//! Allow your users to perform actions by pressing a button.
use crate::overlay;
use crate::widget::tree::{self, Tree};
use crate::{Element, Widget};

use iced_native::event::{self, Event};
use iced_native::layout;
use iced_native::mouse;
use iced_native::renderer;
use iced_native::widget::button;
use iced_native::{
    Clipboard, Layout, Length, Padding, Point, Rectangle, Shell,
};

pub use iced_style::button::{Appearance, StyleSheet};

use button::State;

/// A generic widget that produces a message when pressed.
///
/// ```
/// # type Button<'a, Message> =
/// #     iced_pure::widget::Button<'a, Message, iced_native::renderer::Null>;
/// #
/// #[derive(Clone)]
/// enum Message {
///     ButtonPressed,
/// }
///
/// let button = Button::new("Press me!").on_press(Message::ButtonPressed);
/// ```
///
/// If a [`Button::on_press`] handler is not set, the resulting [`Button`] will
/// be disabled:
///
/// ```
/// # type Button<'a, Message> =
/// #     iced_pure::widget::Button<'a, Message, iced_native::renderer::Null>;
/// #
/// #[derive(Clone)]
/// enum Message {
///     ButtonPressed,
/// }
///
/// fn disabled_button<'a>() -> Button<'a, Message> {
///     Button::new("I'm disabled!")
/// }
///
/// fn enabled_button<'a>() -> Button<'a, Message> {
///     disabled_button().on_press(Message::ButtonPressed)
/// }
/// ```
pub struct Button<'a, Message, Renderer>
where
    Renderer: iced_native::Renderer,
    Renderer::Theme: StyleSheet,
{
    content: Element<'a, Message, Renderer>,
    on_press: Option<Message>,
    width: Length,
    height: Length,
    padding: Padding,
    style: <Renderer::Theme as StyleSheet>::Style,
}

impl<'a, Message, Renderer> Button<'a, Message, Renderer>
where
    Renderer: iced_native::Renderer,
    Renderer::Theme: StyleSheet,
{
    /// Creates a new [`Button`] with the given content.
    pub fn new(content: impl Into<Element<'a, Message, Renderer>>) -> Self {
        Button {
            content: content.into(),
            on_press: None,
            width: Length::Shrink,
            height: Length::Shrink,
            padding: Padding::new(5),
            style: <Renderer::Theme as StyleSheet>::Style::default(),
        }
    }

    /// Sets the width of the [`Button`].
    pub fn width(mut self, width: Length) -> Self {
        self.width = width;
        self
    }

    /// Sets the height of the [`Button`].
    pub fn height(mut self, height: Length) -> Self {
        self.height = height;
        self
    }

    /// Sets the [`Padding`] of the [`Button`].
    pub fn padding<P: Into<Padding>>(mut self, padding: P) -> Self {
        self.padding = padding.into();
        self
    }

    /// Sets the message that will be produced when the [`Button`] is pressed.
    ///
    /// Unless `on_press` is called, the [`Button`] will be disabled.
    pub fn on_press(mut self, msg: Message) -> Self {
        self.on_press = Some(msg);
        self
    }

    /// Sets the style variant of this [`Button`].
    pub fn style(
        mut self,
        style: <Renderer::Theme as StyleSheet>::Style,
    ) -> Self {
        self.style = style;
        self
    }
}

impl<'a, Message, Renderer> Widget<Message, Renderer>
    for Button<'a, Message, Renderer>
where
    Message: 'a + Clone,
    Renderer: 'a + iced_native::Renderer,
    Renderer::Theme: StyleSheet,
{
    fn tag(&self) -> tree::Tag {
        tree::Tag::of::<State>()
    }

    fn state(&self) -> tree::State {
        tree::State::new(State::new())
    }

    fn children(&self) -> Vec<Tree> {
        vec![Tree::new(&self.content)]
    }

    fn diff(&self, tree: &mut Tree) {
        tree.diff_children(std::slice::from_ref(&self.content))
    }

    fn width(&self) -> Length {
        self.width
    }

    fn height(&self) -> Length {
        self.height
    }

    fn layout(
        &self,
        renderer: &Renderer,
        limits: &layout::Limits,
    ) -> layout::Node {
        button::layout(
            renderer,
            limits,
            self.width,
            self.height,
            self.padding,
            |renderer, limits| {
                self.content.as_widget().layout(renderer, limits)
            },
        )
    }

    fn on_event(
        &mut self,
        tree: &mut Tree,
        event: Event,
        layout: Layout<'_>,
        cursor_position: Point,
        renderer: &Renderer,
        clipboard: &mut dyn Clipboard,
        shell: &mut Shell<'_, Message>,
    ) -> event::Status {
        if let event::Status::Captured = self.content.as_widget_mut().on_event(
            &mut tree.children[0],
            event.clone(),
            layout.children().next().unwrap(),
            cursor_position,
            renderer,
            clipboard,
            shell,
        ) {
            return event::Status::Captured;
        }

        button::update(
            event,
            layout,
            cursor_position,
            shell,
            &self.on_press,
            || tree.state.downcast_mut::<State>(),
        )
    }

    fn draw(
        &self,
        tree: &Tree,
        renderer: &mut Renderer,
        theme: &Renderer::Theme,
        _style: &renderer::Style,
        layout: Layout<'_>,
        cursor_position: Point,
        _viewport: &Rectangle,
    ) {
        let bounds = layout.bounds();
        let content_layout = layout.children().next().unwrap();

        let styling = button::draw(
            renderer,
            bounds,
            cursor_position,
            self.on_press.is_some(),
            theme,
            self.style,
            || tree.state.downcast_ref::<State>(),
        );

        self.content.as_widget().draw(
            &tree.children[0],
            renderer,
            theme,
            &renderer::Style {
                text_color: styling.text_color,
            },
            content_layout,
            cursor_position,
            &bounds,
        );
    }

    fn mouse_interaction(
        &self,
        _tree: &Tree,
        layout: Layout<'_>,
        cursor_position: Point,
        _viewport: &Rectangle,
        _renderer: &Renderer,
    ) -> mouse::Interaction {
        button::mouse_interaction(
            layout,
            cursor_position,
            self.on_press.is_some(),
        )
    }

    fn overlay<'b>(
        &'b self,
        tree: &'b mut Tree,
        layout: Layout<'_>,
        renderer: &Renderer,
    ) -> Option<overlay::Element<'b, Message, Renderer>> {
        self.content.as_widget().overlay(
            &mut tree.children[0],
            layout.children().next().unwrap(),
            renderer,
        )
    }
}

impl<'a, Message, Renderer> From<Button<'a, Message, Renderer>>
    for Element<'a, Message, Renderer>
where
    Message: Clone + 'a,
    Renderer: iced_native::Renderer + 'a,
    Renderer::Theme: StyleSheet,
{
    fn from(button: Button<'a, Message, Renderer>) -> Self {
        Self::new(button)
    }
}