use ahash::{HashMap, HashSet};

use crate::{id::IdSet, style, Align, Id, IdMap, LayerId, Rangef, Rect, Vec2, WidgetRects};

#[cfg(debug_assertions)]
use crate::{pos2, Align2, Color32, FontId, NumExt, Painter};

/// Reset at the start of each frame.
#[derive(Clone, Debug, Default)]
pub struct TooltipPassState {
    /// If a tooltip has been shown this frame, where was it?
    /// This is used to prevent multiple tooltips to cover each other.
    pub widget_tooltips: IdMap<PerWidgetTooltipState>,
}

impl TooltipPassState {
    pub fn clear(&mut self) {
        let Self { widget_tooltips } = self;
        widget_tooltips.clear();
    }
}

#[derive(Clone, Copy, Debug)]
pub struct PerWidgetTooltipState {
    /// Bounding rectangle for all widget and all previous tooltips.
    pub bounding_rect: Rect,

    /// How many tooltips have been shown for this widget this frame?
    pub tooltip_count: usize,
}

#[derive(Clone, Debug, Default)]
pub struct PerLayerState {
    /// Is there any open popup (menus, combo-boxes, etc)?
    ///
    /// Does NOT include tooltips.
    pub open_popups: HashSet<Id>,

    /// Which widget is showing a tooltip (if any)?
    ///
    /// Only one widget per layer may show a tooltip.
    /// But if a tooltip contains a tooltip, you can show a tooltip on top of a tooltip.
    pub widget_with_tooltip: Option<Id>,
}

#[derive(Clone, Debug)]
pub struct ScrollTarget {
    // The range that the scroll area should scroll to.
    pub range: Rangef,

    /// How should we align the rect within the visible area?
    /// If `align` is [`Align::TOP`] it means "put the top of the rect at the top of the scroll area", etc.
    /// If `align` is `None`, it'll scroll enough to bring the UI into view.
    pub align: Option<Align>,

    /// How should the scroll be animated?
    pub animation: style::ScrollAnimation,
}

impl ScrollTarget {
    pub fn new(range: Rangef, align: Option<Align>, animation: style::ScrollAnimation) -> Self {
        Self {
            range,
            align,
            animation,
        }
    }
}

#[cfg(feature = "accesskit")]
#[derive(Clone)]
pub struct AccessKitPassState {
    pub nodes: IdMap<accesskit::Node>,
    pub parent_stack: Vec<Id>,
}

#[cfg(debug_assertions)]
#[derive(Clone)]
pub struct DebugRect {
    pub rect: Rect,
    pub callstack: String,
    pub is_clicking: bool,
}

#[cfg(debug_assertions)]
impl DebugRect {
    pub fn paint(self, painter: &Painter) {
        let Self {
            rect,
            callstack,
            is_clicking,
        } = self;

        let ctx = painter.ctx();

        // Paint rectangle around widget:
        {
            // Print width and height:
            let text_color = if ctx.style().visuals.dark_mode {
                Color32::WHITE
            } else {
                Color32::BLACK
            };
            painter.debug_text(
                rect.left_center() + 2.0 * Vec2::LEFT,
                Align2::RIGHT_CENTER,
                text_color,
                format!("H: {:.1}", rect.height()),
            );
            painter.debug_text(
                rect.center_top(),
                Align2::CENTER_BOTTOM,
                text_color,
                format!("W: {:.1}", rect.width()),
            );

            // Paint rect:
            let rect_fg_color = if is_clicking {
                Color32::WHITE
            } else {
                Color32::LIGHT_BLUE
            };
            let rect_bg_color = Color32::BLUE.gamma_multiply(0.5);
            painter.rect(rect, 0.0, rect_bg_color, (1.0, rect_fg_color));
        }

        if !callstack.is_empty() {
            let font_id = FontId::monospace(12.0);
            let text = format!("{callstack}\n\n(click to copy)");
            let text_color = Color32::WHITE;
            let galley = painter.layout_no_wrap(text, font_id, text_color);

            // Position the text either under or above:
            let screen_rect = ctx.screen_rect();
            let y = if galley.size().y <= rect.top() {
                // Above
                rect.top() - galley.size().y - 16.0
            } else {
                // Below
                rect.bottom()
            };

            let y = y
                .at_most(screen_rect.bottom() - galley.size().y)
                .at_least(0.0);

            let x = rect
                .left()
                .at_most(screen_rect.right() - galley.size().x)
                .at_least(0.0);
            let text_pos = pos2(x, y);

            let text_bg_color = Color32::from_black_alpha(180);
            let text_rect_stroke_color = if is_clicking {
                Color32::WHITE
            } else {
                text_bg_color
            };
            let text_rect = Rect::from_min_size(text_pos, galley.size());
            painter.rect(text_rect, 0.0, text_bg_color, (1.0, text_rect_stroke_color));
            painter.galley(text_pos, galley, text_color);

            if is_clicking {
                ctx.copy_text(callstack);
            }
        }
    }
}

/// State that is collected during a pass, then saved for the next pass,
/// and then cleared.
///
/// (NOTE: we usually run only one pass per frame).
///
/// One per viewport.
#[derive(Clone)]
pub struct PassState {
    /// All [`Id`]s that were used this pass.
    pub used_ids: IdMap<Rect>,

    /// All widgets produced this pass.
    pub widgets: WidgetRects,

    /// Per-layer state.
    ///
    /// Not all layers registers themselves there though.
    pub layers: HashMap<LayerId, PerLayerState>,

    pub tooltips: TooltipPassState,

    /// Starts off as the `screen_rect`, shrinks as panels are added.
    /// The [`crate::CentralPanel`] does not change this.
    /// This is the area available to Window's.
    pub available_rect: Rect,

