of these
/// after `Scroll`, and the assertion in `draw_at` is what says so.
#[test]
#[should_panic = "clips to"]
fn a_clipping_widget_reporting_more_than_its_box_is_caught() {
    struct Clipper(StrongWidget);

    impl Widget for Clipper {
        fn draw(&mut self, painter: &mut Painter) -> Size {
            painter.set_mask(UiRegion::FULL);
            painter.widget(&self.0).size()
        }
    }

    let mut h = Harness::new((100, 100));
    let tall = rect(Color::RED).height(400).add_strong(&mut h.rsc);
    let clipper = Clipper(tall).add(&mut h.rsc);
    // `set_root` lays the tree out, so this is where it is caught.
    h.set_root(clipper);
}

/// Content that fits sits in the viewport, not in a box of the window's
/// length anchored at the viewport's start. `Part::From` takes window
/// lengths, so a `rel(1.0)` span in one is the window, and only a scroll
/// filling the window would land right.
#[test]
fn content_that_fits_is_placed_in_the_viewport_and_not_in_the_window() {
    let mut h = Harness::new((400, 400));
    let head = rect(Color::RED).height(100).add(&mut h.rsc);
    let inner = rect(Color::BLUE).height(50).add(&mut h.rsc);
    let scroll = Scroll::new(inner.add_strong(&mut h.rsc), Axis::Y).add(&mut h.rsc);
    h.set_root((head, scroll).span(Dir::DOWN));

    assert_corners!(h, scroll, (0, 100), (400, 400));
    assert_corners!(h, inner, (0, 225), (400, 275));
}