use kahlo::math::PixelSideOffsets;

use crate::{
    input::{MouseButton, MouseCheckStatus},
    layout::{
        HorizontalAlignment, LayoutNode, LayoutNodeAccess, LayoutTreeNode, LeafLayoutNode,
        SizePolicy, VerticalAlignment,
    },
    render::{ColourChoice, RenderTarget, TextCache},
    ui::UIHandle,
    Component,
};

use super::Widget;

#[derive(Clone, Copy, PartialEq)]
enum ButtonState {
    Idle,
    Hovered,
    Clicked,
}

pub struct Button<C: Component> {
    root_layout: LayoutNode,
    label_layout: LeafLayoutNode,
    text_cache: TextCache,
    label: String,
    state: ButtonState,
    hook: Option<Box<dyn Fn() -> Option<C::Msg>>>,
}

struct RootTag;

impl<C: Component> Button<C> {
    pub fn new(uih: &UIHandle) -> Self {
        let mut layout = uih.new_layout_node();
        layout
            .set_width_policy(SizePolicy::expanding(1))
            .set_height_policy(SizePolicy {
                minimum: uih.theme().ui_font_size as usize,
                desired: (uih.theme().ui_font_size * 1.5) as usize,
                slack_weight: 0,
            })
            .set_valign(VerticalAlignment::Centre)
            .set_halign(HorizontalAlignment::Centre);
        *layout.margin_mut() = PixelSideOffsets::new_all_same(uih.theme().border_width as i32);
        Self {
            root_layout: layout,
            label_layout: {
                let mut node = uih.new_layout_node();
                node.set_width_policy(SizePolicy::fixed(0))
                    .set_height_policy(SizePolicy::fixed(0))
                    .set_halign(HorizontalAlignment::Centre)
                    .set_valign(VerticalAlignment::Centre);

                node.into()
            },
            text_cache: TextCache::new_with_font_and_size(
                uih.theme().ui_font.clone(),
                uih.theme().ui_font_size,
            ),
            label: "".to_string(),
            state: ButtonState::Idle,
            hook: None,
        }
    }

    pub fn with_label(mut self, label: &str) -> Self {
        self.set_label(label);
        self
    }

    pub fn set_label(&mut self, label: &str) {
        self.label.clear();
        self.label += label;
        self.text_cache.update(&self.label);
    }

    pub fn set_hook(&mut self, to: Box<dyn Fn() -> Option<C::Msg>>) {
        self.hook = Some(to);
    }
}

impl<C: Component> LayoutTreeNode<RootTag> for Button<C> {
    fn current_node(&self) -> &LayoutNode {
        &self.root_layout
    }

    fn child_count(&self) -> usize {
        1
    }

    fn child(&self, ndx: usize) -> Option<LayoutNodeAccess<'_>> {
        if ndx == 0 {
            Some(self.label_layout.access())
        } else {
            None
        }
    }
}

impl<C: Component> Widget<C> for Button<C> {
    fn poll(
        &mut self,
        _uih: &mut UIHandle,
        input_state: Option<&crate::input::InputState>,
    ) -> Vec<<C as Component>::Msg> {
        self.text_cache
            .update_node_size_hint(&mut *self.label_layout);

        let mut result: Vec<<C as Component>::Msg> = vec![];
        if let Some((istate, area)) = input_state.zip(self.root_layout.render_area()) {
            let saved = self.state;
            match istate.mouse_status_in(area, MouseButton::Left) {
                MouseCheckStatus::Idle | MouseCheckStatus::Leave => {
                    self.state = ButtonState::Idle;
                }
                MouseCheckStatus::Click | MouseCheckStatus::Hold => {
                    self.state = ButtonState::Clicked;
                }
                MouseCheckStatus::Enter | MouseCheckStatus::Hover => {
                    self.state = ButtonState::Hovered;
                }
                MouseCheckStatus::Release => {
                    self.state = ButtonState::Hovered;
                    result.extend(self.hook.as_ref().and_then(|v| v()));
                }
            }
            if self.state != saved {
                self.root_layout.render_needed();
            }
        }

        result
    }

    fn layout_node(&self) -> LayoutNodeAccess {
        LayoutNodeAccess::new(self)
    }
    fn layout_node_mut(&mut self) -> &mut LayoutNode {
        &mut self.root_layout
    }

    fn render<'r, 'data: 'r>(&self, target: &mut RenderTarget<'r, 'data>) {
        target
            .with_node(&self.root_layout)
            .fill(match self.state {
                ButtonState::Idle => ColourChoice::Background,
                ButtonState::Hovered => ColourChoice::Panel,
                ButtonState::Clicked => ColourChoice::Active,
            })
            .border()
            .finish();
        target
            .with_node(&self.label_layout)
            .simple_text(&self.text_cache, ColourChoice::Foreground)
            .finish();
    }
}