    /// Starts off as the `screen_rect`, shrinks as panels are added.
    /// The [`crate::CentralPanel`] retracts from this.
    pub unused_rect: Rect,

    /// How much space is used by panels.
    pub used_by_panels: Rect,

    /// The current scroll area should scroll to this range (horizontal, vertical).
    pub scroll_target: [Option<ScrollTarget>; 2],

    /// The current scroll area should scroll by this much.
    ///
    /// The delta dictates how the _content_ should move.
    ///
    /// A positive X-value indicates the content is being moved right,
    /// as when swiping right on a touch-screen or track-pad with natural scrolling.
    ///
    /// A positive Y-value indicates the content is being moved down,
    /// as when swiping down on a touch-screen or track-pad with natural scrolling.
    pub scroll_delta: (Vec2, style::ScrollAnimation),

    #[cfg(feature = "accesskit")]
    pub accesskit_state: Option<AccessKitPassState>,

    /// Highlight these widgets the next pass.
    pub highlight_next_pass: IdSet,

    #[cfg(debug_assertions)]
    pub debug_rect: Option<DebugRect>,
}

impl Default for PassState {
    fn default() -> Self {
        Self {
            used_ids: Default::default(),
            widgets: Default::default(),
            layers: Default::default(),
            tooltips: Default::default(),
            available_rect: Rect::NAN,
            unused_rect: Rect::NAN,
            used_by_panels: Rect::NAN,
            scroll_target: [None, None],
            scroll_delta: (Vec2::default(), style::ScrollAnimation::none()),
            #[cfg(feature = "accesskit")]
            accesskit_state: None,
            highlight_next_pass: Default::default(),

            #[cfg(debug_assertions)]
            debug_rect: None,
        }
    }
}

impl PassState {
    pub(crate) fn begin_pass(&mut self, screen_rect: Rect) {
        profiling::function_scope!();
        let Self {
            used_ids,
            widgets,
            tooltips,
            layers,
            available_rect,
            unused_rect,
            used_by_panels,
            scroll_target,
            scroll_delta,
            #[cfg(feature = "accesskit")]
            accesskit_state,
            highlight_next_pass,

            #[cfg(debug_assertions)]
            debug_rect,
        } = self;

        used_ids.clear();
        widgets.clear();
        tooltips.clear();
        layers.clear();
        *available_rect = screen_rect;
        *unused_rect = screen_rect;
        *used_by_panels = Rect::NOTHING;
        *scroll_target = [None, None];
        *scroll_delta = Default::default();

        #[cfg(debug_assertions)]
        {
            *debug_rect = None;
        }

        #[cfg(feature = "accesskit")]
        {
            *accesskit_state = None;
        }

        highlight_next_pass.clear();
    }

    /// How much space is still available after panels has been added.
    /// This is the "background" area, what egui doesn't cover with panels (but may cover with windows).
    /// This is also the area to which windows are constrained.
    pub(crate) fn available_rect(&self) -> Rect {
        debug_assert!(
            self.available_rect.is_finite(),
            "Called `available_rect()` before `Context::run()`"
        );
        self.available_rect
    }

    /// Shrink `available_rect`.
    pub(crate) fn allocate_left_panel(&mut self, panel_rect: Rect) {
        debug_assert!(
            panel_rect.min.distance(self.available_rect.min) < 0.1,
            "Mismatching left panel. You must not create a panel from within another panel."
        );
        self.available_rect.min.x = panel_rect.max.x;
        self.unused_rect.min.x = panel_rect.max.x;
        self.used_by_panels = self.used_by_panels.union(panel_rect);
    }

    /// Shrink `available_rect`.
    pub(crate) fn allocate_right_panel(&mut self, panel_rect: Rect) {
        debug_assert!(
            panel_rect.max.distance(self.available_rect.max) < 0.1,
            "Mismatching right panel. You must not create a panel from within another panel."
        );
        self.available_rect.max.x = panel_rect.min.x;
        self.unused_rect.max.x = panel_rect.min.x;
        self.used_by_panels = self.used_by_panels.union(panel_rect);
    }

    /// Shrink `available_rect`.
    pub(crate) fn allocate_top_panel(&mut self, panel_rect: Rect) {
        debug_assert!(
            panel_rect.min.distance(self.available_rect.min) < 0.1,
            "Mismatching top panel. You must not create a panel from within another panel."
        );
        self.available_rect.min.y = panel_rect.max.y;
        self.unused_rect.min.y = panel_rect.max.y;
        self.used_by_panels = self.used_by_panels.union(panel_rect);
    }

    /// Shrink `available_rect`.
    pub(crate) fn allocate_bottom_panel(&mut self, panel_rect: Rect) {
        debug_assert!(
            panel_rect.max.distance(self.available_rect.max) < 0.1,
            "Mismatching bottom panel. You must not create a panel from within another panel."
        );
        self.available_rect.max.y = panel_rect.min.y;
        self.unused_rect.max.y = panel_rect.min.y;
        self.used_by_panels = self.used_by_panels.union(panel_rect);
    }

    pub(crate) fn allocate_central_panel(&mut self, panel_rect: Rect) {
        // Note: we do not shrink `available_rect`, because
        // we allow windows to cover the CentralPanel.
        self.unused_rect = Rect::NOTHING; // Nothing left unused after this
        self.used_by_panels = self.used_by_panels.union(panel_rect);
    }
}